Legumes in forage research programmes for small-scale livestock producers

John R. Lazier

FLAG, ILCA, P.O. Box 5689, Addis Ababa, Ethiopia

Abstract
Introduction
Methods of legume introduction into farming systems
Availability of germplasm for research

Abstract

The emphasis in research for small-scale livestock producers should be on fitting legumes into existing farming systems by means of-such techniques as intercropping, undersowing, hedges, alley-cropping, cut and carry and reserved grazing. Multipurpose legumes warrant particular attention. Genera of potential value for use in small farms, and which are available for testing from ILCA, are given together with information on the environments to which they are adapted.

Introduction

Forage research in the tropics has traditionally emphasized the oversowing of natural grasslands with legumes and the planting of grass-legume pastures. There are good reasons for these approaches. There are large areas of natural grassland in Africa where conditions are unsuitable for cropping and which support mainly livestock. Improved productivity on these lands would, in many countries, significantly increase the productivity of the national herd. However, vigorous and persistent legumes have yet to be identified which can significantly increase grassland productivity under the generally prevailing African conditions of low fertility, low rainfall, poor management and overstocking.

Mixed grass-legume pastures for more intensive, commercial farming conditions have also received considerable research attention. The legumes are grown in mixtures with grass because a pure legume sward will not persist being quickly invaded by weeds due to the increasing soil fertility under the legumes. Such mixed swards, once established, can maintain comparatively high levels of productivity with relatively small labour and fertilizer inputs.

There are factors, however, which indicate that grass-legume mixtures are not the best way of increasing livestock productivity for small-scale farmers. The farmer may not have sufficient land to use for longer term pasture and he may not be prepared to alienate land from cropping, even for a few years, despite the improvements that would occur in soil fertility. In addition, vigorous, stable species combinations which persist are difficult to identify and fairly careful grazing management is often necessary to prevent one component from dominating the pasture. Vigorous legumes are usually identified by researchers long before vigorous grass-legume combinations are identified and their management needs defined, and there is thus a gap of some years between the identification of a productive legume and its introduction. Frequently the final research stages are never accomplished and thus the legume is never introduced at all.

Thus the rapid introduction of legume forage to small farmers is unlikely to be accomplished by the oversowing of natural grasslands or by the establishment of grass-legume pastures.

Methods of legume introduction into farming systems

The small-scale farmers who are most likely to respond to the introduction of legumes as fodder are those who have restricted area for grazing and farming, are dependent on milk and milk products for food and cash and who also cut and carry fodder and have good markets for their animal products.

There are a number of ways in which legumes can be effectively introduced into small-scale farming stems. The effective method or methods will be dependent on the individual farmer, the farming system, the adapted legumes, and the germplasm screened. Some of the more important methods of introduction will be briefly described and some of the legumes identified by ILCA as being of potential value will be listed. Summaries of the promising genera, their environments of adaptation and their areas of usefulness are presented in Tables 1, 2 and 3.

Natural Legume Resources

Frequently there are natural leguminous resources available to the farmer and these can be further developed (Tables 1,2 and 3). In some environmental zones such resources have been critical elements in the farming systems. Natural Acacia woodlands, for example, are used as grazing lands in drier environments. The Acacia enhance grass growth in the wet season, and prolong its growth into the dry season. The Acacia leaves and pods provide significant amounts of high-quality dry-season fodder and thus animals are maintained in reasonable condition through the dry season. At Abernosa Ranch in the Rift Valley of Ethiopia, for example, cattle grazing Acacia woodlands have liveweight gains which are only slightly reduced during the seven month dry season. For male and female Boran cattle gains of 713 and 500 g/day in the wet season and 643 and 456 g/day in the dry season have been recorded (Daboba, personal communication).

There are traditional farming systems in the Sudano-Sahelian zone which utilize A. albida, tall trees which are leafless in the wet season. Farming is done directly under them and the crops are thus able to benefit from the improved soil conditions under the tree canopies.

In areas of higher rainfall and where A. albida is not common, the Acacia trees are thinned and the remaining scattered natural trees are cut back to the main trunk (pollarded) periodically to provide wood for fuel and construction and dry-season fodder.

These valuable resources are frequently destroyed by land clearing and for short-term gains for firewood or charcoal. Research and extension workers should encourage the maintenance and controlled utilization of existing stands, and their re-establishment where they have been destroyed. Research is badly needed to quantify their contribution to productivity.

Herbaceous legumes can also be an important natural legume resource. In the Wolayta region of Ethiopia, an area of high population density with little available grazing land, cut-and-carry feeding of cattle is commonly practiced. Native herbaceous legume (Zornia, Stylosanthes, Desmodium, Neonotonia, etc.) are collected by hand and fed to animals to increase milk yields and improve butter quality. In their search for adapted legume germplasm researchers should not neglect the possibility of enhancing the production of native species and genotypes, particularly those with which farmers are already familiar.

Traditional Legume Crops

In some communities leguminous crops are used as animal feed. It is a common practice for residues of pulse crops to be fed to animals in the dry season. In some cases the crop may be planted solely as animal feed, for example Vigna unguiculata (cowpea) in the Sudano-Sahelian zone of West African. Various species of Erythrina are commonly planted in the middle-altitude regions of Ethiopia for fencing, and/or dry-season fodder. This plant is apparently unpalatable in the wet season, but quite palatable in the dry season.

Researchers should look carefully at the methodologies which farmers have developed and look for ways of enhancing the use of these traditionally developed resources.

Small plots for cut-and-carry Feeding

Small plots of perennial legumes for cut-and-carry feeding of selected classes of stock are particularly appropriate for small-scale farmers. While these plots may have the disadvantage of requiring inputs such as weeding and fertilization, they permit the utilization of a large group of very productive plants which are not normally utilized for cut-and-carry feeding due to their high palatability or sensitivity to mechanical damage by trampling. Viney plants are particularly susceptible to damage by trampling and there are many vigorous and palatable species belonging to the genera Centrosema, Vigna, Phaseolus and Rhynchosia which have potential for cut and carry. In order to encourage rapid regrowth of viney plants, leaves can be stripped from the stems or a generous residual amount of stem can be left on cutting. Almost all leguminous forage genera have some potential for use as cut-and-carry, although the bulkier browse, shrub, sub-shrub and viney species are most useful.

Table 1. Perennial legume genera of forage potential for small-scale farming

Genus

Spmecies

Origin

Potential

Morphology

Rainfall

Altitude

USES

1

2

3

4

5

6

7

8

9

Alysicarpus

2

A

G

Herbs

Moderate-high

Medium-high

x

x

Calopogonium

2

E

G

Vines

Moderate-high

Low

x

x

x

Canavalia

2

E

E

Vines

Low-moderate

Low-medium

x

x

Centrosema

7

E

F-E

Vines

Low-high

Low-medium

x

x

x

Clitoria

1

A

G

Vines

Moderate

Low-medium

x

x

Desmodium

6

E

F-E

Herbs/vines

Moderate-high

Low-medium

x

x

x

x

x

Lablab

1

A

G

Herbs

Low-high

Low-medium

x

x

Lotononis

1

A

E

Herbs

Moderate

Medium

x

Lotus

3

A

G

Herbs

Moderate?

Medium-high?

x

x

Macroptilium

3

E

G

Vines

Moderate

Low-medium

(x)

x

x

Macrotyloma

1

A

E

Vines

Moderate

Medium

(x)

x

x

x

Medicago

1

E

E

Herbs

Moderate-high

Low-medium

x

x

x

Neonotonia

1

A

E

Vines

Moderate

Medium

(x)

x

x

Rhynchosia

3

AE

G

Vines

Moderate

Medium

x

x

Stylosanthes

8

AE

F-E

Herbs

(low) moderate

Low-medium

x

x

x

x

(x)

x

Trifolium

5

AE

E-G

Herbs

Moderate

Medium-high

x

x

x

Teramnus

1

A

G?

Herbs

Moderate

Medium-high

(x)

(x)

Vigna

3

E

G

Vines

Moderate-high

Low-medium

x

x

Zornia

?

AE

F-G

Herbs

Low-high

Low-medium

x

x

x

Table 2. Annual legume genera with forage potential for small-scale farming

Genus

Species

Origin

Potential

Morphology

Rainfall

Altitude

USES

1

2

3

4

5

6

7

8

9

Alysicarpus

2

A

G

Herbs

Moderate

Medium-high

x

x

Arachis

3

A

G?

Herbs

Moderate

Low-medium(?)

x

x

Cassia

1

E

F

Herbs

Low

Low-medium

x

x

Neonotonia

1

E

G

Herbs

Moderate

Low-medium

x

x

Macrotyloma

1

A

F

Herbs

Low-moderate

Low-medium

x

x

Phaseolus sp.

3

AE

F-E

Herbs/vines

Low-high

Low-high

x

x

x

x

Pisum

1

AE

G

Vines

Moderate-high

High

x

x

Stylosanthes

1

E

F

Herbs

Moderate-low

Low-medium

x

x

Tephrosia

2

A

F

Herbs

Moderate-high

Medium-high

x

x

Trifolium

6

A

G-E

Herbs

Moderate-high

Medium-high

x

x

x

Vicia

2

A

E

Vines

Moderate-high

(Medium) high

x

x

x

x

Vigna

1

A

E

Vines

Low

low-medium

x

x

x

Zornia

1

A

F

Herbs

Moderate

Medium

x

x

x

Table 3. Browse species with forage potential for small-scale farming

Genus

Species

Origin

Potential

Morphmology

Rainfall

Altitude

USES

1

2

3

4

5

6

7

8

9

Cajanus

1

AE

E

Shrub

Low-high

Low-medium

x

x

x

x

x

Codariocalyx

1

E

E

Shrub

Moderate-high

Low-medium

x

x

x

x

Desmanthus

1

E

G

Shrub

Low-high

Low-medium

x

x

x

x

x

Desmodium

3

E

G-E

Shrub

Moderate-high

Low-medium

x

x

x

x

Erythrina

2

A

E

Tree

(Low)-high

(Low)-high

x

x

x

x

Gliricidia

1

AE

E

Tree

Moderate-high

Low-medium

x

x

x

x

Leucaena

9

E

E

Tree

Moderate-high

Low-(high)

x

x

x

x

Medicago

1

E

F

Shrub

Low-moderate

Low-medium

x

x

x

x

Prosopis

6

E

?

Shrub

Low

Low-medium?

x

x

x

x

Sesbania

3

AE

E

Tree

Moderate-high

Low-medium

x

x

x

x

x

Key for Tables 1,2,3

Species: Number of species
Origin: A African, E Exotic
Potential: Fair, Good, Excellent, suspected
Rainfall: Low, <800; moderate 800-1,200, high >1,200 mm per annum
Altitude: Low <1,500; medium 1,500-2,000, high >2,000 (at 9 degrees)
Use:
1. pure sward grazed
2. grass-legume mixture grazed
3. reserve fodder
4. inter-crop
5. catch crop
6. under crop
7. cut and carry
8. food and fodder
9. on low potential land

Reserved grazing

Areas of pure or mixed grass-legume swards can be reserved for feeding selected productive classes of animals year-round or during the dry season. These protein or fodder banks are grazed for brief periods daily. The legumes are usually perennial and thus must be drought resistant and unaffected by trampling, although their palatability can be high as the grazing pressure can be controlled. Such areas would normally be larger than those reserved for cut and carry and fencing may be required, although labour inputs would be lower. Useful species and genera for reserved grazing include Pueraria phaseoloides, Stylosanthes, spp. Macroptilium atropurpureum and Zornia spp.

Undersowing in perennial cash crops

There may be opportunities for the sowing of a leguminous ground cover under perennial tree or shrub crops. In the Wolayta region of Ethiopia, for example, the weeds growing beneath coffee and ensete (false banana, a carbohydrate food crop) are cut and fed to livestock. Desmodium intortum has proved to be well adapted to growing under these crops, and is beginning to be planted by farmers for providing better quality fodder as well as providing nitrogen for the cash crop.

Intercropping in annual crops

Legumes can be sown between rows of annual crops. They can be sown at the same time as the crop if they do not compete too strongly with its growth. If they do compete, the farmer may be prepared to cut them back and feed them during the early growing season, or, alternatively, may plant the legume two to four weeks after the cash crop. Perennial and late-maturing annual legumes would then continue to grow after maturation of the main crop, producing additional fodder.

Perennials which can persist through the dry season are particularly useful as they will produce some growth in response to any showers during the dry season and this growth can be grazed as standing hay or used for cut-and-carry fodder. In the following growing season the farmer will have a number of options in the management of his perennial legume. These are to:

(i) cut back the legumes sufficiently severely or frequently to allow rapid establishment of the cash crop;
(ii) allow the legume to regrow and seed after the dry season to provide a permanent cut-and-carry or grazed plot;
(iii) remove the permanent legume stand after a period of years, or cut it back, and plant a regular crop to take advantage of the additional nutrients fixed by the legume.

ILCA has had success intercropping S. guianensis cv. Cook, Macrotyloma axillare and Lablab purpureus in Ethiopia and S. hamata cv. Verano in Nigeria near Kaduna. The annual vine Vigna unguiculata (cowpea) is widely and traditionally intercropped in the Sudan zone.

Catch crop

Legumes which have a short a short life-cycle may have a place as a crop in seasons with unrealiable rainfall, or when planted during or after the maturity of the main growing-season crops to take advantage of residual soil moisture and late rains.

Short-lived annuals adapted to dry conditions which could be useful as catch crops are Macrotyloma uniflorum and Phaseolus acutifolius.

Hedge plantings

Browse species may play an important role in small farms for they can provide natural fencing, fuel, construction material, food and fodder. They may be planted around fields and houses in rows or broadcast in pastures, or in rows in cropped land (alley farming) where the leaves can be used as a fertilizer or mulch, cut and carried as feed, and grazed in situ during fallow periods. Leucaena, Cajanus, Gliricidia, Sesbania and Erythrina are among the more widely planted species.

Low-potential areas

While small farmers will usually not have control of extensive areas of rough land or eroded, infertile areas, even small areas may provide significant additional fodder. Legumes are commonly good pioneer plants. The appropriate legume may be exotic or native and should have a weedy, hardy character. Townsville stylo (S. humilis) is a well known Australian example of an exotic which naturalized and spread on infertile and degraded soils which were unsuitable for cropping. In Ethiopia the native legume S. fruticosa is often the major component of vegetation on eroded areas in certain environmental zones.

Multipurpose crops

A forage plant is much more likely to be attractive to a farmer whose land area is limited if it has more than one use. As has already been mentioned, browse species commonly have multiple uses and there is also a broad range of herbaceous annual legumes whose seeds are used for human food while the stovers are used for fodder. The genus Phaselous contains many of these and within the species P. vulgaris there is a tremendous range of growth forms. P. vulgaris is of American origin and this species is traditionally intercropped with maize. The larger bushy or climbing forms not only produce more fodder, but also more seed. Other species of actual or potential value for Africa include cowpea (V. unguiculata), lablab, pigeon pea (Cajanus cajan), wing bean (Psophocarpus tetragonolobus) and groundnut (Arachis hypogea).

Availability of germplasm for research

ILCA is in the process of establishing a Forage Genetic Resources Section in the Forage Legume Agronomy Unit (FLAG). Currently there are about 8,000 accessions in the collection of African and exotic legume, grass and browse species which have been collected or acquired by the section. These include tropical, sub-tropical, Mediterranean and temperate germplasm. Considerable effort has been put into building a computerized database on passport and site-of-accession environmental data and some of these data are available to researchers in the ILCA Forage Germplasm Catalogue in order that they may ensure selection of germplasm which is appropriate for specific environments. Seeds are multiplied by the section for long-term storage and for provision to researchers.

Because of space considerations most experimental lines are only multiplied to a level of 3,000 seeds to cater for the needs of researchers. Thus only up to 30 seeds can be provided of these lines and researchers must multiply the seed themselves before being able to plant them in trials. Promising experimental and commercial lines are continuously multiplied in small plots and, depending on the quantity of seed available, usually 0.5 g of seed would be available on request, with larger quantities of up to 50 g being available for some commercial lines. These quantities are sufficient for simple screening trials.

The FLAG Unit also has many types of experimental designs available, particularly those for germplasm screening which will utilize minimal amounts of seed. Requests for seed and experimental designs should be forwarded to the Leader, FLAG, P.O. Box 5689, Addis Ababa.