Important forage grasses, legumes and shrub legumes
for tropical zones of Latin America


by Esteban A. Pizarro*


[For details of species in this paper see Grassland Index and Picture Gallery]

[*Contact address]

SUMMARY
INTRODUCTION
GRASSES

Andropogon gayanus
Brachiaria species
Eragrostis tef
Paspalum species
Pennisetum purpurem

FORAGE LEGUMES

Arachis species
Calopogonium mucunoides
Centrosema species
Desmodium species
Macroptilium species
Neonotonia wightii
Stylosanthes species

LEGUMINOUS TREES AND SHRUBS

Leucaena leucocephala
Cratylia genus
Morus species
Bauhinia species
Chamaecytisus palmensis
Lespedeza species

GENERAL CONCLUSIONS AND COMMENTS

REFERENCES

AUTHOR


SUMMARY

This paper reviews forage grasses, legumes and shrub legumes for tropical Latin America.

The tropical area under study covers the well-drained isohyperthermic savannas (Llanos of Colombia and Venezuela); the well-drained isothermic savannas (the Brazilian Cerrados); the humid tropical forests (Amazonia and humid forest sites of Central America) and the subhumid tropical forests (Central America).

Andropogon gayanus is well adapted to acid-soil savannas and cleared-forest ecosystems of tropical Latin America. The agronomic plasticity in A. gayanus is narrow. According to Brazilian statistics there are 3,000,000 hectares under A. gayanus, mainly in the Cerrado ecosystem. Despite this figure, the seed trade is very low in South America and almost nil in Central America.

Brachiaria cultivars have made an impressive contribution to animal production and certainly continue to do so, especially with the release of new cultivars. The superior performance of the first Brachiaria hybrid that reaches cultivar status is a major accomplishment of CIAT´s breeding programme. There is no doubt at all that a new era starts with the Brachiaria genus in the tropical world.

For the savanna ecosystem and regions with a long dry spell, annual and short cycle grasses like Eragrostis tef may have major advantages. Teff is a reliable crop for unreliable climates, especially those with a dry season of unpredictable occurrence and length.

Paspalum is the predominant American genus. Several accessions are adapted to wet sites with very low incidence of spittlebug. From the data presented on accessions variability on agronomic characteristics such as dry matter yield distribution, nutritive value, seed yield and the low incidence of spittlebug there is no doubt at all that Paspalum is an alternative for the acid and low fertility soil of the tropical world. Nowadays pasture technology based on high inputs seems less relevant to the likely needs of the 21st century.

Pennisetum purpureum presents limitations under grazing systems. The actual available elephant grass cultivars are very responsive to fertilizer and therefore not suitable for marginal areas. Another negative feature is the fast drop in nutritive value. There is a real need to develop seed-propagated hybrids, less winter-hardy than the true elephant grass, with higher nutritive value and also to define a companion legume to reduce nitrogen need.

The genus Arachis is naturally confined to Brazil, Bolivia, Paraguay, Argentina and Uruguay. A. pintoi is a multiple-use ground cover crop with a high potential to contribute to sustainable agricultural systems. The high potential animal production per unit area in pastures based on A. pintoi is a reality in tropical areas with no dry season stress and even in areas with 3-4 months dry season and in the seasonally flooded lands of the Brazilian Cerrado. There is an urgent need to expose the material in areas with a high gross return per unit area, such as for hay, as cover in plantation crops, and in dairying. Arachis pintoi is the emerging forage legume in the tropical seed market.

Calopogonium mucunoides although not widely used (like any other tropical legume today in Latin America), it is the most popular legume amongst Brazilian farmers and it is the legume seed produced in greatest volume. C. mucunoides has some limitations, but this conclusion has come from only one accession within the C. mucunoides group. The agronomic evaluation of 215 accessions in the savanna ecosystem showed new light. Two accessions, CIAT 822 and 20709, were outstanding for their leaf retention during long dry seasons.

In spite of a considerable amount of research having been done on the genus Centrosema in the last 40 years, it remains of little agronomic importance. C. brasilianum has shown promise at several locations, but Rhizoctonia foliar blight is a limiting factor.

Desmodium heterocarpon ssp. ovalifolium has spread to most parts of the tropics because of its value as a cover crop in plantations and for grazing. In Latin America, there is only one officially released cultivar of D. ovalifolium, cv. Itabela. Despite the outstanding seed production and adaptation to acid soils and its compatibility with an aggressive grass like Brachiaria humidicola, it has not been successful in adoption and commercialization. Negative attributes of this legume are the undesirable tannin content and competitiveness due to the ascending and climbing growth habit.

Macroptilium atropurpureum is particularly well suited to tropical and subtropical areas. It is not tolerant of low fertility, but its nutritive value, good commercial seed yield, nitrogen fixation, potential contribution to milk production, and especially its potential role in cropping systems, call attention to the need to search for new germplasm. Outstanding new accessions are: BRA-003808, -003522, -003565, -003310, -003379, -003433 and –003468.

During the 1950s Neonotonia wightii, commercial cultivars Cooper, Clarence, Tinaroo and Malawi were promoted and used. Their failure throughout the tropical world was mainly due to the narrow genetic variability, low pest and disease resistence and the emphasis in those days on long-term leys. Today, agricultural systems also look for grass-legume association for easy establishment and especially for easy turnover. The genus Neonotonia may play an important role in this new scenario. Outstanding new genotypes are BRA-001104, -001261, -001341

Stylosanthes genus is an important source of pasture legumes for tropical and subtropical environments. Until now, the two most highly successful materials are S. guianensis cv. Mineirão and S. guianensis CIAT 184 (now cultivar Reyan II). A new S. capitata has been released as cultivar Campo Grande using a novel technique to produce resistance to anthracnose. Further research at farm level in farming systems may be justified.

Leucaena cultivation begun about 2000 years ago and it continues to be cultivated for human consumption in Mexico today, but rarely for forage. Hundreds of papers, reviews, workshops, international projects on research and development have been promoted on this species. Nevertheless the agronomic impact is limited and uncertain.

Cratylia genus is found exclusively in Latin America. Cratylia argentea unlike the other species is found in a broad range of habitats. The nutritive value of C. argentea, measured in terms of crude protein and in vitro digestibility, is similar to that of other common shrub legumes. C. argentea may play an important role in dry ecosystems of tropical Latin America with marginal soils. Simple and effective supplementation strategies can be developed for feeding cattle, sheep and goats.

Morus alba has traditionally been used for feeding the silkworm. Very few agronomic evaluations have been carried out for animal productions purpose. The Morus spp. populations evaluated recently in the Cerrado ecosystem showed high tolerance to drought, high plant survival, and tolerance to cutting at ground level in mid dry season. Considering its high quality and palatability, mulberry should be relatively more valuable as a feed, particularly to lactating cows.

Bauhinia genus is found in tropical parts of Argentina, Brazil Paraguay and Peru, as well as tropical zones of Asia. The indigenous uses of Pata de Vaca are not well documented but it has long held a place in Brazilian herbal medicine. B. cheilantha has been reported as one of the most preferred shrubs species for beef cattle in the Ouricuri region, Pernambuco, Brazil. Bauhinia bongardii is a highly rustic group that supports periodic floods and grows in poor and low fertility soils with high pH. Unfortunately, only one paper has been published on botanical composition and quality of the diet selected by fistulated steers grazing native savannas of the Brazilian Cerrado. It is important to take into account that there are no registered records of available germplasm in seed bank storage in national or international centres.

Chamaecytisus palmensis is a fast-growing shrub or small tree from the island of Las Palmas in the Canary Islands, which produces its main growth in spring and summer. Tagasaste has a deep taproot system that confers considerable drought resistance. Very few germplasm have been evaluated at regional level and with the exception of New Zealand, no centre (including in tropical Latin America) has a representative germplasm collection.

Lespedeza bicolor is a nitrogen-fixing legume planted for wildlife habitat improvement, erosion control, and its leaves produce a heavy soil-protecting mulch. For its positive agronomic qualities this genus may have a place in forage/livestock systems.

The efforts carried out on introduction, evaluation and promotion are very contradictory. For example, Leucaena leucocephala, Stylosanthes guianensis and S. capitata have been broadly investigated and promoted, nevertheless, the seed trade in these mentioned forages is nil. On the other hand, Calopogonium mucunoides, a forage legume, without promotion and also discredited by many investigators is the one most sold and accepted by producers.

In spite of the great effort on methodology, regional evaluation in a network approach, significant investment in training and development of young investigators, just when new available germplasm was ready and available for evaluation in farming systems the outstanding research centres in the region significantly reduced their support and research on forage programmes.

INTRODUCTION

The purpose of this document is to describe the current status of germplasm development in the major ecosystems of tropical America. These ecosystems cover the well-drained isohyperthermic savannas (Llanos of Colombia and Venezuela); the well-drained isothermic savannas (the Brazilian Cerrados); the humid tropical forests (Amazonia and humid forest sites of Central America) and the subhumid tropical forests (Central America).

The most important environmental attributes are altitude, that ranges from 200 to 1000 masl; average annual precipitation, which varies from approximately 1600 to over 4000 mm; the number of dry months, that range from 0 to 6 with mean temperature ranging from 22.8 to 26.5 oC; and the main soil orders which comprise oxisols, ultisols, entisols and inceptisols.

More than 1000 grasses and legumes as well as nearly 200 accessions of woody shrub or tree legume species have been screened and evaluated in the last 30 years. Today, some germplasm has reached the pre-release stage or the released category.

This paper reviews the importance of available commercial forage grasses such as Andropogon gayanus, Brachiaria spp., Paspalum spp., Pennisetum spp., and potential ones like Eragrostis tef. The main forage legume genera discussed are Arachis spp., Calopogonium mucunoides, Centrosema spp., Desmodium spp., Macroptilium spp., Neonotonia wightii and Stylosanthes spp. The role of woody legumes is summarized. The agronomic importance of Leucaena leucocephala, and the role of Cratylia argentea, Morus spp., Bauhinia species such as Bauhinia bongardi and Bauhinia cheilantha, Chamaecytisus palmensis, and Lespedeza bicolor is discussed.

GRASSES

ANDROPOGON GAYANUS

Andropogon gayanus Kunth belongs to the tribe Andropogoneae within the Panicoideae. The genus Andropogon comprises about 100 annual and perennial species, which occur throughout the tropics with particular prolificacy in Africa and America. Varietal characters are based principally on the hairiness of spikelets. At present, four botanical varieties of A. gayanus are recognized: the variety gayanus (syn. var. genuinus Hack.); variety tridentatus Hack.; variety polycladus (Hack.) W.D. Clayton (syn. Var. squamulatus (Hochst.) Stapf and the variety bisquamulatus (Hochst.) Hack.

Andropogon gayanus is a tall, coarse, erect, perennial bunch grass with a culm height of 1–3 m. As a result of short rhizome internodes and intravaginal branching, it forms tussocks up to 1 m diameter. Leaves are pubescent on both sides, particularly when young, and often glaucescent and scabrid along margins. The mode of reproduction is sexual, involving cross-pollination by wind. It has a short-day flowering response, so higher latitudes favour flowering synchrony. Seed quality is extremely variable.

Main agronomic features and potential uses. Andropogon gayanus var. bisquamulatus is well adapted to acid-soil savannas and cleared-forest ecosystems of tropical America, the monsoonal tropics of northern Australia, and the low rainfall areas of India and Africa.

Yields obtained from Andropogon gayanus in many trials in tropical America generally are higher than the native grasses (Grof and Thomas, 1990). One the main agronomic problems are the difficulty of establishment. In a RIEPT survey farmers complain that within commercial available grass forages, A. gayanus was the most difficult to establish, with more than 50 percent failure at establishment (Table 1).

Although A. gayanus is tolerant to tissue desiccation and capable of using the water in the soil profile efficiently during dry periods while maintaining its photosynthetic and metabolic activity even during severe drought; the quality of the standing forage is very poor (Table 2). In the last 25 years the situation changed. Today, there are other forage options for the dry season in tropical America. The plasticity in A. gayanus is narrow. Standing hay is low in quality and nutritive value.

In relation to pests and diseases A. gayanus CIAT 621 is quite resistant to spittlebugs of the three main genera, Aenolamia, Deois and Zulia, but its usefulness is commonly limited by leaf-cutter ants of the genera Atta and Acromyrmex. Ant populations increase rapidly in A. gayanus pastures, but tend to decrease in pastures of the resistant Brachiaria humidicola.

Future perspectives and limitations. According to Brazilian statistics there are 3,000,000 hectares under Andropogon gayanus, mainly in the Cerrado ecosystem. Despite this figure, the seed trade in Andropogon gayanus is very low in South America and almost nil in Central America (Tables 35 and 36). In Brazil, the total amount of seed sold in the last two years only reached 2 percent of the total volume, being 83 percent for Brachiaria genus (Table 35). Another concern has been the threat of A. gayanus in some ley-farming areas through its facility to spread by wind in the savanna area.

Inclusion of shrub legumes has been proposed in areas of Andropogon gayanus to improve the diet, especially in the dry season. In more intensive farming systems nutritive value, easy establishment, easy turnover and plasticity may play an important role in this emergent scenario. Other negative factors frequently mentioned by cattlemen are its low aggressiveness, erect growth, and consequent low soil coverage. It seems that Andropogon gayanus’ place would be relegated to marginal areas of low fertility and acid soils.

Table 1. Farmer survey on the establishment of forage grasses and the percentage requiring replanting

Grasses

Replanting Required (%)

Andropogon gayanus

50

Brachiaria decumbens

18

Panicum maximum

16

Brachiaria brizantha

9

Brachiaria dictyoneura

0

Adapted from: Pizarro, 1992

 

Table 2. Plant yield components at 60 days regrowth in the dry season in the Cerrado ecosystem

Plant components %

A. gayanus cv. Planaltina

B. brizantha CIAT 16488

Dead material

89

54

Green leaf

9

26

Green stem

2

20

Adapted from Pizarro, 2001a

 

BRACHIARIA SPECIES

The taxonomic position of the various Brachiaria species commonly used in pastures is unclear. Old names have been perpetuated in published literature, which continues to cause confusion. The genus Brachiaria, tribe Paniceae, includes about 100 species, which occur in tropical regions and subtropical regions of both eastern and western hemispheres, but mostly in Africa.

Their introduction to Brazil goes back more than 100 years, when Brachiaria mutica came with African slaves as bedding material (Parsons, 1972; Sendulsky, 1978).

Between 1972 and 1984 fewer than 70 accessions were available. Development of new cultivars depend on germplasm diversity, which was virtually nonexistent in America until a large collecting effort was undertaken by CIAT and ILRI under the auspices of the International Board for plant genetic Resources - IPGRI and collaboration of national institutions in six East African countries (Keller-Grein et al., 1996).

The most important commercial species are of African origin Brachiaria arrecta, B. brizantha, B. decumbens, B. dictyoneura, B. humidicola, B. mutica, and B. ruzizienzis, have been used as fodder plants, particularly in tropical America. Today in Brazil, nearly 100,000,000 hectares are covered by sown pastures, where more than 60 percent are Brachiaria species. Similar patterns of evolution are found in most countries, as the recent release in Costa Rica of B. brizantha CIAT 26110 as cv. Toledo and cv. Victoria in Brazil.

Brachiaria is now the most widely used tropical grass genus, especially in Central and South America. The trade seed market confirms the facts (Tables 35 and 36).

Agronomic performance across ecosystems

Tropical America savannas – Cerrado ecosystem. The savanna ecosystem is varied and extensive, covering about 250,000,000 hectares in South America. The most relevant sub ecosystems are the Cerrados and the Llanos. The Cerrado ecosystem characterized by a well-defined dry season and acid, low fertility soils. A few Brachiaria species have shown wide adaptation and are extensively used. These were introduced from Africa in the 1950s and 1960s, and spread, at first, vegetatively and then by seed, covering today an estimated 100,000,000 hectares.

New germplasm has become available since 1980, when collecting trips were undertaken in East Africa, and intensive evaluation programmes were developed throughout the region. Grasses of the Brachiaria genus are extremely important forages for cattle. In Brazil, carrying capacity was increased from 0.4 head ha-1 on native savanna pasture in 1950, to 0.7 head ha-1 in 1990, a 73 percent increase due mainly to the use of improved pastures, especially Brachiaria. The choice of cultivars for improving pastures has been extremely limited but the few commercial cultivars of Brachiaria have shown good adaptation and production. These reproduce by apomixis which results in extensive areas planted to a single genotype. Consequently, problems such as the massive attack of spittlebugs (Homoptera:Cercopidae) have arisen.

Despite important constraints, Brachiaria cultivars have made an impressive contribution to animal production and certainly continue to do so, especially with the release of new cultivars. In 1987, EMBRAPA introduced a large Brachiaria germplasm collection from CIAT, and agronomic evaluation began in both the Cerrados Agricultural Research Centre (EMBRAPA-CERRADOS) and the Beef Cattle Agricultural Research Centre (EMBRAPA-CNPGC), respectively.

More than 340 accessions of 12 Brachiaria species were evaluated in small plots from 1987 to 1992 at EMBRAPA-Cerrados. Of the collection, 52 percent are accessions of Brachiaria brizantha, which was by far the most variable and promising species represented. Dry matter yields (DMY) for the best-adapted accessions, 85 percent of which were B. brizantha, ranged from 16-to 21 t ha-1 in the rainy season. Dry season DMY were lower, although several accessions performed better than commercial cultivars. Seed yields showed a wide range of variability among accessions (4 to 155 kg ha-1). Several accessions out yielded cv. Marandu, representing distinct growth forms with specific agronomic characteristics (Grof, 1989, Grof et al.,1 989a).

At EMBRAPA-CNPGC, 320 accessions were evaluated. From these, eleven superior accessions of Brachiaria brizantha, one of Brachiaria jubata, and two of Brachiaria humidicola were selected. B. brizantha presented the widest diversity and the highest production. The selected accessions have a high leaf- to-stem ratio, fast regrowth, and a good seasonal distribution of total yield. The main results are summarised in Table 3.

From a new group of 200 accessions introduced from CIAT in 1994 and the results obtained in the Cerrados Centre, a common group was selected for regional agronomic and grazing trials (BRA-002801, -002844, -003000, -003204, -003247, -003361, -003387, -003395, -003441, -003450, -003484, -003719, -003824, 003891, -003948, 004308, -004391, -005011, -005118).

Tropical America savannas – Savanna ecosystem. The list of materials evaluated includes 376 accessions of twelve Brachiaria species, of which B. brizantha comprised 52 percent and B. decumbens, B. humidicola and B. ruziziensis together another 35 percent.

The first field evaluation emphasized the identification of spittlebug-resistant Brachiaria accessions. Five B. brizantha accessions CIAT 6690, 16126, 16388, 16827 and 16829 and the control cv. Marandu (CIAT 6297), were selected for a grazing experiment, using Centrosema acutifolium as the associated legume. Later (1991–1994), a second set of 186 accessions from ten different species of Brachiaria was evaluated at Carimagua, Colombia.

In another trial, including more than fifty Brachiaria humidicola accessions were evaluated to identify environmentally adapted accessions with better nutritive value and seed production than the commercial cv. Humidicola – CIAT 679. The variation among accessions was very great.

After fourteen years of evaluation in the Tropical Pasture Program of CIAT a list of twenty accessions were selected for regional evaluation through Colombia (CIAT 606, 6133, 6387,16113, 16121, 16212, 16315, 16322, 16327, 16467, 16488, 16497, 26110, 26124, 26180, 26318, 26556, 26562, 36060 and 36061).

Tropical America: Costa Rica and Central America

In 1987, in a joint project between CIAT-CATIE and MAG it was introduced a large Brachiaria germplasm collection from CIAT, and agronomic evaluation began in the humid tropics in Guápiles, Costa Rica. More than 250 accessions of 12 Brachiaria species were evaluated in small plots from 1987 to 1992. Of the collection, 52 percent comprises accessions of B. brizantha, was by far the most variable and promising species represented. A summary of the main agronomic attributes evaluated in the collections is presented in Table 4.

Grazing studies

Small-plot evaluation in mixtures under grazing. A series of small-plot grazing trials, including various Brachiaria species and accessions, was conducted at the Carimagua Research Station, to study the compatibility of adapted grasses and legumes and their persistence in mixtures. From many studies in Brachiaria species and selected legumes in each period like Desmodium incanum, D. ovalifolium, Centrosema acutifolium, Stylosanthes capitata, only the association with Pueraria phaseoloides and Arachis pintoi persisted for more than six years (Pizarro, 2001a).

Brachiaria and Arachis pintoi associations.

Comparing different species and accessions of Brachiaria, the highest growth rate and total annual DM yield of A. pintoi CIAT 17434 (cv. Maní Forrajero Perenne) were recorded in association with cv Llanero (Grof 1985).

Legume content in associations with B. brizantha CIAT 664, B. dictyoneura cv. Llanero, B. humidicola cv. Humidicola, and B. ruziziensis CIAT 6291 increased with time, to as much as 36 percent and 44 percent in cv. Llanero and cv. Humidicola pastures, respectively. The highest legume contents occurred in the associations with B. brizantha (72 percent) and B. ruziziensis (70 percent) because spittlebug attack permitted the legume to colonize the areas left by the grass.

In a subsequent trial, with other B. humidicola accessions (CIAT 679, 6369, 6705, and 6709) and B. brizantha cv. Marandu, the proportion of A. pintoi increased overtime, leading to legume dominance in the associations with CIAT 6369 and 6709 at the end of the experiment. The other associations were more balanced. Grazing pressure had no effect on the performance of these associations.

Regional experience with Brachiaria in the tropical America humid lowlands

In the American humid lowlands, Brachiaria is almost exclusively planted as a monocrop. As a monocrop B. decumbens has two drawbacks. One is the increase in photosensitization and the other one, is the higher susceptibility to spittlebugs when compared with grass-legume mixtures.

Brachiaria decumbens compatibility with legumes is reported with Desmodium ovalifolium cv. Itabela; Centrosema macrocarpum CIAT 5713; Pueraria phaseoloides and A. pintoi cv. Amarillo (Argel and Keller-Grein, 1996).

Brachiaria humidicola cv. Humidicola is a stoloniferous grass that tolerates waterlogged soils although it can withstand dry periods. Due to its stoloniferous growth habit, it is reputedly difficult to associate with tropical forage legumes. However, productivity and stable associations have been reported with D. ovalifolium cv. Itabela in Brazil, Colombia and Perú and with A. pintoi cv. Amarillo. Other less persistent associations have been reported with Calopogonium macrocarpum CIAT 5062, C. brasilianum CIAT 5234, C. mucunoides and P. phaseoloides (Argel and Keller-Grein, 1996).

Brachiaria dictyoneura cv. Llanero is regarded as a medium-quality grass that tolerates heavy grazing. It is not highly competitive during establishment, which favours forage legumes. Successful and very productive associations have been reported with C. acutifolium, C. macrocarpum, Stylosanthes guianenssis, A. pintoi, P. phaseoloides and D. ovalifolium. However it showed poor ability to compete for light when intercropped with either Vigna unguiculata or Glycine max (Argel and Keller-Grein, 1996).

The final commercial cultivars used in the region, B. brizantha cvs. La Libertad and Marandú have been available to farmers for the past fifteen years. Cultivar La Libertad adapts to less fertile soils than cv. Marandu. On the other hand, cv. Marandu associates well with D. ovalifolium, C. brasilianun, C. macrocarpum, C. mucunoides, P. phaseoloides and A. pintoi. This grass apparently competes efficiently with companion crops. Pérez et al. (1993) reported that intercropped with soybean, it yielded 66 percent of the yield in monoculture, suggesting shade tolerance and efficient use of light and soil nutrients.

A number of grazing experiments have been recorded. Ibrahim (1994) found high DMY, particularly at the low stoking rates of 1.75 animal units ha-1, when associated with A. pintoi, C. macrocarpum CIAT 5713, or S. guianensis CIAT 184. Arachis pintoi cv. Amarillo persisted over 3 years under grazing, especially at the high stoking rate (3 head ha-1). After four years of grazing, the association yielded an annual 990 kg ha-1 of beef; 300 kg–1 more than did the grass alone.

Regional experience with Brachiaria in Australia, the South Pacific and Indonesia.

In pastures where N is deficient, B. decumbens and B. humidicola can coexist with adapted legumes. In Australia, C. mucunoides combines well with B. decumbens and D. heterophyllum as has Vigna parkei cv. Shaws. The most promising legume, however, is A. pintoi cv. Amarillo.

In the South Pacific, smallholders combine B. decumbens or B. humidicola with D. heterophyllum, Vigna hosei, C. pubescens, Aeschynomene americana cv. Glenn, A. pintoi and A. repens. In Fiji, A. pintoi formed stable mixtures with both grasses. Similarly B. decumbens combined successfully with A. glabrata in Indonesia (Stür et al., 1996)

Regional evaluation: RIEPT survey

In addition to the multilocational testing of Brachiaria species in the South America savanna ecosystem, a survey on Brachiaria spp. was carried out within the International Tropical Pastures Evaluation Network (RIEPT, its Spanish acronym, Pizarro, 1992). The objective was to get from local agronomists the experience of local farmers and researchers in the principal genera/species of grasses used in the region as well as to know about problems related to establishment, aggressiveness and to know their comments and recommendations for future research.

In relation to failures at establishment, the data collected appointed Andropogon gayanus as the "outstanding" grass in that sense. A. gayanus failure is 50 percent of the cases reported while Brachiaria spp. only fails in 12 percent of the cases. The main reason for this behaviour is the quality of seed that comprises for more than 70 percent of the problems at establishment. Important data was collected on the different capacity for seed production among localities. In nearly all the cases A. gayanus produced good seed. The genus Brachiaria has a variable degree from 30 percent for B. ruziziensis up to 80 percent of success for B. decumbens.

Important data was collected on the different capacity for seed production among localities. In nearly all the cases A. gayanus produced good seed. The genus Brachiaria has a variable degree from 30 percent for B. ruziziensis up to 80 percent of success for B. decumbens.

Within the grasses evaluated B. humidicola, B. dictyoneura and B. decumbens presented the highest degree of aggressiveness. They are on top of the ranking followed by B. brizantha with the lower index among the genus.

The ranking of the selected grasses among the Brachiaria genus, B. decumbens was the leader. The selection criteria currently used need to be revised. The fact that farmers continue to show preference for B. decumbens cv. Basilisk despite its high susceptibility to spittlebugs indicates that they value its forage agronomic attributes. The main reasons given by farmers for the success of the genus Brachiaria are: a) Plasticity in the management; b) Easy recovery through the soil seed-bank; c) Stockpiled alternatives; d) Good seed yield; e) Good recovery from ants and f) Fire tolerance.

Future perspectives

The superior performance (Table 5) of the first Brachiaria hybrid that reaches cultivar status is a major accomplishment of CIAT´s breeding program. There is no doubt at all, that a new era starts with the Brachiaria genus in the tropical world. Exposing new materials as early as possible to farmers will contribute to the selection of new Brachiaria germplasm with high chances of adoption.

We need to call for definition of a companion legume. In the long term, grass monocultures, without associated legumes, constrain productivity (Armstrong et al., 1999a and b). Also, it is very important to bear in mind that Brachiaria is not the only fodder or grass. A severe pest attack like spittlebug may be devastating and very dangerous, if beef cattle industry relies on one forage species only. We need to encourage farmers to look for diversity, seeking a mixture of species that can be used similarly.

Table 3. Agronomic performance of the Brachiaria collection in Brazil

Species

EMBRAPA - CNPGC

EMBRAPA - Cerrados

Leaf DM t ha -1

B. brizantha

2 – 9

2 – 10

B. decumbens

1 – 6

1 – 5

B. humidicola

2 – 4

0.5 – 2

B. ruziziensis

2 - 3

0.5 - 2

Table 4. Brachiaria performance in Central America

Agronomic attributes

Mean

Range

DMY t. ha –1

3

0.2 – 6

Leaf:stem ratio

1.1:1

0.4 – 5

Leaf CP %

14

9 – 20

Stem CP %

7.5

4 – 12

Leaf IVDMD %

68

54 – 80

Stem IVDMD %

60

45 – 77

Rooted nodes.m2

100

0 - 400

Table 5. Milk production grazing Brachiaria *

Grass

Milk yield, kg.cow.d -1

Trial 1

Trial 2

B. decumbens cv. Basilisk

7.0 a **

7.6 b

B. brizantha cv. Marandú

6.7 ab

-

B. brizantha cv. Toledo

6.3 b

6.5 b

Brachiaria hybrid cv. Mulato

-

8.1 a

* Adapted from: Avila et al., 2000

**a, b values within experiments with the same letters are not different (P< 0.05)

ERAGROSTIS TEF

Eragrostis tef (Zucc.) Trotter, (synonyms E. abessinica, E. abyssinica and Poa abyssinica.) is a C4 plant, having Kranz anatomical characteristics, and it is intermediate between tropical and temperate grass. The use of teff can be traced back to about 3359 BC (Mengesha, 1965).

Teff can be cultivated under a wide range of environmental conditions under water-logged to drought conditions. Teff can give a crop in a relative short growing season and produce both grain for human food and fodder for cattle. Publications in the United States describes teff grain as being marketed as a health food product, or used as a late planted emergency forage for livestock.

Taxonomy and Morphology

Eragrostis is a member of the tribe Eragrosteae, sub-family Eragrostoideae, of the Poaceae (Gramineae). There are approximately 300 species in the genus Eragrostis consisting of either annuals or perennials that are found over a wide geographical range. Eragrostis species are classified based on characteristics of culms, spikelets, lateral veins, pedicels, panicle, flowering scales, and flower scale colours. Recently, the taxonomy of teff has been clarified by numerical taxonomy techniques, cytology and biochemistry (Costanza et al., 1979).

Teff is a fine stemmed, tufted annual grass. The plant has the appearance of a bunch grass, having large crowns and many tillers. The inflorescence is an open panicle and produces small seeds. The roots are shallow and develop a massive fibrous rooting system.

Agronomy

Very few agronomic evaluations have been carried out in tropical America. The pilot trials conducted gave confidence. Forage yields of teff have ranged from 2 to 8 t. ha-1, depending upon planting date and number of cuttings and with a crude protein content ranging from 12 to 20 percent. The few accessions evaluated were relatively free of diseases when compared to other cereal crops.

As a fodder, the teff plant is cheap to raise and quick to produce. Its straw is soft and fast drying. It is both nutritive and extremely palatable to livestock. Its leaf:stem ratio is high (75:25), with 65 percent IVDMD on average. Most of the available germplasm are kept at the University of Illinois and in Ethiopian Agricultural Research Centres.

Future prospects

For the savanna ecosystem and regions with a long dry spell, annual and short cycle grasses like Eragrostis tef (plants can mature in 4 months from seed) may have major advantages. The main positive characteristics are: It can be grown under moisture-stress areas, under waterlogged conditions and its straw is a valuable animal feed during the dry season when there is acute shortage of feed. It is highly preferred by cattle and suitable for deferred grazing in areas with long dry spell, like the savannas of Brazil. Teff is a reliable crop for unreliable climates, especially those with dry season on unpredictable occurrence and length

PASPALUM SPECIES

Paspalum is a grass genus widely distributed from temperate to tropical regions, especially in the Western Hemisphere. It is particularly abundant in central and southern Brazil, eastern Bolivia, Paraguay, northern Argentina and Uruguay. Within grasses, Paspalum is the predominant American genus. It contains approximately 400 species, most of which are good for grazing. Several accessions are adapted to wet sites with very low incidence of spittlebug. This last characteristic is the major limiting factor of exotic species such as Brachiaria decumbens and B. humidicola. Most species are perennial and a large number of them furnish excellent grazing in native grassland on this region. Only a few species have been cultivated as forage

Agronomic characteristics and potential use in tropical America

In the Cerrado ecosystem, a set of 42 native accessions was evaluated (Valls et al., 1993). The DMY in the first ten months after establishment ranged from 350 to 4500 kg ha-1. The first regrowth (47 days from the start of the rainy season) ranged from 400 to 4000 kg ha-1. The mean DMY accumulated during two rainy seasons ranged from 0.5 to 21 t ha-1. In a seasonally flooded land in the Cerrado ecosystem total annual DMY ranged from 2.0 to 29 t ha-1 (Grof et al., 1989b). Mean DMY accumulated during the dry season (May-October) for the 29 surviving accessions ranged from 20 to 1500 kg ha-1 (Table 6). Only two accessions BRA -012874 and BRA -009610 reached more than 1 t DM ha-1 with 30 and 34 percent of green leaf-stem material retention, respectively. The green leaf content at the end of the second dry season (282 mm accumulated rainfall) ranged from 0 up to 63 percent. The highest leaf retention during the dry season was 63 percent for Paspalum spp. BRA -010154.

Seed yields were variable (0 - 1.500 kg ha-1 of pure seed) and related to the flowering cycle. The early flowering type reached a pure seed yield of 113 + 115 kg ha-1, the intermediate group 420 + 568 kg ha-1 and the late flowering type 844 + 588 kg ha-1. Although pure seed yield were variable in the evaluated collection (Table 7) they were higher than the ones reported by Grof et al., (1989a) for Brachiaria spp. (4 to 155 kg ha-1) at the same experimental site and for Cameron and Humphreys (1976) for the P. plicatulum cv. Rodd's Bay (61 to 360 pure seed yield with 0 to 400 kg N ha-1, respectively).

The work supports the evidence that the Paspalum accessions under evaluation present a high and relatively constant seed yield and better synchronization of flowering than many tropical pastures grasses evaluated in the area. Similar consideration has been quoted by Stür and Humphreys (1987) for P. plicatulum cv. Rodds Bay vs. B. decumbens cv. Basilisk.

After these preliminary and encouraging results a new set of 84 native Paspalum accessions, plus the most important commercial cultivars of other genera and species were evaluated. A cluster analysis procedure was applied. Three main groups were obtained. The cluster with the highest yield included the commercial cultivars of Andropogon gayanus cv. Planaltina, Brachiaria brizantha cv. Marandu and Panicum maximum cv. Vencedor and four of the 84 Paspalum accessions under test. The mean CP was 9.4 + 1.49 percent and the mean IVDMD 46 + 7.24 percent with thirty-four units of difference between accessions (30 percent for BRA -012921 to 64 percent for BRA -003824, -014851, -018996). Exotic African grasses in the genus Brachiaria had similar values (Table 8).

Another important characteristic under evaluation in the new Paspalum accessions is the yield response of some of them to increased fertility. The data showed a mean average increase of 250 percent in DMY when the fertilizer was increased from the pasture establishment level to crop establishment rates.

Some of the outstanding attributes mentioned before, such as good seed yield, similar nutritive value to exotic commercial grasses, ease for eradication, high resistance to spittlebug and the high DMY obtained in seasonally flooded situations call for more attention and evaluation of this American genus in the Cerrado and in the Humid Tropics of Tropical America. Recent publications analysed and report agronomic data and appoint other potential use (Batista and Godoy, 2000). Fortunately, in other parts of the world, some species, especially P. atratum are receiving attention. Brazilian germplasm has been released in Argentina, Australia, Asia and United States.

Paspalum atratum: Agronomic performance in South America, United States, Australia and Asia

South America

In Corrientes-Argentina, P. atratum cv. Cambá-FCA exhibits conditions of adaptability for poor and well-drained soils (Quarín and Urbani 1993). In Rondonia State-Brazil, Costa et al. (1999a) evaluated the agronomic performance of P. atratum BRA-009610. DMY ranged from 1.4 to 6.4 t DM ha-1, with 6 to 12 percent CP. The same authors evaluated the behaviour and agronomic potential from different tropical grasses as a ground cover in well-established rubber plantations. The grasses B. brizantha cv. Marandu, B. humidicola and P. atratum BRA-009610 were outstanding for yield, stability and ground cover (Costa et al., 1999b).

In relation to agronomic trials there is only one experiment related to date of establishment and seeding rate, emphasizing the need of over four kg ha-1 when weeds were present (Carvalho et al., 1997). The same authors suggested that establishment in the Cerrado need to be done between October and December. Later, poor establishment was obtained.

The effect of the animal on the pasture and their reverse consequence was evaluated in P. atratum BRA-009610 (EMBRAPA-Cerrados named recently as cv. Pojuca) associated with A. pintoi BRA-031143 during four years (Barcellos et al., 1997). Rates of daily weight gain obtained were compatible to those found in A. pintoi cv. Amarillo in association with Brachiaria spp. High annual yield per hectare in tropical ecosystems is reached only when forage species have high yield potential and when nitrogen is applied. The available data on beef cattle production with Paspalum species is presented in Table 9.

Table 6. Dry matter yield in outstanding Paspalum spp. accessions in the Cerrado ecosystem, Brazil *

Growing season

DMY t.ha -1

Wet season

2 – 30

Dry season

0.5 - 2

*Adapted from: Grof et al., 1989b and Valls et al., 1993

Table 7. Pure seed yield in Paspalum accessions

Species

Seed yield g.ha -1

P. atratum

200

P. dilatatum

40 – 560

P. guenoarum

500

P. notatum

220 – 350

P. plicatulum

60 – 400

Paspalum spp.

200 - 900

Table 8. Dry matter yield and nutritive value in Paspalum and commercial grasses

Grass

DMY

t ha –1

CP

IVDMD

percent

B. brizantha

11

11

62

C. dactylon

6 – 10

12

60

H. altissima

4 – 8

12

60

P. atratum

9 - 11

11

59

Table 9. Paspalum: Beef cattle production from grazing trials

Species kg animal-1 d-1 kg meat ha-1 Source
P. plicatulum cv Rodd´s Bay 0.340 _ Whiteman et al. (1985)
P. plicatulum - 740 Bisset (1975)
P. nicorae 1.2 - Cook, B. (Personal comm)
P. atratum 0.600 460-680 Kalmbacher et al. (1997)
P. atratum cv. Suerte 0.710 240 Kretschemer et al. (1994)
P. atratum + A. pintoi 0.100-0.700 550-800 Barcellos et al. (1997)

United States

The grass Paspalum atratum cv. IRFL 658 was evaluated under grazing at Florida State University-USA. The IVDMD ranged from 50 to 68%, mean CP 11 percent and a mean seed yield of 200 kg ha-1. In Florida, Kretshmer et al. (1994) reported a live weight gain of 0.710 kg a-1 d-1 and 240 kg ha-1 in 100 grazing days. The same authors results is competitively against P. notatum and Cynodon dactylon. Kalmbacher et al. (1997) quoted that Suerte Atra Paspalum is a cultivar owned by the University of Florida, emphasizing that this grass has a unique combination of rapid establishment from seed and adaptation to wet, acid and infertile soils. Is also, said to be excellent for growing cattle and it is pest and disease resistant. Data are reported in Table 9.

Australia

This grass is yet to prove itself in Queensland. Bruce Cook (personal communication) said that it has many useful qualities including good palatability, late flowering and reasonable seed set, although it isn't very drought hardy nor frost tolerant. It is really competing for a place with Setaria spp. since both are adapted to moist, occasionally waterlogged conditions. Paspalum atratum has the advantage over Setaria in remaining apparently less fibrous, due largely to the restricted flowering season. In Australia P. atratum was released as cv. Hi-Gane, which is the same variety as cv. Suerte in the USA. At this moment probably no more than 50 ha-1 are sown.

Indonesia, Philippines and Thailand

Although recently introduced to this part of the world, its agronomic evaluation, multiplication and adoption are very dynamic. During 1999, two tons of pure seed were produced for regional evaluation (Werner Stür, personal communication). On the other hand, the exposure of the new germplasm to farmers’ fields has resulted in new alternative uses. Paspalum atratatum BRA-009610 cv. Ubon, is at this moment in more than 500 farms. Recent reports mentioned that Ubon Paspalum is selling like hot cakes and it is quoted to be the best grass for former rice paddy fields. Local farmers call P. atratum cv. Ubon, the grass for wealth (Bela Grof and Michael Hare, personal communication).

Future prospects, comments and considerations

Despite 100 years of agricultural research and considerable investments in intensive pasture and animal research based on exotic forages, indigenous grasses like Paspalum, grown with relatively low inputs, continue to make a significant contribution to livestock industries. From the data presented on accessions variability on agronomic characteristics such as production, dry matter yield distribution, nutritive value, seed yield and the low incidence of spittlebug there’s no doubt at all that Paspalum is an alternative for the acid and low fertility soil of the tropical world. Nowadays pasture technology based on high inputs seems less relevant to the likely needs of the 21st century.

PENNISETUM PURPUREUM

Introduction

Elephant grass, Pennisetum purpureum (L.) Schumach., also known as Napier grass, a native of Africa, is a cane-like grass, with strong stems which may reach a height of 6 m. In 1913 the USDA introduced it to the southern states of for trial. Elephant grass has been introduced into nearly all-tropical and subtropical regions from sea level to altitudes of 2000 where rainfall exceeds 1000 mm. In 1920 it was introduced to Brazil. In Minas Gerais State 7,000 ha with an average of 8 ha per farm is reported. Actually in Brazil, there are at EMBRAPA National Milk Research Centre 120 accessions of P. purpureum with more than 10 commercial cultivars (Table 10), 20 accessions of Pennisetum spp. and 53 accessions of P. glaucum. Although the figure is high, the genetic variability within the species is very low. Elephant grass has been only limitedly used as a forage plant in tropical America. It has been used largely as stand-by green-chop feed for dairy farms.

Distribution and adaptation

Pennisetum purpureum grows best when temperatures are high (300 C– 350C), yet it will tolerate cool temperatures down to 100C before growth ceases. Frost will kill top growth but leave roots unharmed; however, if the soil freezes (as in many areas of South America), root damage will occur and plant loss will result. Periods of drought restrict growth however, with the onset of rains, plant resume rapid growth. The grass will not tolerate water logging or flooded conditions, and it is not adapted to wet soils where P. atratum cv. Pojuca thrives. Is a robust perennial bunch-grass consisting of many cane like stems up to 3-4 cm thick that grow to heights of 2-6 m. Elephant grass is very responsive to fertilizer and is one of the fastest-growing, highest-yielding grasses.

Main agronomic features and potential use

Despite its positive attributes such as being one of the fastest-growing and highest-yielding grasses, few national and international centres are interested in its agronomy or in a breeding project. Fortunately, since 1985 a great effort have been taking place by EMBRAPA-CNPGL (EMBRAPA National Milk Research Centre) and Florida University. Since then, several cultivars and fifty accessions have been tested in a network approach in twelve Brazilian States. From the above-mentioned work P. purpureum cv. Pioneiro was released. The DMY of cv. Pioneiro ranged from 35-to 45 t DM ha-1 year-1 with good adaptation to the SE and central West areas. Although high DMY is achieved with this new cultivar, the nutritive value is similar to the old commercial cultivars (Table 11)

In a very short period new cultivars of this important grass should be available for tropical America (Antonio Vander Pereira, personal communication). At EMBRAPA-CNPGL, significant work is under way. Results on the use of elephant grass for milk production are mainly conducted during the rains with the use of concentrate, mainly due to the relative low nutritive value of the grass. In Table 12, is a summary of the potential milk yield.

Table 10. Main commercial cultivars of Pennisetum in Brazil *

Anão Roxo
Cubano Taiwan A - 143
Merker Taiwan A – 144
Merkeron Taiwan A – 146
Mineirão Taiwan A - 148
Napier Vrukwona
Puerto Rico Pioneiro

* High number of cultivars but low genetic variability

Table 11. Dry matter yield and nutritive value of P. purpureum cv. Pioneiro

Regrowth days

DMY t ha-1

CP percent

35

21

14

70

38

12

105

32

8

Adapted from Vilela, H. (personal communication)

Table 12. Forage quality and average daily milk yield of Holstein x Zebu cows grazing elephant grass in the rainy season

Item

Treatments

 

Grass

Grass + Concentrate

Milk (kg with 4% fat)

11.4 a

12.6 b*

CP percent

13

13

IVDMD %

60

62

Adapted from: Fermino Deresz (EMBRAPA – CNPGL, personal communication)

*Means followed by the same letter are not significantly different (P<0.05).

Future perspective and limitations

Elephant grass presents limitations under grazing systems, related to the quantity and quality during part of the year (Aroeira et al., 1999). Periods of low temperature, common in many areas of tropical America reduce growth. The actual available elephant grass cultivars are very responsive to fertilizer and therefore not suitable for marginal areas. Another negative feature well documented in the literature is the fast quality drop in nutritive value and the common sub products (hay and/or silage), which are lower in quality when elephant grass was substituted for example for corn silage in the diet of lactating cows. Recent data (Faria et al., 1998), reports that P. purpureum has moderate to severe infestations of spittlebug (Prosopia spp. and Moacis latipes). Also mites are increasing in damage. There is a real need to develop seed-propagated hybrids, less winter-hardy than the true elephant grass, with higher nutritive value and also to define a companion legume to reduce nitrogen need.

FORAGE LEGUMES

ARACHIS SPECIES

The genus Arachis is a member of the Leguminosae-Papilionoideae (Fabaceae sensu stricto), tribe Aeschynomeneae, subtribe Stylosanthinae. The genus Arachis is naturally confined to Brazil, Bolivia, Paraguay, Argentina and Uruguay (Valls and Simpson, 1994). About 60 of the probably 80 species are endemic to one of those countries. Most of the research into species with forage value has been limited to species of sections Caulorhizae (A. pintoi and A. repens), Rhizomatosae (A. glabrata) or Procumbensae. Today, more than 250 accessions are available in EMBRAPA-CENARGEN. A brief summary of the outstanding data is reported for the main ecosystems of tropical America

Arachis pintoi behaviour in the savannas and humid tropics of tropical America

Although agronomic evaluation of A. pintoi in South America was only started in 1976 by Bela Grof at CIAT-Quilichao, more than 100 agronomic trials have been carried out.

Savannas

Since 1976 until 1992 most evaluation has focused on A. pintoi CIAT 17434, today cv. Amarillo. Performance in these regional evaluations (through the RIEPT) was considered poor to regular compared to other legumes. On the other hand, its performance in mixture with grasses under grazing was so superior to that of other legumes that it encouraged researchers to release the accession as cultivar "maní forrajero perenne" despite its poor to middling agronomic background.

Cerrado ecosystem

Well-drained plains dominate, but these are intersected with poorly drained lowlands that comprise 30 percent of the total area. In 1987 Arachis germplasm were evaluated in the lowlands and since 1991 in the well-drained plains (Pizarro and Rincón, 1994).

Seasonally flooded land

Evaluation of thirty-three accessions of Arachis species began in 1990. All plant components were estimated. The accumulated total DMY within the eleven pre-selected accessions ranged from 9-to 24 t ha-1 within the two years of evaluation. Edible green dry matter during the wet season ranged from 2 to 9 t ha-1 and from 2 to 4 t ha-1 during the dry period (Pizarro and Rincón, 1994). The ratio DMY efficiency/precipitation ranged from 2 to 7 kg DM ha-1 mm in the rainy season and from 12 to 23 kg DM ha-1 mm in the dry season on seasonally flooded land.

An important feature of the Arachis genus is the different capacity for ground cover between accessions and species. Within the evaluated germplasm, the colonized area over time ranged from 128 to 198 percent over the first 480 days from sowing.

A second set of forty-eight accessions of A. pintoi and A. repens associated with P. atratum BRA-009610 was evaluated in the two principal landscapes (savanna and the seasonally flooded land). The range of ground cover at nine weeks of growth varied from 65 percent to 100 percent for different accessions. The most outstanding accessions after one year from establishment were: (A. repens BRA -031861 and A. pintoi BRA/CIAT -031143/22160, -030449, -031836, -031828, -031844, -031135, -015121/18748, -013251/17434, -030546 and -015598/18750).

A third set of eighty accessions were tested associated with B. decumbens CIAT 16488 . During establishment, detailed data such as growing capacity of primary, secondary, tertiary, etc. stems were recorded. There were large differences in the maximum diameter reached and in the number of primary and secondary stems at 39 and 148 days from planting. The mean daily growth of the primary stems within accessions was 5, 3, and 2 mm d-1 at 39 days of growth and 6, 5, and 3 mm d-1 at 148 from sowing in three of the outstanding accessions (BRA/CIAT -031143/22160; -013251/17434 and -015121/18748, respectively, Pizarro and Carvalho, 1996a).

Well-drained savannas

A special emphasis was put on this area for two important reasons. First, the lack of legume germplasm for this ecosystem and second to select within the new collected Arachis germplasm suitable accessions with faster establishment and especially, drought tolerance. Several experiments were conducted between 1991 and 1997 in order to know if A pintoi will survive the normal long dry spell (4-6 months, with high temperature and very low relative humidity). In a pilot trial, it was observed that A. pintoi BRA/CIAT -031143/22160 survived four long dry spell seasons, with considerable green leaf retention and DM production. Green leaf percentage drop from 38 percent from the middle of the dry season up to 15 percent at the end of the dry spell. On the other hand, the total DMY increases up to 1.2 t ha-1 at the end of the dry season. Although yields are not as high as other forages, the green DMY ranged from 3.6 t ha-1 from the middle of the dry season up to 1 t ha-1 at the very end. The pure soil seed-reserve reached 720 kg ha-1 at 18 months from planting. The data presented in Tables 13 and 14 summarise six years of evaluation on adaptation production and nutritive value.

The pre-selected 22 percent of the Arachis germplasm deserve regional agronomic evaluation. The green leaf retention during the six-month dry spell in the Cerrado confirms the potential contribution of the Arachis genus.

Humid tropics

The adaptation of A. pintoi (mainly CIAT 17434) in the humid tropics of South America, using the same methodology as in the savannas was better than in the Llanos of Colombia, with an agronomic performance ranging from poor to excellent and with higher DMY and ground cover. In recent trials under edaphoclimatic conditions of the piedmont of Colombia’s Eastern Plains new accessions were faster in establishment and higher in production than A. pintoi cv. Maní Forrajero Perenne (Rincón, 2001). The outstanding accessions are A. pintoi CIAT 22160, 18748 and 18744.

In Central America and the Caribbean, agronomic performance is outstanding so far. Dry matter yield ranged from 1-to 4 t ha-1 in a twelve-week growth period (Argel, 1994). Also promising results are obtained in those accessions taken into account. For example in Ecuador accessions CIAT 18751 and CIAT 18748, gave better yield than A. pintoi cv Amarillo (Pizarro and Rincón, 1994). Also in the Central America region, accession CIAT 18744 is outstanding and was released as cv. Porvenir (Argel and Villareal, 1998). To Sum up A. pintoi grows well on a wide range of soils with textures varying from heavy clay to sand, but seems to grow better in sandy loams if moisture is not limiting. In general, DMY of A. pintoi in different ecosystems is a response to differences in soil and climatic conditions.

Agronomic features: Establishment

The slow establishment of A. pintoi CIAT 17434 is relatively well documented (Pizarro and Rincón, 1994). In general, experimental data shows that better soils; higher rainfall and fertilizer placement the seed increase the rate of establishment. Experiments to study the effect of the level of fertility on the rate of establishment and yield were conducted. Three accessions (BRA/CIAT –015598/18750; -031143/22160 and BRA -031852) were planted in a red-yellow latosol in order to measure the response to phosphorus. When the level of P2O5 increase from 50 to 200 kg ha-1 the response in dry matter yield ranged from 72 percent to 116 percent (Góis et al., 1997). Fortunately, there are big differences in the rate and speed of ground cover in the newly available germplasm. Other ways that can be used for improvement is perhaps the association of A. pintoi with other species within the genus like A. hypogaea and A. sylvestris both with a recognized annual cycle and fast to very-fast establishment (Pizarro, 2001a).

Drought tolerance

Some basic principles of drought tolerance have been presented and discussed by Pizarro and Rincón (1994). The doubt about the drought tolerance of A. pintoi in association with grasses on the higher parts of the landscape in the Cerrado ecosystem is today questionable. However, six years results from A. pintoi accessions and A. glabrata were conclusive. In A. pintoi BRA/CIAT -031143/22160 the green dry matter percentage ranged from 38 percent to 15 percent at the end of the second dry period. The high proportion of the root component in this accession was 58 percent with a total root DMY of 17 t ha-1, with 60 percent of the root-system in the top 30 cm, penetrating to 1.95 meters. This agronomic attribute might have helped in the efficient absorption and utilization of water and nutrients under stress conditions. The deep-root system also detected in the drought tolerant rice crops under upland conditions, support these findings.

In the literature some studies demonstrated that, under water stress, peanut roots (A. hypogaea) reached greater depth compared to non-stressed peanut roots (Pizarro et al., 1996b). Another favourable point for the survival of A. pintoi in these severe conditions is the fast and high soil seed-bank built by this legume. For example, the recovered pure seed yield at 15 months after planting in a red-yellow latosol with 65 percent clay content ranged from 50 to 600 kg ha-1 for the A. pintoi group.

Seed production

Data to date (mainly on one accession) confirm that A. pintoi cv. Amarillo is a prolific seeder (Pizarro and Rincón, 1994). The new germplasm under evaluation confirm this but also show a huge difference in seed production between accessions within the A. pintoi group and also within the A. repens group, always vegetatively propagated due to the reported lack of producing seed (Pizarro et al., 1993). A summary of the main data is presented in Table 15.

With this outstanding agronomic attribute the main constraint is seed harvesting. The over-claimed mechanical problem is not a valid one. In first place, the Australian seed-harvesting machine is a reality as are the different types of seed harvesting machine designed to collect difficult agricultural products such as: cassava, carrots, peanuts, potatoes and sugar beet. Future agronomic selection criteria should incorporate measurements on peg length and resistance as the native people of South America did on A. hypogaea decades ago.

Information on crop management is needed, especially on the effect of mowing and /or grazing on seed yield. The effect of the removal of herbaceous portions on seed production is well known. The intensity of this effect depends upon the amount and frequency of defoliation, and the time in the growing season when removal takes place (Pizarro et al., 1998). Preliminary data suggest that drastic defoliation between three and six months after planting greatly reduce seed production comparing when the cutting was made after peak flowering took place (700 vs. 180 kg ha-1).

Potential contribution of A. pintoi as a ground cover

Results indicate that A. pintoi is a multiple-use ground cover crop with a high potential to contribute to sustainable agricultural systems (Ayarza et al., 1998). Compared with traditional cover species such as Centrosema pubescens and Pueraria phaseoloides, A. pintoi has the advantage of a no twining habit, with a substantial reduction in maintenance costs. Although only about 6500 ha-1 are planted, mainly in USA, Australia, Colombia and Costa Rica, the potential as a ground cover in the tropical world exists (Table 16). The main agronomic features for that purpose are: wide adaptation range, persistence, easy vegetative establishment, good spread, shade tolerance and the choice of seeding or non seeding accessions. In some parts of the world like Hawaii, Arachis pintoi, known as Golden Glory, is becoming popular as landscape groundcover (Hensley et al., 1997).

Animal production

Annual live weight gains of steers grazing pastures with A. pintoi have ranged from 130 to 183 kg head-1 and from 390 to 920 kg ha-1 (Table 17). The effect on milk production has been measured in Costa Rica. In association with Cynodon nlemfuensis, milk production increased 17 percent over that of the grass alone fertilized with nitrogen (van Heurck, 1990). The high potential animal production per unit area in pastures based on A. pintoi is a reality in tropical areas with no dry season stress and even in areas with 3-4 months dry season (i.e., Llanos of Colombia, Lascano, 1994) and in the seasonally flooded lands (Table 17) of the Brazilian Cerrado, (Barcellos et al., 1997).

Arachis glabrata

A. glabrata is a long-lived rhizomatous groundnut. It was introduced to Florida, USA in 1936 by F. H. Hull from Brazil. Although with ample distribution in the states of Mato Grosso and Mato Grosso do Sul in Brazil and more than 300 accessions available, only few accessions of the section Rhizomatosae have developed into a potential forage crop in the United States. A review by French et al. (1994) covers the current status both as forage and as a ground cover crop. Only a brief summary of the more relevant data on cv. Florigraze will be presented. The superior persistence and longevity of this cultivar is mainly due to the superior insect resistance and low susceptibility to diseases.

Agronomic characteristics

The DMY of this outstanding cultivar ranged from 3-16 t ha-1. The effect of fertilization on DMY is limited and contradictory (French et al., 1994).The other two agronomic treatments that affect DMY are clipping height and frequency of cutting (French et al., 1994)

Establishment

A general statement is that A. pintoi, A. repens and A. glabrata are very slow to slow to establish (Argel, 1994). Results showed that the rate of increase in ground cover seems to be related to availability of moisture and soil fertility (Pizarro and Rincón, 1994). As was shown earlier, there are big differences in the rate of ground cover in the new available germplasm of A. pinto and A. repens. Recent exploratory collecting trips (looking for variability within A. glabrata) have shown that we can still expect to find in the wild, accessions with high differences in ground cover, seed production and leaf-stem ratio.

Animal performance

Individual animal live weight gains in pastures based on A. glabrata cv. Florigraze have been high. French et al. (1994) reported that in two grazing seasons steers in a Florigraze pasture gained on average nearly 1 kg head day-1 (Table 18). In Brooksville, Florida, live weight gains during the grazing season ranged from 700 to 900 g head day-1 in a mixture of Cynodon and Paspalum spp. with rhizomatous peanut cv. Florigraze (French et al., 1994). Results in the United States reported by French et al. (1994) showed the potential use of the rhizomatous peanut as grass, hay and silage for dairy cattle, gestating sows, meat goats, horses and poultry.

Arachis hypogaea as a forage crop

Linnaeus described Arachis hypogaea, the common groundnut, in 1753. However the main economic constraints on the use of the entire crop as forage are the annual life cycle, variable reseeding, and expensive seed. In spite of these, annual species are used successfully for pastures in regions with pronounced regular summer or dry winter or cold seasons. In these "drought-evaders" their persistence rest on adaptations that enable reproduction to occur under grazing. Such is the case with the Arachis genus in nature. Another important agronomic characteristic that is taking place in this ecosystem is the coincidence of flowering with peak pasture growth, which reduces the risk of reproductive failure, as happen in Trifolium repens.

Persistence of annual legumes is achieved through prolific seeding coupled with varying degrees of hard-seededness. In order to select germplasm of A. hypogaea as an associated partner or as a pure crop it was necessary in the first place, to screen the material available. Seventy accessions of A. hypogaea were evaluated. Based on the results A. hypogaea IAC 5554, 5054, 5480, 5069, 2233, 5015 and ICRISAT 11326, 11341, 11317, 11328, 11312, 11342, 11331 deserve further evaluation (Pizarro et al. 1996b, Tables 19 and 20).

Therefore with this alternative, the soil will be covered fast with the annual species, while the perennial such as A. pintoi with a ground cover ranging from 164 percent to 305 percent one year after planting and a DMY accumulated varying from 2.6 to 4.3 t ha-1, will be available latter as the annuals dry or die (Table 21). The agronomic practice with a mixture of annuals and perennial components is not new, and it is really what nature offers to us. Another important agronomic characteristic of annual Arachis species is the early onset of nitrogen fixation (Table 22).

Table 13. Dry matter yield and quality of forage Arachis *

<

Species

DMY t ha –1

IVDMD percent

Arachis glabrata

3 – 16

60 – 70

A. pintoi

0 – 36

50 – 75

A. repens

0 – 11

50 - 60

* Adapted from: Pizarro, 2001a

Table 14. Digestibility of plant components in Arachis pintoi*

Accession
BRA number

Leaf

Stem

Litter

Roots

Percentage

-013251

60

64

33

60

-015598

60

61

26

58

-031143

63

68

32

68

* Adapted from: Pizarro and Carvalho, 1996a

Table 15. Seed yield at 15 months from establishment in Arachis species *

Species

Pure seed yield
t ha -1

A. pintoi

1

Range

0 – 7

A. repens

0.1

Range

0 – 0.4

* Adapted from: Pizarro, 2001a

Table 16. Potential number of hectares of four plantation tree crops where Arachis pintoi could be used as a cover crop

Plantation

Asia

Brazil

Colombia

Citrus

-

1,000,000 **

1,000,000 **

Coffee

-

2,500,000 **

2,000,000 **

Rubber

8,850,000 *

80,000 **

-

Coconut and Banana

10,000,000 **

-

-

* Rubber Association (Anil Lal, personal communication), ** Pizarro and Carvalho 1996a.

Table 17. Animal live weight and milk yield in A. pintoi grass based pasture *

 

Live weight gains

Site

Grass

Grass alone

Grass plus Arachis

 

kg hd-1

kg ha-1

kg hd-1

kg ha-1

Colombia B. dictyoneura

122

366

152

456

  B. humidicola

96

288

130

390

Costa Rica B. brizantha

126

378

183

549

Brazil P. atratum

-

-

-

630

  B. dictyoneura

-

-

-

920 **

 

Milk yield, kg cow-1 d-1

Grass plus 100 kg N h-1

Grass plus Arachis

Costa Rica C. nlemfluensis

7.7

8.8

* Adapted from: Lascano, 1994; van Heurck, 1990 and Barcellos et. al., 1997.

** (A. pintoi cv. Belmonte BRA-031828. José M. Pereira–CEPLAC, personal communication)

Table 18. Live weight gain when animals graze pastures based on A. glabrata

Grazing seasons

Grass

Grass + A glabrata

 

g head-1day –1

1

370

980

2

513

1100

Adapted from: Pizarro, 2001a

Table 19. Yield and quality in Arachis hypogaea germplasm *

State and Country

DMY

CP

IVDMD

 

t ha –1

percent

Florida, USA

4 – 9

12 – 20

56 – 72

Planaltina, Brazil

1 – 5

15 – 24

57 - 78

* Adapted from: Pizarro et al., 1996b

 

Table 20. Yield and quality in Arachis hypogaea selected germplasm

Accession number

Instituto Agronómico de Campinas – IAC, Brazil

DMY

Seed yield

CP

IVDMD

t.ha –1

Percent

5554

5 *

2 **

20 *

72 *

         

* 90 and ** 180 days of regrowth

Table 21. Ground cover of Arachis species in the Cerrado ecosystem

Species

Ground cover percent (12 weeks from planting)

A. hypogaea

95

A. pintoi + A. hypogaea

75

A. pintoi

50

A. glabrata

4

Adapted from Pizarro, 2001a

Table 22. Estimates of plant nitrogen derived from symbiotic N2 fixation *

Species

Total crop N

N 2 fixed

kg N ha -1

A. hypogaea

126 – 275

32 – 152

C. pubescens

300

150

M. atropurpureum

76 – 95

59 – 79

Stylosanthes spp.

136 – 202

126 - 141

* Adapted from Pizarro, 2001b

Table 23. Available cultivars of Arachis pintoi

Amarillo * Australia 1987
Maní Forrajero Perenne* Colombia 1992
Pico Bonito * Honduras 1993
Maní Mejorador * Costa Rica 1994
MG 100 * Brasil 1994
Maní Forrajero * + *** Panamá 1997
Golden Glory ? Hawaii 1997
Alqueire ** Brasil 1998
Porvenir *** Costa Rica 1998
Belmonte **** Brasil 1999

*BRA-013251; **BRA-037036; ***BRA-012122; ****BRA-031828

Future perspectives for the Arachis genus

There is no question about the potential value of Arachis species for forage, hay, and as cover crops. But the reality, despite the new available cultivars (Table 23), is that large areas have not yet been planted on a commercial scale. Why is adoption so low?. Some researchers feel the main limitation is that farmers are not aware of the product. But this is certainly not the only limitation. In terms of the cost of planting and the time before it makes a significant contribution to a grass-legume association, it is a relatively expensive technology for a farmer to introduce. There is an urgent need to expose the material in areas with a high gross return per unit area, such as for hay, as cover in plantation crops, and in dairying. Finally, large paddock-sized demonstrations of new promising material should be used on private farms, as a very positive way of increasing the level of farmer awareness and their use. The "seeing is believing attitude" appears to be an important factor.

From 8-27 May, 2002 an Arachis spp. collection trip (English version) was undertaken in Paraguay.

CALOPOGONIUM MUCUNOIDES

Calopogonium mucunoides Desv., also known as C. esterocarpum Urb., and Stenolobium brachycarpum Benth, is indigenous to tropical America and the West Indies but it is wide-spread in the tropics of Asia and Africa through introduction in the early 1900s. This vigorous vine, twining up to 1 m or more, has densely pilose stems and trifoliate leaves, with leaflets elliptic or ovate or rhomboid-ovate. Flowers, initiated by short days, are blue to purple and produce brownish pods containing three to eight compressed squarish seeds. Calopo or (calopog?nio, falso oró), grows rapidly in the tropics, but in higher latitudes where frost occurs, its growth is reduced and seed production limited. Like tropical kudzu Pueraria phaseoloides, it is used as a cover crop in plantations.

Although not widely used (like any other tropical legume today in America), it is the most popular legume amongst Brazilian farmers and it is the legume seed produced in greatest volume in Brazil (Table 35). C. mucunoides has some limitations. This conclusion came into from only one accession within the C. mucunoides group.

Agronomic performance of newly available germplasm

The agronomic evaluation of 215 accessions in the savanna ecosystem showed new light. (Pizarro et al., 1996a and Pizarro and Carvalho, 1997). There were significant differences in production (1 - 4 t ha-1), seed yields (100 - 850 kg seed ha-1) and nutritive value (38 - 60 percent IVDMD). The number of rooted nodes ranged from 8 - 150 m-2 (Table 24). Sixty percent of the collection had a mean number of rooted nodes ranging from 50 - 100 m-2. The range and number of rooted nodes is higher than the reported figures for C. acutifolium and P. phaseoloides (Pizarro and Carvalho 1997).

In vitro DMD was correlated with the number of epidermal hairs per unit area (Table 25). Also, it was found that plant parts are responsible for forage quality. Within accessions, IVDMD was similar for the various plant components, with the exception of green pods that were more digestible (Table 26). Another factor investigated in an effort to understand the effect of density of epidermal hairs on C. mucunoides quality was the chemical composition around hairs. The commercial cultivar and the two less hairy accessions were analysed for lignin and cutin concentration. Hairs at the base were bicellular and the basal cells were impregnated with lignin and cutin. All these components present diffusal barriers that impede digestibility of intact tissue. The present results may explain in part the low digestibility and acceptability of the commercial cultivar. New alternatives are available for such a valuable, productive and persistent tropical forage legume. Seventeen new accessions were selected (CIAT 729, 822, 884, 887, 7722, 8404, 8405, 8513, 9111, 9450, 17887, 18065, 18107, 18564, 20676, 20709 and 20845). Two accessions, CIAT 822 and 20709, were outstanding for their leaf retention during long dry seasons.

Table 24. Number of rooted nodes in the Calopogonium mucunoides collection

Groups

Rooted nodes/m2

1

70 – 150

2

50 – 69

3

36 – 49

4

31 – 35

5

20 – 30

6

8 - 19

Table 25. Relationship between number of epidermal hairs and IVDMD in pre-selected Calopogonium mucunoides accessions

Hairiness

IVDMD, percent

Low density, 10 hairs mm–2 (22% of the collection)

58* a

High density, 34 hairs mm-2 (78% of the collection)

52 b

*Means followed by the same letter are not significantly different (P<0.05).

Table 26. IVDMD in plant components in preselected accessions of C. mucunoides

Plant components Hairy accessions 34 ± 5 hairs mm-2 Less hairy accessions< 10 hairs mm-2

IVDMD percent

Whole leaf 41 a* 52 a
Leaf without vein 41 a 49 a
Vein 40 a 50 a
Stem 42 a 52 a
Green pods 48 b 60 b

*Means with accessions followed by the same letter are not significantly different (P<0.05).

Potential use, comments and future

It is a myth that at all times cattle dislike grazing calopogonium, young seedlings are palatable (McSweeney and Wesley-Smith, 1986) and adult plants are grazed in the dry season (Seiffert and Zimmer, 1988). The low intake is not due to any toxic effect of the plant and it has been confirmed that the density of epidermal hairs may deter animals from eating. Its role is more as a reliable basic feed, green cover or green manure, rather than as high quality forage.

CENTROSEMA SPECIES

Centrosema is a member of the diverse Phaseoleae, one of the largest leguminous tribes. Together with Clitoria, Clitoriopsis, and Periandra, it forms the subtribe Clitoriinae.

Thirty-one of the 35 species recognized occur in tropical Brazil, the most important centre of species diversification of Centrosema. The species with more advanced agronomic evaluations are: Centrosema pubescens, C. brasilianum, C. acutifolium, C. macrocarpun and C. tretragonolobum.

Centrosema pubescens extends from near the Tropic of Cancer in Cuba, through the tropical belt, to the Tropic of Capricorn. It is particularly frequent in northern South America, Central America, and the Caribbean. The altitudinal range is 10 to 1,600 masl. It is usually a high rainfall species although a series of accessions are particularly from northeast Brazil, Colombia, Venezuela and Mexico.

The distribution of Centrosema brasilianum extends south almost to the Tropic of Capricorn. The species is particularly frequent in northeast Brazil and in Venezuela. C. brasilianum is a tropical lowland species. The collection comprises about 250 germplasm accessions, although only a small proportion have been evaluated at regional basis.

The distribution of Centrosema acutifolium is disjoint and not well understood. There is a small distribution pocket between latitudes 40 and 60 north at both sides of the Orinoco River, and a considerably more extended distribution in Brazil, particularly in the central west region. Based on the germplasm material collected so far, C. acutifolium comes from truly tropical lowland sites in the savanna and forest-edge environments with medium to high rainfall (1300 – 2200 mm. year-1) and 3 to 5 dry months.

In the southern hemisphere, locations of Centrosema macrocarpum are scattered and slightly overlap the distribution of other species, whereas in the northern hemisphere, it is particularly frequent in northern South America, Central America and Mexico. C. macrocarpum has been found in regions with an annual rainfall as low as 450 mm and as high as 4000 mm. Again, only a small part of the collection (> 350 accessions) have been evaluated. Finally, the other species evaluated in America is C. tetragonolobum. This one is closely related to C. brasilianum with a restricted distribution in Colombia and Venezuela, where rainfall is high (2100 – 2500 mm), with the dry season lasting 3 to 4 months. Their available collection is small, probably with a narrow genetic base.

Agronomic performance of newly available germplasm

Nearly 1000 accessions of this genus have been evaluated in the Cerrados centre for the savanna ecosystem between 1974 and 1995, without success. The last evaluated set of thirty-nine accessions of C. acutifolim; seventeen of C. brasilianum and twelve of C. tetragonolobum was measured. Only C. brasilianum was the only species of those evaluated for more than 20 years that merits further assessment within the Cerrados ecosystem (Table 27). The other species (C. acutifolium and C. tetragonolobum) presented limitations such as reduced flowering; low seed yield potential, and high susceptibility to pests and diseases.

C. brasilianum accessions CIAT 5234, 5178, 5667, 5671, 15387, 15521, 15522 and 15524 are promising and should be evaluated at regional level in association with grasses and under grazing, avoiding the over emphasis on dry matter determination under cutting, comparing different genus and species. What do we achieve by statistical comparisons on DM production of radically different species?

Table 27. Pure seed yield in outstanding Centrosema spp accessions*

Centrosema species

DMY t ha -1

Seed yield kg ha -1

IVDMD percent

C. acutifolium

2 - 4

1 - 30

45 - 50

C. brasilianum

1 - 6

0 - 90

44 - 58

C. tetragonolobum

4 – 5.5

0

37 - 52

* Adapted from Pizarro et al., 1991 and Pizarro and Carvalho, 1996b

Limitations and future perspectives

The high incidence of mycoplasma, leaf spot, rhizoctonia and the low seed yield achieved in this ecosystem reduce the position of the genus in the American savannas. Often, the seed yield capacity of forages is tested only in the final stages of their development. A more efficient strategy would be to screen and select plants for seed yield at an early stage.

Despite considerable amount of research having done on the genus Centrosema in the last 40 years, it remains of little agronomic importance. From the results achieved, C. brasilianum should be evaluated at regional level in association with grasses at a higher fertility level. C. brasilianum has also shown promise at several locations in Colombia, Venezuela, Brazil, Central America and Mexico, but Rhizoctonia foliar blight is a limiting factor (Argel et al., 1990; Grof et al., 1990)

Centrosema rotundifolium is an amphicarpic wild legume whose potential for pasture on acid soils of low fertility in the semi-arid tropics has only recently been recognized. Its amphicarpy contributes to the regeneration potential from the soil seed bank and thus to the persistence of pasture components. Little is known so far concerning the mechanism of amphicarpy and the effect of environmental factors on belowground seed production.

DESMODIUM SPECIES

There are about 300 species in this genus. Several have been used successfully as forages, but only in limited climatic zones, while many others have been studied experimentally. As is typical of the tribe Desmodeae, which contains about 27 mostly tropical genera, most Desmodium species are native to the Sino-India region.

Desmodium heterocarpon (L.) DC. ssp. ovalifolium (Prain) Ohashi (cv. Itabela in Brazil) is native to tropical Southeast Asia from northern Thailand to southern Sumatra and probably also in the Burma-Laos-Vietnam-Cambodia area. Recently subspecies ranking was assigned rather than the species classification, D. ovalifolium (Ohashi, 1991). It has spread to most parts of the tropics because of its value as a cover crop in plantations and for grazing (Schmidt, A. and Schultze-Kraft, R., 1997 and 1999). Flower colour varies from purple to dark pink, turning to bluish when flowers are wilting. Seedlings and young plants are unifoliolate, whereas older plants are typically trifoliate. This low-growing, stoloniferous perennial herb can produce ascending growth in undisturbed swards. It is shade-tolerant and aggressive once established and has woody stems that form a dense thicket. Compared with D. heterocarpum (carpon desmodium), it is less palatable to cattle and has lower-quality forage because of its higher tannin concentration.

Agronomic performance of newly available germplasm

Recently, for more than three years 133 accessions of Desmodium spp., were evaluated in the Cerrado ecosystem with two levels of fertility. D. heterocarpum (fifty accessions), D. barbatum (fifteen accessions) and D. velutinum (sixty eight accessions) did not persist due to poor establishment, low drought tolerance and high susceptibility to nematodes.

In America, there is only one officially released cultivar of Desmodium ovalifolium, cv. Itabela, for the cacao production zone of the Atlantic coast of Brazil. This accession (CIAT 350) has disease and nematode problems in the Llanos but resistant accessions have been identified in Brazil as well as in the Llanos and in the Philippines. Despite the outstanding seed production and adaptation to acid soils and its compatibility with an aggressive grass like Brachiaria humidicola, it has not been successful in adoption and commercialisation.

Main deficiency

A negative attribute of this legume is their undesirable tannin content and it’s competitiveness due to the ascending and climbing growth.

In the future, the use of forage plants in the tropic will concentrate more and more in two main areas:

  1. in the marginal lands that, due to climatic limitations, edaphically and/or topographically, they don't allow production of intensive commercial cultivations and where extensive pastures of low inputs are the only viable option of use, and
  2. in such integrated production schemes as agro-sylvopastoral systems combining animal production with cultivations or plantations of trees, respectively. These characteristics are considered key in the process of the development and in the selection criteria for forages for these areas. They call for low input requirements, tolerance to mismanagement and the capacity of contributing to the conservation and the improvement of the soil. Due to their capacity to fix atmospheric nitrogen, their deep rooting system and their high nutritious value, the leguminous play an important part in beef cattle production as well as in soil improvement.

The search for those characteristics should not be based exclusively on the current readiness of massive collections of some genera or species. Having a vast collection of accessions (>140) and references (> 650; Schmidt, 2000), like it is the case of D. heterocarpon (L.) DC. ssp. ovalifolium) doesn't justify halting the search of new forage legumes with more plasticity, wide spectrum on agronomic uses, higher nutritive value and free of anti-quality factors. This is not the case of D. heterocarpon (L.) DC. ssp. ovalifolium where their main uses is as a cover crop in tree plantations, erosion control and soil conservation on steep slopes (Pizarro, 2001a).

MACROPTILIUM SPECIES

Macroptiliumspecies occur in tropical and subtropical America and the West Indies. They are commonly considered weeds in waste places and along roadsides.

Macroptilium atropurpureum (DC.) Urban., known trough cv. Siratro is a creeping, twining, climbing and viny tropical perennial legume for grazing or left as a standover to help fill late autumn/winter feed gaps. It is particularly well suited to tropical and subtropical areas receiving 700-1000 mm rainfall. It is not as tolerant of low fertility as Stylosanthes, but its nutritive value, good commercial seed yield (100 – 800 kg ha-1), nitrogen fixation (up to 160 kg N ha-1), potential contribution to milk production, and especially its potential role in cropping systems, call the attention for searching for new germplasm. Native to tropical and subtropical America from southern US to Peru, widely cultivated and naturalized.

Agronomic performance of newLY available germplasm

Sixty-three genotypes of Macroptilium atropurpureum and twelve Macroptilium sp. were evaluated for agronomic adaptation, green leaf retention in dry season, pests and diseases resistance, and seed yield. Attributes evaluated by scores were transformed to indexes, joined with seed yield data and submitted to cluster analysis by complete linkage method. Two principal clusters were obtained, showing high performance genotypes. Outstanding genotypes were M. atropurpurem BRA-003808, -003522, -003565, -003310, -003379, -003433 and -003468 (Table 28, Pizarro, 2001a and Ramos et al., 2000a)

Main attributes

Has resistance/tolerance to root knot nematodes, and is moderately tolerant to amnemus weevil larvae (Pizarro, 2001b) Also, it is relatively competitive against weeds and can fix large amount of nitrogen.

Main defects

As with most of the viny tropical legumes, it succumbs to continuous heavy grazing. It does not tolerate poor drainage or prolonged flooding. Rust is the most serious disease in Siratro (but a newly released variety ‘Aztec’ has resistance). Atro is susceptible to halo blight and rhizoctonia, which can sometimes produce some leaf damage. Rhizoctonia violet root rot can kill some plants, but it is not a significant problem. Like Neonotonia, this genus can play an important role in a new scenario of ley farming systems.

Table 28. Main agronomic features in new outstanding Macroptilium accessions

Group Accession BRA number Agronomic index*, percent Range Mean
1

(n=20)

2968-2984-3255-3263 Adaptation 21-68 49
3328-3352-3425-3492 Leaf retention in the dry season 17-70 54
3506-3514-3549-3581 Pest resistance 73-87 85
3590-3611-3620-3689 Disease tolerance 43-70 54
3697-3816-3824-3841 Pure seed yield (kg ha–1) 54-300 159
2

(n=26)

1287-1538-3271-3280-3298 Adaptation 49-78 67
3301-3395-3409-3417 Leaf retention in the dry season 52-83 71
3441 (cv. Siratro) -3450 Pest resistance 73-87 80
3476-3557-3573-3603-3638 Disease tolerance 43-65 54
3662-3671-3701-3719-3727 Pure seed yield (kg ha–1) 137-405 265
3735-3743-3760-3794-4529      
3

(n=9)

3336-3344-3361 Adaptation 70-86 77
3387-3565-3654 Leaf retention in the dry season 74-91 79
3778-3786-3808 Pest resistance 77-83 81
  Disease tolerance 47-67 56
  Pure seed yield (kg ha–1) 391-628 509
4

(n=5)

3310-3379-3433 Adaptation 73-84 81
3468-3751 Leaf retention in the dry season 80-89 85
  Pest resistance 73-83 80
  Disease tolerance 63-80 72
  Pure seed yield (kg ha–1) 305-453 373
5

(n=1)

3646 Adaptation - 70
  Leaf retention in the dry season - 61
  Pest resistance - 53
  Disease tolerance - 97
  Pure seed yield (kg ha–1) - 55
6

(n=1)

3522 Adaptation - 86
  Leaf retention in the dry season - 85
  Pest resistance - 83
  Disease tolerance - 80
  Pure seed yield (kg ha–1) - 842

*Maximum value for the index = 100

NEONOTONIA WIGHTII

Neonotonia wightii (Wight & Arn.) J. A. Lackey, belongs to the subgenus Glycine, which is entirely African in origin. It is found in the East Indies, tropical Asia, and Ethiopia, through east and central Africa and down to southern Africa, where it occurs in the warmer parts of the Transvaal, Natal and East Cape Province. The synonyms that appeared in the literature is Glycine javanica L., and the following common names are perennial soybean, soja perenne, glycine, and fundo-fundo. Best adapted for tropical and sub-tropical areas with rainfall of 750-1500 mm per year. Often used as fodder or a cover crop.

Botanical description

Herbaceous perennial with strong taproot and trailing climbing and twining stems. Stems slender and well branched, and under grazing may arise from a crown below the soil surface; runners frequently root at the nodes and are moderately hairy. Leaves, pinnately trifoliate with ovate leaflets 5 to 10 cm long and 3 to 6 cm wide, with short hairs on both surfaces, and small triangular stipules. Elongated racemes from 4 to 30 cm long bear clusters of white or violet flowers 5 to 8 mm long. In some varieties the flowers become yellow or orange-yellow. Pods are hairy, straight or slightly curved, 1 to 4 cm long, about 3 mm wide, with three to eight seeds. Seeds vary in size, shape and colour, depending on variety. The main subordinate taxa cited in the literature are: N. wightii var. mearnsii; N. wightii var. petitiana; N. wightii subsp. Pseudojavanica; N. wightii var. longicauda; and N. wightii var. wightii.

Frost tolerance and regrowth after frost

Frost causes leaf shed, but the plant has some degree of frost tolerance. Tolerance to cold is greater in cv. Tinaroo than in cultivars Cooper and Clarence. Glycine is more tolerant to frost than Centrosema pubescens, and leaf shedding is less than Pueraria phaseoloides.

Soil requirements

The commercial cultivars perform best in deep, freely drained latosolic soils derived from basic igneous rocks, on self-mulching black soils and fertile alluvial soils. It is not suited to acid podzolic soil or solodic soils. It prefers free-draining loams to clays of basaltic or alluvial origin. Prefers a pH above 6.5, but can grow at pH 6.0 if adequate lime is present. The imported commercial cultivars were not adapted to tropical America. There is a great scope in the new pre-selected germplasm as we can see in Table 29.

Neonotonia as a cover crop

A recent study was conducted in Ninole, Hawaii to provide dryland taro growers with an alternative to herbicides for weed control. Various leguminous cover crops were evaluated for growth, shade tolerance and weed suppression potential. The legumes used were Arachis pintoi, Lablab purpureus cv. Rongai, Lotononis bainesii and Neonotonia wightii cv. Tinaroo. Although lablab bean and 'tinaroo' glycine suppressed weeds most effectively, their twining growth habit made it difficult to harvest the crop. Lablab bean and 'tinaroo' glycine both have the potential to become weedy, because of their aggressive growth and twining habit. The authors said that perennial peanut appears to be the most suitable cover crop species, even though it was slow to establish. A higher seeding rate is recommended to establish a quick, dense cover.

Agronomic performance of newly available germplasm

During the 1950s the commercial cultivars Cooper, Clarence, Tinaroo and Malawi were promoted and used. Part of their failure trough the tropical world was mainly due to the narrow genetic variability available, low pest and disease persistence and the emphasis in those days on long-term leys. Today, agricultural systems also look for grass-legume association for easy establishment and specially for easy turnover. The genus Neonotonia may play an important role in this new scenario (Pizarro, 2001a).

For that reason, thirty new genotypes of Neonotonia wightii were evaluated in respect of agronomic adaptation, green leaf retention in the dry season, pests, diseases resistance, and seed yield. Attributes evaluated by scores were transformed to indexes, joined with seed yield data and submitted to cluster analysis by complete linkage method. Clusters were obtained, grouping genotypes with high adaptation and low and/or unstable seed yield. Outstanding genotypes were N. wightii BRA-001104, -001261, -001341, and cv. Clarence. Forage attributes and seed production were poorly related (Table 29, Pizarro, 2001b and Ramos et al., 2000b).

There are several positive characteristics are the new material for tropical America. First is the adaptation of this material to the region, second the high leaf retention recorded in a difficult ecosystem like the Cerrados and finally the outstanding seed yield reaching up to more than 1 t per hectare.

Table 29. Main agronomic features in new outstanding Neonotonia wightii accessions

Group Accession BRA number Agronomic index, percent Range Average
1

(n=11

1112-1163 Adaptation (%) 54-73 65
1180-1198-1210-1228 Leaf retention in the dry season 35-59 49
1317-1350-1368 Pest resistance 50-83 71
(cv. Clarence and cv. Cooper) Disease tolerance 70-90 82
  Pure seed yield (kg ha–1) 0-573 293
2

(n=7)

1091-1104-1121 Adaptation (% 57-83 67
1139-1147-1201-1261 Leaf retention in the dry season 65-87 74
  Pest resistance 63-83 73
  Disease tolerance 80-87 83
  Pure seed yield (kg ha–1) 602-904 708
3

(n=4)

1252-1279-1333-1376 Adaptation(%) 78-87 82
  Leaf retention in the dry season 65-87 74
  Pest resistance 70-83 77
  Disease tolerance 87-97 92
  Pure seed yield (kg ha–1) 3-167 98
4

(n=2)

1295-1384 Adaptation 22-43 31
  Leaf retention in the dry season 17-37 29
  Pest resistance 87-93 90
  Disease tolerance 80-93 84
  Pure seed yield (kg ha–1) 0-49 27
5

(n=3)

1155-1325-1341 Adaptation 60-75 66
  Leaf retention in the dry season 37-67 49
  Pest resistance 80-83 81
  Disease tolerance 60-77 67
  Pure seed yield (kg ha–1) 831-1.294 1.008
6

(n=1)

1171 Adaptation - 52
  Leaf retention in the dry season - 24
  Pest resistance - 73
  Disease tolerance - 80
  Pure seed yield (kg ha–1) - 820

a Maximum value for the index= 100 percent

Main attributes

During the 1950s the commercial cultivars Cooper, Clarence, Tinaroo and Malawi were promoted and used. Part of their failure trough the tropical world was mainly due to the narrow genetic variability available, low pest and disease persistence and the emphasis in those days in long-term leys. Today, agricultural systems also require grass-legume mixtures of easy establishment and especially for easy turnover. The genus Neonotonia may play an important role in this new scenario. Neonotonia is an excellent legume, palatable, and combines well with grasses and produces a heavy crop of seed.

Main deficiency

Any new commercial option for tropical America.

STYLOSANTHES SPECIES.

Introduction

Stylosanthes is a genus of the subtribe Stylosanthinae, tribe Aeschynomeneae, subfamily Papilionoideae, family Leguminosae, with its natural distribution in tropical, subtropical and temperate regions of the Americas, in subtropical Africa and South-east Asia. Of the 25 genera and approximately 475 species in the tribe Aeschynomeneae pasture legumes are known only from the genera Aeschynomene, Zornia, Stylosanthes and Arachis.

The genus Stylosanthes with about forty-four species and sub-species is an important source of pasture legumes for tropical and subtropical environments. Although S. humilis and S. guianensis have been recognized for at least 80 years, all cultivars with the exception of cv. Schofield have been developed within the last 45 years. Up to 1982-83, thirteen cultivars had been released in Australia from five species and eight cultivars from three species in South America.

Several species of Stylosanthes have potential or actual economic application in the Cerrados. Commercial cultivars of stylo selected in Australia and the Brazilian cultivar IRI1022 were devastated by anthracnose (Colletotrichum gloeosporioides Penz. et Sacc.) in the early 70’s. The disease is endemic to the Americas where specialized forms of the pathotype exist. Stylo anthracnose was first recorded in Brazil in 1937 and now is known to be widespread in all countries where the species is endemic as well as in situations where stylo is introduced. Disease severity varies among species, botanical varieties and across ecosystems. Ninety two percent susceptibility was recorded among accessions of var. vulgaris, while 40 percent of var. pauciflora were found to be susceptible to anthracnose (Grof, personal communication). Most of the South American data on Stylosanthes is from Brazil and Colombia. Research to date on available germplasm and commercial cultivars od Stylosanthes guianensis var. guianensis shows that they have been devastated in savanna areas but persist in forest regions of Brazil, Colombia and Peru with only light levels of disease.

Agronomic performance of newly available germplasm

The greatest potential for increasing animal production in the tropics of South America exists in the vast areas of acid, infertile soils particularly the oxisol-ultisol association. Despite the effort and investments made, mainly by Australia, Brazil and international centres like CIAT, most of the available cultivars, were devastated by anthracnose (Colletotrichum gloesporioides Penz. et Sacc.). Until now, the two highly successful materials are S. guianensis cv. Mineirão and S. guianensis CIAT 184 (now cultivar Reyan II). Stylosanthes guianensis cv. Mineirão a late maturity type, poor seed producer and with less agronomic plasticity than other tropical forage legumes.

Ecotypes of S. guianensis var. guianensis tardío type show better anthracnose tolerance than common types but low seed yields are a problem. In the Cerrados of Brazil, flowering and seed maturation occur during the dry season when moisture is limited and night temperatures are relatively low. Little variation in flowering time exists in ecotypes evaluated. Modest attempts are being made to increase yield defoliation and supplementary irrigation.

The luck of a long research tradition and the search for a miracle make people forget that often the plants with high seed yields, but compromises the management, harvesting and processing result in lowered final yields. This is the case for S. guianensis cv. Mineirão when with only three strategic irrigations in the middle of the dry season showed significant seed yield increase (Pizarro et al., 1995a). In a field trial, irrigation was applied when soil tension was less than 6 bars. In each irrigation, 90 mm were applied. Results show that it is possible to produce up to three times more pure seed yield when irrigation is applied, Table 30.

Table 30. S. guianensis cv. Mineirão: Effect of strategic irrigation on seed yield

Dry season

Pure seed yield (kg ha-1)

 

Irrigation

Without irrigation

August 5

*211 a

79 b

August 10

258 a

88 b

August 19

333 a

82 b

* Values followed by the same letter do not differ (Duncan, P < 0.05)

Stylosanthes guianensis as standing hay in the Cerrado ecosystem

One of the important uses of a forage legume in this ecosystem with an average of 4 to 6 months of dry season is to provide food for those critical periods. With that objective it was evaluated in two different farms. The results presented in the Table 31 show that the content of leaves in the standing hay is extremely low. These results confirm the low plasticity of uses of S. guianensis in the Cerrados ecosystem.

Table 31. Percentage of leaf retention in the dry season by Stylosanthes guianenis cv. Mineirão in the Brazilian Cerrado *

Locations

Leaf retention during the dry season on S. guianensis standing hay, percent

Length of the dry season, days

Farm

0

90

150

1

40

15

10

2

45

36

16

*Adapted from Pizarro, E. A. (unpublished data)

With the special effort and technical support and enthusiasm from Dr. Bela Grof a new Stylosanthes guianensis have recently been selected in Brazil (Grof et al., 2001a). This intervarietal hybrid stylo (S. guianensis var. vulgaris x var. pauciflora) with durable quantitative resistance to anthracnose, mid-season harvest maturity, high DMY and good seed yield was developed at EMBRAPA National Beef Cattle Research Centre (EMBRAPA-CNPGC). The authors claim that the distinct advantage of composite hybrids is their considerable genetic diversity in contrast to pure-line cultivars.

During 2000, a new Stylosanthes capitata (based on seventeen genotypes of S. capitata and six of S. macrocephala) have been released as cultivar Campo Grande using a novel technique to produce resistance to anthracnose in EMBRAPA-CNPGC (Grof et al., 2001b). Mean DMY ranged from 5.7 t ha-1 to 13.4 t ha-1. Seed-yields in-pod ranged from 245 kg ha-1 to 614 kg ha-1. This multicross with its diverse genetic make-up has a wide application in the acid–soil savannas of tropical America mainly due to its good seed yields and its resistant to anthracnose as well.

Future, research problems and conclusions

Further information is needed on the pathogenic variation of Colletotrichum in different locations. The different response to anthracnose of S. capitata ecotypes in Colombia and Brazil is a further example of this variation and emphasizes the importance of screening in the centre of diversity of the species.

Seed production technology for many of the species being used is still working out and most have a short history of commercial development. Hence it is not surprising that commercial yields of seed for many species is unsatisfactory. Improved seed production techniques are considered vital to increased pasture development. Further work is required to understand dormancy mechanisms and improve the reliability of seed germination.

Further research at farm levels in farming systems may be justified with the selected and released new material from EMBRAPA Beef Cattle Center-EMBRAPA-CNPGC in Campo Grande, Brazil (Grof, 2001 a and b). Because most of the 50 million hectares of pure grass pastures in central Brazil are degraded, introducing legumes such as Stylosanthes could be one way of efficiently restoring pastures.

Also, further agronomic uses need to be developed with Stylosanthes, like fallow improvement, intercropping with perennial crops and as leaf meat for pig and chicken (Ayarza et al., 1999 and Dr. M. D. Hare, Agronomy Institute, Ubonratchathani, Thailand, personal communication).

LEGUMINOUS TREES AND SHRUBS

LEUCAENA LEUCOCEPHALA

Leucaena leucocephala (Lamb) de Wit, known as leucaena, leucena, guaje, tamarindo silvestre, ipil-ipil, koa haole, cvs. Peru, El Salvador, Cunningham, K8 among other K numbers in Hawaii, is native to Guatemala and surrounding Central American countries. There is evidence of indigenous use of unripe Leucaena pods and seeds for human consumption in the Tehuacan Valley in Mexico dating back to 6800 BC.

It seems that Leucaena cultivation may have begun about 2000 years ago (Hughes 1998a) and continues to be cultivated for human consumption in Mexico today, but rarely for forage. This species is a highly self-fertile polyploid, so that further movement of the introduced variety, was of almost identical genetic material. The spread of readily harvestable seed from farmer to farmer and country-to-country has resulted in over-reliance on an extremely narrow genetic base (Hughes 1998a and b). This original leucaena, now known as the "common weedy type", has invaded disturbed sites, and had become a weed in many countries.

After a long period of disagreement, Leucaena has finally been described in detail, agronomically and nutritionally (Shelton et al., 1998) and 22 species have been named, compared with only 17 species in an earlier report (Shelton and Jones, 1995; Shelton, 2001). This is not the case with all important and promising genera.

Hundreds of papers, literature reviews, many workshops, several international projects on research and development have been promoted in this species. Nevertheless the agronomic impact is limited and uncertain. In Australia, large-scale Leucaena leucocephala plantings are occurring because farmers appreciate that leucaena-grass systems are both sustainable and highly productive. This particular production system allows them to produce cattle with high domestic value and for export to East and Southeast Asia (Larsen et al., 1998).

Animal Productivity and Management

Once established, forage legume systems can deliver sustainable high productivity. This has been shown in Australia where the oldest leucaena / grass systems have been grazed for over 30 years and remain productive. In Central Queensland, live weight gains of 1.26 kg/day have been achieved over 100 days in leucaena - buffel grass pastures (Larsen et al., 1998). This greatly exceeds that obtained from herbaceous grass/legume pastures in similar environments. Other advantages of the leucaena/grass systems compared to herbaceous grass/legume pastures in Australia include the relatively easy maintenance of grass-legume balance; the high level of N cycling and control of run-off during heavy precipitation and excellent infiltration thus minimizing soil erosion (Shelton, 2001).

Palatability

Palatability is a complex issue with tree legumes. There are reports of low and high palatability in shrubs forage legumes (Faint et al., 1998). We would like to emphasize that the length of time of exposure to feeds is an especially crucial parameter measured mainly in the standard palatability five days worldwide trials used. Reflection and change is needed on this topic as well as on the total dry matter yield parameter universally used for forage selection. Educational programs are required to inform researchers, extension workers and farmers of the value of "apparently unpalatable" plants, including methods to overcome the initial reluctance of inexperienced animals to consume new materials.

Diseases and pests

Diseases and insects of forage tree legumes limit productivity worldwide. As the use of tree legumes is expanding, pest problems are likely to increase in occurrence and severity, yet the extent of knowledge of diseases and insects of tree legumes is generally poor. There is data providing lists of pathogens but little information on their significance or on pathogenic variability (Lenné 1992). Disease and insect pests are reviewed by various authors (Lenné and Boa 1994; Boa and Lenné 1995). The leucaena psyllid (Heteropsylla cubana) is the most studied pest. While chemical control measures are effective and biological control using predatory insects is partially effective, the most practical, the most cost-effective, and the most ecologically sound approach is the use of resistant varieties.

Tannins

An aspect of forage quality that deserves special mention is the secondary plant compounds, which are common in tree legumes. They appear to have no functional role, although they may impart ecological advantage by limiting or preventing damage from insects, fungi, bacteria, protozoa or grazing animals. In particular, many tree legumes species contain condensed tannins (CT). These compounds are highly polymerized proanthocyanidins composed of flavanoid units with molecular weight from 1000-20,000. Tannins may have positive and negative effects on feed quality for ruminants. They bind with protein (astringency) reducing digestibility of dietary protein in the rumen, but the effect may be positive if the protein is released post-rumenally (McNeill et al., 1998).

Germplasm conservation

In Leucaena, the majority of species are of no conservation concern. However, three species, L. matudae, L. magnifica and L. involucrata are rare and threatened. There are less than 400 known individual plants of L. magnifica (Hughes 1998a). Leucaena is now naturalized in the Philippines where it is the principal source of tree fodder and of fuel wood. This species underpins a sustainable, highly productive beef cattle production system in northern Australia (Middleton et al., 1995).

Integrating forage tree legumes into farming systems and farmer uptake

Examples of successful adoption of exotic and indigenous tree legumes, for multi-purpose use, including forage are numerous. Outstanding examples are Leucaena leucocephala in Australia (Middleton et al. 1995) and Asia (Moog et al. 1998) but not significantly in Africa (Shelton, 2001) and South America (Argel and Lascano, 1998).

Nevertheless, despite high levels of promotion, farmer uptake has been lower than anticipated. Recent attempts to achieve adoption of complex agro forestry packages, such as alley cropping, have been only partially successful due to unrecognised failings in approach (Gutteridge, 1998). Although the forage bank concept has been shown to be feasible in tropical Africa (Shelton, 2001), rate of adoption has been low.

There have been many reasons advanced to explain success or failure in anticipated levels of adoption (Larsen et al., 1998). Simple innovations e.g. a new variety overcoming a key problem, may be adopted with relatively little intervention. However, complex innovation, involving a new farming system, generally requires sustained, high profile intervention.

Future, comments and limitation

Interestingly, successful tree legume-based interventions have commonly involved long-term, top-down extension methodologies. The need for institutional direction and long-term commitment may be necessary due to the complexity of many of the tree legume systems being promoted. However, successful adoption of tree legume interventions through a process of on-farm and participatory research has also been a consistent theme.

?Perhaps the most important elements of successful adoption are the time, enthusiasm and long-term commitment of farmers, researchers, and extension agents involved. Successful innovation needs champions to ensure continuity of interest and support over an extended time period (often > 10 years and sometimes up to 30 years).

One thing is certain – without improved levels of adoption, and more explicit demonstration of the relevance and benefits of forage tree legumes, the good will and support of funding and donor agencies will be limited.

There are only a small number of farmers using multi-purpose trees (MPT), but they cover a wide range of ecological environments. Many existing MPT plantings worldwide are from a narrow germplasm base, and access to the highest quality varieties needs to be improved. Apart from improved distribution networks, further study of taxonomy and nomenclature of important genera is required. There is opportunity for mixed use of both native and exotic MPT to suit both environmental and production objectives.

The range of MPT that will be valuable as forage is restricted by low palatability and low nutritive value of many species. This is primarily due to their high content or anti-nutritive compounds such as tannins. No doubt at all that L. leucocephala has been discussed and plenty of literature is available. The disadvantage is its content of mimosine which is liable to cause coat shedding, unthriftiness and even death in stock, and principally its environmental limitation of not tolerating low fertility and acid soils (Mullen et al., 1998) and even most important to the lack of available edible green dry matter in the dry season (Zoby, 2000). For this agronomic main attribute it was selected and promoted for the Cerrado ecosystem without any success at all. For the rainy season, there are more suitable, nutritive and persistent forage species than L. leucocephala.

CRATYLIA GENUS

Cratylia is a genus comprised of five shrub species. It is found exclusively in South America, east of the Andes and south of the Amazon River. The distributions of Cratylia species are, in general, restricted to a given type of vegetation. Thus, C. mollis is found in the Caatinga ecosystem, C. hypargyrea in the perimeters of the Atlantic Zona da Mata region, C. bahiensis in the seasonal forest of southeast Bahia, and C. intermediate to the west of the Paraná and to the northeast of the Misiones province.

Cratylia argentea unlike the other species is found in a broad range of habitats, such as the Cerrados, Mata Ciliar, in the margins of the Caatinga-Cerrados transition, and in the seasonal forests. It is extensively distributed, from western Peru to the state of Ceará in Brazil. Data on distribution is limited, morphological differentiation indicates that the Cratylia genus may have originated recently, and that its history appears to be associated with the repeated process of expansion and retraction of the native savanna vegetation during the Quaternary period (Queiroz and Coradin, 1995).

At least two species, C. argentea and C. mollis, have an acknowledged forage potential. Cratylia mollis, however, does not seem to have morphological differentiation at the ecotype level, since the same forms are found from the central-east part of the state of Piauí to the north-north of Bahia in Brazil.

Cratylia argentea, presents in addition to its typical form in the Cerrados of central Brazil, other distinct ecotypes that are common in the iron-rich soils of the Caatinga-Cerrados area and in the seasonal forest located on the eastern slopes of the Andes. These variations are evidenced in the germplasm collection (Pizarro et al., 1997a).

Regional agronomic evaluation and adaptation

Brazil: Northeast

The semi-arid region of north-eastern Brazil covers approximately 100 million hectares, and its cattle raising and goat production play an important role in the country’s economy. Among the native plants of the region, Cratylia mollis Mart. (Camaratuba) is a legume of high quality for ruminants, contributing up to 18 percent of ruminants diets (Sousa and Oliveira, 1995). After 12 years of cultivation and evaluation it still persists, producing between 1 and 3 t.ha-1 of edible dry matter, with and IVDMD ranging from 45 to 56 percent with a CP content of 18 to 23 percent.

South of Minas Gerais State. Zona da Mata

Zona da Mata region of Minas Gerais, is characterized by mountainous topography, the presence of low fertility, highly acid red-yellow latosols, and the predominance of naturalize pastures of molasses grass (Melinis minutiflora). In studies carried out in the National Milk Cattle North – EMBRAPA-CNPGL, Cratylia argentea showed slow initial growth but, after establishment, produced high amount of dry matter, with crude protein between 20 and 28 percent. In fertilization pilot trials, C. argentea gave a significant response to the application of phosphorous (Xavier Ferreira and Carvalho, 1995).

Cerrado ecosystem

Between 1991 and 1995, 10 genera and 88 accessions of shrub species were evaluated in the Brazilian Cerrados. The total cumulative DM production of these species during the first year of growth ranged between 0.5 t.ha-1 for Cratylia argentea CIAT 18516 and 2.5 t.ha-1 for Mimosa sp. CNPAB 0040. Among the accessions of C. argentea, edible DM production ranged between 0.5 t.ha-1 (CIAT 18516) to 2.2 t.ha-1 (CIAT 18675).

Although C. argentea CIAT 18516 is the accession that has been most widely tested in Central America, its production was the lowest in the Cerrado ecosystem. Despite the limited number of accessions of this legume that were available at that time (11), large variations have been observed in leaf stem and stem production and leaf:stem ratios. Variation has also been found in quality (Table 32).

Also, the development and distribution of the root system of four contrasting Cratylia accessions was evaluated. Preliminary results, 4.5 years after seeding, suggest that the greater production capacity and leaf retention of Cratylia during the dry season, as compared with Leucaena leulocephala, may be related to the root system. Roots of C. argentea CIAT 18516 and 18675 reached a depth between 2.0 and 1.30 m, respectively, while those of L. leucocephala BRA-001922 only penetrated up to 0.65 m and those of L. leucocephala cv. Texas, up to 0.4 m (Pizarro et al., 1995b).

It is important to highlight the good performance of all C. argentea accessions tested, especially regarding leaf retention, maintenance of the green colour of leaves during the dry season, the nutritive value in the attached leaves and dropped leaves (CP 9.3 ± 0.6 percent and IVDMD 45 ± 2.2 percent), the low disease incidence and the good seed production (50 to 150 kg pure seed per ha).

Table 32. Edible DM yield, and leaf:stem ratio in pre-selected C. argentea accessions

CIAT

Edible leaf DM

Edible stem DM

Leaf:stem ratio

Leaf loss

Accession No.

kg ha –1

 

g plant-1

18675

1572 a *

575 abc

2.69 abc

175

18674

1450 ab

440 bn

3.09 a

150

18676

1185 ab

655 abc

1.88 bcde

100

18668

1175 ab

872 ab

1.37 e

187

18667

980 ab

317 bc

2.95 ab

187

18957

795 ab

572 abc

1.67 cde

37

18666

640 ab

425 bc

1.49 de

100

18673

547 ab

217 c

2.51 abcd

125

18516

320 b

150 c

2.06 abcde

25

Colombia

Cratylia argentea has shown to be well adapted to acid soils of medium to low fertility in Quilichao, Colombia. The species tested revealed the most vigour in the humid tropics with relative fertile soils (Argel and Lascano, 1998). Seed yields were higher than those recorded in the Cerrados ecosystem (Table 33).

Table 33. Pure seed yield in Cratylia argentea accessions in Quilichao, Colombia *

CIAT No.

Pure seed yield

 

kg ha -1

18516

655

18668

537

* Adapted from Maass, 1995

Costa Rica, México and Central America

This legume was introduced to Costa Rica in 1987 for regional evaluation in Mexico and Central America. Preliminary reports indicate that this shrub legume adapts better to well drained savanna and humid and sub humid ecosystem with moderate fertile soils. The more advanced evaluated accession regionally is C. argentea CIAT 18516 (probably in February 2002, cv. Veraniera, Argel et al., 2001). Reported yields of edible dry matter (EDM) are variable from a mean of 8 g EDM per plan per cut in Isla, Mexico every 4 weeks, up to 123 g EDM per plan per cut, every 8 to 14 weeks in Atenas, Costa Rica. Differences are due to site effects but also to cutting height and plant density variations. In this region C. argentea shows good regrowth after cutting, particularly during prolonged dry periods (five or more). The edible dry matter yield during this particular period ranged between 30 percent to 40 percent of the annual production. In the whole region C. argentea flowers and set seed of good quality, but there are not reported studies yet of crop management for seed production (Argel, 1995).

Production and quality of seeds

Seed set in C. argentea is abundant but little synchronized. It begins toward the end of the rainy period in the lowland humid tropics. The plants can flower in the year of establishment, but seed yields are low. The flowering period is prolonged over 3 months and it is common to see the presence of natural pollinators (Centris longimana, Xylocopa frontalis, and Xylocopa spp.) The maturation of the first fruits is approximately 1.5 months after the start of pollination and extends for 2 to 3 months. For this reason, the seed harvest is a continuous process that can be prolonged during most of the dry period (February to March, in Costa Rica).

Seed yields depend on the genotype, age of the plant, handling of the cut and of the prevalent environmental conditions during flowering and fructification. In Atenas, Costa Rica, 3 year-old plants, cut to 30 cm of height and fertilized at the beginning of the rainy period, produced 50 to 70 g of pure seed per plant. The seed of C. argentea does not have marked physical latency (hardness) nor physiologic, and it can lose viability relatively quickly if it is stored in the prevalent environmental conditions of temperature and humidity in tropical America.

Nutritive value

The nutritive value of Cratylia argentea, measured in terms of crude protein and in vitro digestibility, is similar to that of other common shrub legumes (i.e. Gliricidia sepium, Calliandra calothyrsus, and Erythrina poeppigiana) that are, however, only marginally adapted to acid soils. Cratylia argentea has only trace amounts of tannins; its nutritive value, however, is higher than that of the other semi-shrub legumes well adapted to acid soil, which have high levels of tannins (i.e., Flemingia macrophylla and Codariocalyx gyroides).

The intake of immature and fresh forage of C. argentea is low, but increases when the forage withers or dries in the sun, or when offered mature. This effect on intake is possibly associated with the presence of an unidentified non-nutritional compound (Raaflaub and Lascano, 1995). The inclusion of increasing levels of C. argentea (0 percent to 40 percent of the forage on offer) in mixtures with low-quality grass increased total intake linearly, but similarly decreased the digestibility of the sheep diet. Also, supplementation of C. argentea (7 g to 10 g DM/kg LW per day) to cows grazing Brachiaria spp. pastures had a positive effect on daily milk production (an increase of 8 percent to 14 percent) during the dry season, and, to a lesser extent, during the rainy season with an increase from 0 percent to 7 percent (Lascano, 1995; Wilson and Lascano, 1997).

This promising legume is a potential source of protein during the dry season in different regions of tropical America. Therefore, high priority should be given to its evaluation, both in germplasm development and in the use in cattle production systems in the tropics. Research should be conducted to design strategies that use this legume as a supplement, both in cut-and-curry and in grazing systems, in relation to the quantity and quality of the animal basal diet and nutritional requirements. This research should be complemented with on-farm trials and subsequently validated by producers in different production systems.

On-farm studies conducted on hillsides of the Pacific region of Costa Rica showed that foliage of C. argentea (multipurpose species), used as a dry season supplement for livestock, resulted in significant improvements (> 30 percent) in intake of dried Hyparrhenia rufa grass (Ibrahim et al., 2001). The use of C. argentea and sugar cane as supplement for dual purpose cows in the dry season resulted in daily milk yields of 5 to 6.5 kg/cow/day which is of much significance considering cows usually produce an average of 3 kg/cow/day in the dry season.

Available germplasm

Due to the positive expectation of this novel legume, several collection expeditions were carried out. Expeditions were conducted in the states of Goias, Mato Grosso and Tocantins in Brazil, where the northern diversity of the species is located. More than 70 new populations were identified (Pizarro et al., 1997a); these were located between 120 and 160 S, and between 460 and 580 W, from 180 to 810 masl, in soils that were mostly well-drained sandy loam, with variable chemical characteristics. Flowers were typically pink-violet (one population had white flowers) and fructification and seed production were abundant.

During the collecting trips its was observed and documented that C. argentea recovered very well after burning, cutting, or grazing. Unfortunately the available new germplasm was neither multiplied nor agronomically evaluated.

Main limitations and future work

The first Cratylia argentea collection, does not adapt well to altitudes above 1200 masl, in the most advanced accessions in evaluation (CIAT 18516 and 18668). This legume is slow to establish, although it is quicker than that of other available shrub legumes. The forage yields are low during the first year of establishment. In preliminary observations it was registered that during the establishment period (more than six months), the main development was in the root system. Cratylia argentea may play an important role in dry ecosystems of tropical America with marginal soils. Simple and effective supplementation strategies can be developed for feeding cattle, sheep and goats.

MORUS SPECIES

Mulberry (Morus alba) is a tree, often pruned to shrub proportions, that has traditionally been used for feeding the silkworm. It belongs to the order of Urticales, to the Moraceae family and to the genus Morus, with more than 30 species and 300 varieties. It comes from China and other species originate in other temperate countries, and despite this, they can be considered "cosmopolitan" for their capacity of adaptation to different climates and altitudes.

Morus spp. leaves have been the traditional feeding for the silk worm (Bombyx mori). There are mulberry varieties for many environments, from sea level to altitudes of 4000 masl, and from the humid tropics to semi-arid lands. The main use of mulberry globally is as food for the silk worm, but depending on the location, it is also appreciated for its fruit, as a vegetable, for its medicinal properties in infusions, landscaping and as animal feeding.

In Peru, the multiple uses of mulberry have been recognized (Zepeda, 1991). There are several places where mulberry is utilized traditionally as a feed in mixed forage diets for ruminants, like in certain areas of India, China and Afghanistan.

In Italy there has been several studies on the use of mulberry for dairy cows and other domestic animals (Maymone et al., 1959; Bonciarelli and Santilocchi, 1980; Talamucci and Pardini, 1993) and in France there was a research project to introduce mulberry in livestock production (Armand and Meuret, 1995). But it was only in the eighties that specific interest in the intensive cultivation and use of mulberry as animal feed started in Latin America. It is surprising; that a plant, which has been improved for leaf quality and yield to feed an animal like the silk worm, which has high nutritional feed requirements, received limited attention by livestock producers, technicians and researchers.

Like several significant breakthroughs in science and technology, the discovery of the value of mulberry as a high quality feed in Latin America happened serendipitously. A Costa Rican farmer of Chinese origin, whose silk project failed, fed mulberry leaves to his goats and was impressed by its palatability and by the performance of his animals. He communicated his observations to scientists of the Tropical Agriculture Research and Training Center (CATIE), who were receptive to the farmer's news and smart enough to include mulberry in their tree fodder evaluations and later in agronomic and animal performance trials (Sánchez, 2000). In Africa, the International Center for Research in Agroforestry (ICRAF) in Kenya and the Livestock Production Research Institute in Tanzania, have conducted successful agronomic and animal trials by themselves, apparently without being aware of the interest elsewhere.

Genetic resources

Mulberry belongs to the Moraceae Family (Subtype Angiosperms; Class Dicotyledons; Subclass Urticales) and there are several species: Morus alba, M. nigra, M. indica, M. laevigata, M. bombycis, etc. which have been used directly, or through crossings and induced mutations, for the development of varieties to support silk worm production. The diploid M. alba (2n=2x=28) is the species most widely spread, but polyploid varieties, which originated in various research stations in Asia, show greater leaf yields and quality. In general, polyploid varieties have thicker and larger leaves with darker green colour, and produce more leaves than the diploid. There is a large variation in leaf production and in leaf quality emphasizing the huge potential for identifying suitable germplasm for any specific environment.

From Asia, it was introduced in Brazil in colonial times. Nowadays, mulberry is widely known, frequent in orchards, recreational rural households and gardens. Its fruits are very well appreciated for direct consumption and for making marmalades. However, commercial mulberry cultivation occurs only in regions where it is associated with sericulture. According with the latest statistics, the mulberry area in Brazil covers approximately 38,000 hectares. Paraná state being the largest concentration of that area with 32,400 hectares, followed by western portion of state of São Paulo, with 4,600 ha and by smaller areas in states of Goiás, Mato Grosso do Sul, Minas Gerais and Santa Catarina.

In Brazil, the totality of cultivated mulberry varieties appear to belong to Morus alba. In São Paulo State, there are various active germplasm banks with more than 100 introductions (De Almeida and Fonseca 2000). Little information is available regarding which clones are used in the 38,000 ha planted with mulberry. Commercial companies have disseminated the Miura and Korin clones, due to the great supply of planting material. These clones together with the Calabresa variety make the large majority of cultivated area.

Very few agronomic evaluations have been carried out in Brazil for animal productions purpose. In the Cerrado ecosystem a set of 15 Morus spp. introductions were tested for tolerance to drought, leaf yield, regrowth capacity and leaf:stem ratio. The IZ hybrids 3/2, 10/1, 10/4, 10/8, 10/1, 15/7, 56/4, 57/2, the cultivars Calabresa, Rosa, Serra das Araras, Yamada and the collected germplasm in Minas Gerais and Goias State (EAPM001, EAPM002 and AKBRM001), deserve further agronomic evaluation.

The Morus spp populations evaluated recently in the Cerrado ecosystem showed high tolerance to drought, high plant survival, and tolerance to cutting at ground level in mid dry season (Pizarro et al., 1997b)

Agronomy, nutritive value and potential use in animal production

Yield

The production of leaf of mulberry depends on the variety, on the location, on the plant density, fertilizer applications and on harvesting techniques. Yields of 10 t DM ha –1 year-1 have been reported in India and Costa Rica (Mehla et al., 1987; Sánchez 2000). Maximum dry matter yields of edible material (leaves and young stems) and total fresh biomass were 16 and 45 t ha-1 year-1, respectively. Total leaf dry matter yields of less than 10 t ha -1 year-1 could be expected under less intensive production (Sánchez 2000). It should be noted that, among plant fractions, leaf gave the highest yield with approximately 55 percent of total biomass. Adding the young stem fraction of 12 percent, it can be inferred that over 60 percent of total biomass is edible. These results are superior to those of other conventional forages until today evaluated.

Composition and nutritive value

Crude protein content in leaves varies from as low as 15 percent to 30 percent depending on the variety, age of the leaves and growing conditions. In general, crude protein values can be considered similar to most legume forages. Considering that DM production reaches 9.5 t/ha during the dry period, with 15.6 percent crude protein, it is possible to produce 1.5t of crude protein/ha, which is equivalent to the yield of transgenic soybean in one year (Preston, 1999). This means that mulberry can produce three times more protein than transgenic soybean in a year.

Fibre fractions are low in mulberry leaves compared to other forages. Shayo (1997) reported lignin contents of 8.1 percent and 7.1 percent for leaves and bark, respectively. Leaf digestibility in vivo and in vitro is very high (>80 percent) and total digestibility is higher than that of most tropical forages (Benavides, 2000).

Palatability

One of the main features of mulberry as forage is its high palatability. Small ruminants avidly consume the fresh leaves and the young stems first, even if they have never been exposed to it before. Animals initially prefer mulberry over other forages when they are offered simultaneously. Cattle consume the whole biomass if it is finely chopped. There is a report (Jegou et al., 1994) of ad libitum dry matter intake of 4.18 percent of liveweight, which is much higher than in other tree fodders. Jayal and Kehar (1962) reported dry matter intakes of mulberry leaves of 3.44 percent of body weight in sheep under experimental conditions.

Animal performance with mulberry

Ruminants

Although the feeding value of mulberry for dairy cattle has been recognized for some time in Italy, and it has been traditionally used in Himalayan countries, the research on mulberry for ruminants has been limited (Sánchez, 2000). Jayal and Kehar (1962), based on the high digestibility values of M. indica leaves, suggested that they could be used as supplements for lower quality forages. Mulberry was used to replace grain-based concentrates in lactating cows with excellent results. Yields did not decrease significantly when 75 percent of the concentrate was replaced with mulberry. Milk production increased with the levels of mulberry offered to goats on a King grass diet (Rojas and Benavides, 1994).

At CATIE, Costa Rica, a module of two dairy goats being fed exclusively with forage from 775 m -2 of mulberry, in association with Erythrina berteroana just as green manure, and from 425 m -2 of King grass, produced an average of 4 kg d –1, equivalent to over 12000 kg ha –1 year (Oviedo et al., 1994). Liveweight gains of bulls belonging to the Romosinuano breed fed elephant grass, increased to over 900 g d-1 when mulberry was offered as a supplement at 1.7 percent of their body weight on a DM basis (González, 1996). In lambs, gains reached 100g d-1 when King grass was supplemented with 1.5 percent DM of mulberry (Benavides, 1986).

Livestock production systems

The traditional way of using mulberry as animal feed in silk producing areas is by providing ruminants with the residue left by the silk worm. A model of sericulture and milk production has been proposed by Mehla et al. (1987), in which dairy cows receive mulberry residue and concentrates. Mulberry foliage can constitute the supplement to low quality forage based diets or as the main component of the ration. A natural association of mulberry and livestock occurs in regions (e.g. Near East and Central Asia) where mulberry trees are kept for fruit production. Fallen leaves in the autumn are consumed by domestic animals. Since fruit ripening happens in late spring or early summer, it may be possible to harvest leaves for forage one or more times before the winter. The only suggestion of utilizing mulberry for direct grazing came from Talamucci and Pardini (1993) who proposed a complementary association with clover (Trifolium subterraneum) for sheep and cattle grazing.

Consideration, conclusions and remarks

The data presented and the international literature (Sánchez, 2000; Benavides, 2000), indicated that Morus trees are intensively grown (e.g. southern Europe, India) for their leaves as food for silkworms. Fruits may be eaten raw or cooked and used as an ingredient of a particularly seductive drink known as Mulberry Wine. Wild birds, poultry, and hogs are fond of fruits. Mulberry leaves are sometimes eaten as a vegetable and are useful as a cattle fodder. Being nutritious and palatable, they are said to improve milk yield of dairy animals. Mulberry wood is valued for sporting goods due to its elasticity and flexibility when steamed, being considered as good as ash. Considering its high quality and palatability, mulberry should be relatively more valuable as a feed, particularly to lactating cows. Substituting concentrates for mulberry in supplements for grazing dairy cows did not affect milk yield or quality. At the same time, the use of mulberry can decrease feeding costs and the use of concentrates. The main positive characteristics in relation with other shrubs forage trees are presented in Table 34.

Table 34. Main positive agronomic characteristics in Morus spp. in relation to the actual available shrub options in the tropics

Genus/species

Vegetative propagation Establishment Soil acidity tolerance Multipurpose
use
Leaf retention in the dry season Nutritive value
Codariocalyx gyroides Difficult Slow High Low Low Medium
Cratylia argentea Difficult Slow Very high Medium Very high Medium
Gliricidia sepium Easy Slow Low Medium Medium Medium
L. leucocephala Difficult Very slow Very low High Very low High
Mimosa sp. Unknown Slow High Low High Low
Morus spp. Very easy Fast High Very high High Very high

Although the genus Morus presents a lot of positive characteristics as a versatile forage alternative, the use in animal production systems in the tropical world is very limited. It is surprising, that a plant that has been improved for leaf quality and yield to feed the silk worm, which has high nutritional feed requirements, received limited attention by livestock producers, technicians and researchers. Despite or in contrast with the effort carried on difficult shrubs forage trees like Leucaena leucocephala in acid soils and the research and effort on Codariocalix gryroides as a grazing shrub legume, very few national and international efforts have been on the genus Morus.


Also it would be important in future agronomic work the correct botanical identification of the germplasm, in order to use the natural agronomic advantage of the different species. For example, it is well known that Morus alba L, present a faster growing development than Morus nigra and Morus rubra. Unfortunately, many of the references on mulberry in the literature do not specify which species or varieties were used or evaluated. In our opinion, most of the research work done on forage and legume evaluation, is still carried out in the traditional way at the experimental station. Participatory research in farmers field may play an important role in the adoption and in the design of new alternative uses.

BAUHINIA SPECIES
Introduction

These beautiful, tender trees and shrubs, which grow from 5 to 9 meters in height with large divided leaves resembling a cow's hoof, that is distinctive to the Bauhinia genus. It produces large drooping may be white, pink or purple flowers and a brown seedpod, which looks like the mimosa seedpod. It can be found in the rainforests and tropical parts of Peru and Brazil, as well as tropical zones of Asia, eastern Paraguay and north-eastern Argentina (Fortunato, 1986). It is quite prevalent in Rio de Janeiro and Brazil's Atlantic rainforest in the South.


The indigenous uses of Pata de Vaca are not well documented but it has long held a place in Brazilian herbal medicine. It is described as hypoglycemic, depurative, and diuretic and has been used for over 60 years to balance blood sugar levels in diabetics. It is considered a good blood cleanser and the leaf decoction is used internally and externally for elephantiasis and snakebite as well as other skin problems including those of a syphilitic nature. It is well established in Brazilian herbal medicine and highly regarded as treatment for diabetes, even being called "Vegetable Insulin." It is widely used in South America by diabetics to help balance blood sugar levels as well as other symptoms produced by diabetes like polyuria, renal disorders, and other urinary problems. Pata de Vaca leaves and teabags are a common item on pharmacy shelves in South America and normally a leaf tea is drunk after each meal to help balance sugar levels.

Bauhinia cheilantha

Potential agronomic use

B. cheilantha (mororó, pata de vaca, uña de vaca) has been reported as one of the most required shrubs species from beef cattle in the Ouricuri region, Pernambuco, Brazil (Araújo and Vieira, 1990; Lima, 1989, and Oliveira and Silva, 1988).In this work, it is mentioned that 30 percent of the farmers are in favour of replanting grazing paddocks with native and useful shrubs species, like B. cheilantha.

De Albuquerque (1999) studied the effects of cattle grazing on range dynamics of the Caatinga, which is deciduous dry woodland, covering most of the semi-arid Brazilian Northeast. Three stocking rates were studied, in addition to an ungrazed exclosure. There was no effect of stocking rate or grazing system period on the frequency of the herbaceous species. They were, however, differences by death rates in easily broken shrub species, Lippia microphylla and Cordia leucocephala, but not in B. cheilantha. The nutritive value of B. cheilantha is reasonable. The crude protein content is 15 percent with an IVDMD of 53 percent. These values are superior to most of the conserved forages in the region (Pizarro 1978; Vera and Pizarro 1999).

Bauhinia bongardii

Bauhinia bongardii (also known as B. cheilanta denominated popularly as mororó, pata de vaca) is a highly rustic group that supports periodic floods and it grows in poor and low fertility soils with high pH. Unfortunately, only one paper has been published on botanical composition and quality of the diet selected by fistulated steers grazing native savannas of the Brazilian Cerrado.

The selected diet was 40 percent higher in crude protein and 38 percent higher in IVOMD than the native pasture. Within the group of grasses and bushes, the species preferred by the animals were Serjania sp., Bauhinia bongardii, Sida spp. and Cassia spp. These groups of species constitute 64 percent of the diet in the dry period (Escuder et al., 1979).

Propagation

These trees may be increased by seeds, suckers, or stem cuttings rooted in a warm propagating case in the greenhouse. Remember, if trees with a single trunk are wanted, prune out the excessive side shoots while they are still young plants.

Conclusions and future work

The genus Bauhinia contains about 200 species scattered throughout the tropics. About 50 of them have been cultivated exclusively as ornamentals in South China, Southeast Asia and Burma. The plants grow well in a wide range of poor soils, alkaline or acids, rocky or sandy. B. cheilantha has been mentioned with good agronomic characteristics in the dry ecosystem of the Caatinga. The other specie, B. bongardii was one of the various shrubs legumes identified in the diet of young steers at the end of the dry season in the Brazilian Cerrado. More emphasis and work need to be done in this area, especially for the ample natural presence and distribution of this legume in tuff ecosystems, such as the Caatinga and the Cerrado, and for the luck of scientific data on the agronomic potential of the genus in farming systems. Also, it is important to take into account that there are no registered records of available germplasm in the seed banks storage in national or international centres.

CHAMAECYTISUS PALMENSIS

Chamaecytisus palmensis (was Cytisus proliferus) (tree lucerne, tagasaste) is a member of the Fabaceae family. It holds promise for use in tropical highlands, Mediterranean climates and temperate regions. C. palmensis is a small shrubby tree indigenous to the dry volcanic slopes of the Canary Islands. Is an upright bushy shrub or small tree to 4m, with drooping, softly hairy branches and leaves with three leaflets. The scented, creamy-white flowers are produced in winter and early spring. It is thornless and generally well branched. In the Canary Islands, farmers are completely dependent on tagasaste for forage during the long dry summers. Tagasaste regenerates prolifically from seed and has naturalized in almost all areas where it has been planted, along roadsides or in adjacent bush land. On lateritic soils in higher rainfall areas it is a serious invader of disturbed bushland.

Agronomy

Fast growing evergreen woody large shrub or small tree. Drooping branches with green leaves. For cultivation it prefers a well-drained sandy soil with pH of 5.0-7.0 in full sun. Grows well with an annual rainfall of 350-1,600 mm and can survive winters of -9°C.

Main agronomic uses

Canary Island farmers have traditionally depended on Tagasaste for fodder during the long dry seasons. The leaves contain 20 to 40 percent protein with no reported toxicity. Presently, Australian and New Zealand farmers are using the tree in cut and carry systems, since grazing animals, pigs and poultry readily consume its leaves. Sheep will eat the bark and kill the tree if it is not protected. Research results from Western Australia and New Zealand suggest edible dry matter yields of 11 tons/ha/yr are obtainable in good growing conditions. Tagasaste prefers well-drained sandy soils, but thrives on gravels, loams, limestone and laterites. Slag heaps and mining dumps can also reportedly be planted with the tree. It thrives with annual rainfall of 350 to 1600 mm and soil pH of 5.0 to 7.0, and survives winters of -9 degrees C.

An early bloomer, it works well in bee-keeping systems and exhibits few insect pest problems. It uses the same Rhizobium inoculants as cowpeas. It is a drought-tolerant, shrub/tree legume, which is naturalized today in many parts of New Zealand. It is potentially useful supplementary forage for sheep and cattle, particularly in summer and early autumn.

Potential agronomic uses

Newly available germplasm

Tagasaste is highly variable for a range of attributes and in the 1980s, 16 lines were identified which had improved production, habit, frost and disease tolerance. From 1993 to 1996, this germplasm was evaluated for morphological and chemical attributes at two sites, to select material for release. Differences in survival and growth of the lines between sites were the major finding. Average plant survival of lines was higher in selected accessions (89 vs. 58 percent). The total N content of new selected lines was 25 percent higher than control lines (33 vs. 26 g N/kg DM), whilst in vitro digestibility of herbage from all lines was 75 percent.
Two lines, AL2244 and AL2432, which had high survival, and means for other attributes which were similar to or exceeded the site mean for all lines, were selected to comprise the final release. Seed of these lines is being increased.

Propagation

Seed or cuttings mainly propagate it. Tagasaste seeds (about 45,000/kg) should be scarified in hot water prior to planting. Tagasaste regenerates prolifically from seed and has naturalised in almost all areas where it has been planted. On lateritic soils in higher rainfall areas it is a serious invader of disturbed bushland.

Tagasaste can be planted as a hedge and also has potential for alley cropping systems. The tree readily coppices and, during the 2- to 3-year establishment period, can be pruned back to the ground to encourage multiple stems and to protect from grazing animals.

Summary and future work

Chamaecytisus palmensis is a fast-growing shrub or small tree from the island of Las Palma in the Canary Islands, which produces its main growth in spring and summer. Different genotypes vary in the degree of branching and the height at which apical dominance is lost. Types with dense branching close to the ground, are the most productive and best suited for browsing, and make fast regrowth. Tagasaste has a deep taproot system that confers considerable drought resistance. Very few germplasm have been evaluated at regional levels and with the exception of New Zealand, any center in tropical America has a representative germplasm collection.

LESPEDEZA SPECIES

The name was changed for Kummerowia (Wiersema et al., 1990). Lespedeza spp. although it is not an important legume in the tropics, is a crop of major importance in south-eastern United States. Lespedeza is grown for hay and pasture, soil improvement, erosion control, seed, and its benefit to wildlife.

Two types of lespedeza are grown; annual and perennials. The annuals, which are the most important, include 'Common' and 'Kobe' (L. striata) and 'Korean' (L. stipulacea). Stocker systems in the Southern Great Plains are seasonally integrated to utilize two forage sources, winter wheat and warm season perennial grasses, such as Bermuda grass. In such systems two problems exist. First, keeping the wheat fields covered in the summer to protect them from erosion and providing a constant supply of high quality forage. A research project was conducted to determine the feasibility of using Lespedeza, an annual warm season legume to protect the field from erosion and to provide high quality forage in late summer when warm season perennial grasses are low in quality. Three Lespedeza varieties of different maturity dates were seeded into winter wheat during the spring. Wheat was utilized for either a grain crop or forage for grazing. Lespedeza did not begin active growth until the wheat crop had been removed by either method, indicating that Lespedeza does not compete with wheat for moisture and nutrients. Overall later maturing varieties were more productive than earlier ones. However, once an adequate photosynthetic base had been established, Lespedeza could produce an average of 36 kg of dry matter/ha/day, which would be adequate enough to meet the daily nutrient needs for three 300 kg stocker cattle at a projected average daily gain of 1 kg. Lespedeza can be incorporated into a continuous winter wheat system to provide high quality forage during the summer fallow period.

The most common perennial is 'Sericea' (L. cuneata) also known as shrub lespedeza. Three other perennial or shrub lespedezas, grown to a limited extent, are L. bicolor, L. intermedia and L. japonica.

Future potential lespedeza shrubby species

Lespedeza bicolor

Several shrubby species such as L. bicolor Turcz., L. thunbergii (DC.) Nakai, L. cyrtobotrya Miq., and L. japonica L. Bailey, have value for soil conservation, as food and also as ornamentals.

Origin and distribution

L. bicolor is native to North China and Japan but has naturalized in the SE of USA. As a result, naturalized plants can be found growing along roadsides, in fields and clear cuts, and in any open, well-drained site. In addition to its use as an ornamental, it was planted in many areas for erosion control. It occurs at elevations from sea level to 800 masl. It is capable of maintaining itself on acidic and nutrient-poor soils. It is not frost tolerant and is often killed to the ground by the first killing frost. L. bicolor is somewhat shade tolerant.

Plant description

L. bicolor (Shrub bushclover, bicolor lespedeza, shrub lespedeza, Japanese bushclover) is a medium growing deciduous shrub. The small trifoliate leaves, the individual flowers, and the one-seeded joint less pods characterise the lespedezas. L. bicolor has no taproot but does have a much branched, well-nodulated, lateral root system.

The flowers of the lespedezas are of two types: petaliferous (or chasmogamous) and apetalous (or cleistogamous). In the latter, the petals never unfold, so the flower has the appearance of remaining in the bud stage and in which only self-fertilization takes place. The flowers are conspicuous in the shrubby species but are inconspicuous in most of the herbaceous perennials or annuals. The apetalous flowers are all inconspicuous. The reason for the development of the two kinds of flowers on lespedeza is unknown.

Agronomy

Easily grown in a well-drained light loam in full sun. Succeeds in light shade and in dry soils. The top growth is not very cold tolerant, although the rootstock is hardy to about 25°C. Plants are usually cut back to the ground in all but very mild winters, though they generally resprout well from the base in the following spring and flower in late summer. Lespedezas are drought-resistant, warm-weather plants.

L. bicolor has been grown in Japan for hay. Yields and quality are good. L. bicolor seeds are high in protein content but are generally low in digestibility. It has been planted on infertile acidic soils, also on sandy soils with high success. It has no significant disease or insect problems. L. bicolor is a nitrogen-fixing legume planted for wildlife habitat improvement, erosion control, and stabilization along stream banks and steep slopes and its leaves produce heavy soil-protecting mulch.

Other uses and values

L bicolor is a good source of pollen for honeybees. Tryptophane-derived alkaloids provoking uterus contracting or hallucinogenic properties have been isolated in Japanese laboratories from L. bicolor var. Japonica L. bicolor will sprout from the root crown following top-kill. Both on-site, fire-scarified seeds and off-site seeds are important sources for colonizing burned areas.

Post-fire regeneration strategy

L. bicolor generally increases in density under a frequent burning regime, because it sprouts from the root crown after top-kill and establishes new individuals from both on and off-site seed sources. This is an important attribute in farming system where fire is a routine practice.

Future work

To be recognized as a useful legume, the annual striate lespedeza waited for nearly 100 years in the United States. A similar situation took place with the perennial lespedeza, which was introduced to United States from Japan in 1890 but did not become important until late 1930s. Most of the research work on grass and legume evaluation in tropical America is discontinuous and instantaneous. For the positive agronomic qualities, its tolerance to low fertility and acid soils, drought-tolerant, non-bloating legume and good seed yield producers should be emphasised; this genus may have a place in forage/livestock systems.

GENERAL CONCLUSIONS AND COMMENTS

The efforts carried out on introduction, evaluation and promotion are very contradictory. For example, Leucaena leucocephala, Stylosanthes guianensis and S. capitata have been broadly investigated and promoted, nevertheless, the seed trade in these mentioned forages is nil (Table 35). On the other hand, Calopogonium mucunoides, a forage legume, without promotion and also discredited by many investigators is the one most sold and accepted by producers (27 t sold in Brazil, Table 35). Farmers participating in the research and development process can accomplish this. The emerging forage legume in the seed market is Arachis pintoi (Tables 35 and 36).

Despite the great effort on methodology, regional evaluation in a network approach, significant investment in training and development of young investigators and just when new available germplasm was ready and available for evaluation on farming systems the three outstanding research centres (CSIRO, CIAT and EMBRAPA), significantly reduced their support and research on forage programs.

In future, the use of forage plants in the tropics will concentrate more and more in two main areas:

  1. in marginal lands that, due to climatic limitations, edaphically and/or topographically, they don't allow production of intensive commercial cropping and where extensive pastures of low inputs are the only viable option of use, and
  2. in integrated production systems such as the agro- sylvo-pastoral.

These characteristics are considered key in the process of the development and in the selection criteria for forages for these areas. They require low requirements of inputs, tolerance to mismanagement and with the capacity of contributing to the conservation and the improvement of the soil. Due to their capacity to fix atmospheric nitrogen, their deep rooting system and their high nutritious value, the leguminous play an important part in the beef cattle production as in soil improvement.

The search of those characteristics should not be based exclusively on the current availability of massive collections of some genera or species. Having a vast collection of accessions, like the case of D. heterocarpon (L.) DC. ssp. ovalifolium does not justify cessation of the search for new forage legumes with more plasticity, wide spectrum of agronomic uses, higher nutritive value and free of anti-quality factors. This is not the case of D. heterocarpon (L.) DC. ssp. ovalifolium where their main use is as a cover crop in tree plantations, erosion control and soil conservation on steep slopes (Pizarro, 2001a).

Table 35. Total amount of forage seed commercialised in Brazil *

(Mean for 2000 and 2001)

Grasses

t of seed

percent of total

Andropogon gayanus

191

2

Brachiaria brizantha - Marandú

5,657

62

B. brizantha – MG4

324

4

B. decumbens

873

10

B. dictyoneura

148

2

B. humidicola

180

2

Paspalum notatum

11

0.1

Pennisetum americanum

205

2

Panicum maximum cv. Tobiatão

24

0.3

P. maximum cv. Tanzania I

874

10

P. maximum cv. Mombaça

381

4

Legumes

Arachis pintoi

3.5

0.04

Calopogonium mucunoides

27

0.3

Pueraria phaseoloides

1

0.01

Total

8,900

* Adapted from: Matsuda Sementes, Brazil

Table 36. Total amount of forage seed commercialised in Costa Rica *
(Mean for 2000 and 2001)

Grasses

t of seed

percent of total

Andropogon gayanus

0.3

0.06

Brachiaria decumbens

102

21

B. brizantha

312

66

B. dictyoneura

5

1

B. humidicola

10

2

Panicum maximum

28

6

Paspalum notatum

7

1

Legumes

   
Arachis pintoi

7.75

2

Calopogonium mucunoides

1

0.2

Neonotonia wightii

0.5

0.1

Mucuna pruriens

2

0.5

Pueraria phaseoloides

0.6

0.1

Total

476

 

*Adapted from: Oficina Nacional de Semillas and Semillas Tempate, Costa Rica

The contradictory experience in the Llanos of Colombia between standard cutting trials in small plots vs. grazing experiments in association with a grass, suggests that traditional evaluation procedures for legumes and especially a stoloniferous one like A. pintoi need to be questioned and urgently modified. Results from clipping experiments can be misleading, because of the artificial nature of defoliation, unless the experiments are designed specifically to investigate problems that have arisen under grazing. Perhaps, most of the agronomic type-clipping trials are conducted in a manner where DM determinations are over emphasized, and this data churned into a computer in an unconsidered manner. What do we achieve by statistical comparison of DM productivity of radically different species? Let us not fall into the trap of imbalance between computer and agronomic capacity.

In tropical America, grasslands studies need to be intensified Grass-legume agronomy studies must fundamentally have an ecological approach. We must take into account the environment under which their leys are growing, and that environment embraces soil, animal and climate. The grass-legume sward is obviously of great economic significance to the world over. The development of new cultivars is an on-going project, and new accessions of old and new genera need to be collected and evaluated under farm conditions.

REFERENCES

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Argel, P. 1994. Regional experience with forage Arachis in Central America and Mexico. In: Kerridge. P.C. and Hardy, B. (eds) Biology and Agronomy of Forage Arachis. Centro Internacional de Agricultura Tropical. pp. 134-143.

Argel, P. and G. Keller-Grein. 1996. Regional experience with Brachiaria: Tropical America-Humid Lowlands. In: Miles, J.W., Maass, B.L. and do Valle C.B. (eds) Brachiaria: Biology, Agronomy, and Improvement. Centro Internacional de Agricultura TropicalCIAT. Cali, Colombia. pp.205-224.

Argel, P. J. 1995. Evaluación Agronómica de Cratylia argentea en México y Centroamérica. En: Potencial del Género Cratylia como Leguminosa Forrajera. In: Pizarro, E. A. y Coradin, L. (eds.). EMBRAPA, CENARGEN, CPAC y CIAT, Memorias Taller sobre Cratylia realizado del 19 al 20 de julio de 1995 en Brasilia, Brasil. pp. 75-82.

Argel, P. J. and C.E. Lascano. 1998. Cratylia argentea (Desvaux) O. Kuntze: una nueva leguminosa arbustiva para suelos ácidos en zonas subhumedas tropicales. Pasturas Tropicales, 20:37-43.

Argel, P. J. and M. Villareal. 1998. Nuevo maní forrajero perenne (Arachis pintoi Krapovickas y Gregory), Cultivar Porvenir. Leguminosa herbácea para alimentación animal, el mejoramiento y conservación del suelo y el embellecimiento del paisaje. Ministerio de Agricultura y Ganadería de Costa Rica (MAG), Centro Internacional de Agricultura Tropical (CIAT). Boletín Técnico. 32p.

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AUTHOR

Estaban A. Pizarro

Private consultant

Mailing address:

Rambla M. Gandhi 193 Apt. 601

11300 Montevideo - Uruguay

pizarro@adinet.com.uy