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]
SUMMARY
INTRODUCTION
GRASSESAndropogon gayanus
Brachiaria species
Eragrostis tef
Paspalum species
Pennisetum purpuremLEGUMINOUS TREES AND SHRUBS Arachis species
Calopogonium mucunoides
Centrosema species
Desmodium species
Macroptilium species
Neonotonia wightii
Stylosanthes species
Leucaena leucocephala
Cratylia genus
Morus species
Bauhinia species
Chamaecytisus palmensis
Lespedeza speciesGENERAL CONCLUSIONS AND COMMENTS
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.
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.
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
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 (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 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.
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.
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 numberLeaf
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 -1A. 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 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 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. b