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Techniques for introducing forage legumes to the small-scale farmers of the semi-arid region of Kenya

D.M.G. Njarui
National Dryland Farming Research Station,
P. O. Box 340, Machakos, Kenya.


Abstract
Introduction
Materials and methods
Results and discussion
Introduction of legumes into farming systems
Conclusions
Acknowledgements
References


Abstract

A range of forage legumes which are well adapted to the semi-arid mid-altitude environments of Kenya have been identified in trials lasting several growing seasons. Growth habits and persistence within the plant genotypes selected vary from short-lived annuals to perennials. Data have been obtained on agronomic performance and phenological characteristics in a range of temperature moisture environments in eastern Kenya.

Possible ways of integrating these forage legumes into existing farming systems will include undersowing or intercropping with cereals, use on erosion control bunds or terrace banks, in the improvement of degraded, non-productive grassland, or in simple cut-and-carry fodder plots. The possibility of using these techniques with individual legume genotypes is discussed in this paper. With successful introductions into farm systems, it is likely that the legumes will increase soil fertility, reduce soil erosion and consequently increase livestock and cereal production.

Introduction

Semi-arid regions cover about 59% (342,000 km2) of the total land area in Kenya. Soils range from clays to well drained reddish and stony sands. The eastern region has a marked bimodal rainfall pattern with two pronounced wet and dry seasons (Kusekwa, 1985). Annual rainfall averages 500-800 mm, but is irregular and erratic with pronounced erosive downpours and long drought periods. These attributes make mixed farming (crops/animal production) in the semi-arid environment a risky enterprise (Rukandema, 1984).

Rapid increases in population densities and intensity of cultivation and grazing within the smallholder farming systems have resulted in severe depletion of soil fertility and severe soil erosion. On the cultivated lands, contour bunds and terraces are commonly used for controlling erosion. These are sometimes planted with grasses but commonly left bare, making them a target of erosion. On grazing lands continual intensive defoliation and trampling have led to land denudation, insufficient regrowth and the development of marked erosion in many areas.

In some grazing lands, adequate perennial grasses are present but it has been estimated that livestock carrying capacity in lowland Machakos (and similar semi-arid areas) is 1.5 ha to 6 ha/livestock unit, an indication of poor quantity and quality pastures (Wheeler and Jones, 1984).

Forage legumes do not feature prominently in the existing farming systems, despite their potential to improve soil fertility, check soil erosion and contribute to the livestock feed resource base. It has been suggested (Thairu and Tessema, 1987) that productive legumes are absent from pastures in the semi-arid regions for various reasons including:

i) failure to tolerate heavy grazing
ii) drought susceptibility and
iii) non-availability and high cost of seeds

The research programme described in this paper has concentrated on the search for adapted species over the last 4 years and is now shifting emphasis to the search for places where the adapted species identified can be fitted into the farming systems. Special techniques may be required to integrate forage legumes into the farming systems of the semi-arid regions.

Materials and methods

More than 160 accessions of forage legumes from 23 genera were tested over six growing seasons. The main experiments were conducted on row plots at Katumani (altitude 1600 m, mean annual rainfall 717 mm, mean annual temperature 19.6°C, soil type: chromic luviso, pH 6.5) and Kiboko (975m, rainfall 595 mm, mean temp. 25.7°, soil type: rhodic ferrasol, pH 5.8). Further assessments were made of swards in selected accessions at four other locations (Kiboko, Mua Hills, Maruba and Ithookwe) (See Menin et al, 1989).

The evaluation was in double row plots (2 m row × 1.5 m inter-row) and in multi-planting sward plots (16 m2, of 20 best-bet accessions) in a randomized complete block design with 3 replaces. Two weeks after legume seedling emergence a basal fertilizer was applied along one row of the row plots and evenly broadcasted over the entire sward plots.

Monthly agronomic and phenological characters recorded included plant population, heights, plant development (e.g. flowering, seeding) visual bulk ratings (cumulative herbage on a scale of 1-5) and pest/disease incidence. In addition, the multi-planting swards had the objective of measuring seasonal dry matter production.

In the multi-planting swards, at 4 sites, a total of 12 plantings were done in 5 seasons although not every site was planted in each season. Each planting consisted of 3 reps of 20 accessions. Eleven accessions were common to all plantings white another 12 accessions were grown in a reduced number of plantings.

Results and discussion


Individual assessment


Results of the row plot experiments, involving numerous observations of yield (bulk dry matter assessments), persistence, drought tolerance, seed production etc., allowed a ranking of the performance and adaptability of the individual accessions. These are listed below, and in Tables 1, 2 and 3 and in Figure 1.

The sward experiments allowed a more systematic analysis of yield and adaptability. An example of the data being obtained is given in Figures 1. Each curve on Figure 1 represents either linear or quadratic regressions with 10-12 data points per accession and coefficients of determination (r2) normally in the range 80 to 90%.

Individual assessment

(a) Shore-lived annual forage legumes

Because of the prolonged dry period in this environment, annual legumes might be better adapted than the perennials. Annual legumes can often self-regenerate from seed where the wet season is short.

Suitable potential species and cultivars of annual legumes have been identified, notably Centrosema pascuorum cv. Cavalcade (K14418), Aeschynomene americana cv. Glenn (K19897), Macrotyloma africanum CP 24972 (K14348) and Centrosema virginianum CP 2748 (K14399).

These are fast growing, prolific seeders with excellent regeneration. A difficulty with cv. Cavalcade is that its seeds are carried away by harvester ants into their nest. Otherwise establishment of these annuals is easy. They are non-aggressive in their growth pattern, and thus suitable for cereal intercropping. Because of their fast maturity, they are able to escape the dry period.

b) Long-lived annual forage legumes

These are sometimes referred to as short-lived perennials. Favourable soil temperatures and moisture initiate fast germination followed by excellent herbage growth during warm weather.

A good example is Lablab purpureus cv. Rongai - a rampant and vigorous multi-purpose legume. The grain can be used as human food and the residues can be fed to animals. It forms a Table 1: Short-lived annual legumes for use in the semi-arid region.

Table 1. Short-lived annual forage legumes for use in the semi-arid region.


Species


Cultivar/
CPI


K. No.


Morph.

Evaluation*


Seed yeild


DM Prod


Uses

Early growth

Rege

Centrosema pascuorum

Cavalcade

14418

herb

E

F

E

G

1.5

Aescjnomene americana

Glenn

19897

herb

E

E

E

6

4.5

Macrotyloma africanus

24972

14338

herb

E

E

6

F

1.5

Centrosema virginianus

C02748

14399

herb

F

P

G

F

1.5

Table 2. Persistent annual forage legumes for use in the semi-arid region


Species


Cultivar/CPI


K. No.


Morph.

Evaluation*


Seed yeild


DM Prod


Uses

Early growth

Rege Pere

Alysicarpus rugosus

52351

14384

herb

G

F

G

G

1.4

Cassia rotundifolia

Wynn

18177

herb

E

E

E

F

2.5

Lablab purpureus

Rongai

14420

herb

E

P

F

E

1,4,5

Stylosanthes hamata

Verano

14428

herb

E

E

G

F

2,5

Table 3. Perennial forage legumes for use in the semi-arid region

Key for table 1.2.3

P - Poor
F - Fair
G - Good
E - Excellent

USES

1 - Intercropping

Rege - regeneration

2 - Improvement of grazing land


3 - Terrace bank stabilisation

Pere - Perennation

4 - Cut-and-carry fodder banks

Adapt - Adaptability

5 - Ley farming


* based on VBRS.

Figure 1. Dry matter yields of some forage legumes relative to the mean yield of all accessions when grown as awards in a number of environments. (* - 1:1 line)

Figure 2. Changes in visual ratings of bulk dry matter (VBR) with time for three forage legumes at Maruba, Machakos.(a)

Figure 2. Changes in visual ratings of bulk dry matter (VBR) with time for three forage legumes at Maruba, Machakos.(b)

Figure 2. Changes in visual ratings of bulk dry matter (VBR) with time for three forage legumes at Maruba, Machakos.(c)

(a) Lablab purpureus
(b) Desmanthus virgatus
(c) Macrotyloma africanum

- - - - with basal fertilizer
- - - - - no fertilizer

suitable intercrop with cereals. Cassia rotundifolia cv. Wynn (K18177) and Stylosanthes hamata cv. Verano (K14428) are prolific seeders. They have ability to colonise quickly due to excellent regeneration from seed. Seeds of Cassia rotundifolia cv. Wynn are usually carried by harvester ants thus lowering the regenerative capacity. Alysicarpus rugosus CP 52351 (K14384), is a good seeder but regenerates poorly due to hard seedness. It establishes a good stand if seeds are well scarified. It is non-aggressive and thus suitable for intercropping.

c) Perennial forage legumes

Although rainfall limits production in semi-arid areas, favourable temperatures, light intensities and substantial storage of moisture after rains offer opportunities for growing reasonable good quality herbage from mixtures including perennial legumes.

Some Stylosanthes, Desmanthus and Macroptilium spp are outstanding in dry matter production and wider adaptability in the semi-arid zone. They have excellent perennation, good regeneration and remain green during the dry period. Other notable genera are Macrotyloma, Rhynchosia, Neonotonia and Clitoria. Initial establishment of most of these perennials is slow, but they tend to be more productive in the second season. This is an advantage if intercropped with cereals since the cereal crop will have time to establish without much competition.

Desmanthus virgatus cv. CPI 40071 (K14456) is a deep rooted species, which firms the surrounding soil, making it suitable for stabilizing terrace banks. This species tends to shed leaves during the dry season, but this forms a mulch which releases nitrogen after decomposition.

The Stylosanthes spp are prolific seeders. Their ability to colonize low fertility soils is an advantage. S. scabra cv. Fitzroy and Stylosanthes fruticosa cv. CPI 41219A (K14426) are slow to establish but persist well and are vigorous in the second season. Similarly, Clitoria ternatea, cv. CPI 48337 (K14403) grows quickly in the second season. This species is attacked by powdery and downy mildew at maturity. There are wild types growing on the semi-arid zone of eastern Kenya especially in black cotton soils.

Macrotyloma axillare. cv. Archer (K14462), Neonotonia wightii, cv. K2366 and cv. Cooper and Macroptilium atropurpureum cv. Siratro (K14461) all form a good early stand. Together with their excellent perennation, this makes them suitable for several farm situations.

Introduction of legumes into farming systems

Forage legume research in the semi-arid Kenya has lagged behind that in the high potential areas, so that relevant technology for farmers has not been developed. Forage legumes can best be introduced as part of an overall farming system. Legumes which could be used to provide ground cover on arable land and high quality livestock feeds during the dry season should be given priority.

a) Intercropping

Intercropping is defined as growing a mixture of two or more crops simultaneously on the same field. In semi-arid eastern Kenya, most of the legume/cereal intercropping involves grain legumes, such as Cajanus, Lablab and Vigna (Chabeda, 1986). The extent to which forage legumes can be used in such mixtures is not known. The advantages that have been advanced (Nnadi and Haque, 1986) for such an intercropping are:

i) the possibility of nitrogen accretion from the legumes to cereals,
ii) maintenance of a continuous feed supply during the dry season,
iii) more efficient utilisation of low quality cereal residues through the addition of high-potential forages
iv) increased crop productivity, and
v) greater security of return compared to sole cropping

Forage legumes growing in association with cereal crops will compete for limiting resources, particularly water. More research is needed before we can determine whether the short term negative effects of such competition is balanced by the potential long-term benefits of forage legumes.

b) Improvement of grazing land

Eroded, infertile land could provide significant additional forages. Legumes are commonly good pioneer plants (Russo, 1986; Lazier, 1987). If legumes are oversown into existing grass, they can dominate pastures and substantially improve their production and quality over dry periods. Persistence of the legumes depends on the existence of a sufficient quantity of germinable seed at the start of the growing season and persistent effective rhizobial associations (Wheeler and Jones, 1984).

In view of excessively high stocking rates, farmers will have to adjust livestock numbers to the available feed supply by selectively culling unproductive animals and increasing animal feed production per unit area. Initially, avoidance of grazing on areas where young forage legumes have been introduced is a pre-requisite to any improved management. Later, light grazing can be allowed to reduce competition from native vegetation and promote establishment of the sown species. Grazing of stylos which are hard-seeded can enhance germination since the seed passes through the ruminants, alimentary canal where there is slight scarification. Soil disturbance by grazing animals can allow seed cover and germination at the onset of rains.

A main target area for introducing legumes will be denuded bare areas where there are scattered grasses. The use of "matengo pit" technology can provide micro-catchments to aid establishment (Gichangi, E.M.G, Soil conservation, Ministry of Agriculture, Kenya, personal communication). Attempts will be made to oversow strips and broadcast seeds into native pastures during the more reliable short rainy season.

The success of forage legumes in grazing lands will depend very greatly on the grazing pressure they experience. The possibility of raising production per animal and reducing animal numbers per unit of grazing land is an important subject for research.

c) Terrace bank stabilisation

Although rainfall is limiting in the semi-arid region, usually it occurs as large erosive storms which can, among other effects damage the bare banks of terraces on cropland. Perennial grasses are used in some cases to stabilize these structures, but the potential role of deep-rooted, perennial shrub legumes has received little attention. During the dry season, they could be slashed for animal feed. They could also provide some mulch and improve soil fertility within the cultivated terrace bank.

d) Cut-and-carry fodder plots

Fodder banks, concentrated units of forage legumes, (Mohammed-Saleem et al 1986) could be planted and maintained for several seasons near homesteads or in a block of land which is fenced to deter grazing and allow protein accumulation. During the dry season, these could be cut to provide additional protein for sedentary animals. Labour would be required to cut-and-carry forages and to manage the animals.

Farmers could restrict feeding of fodder banks to only the most responsive animals in the herd (e.g. lactating cows). It is probably important to ensure sufficient seed-drop and stubble at cutting for regeneration in the following seasons.

e) Ley farming

Ley farming, rotation of cereals and forage legumes, emphasizes long-term soil fertility management for sustained crop production. In many farming systems across the world, the presence of legumes has been found to increase soil nitrogen through fixation of atmospheric N and decay of plant residues or root nodules.

Although fertilizers can replenish soil nutrients and meet crop requirements, they are too expensive for the low income small-scale farmers. A fast-growing legume cover crop would protect the soil, improve soil structure, improve water infiltration and reduce erosion. If in the subsequent season a cereal crop is grown, it may benefit from the residual effects of the legumes.

However the inclusion of forage legume leys in the cereal crop rotation means that some land is taken out of food crop production for at least one and possibly 23 seasons with the slower growing species. Hence research is needed to determine this loss in production is balanced by enhanced production from the cereal crops following the legumes.

Conclusions

The potential productivity of semi-arid environments could be more fully exploited by better and greater use of grain and forage legumes. Total land area is not such a limiting factor, in introducing cultivated pastures and forage crops because farmers cultivate no more than 56% of their holding (Tessema and Emojong 1984; Tessema et al 1985). The fact that most land is demarcated and privately owned offers scope for both intercropping legumes with cereals improving natural pastures with legumes and instituting proper grazing management.

Although at present farmers find it difficult to allocate their land and labour to growing forage crops, once the benefits from forage legumes in providing nitrogen for increased livestock and crop production are realised, this barrier might be overcome.

Seventeen potentially useful forage legume accessions are being multiplied. These are legumes identified from the GOK/ACIAR legume evaluation programme for the semiarid region of Kenya (Njarui et al - unpublished). See Appendix 1. Harvested seeds will be distributed to farmers through extension officers and to interested researchers. However, small quantities of the seed could be obtained through the Director, NDFRS, Katumani, P. O. Box 340 Machakos. Kenva.

Acknowledgements

The author wishes to thank Mr. P.K. Kusewa, Centre Director, NDFRS, Katumani and Dr. B.N. Majisu, Director, KARI, for permission to publish this paper. Financial support for the legume evaluation programme was provided by the Australian Centre for International Agricultural Research through the ACIAR/CSIRO Dryland project. The assessments reviewed in this report are the result of collaboration between the author and Mr. W.M. Beattie, Dr. B.A. Keating and Dr. R.K. Jones. Useful guidance received from Dr. M. Karachi is appreciated. Dr. B.A. Keating, Dr. J.R. Simpson and Ms R. Wangaliwa assisted in the preparation of this paper.

References

Chabeda, A.E.O. 1986. Drought resistance in some Kenya grasses and legumes. Annual report (1985-1986), Nat. Agric. Stn. Ben., Kitale, Kenya.

Kusewa, P.K. 1985. Pasture and fodder crops for dryland areas: In: Wafula, M. and Okwach, G.E. (eds): Agricultural Research and Extension of Drylands of Kenya. UNDP/FAO Dryland Farming Research and Development Project KEN/91/011, Katumani, Kenya.

Lazier, J.R. 1987. Legumes in forage research programmes for small-scale livestock production. In: J.A. Kategile, A.N. Said, and B.H. Dzowela (eds). Animal Feed Resources for small-scale livestock producers. Proceedings of the second PANESA workshop, held in Nairobi, Kenya 11-15 November, 1985. IDRC manuscript Report - Canada. pp. 259-267.

Menin, L.K. Beattie, W.M. Njarui, D.M., Keating, B.A., and Jones R.K. 1989. Adaptation of forage and browse legumes to the semi-arid mid-altitude regions of Kenya - an interim report. A paper presented at the Pasture Network for Eastern and Southern Africa (PANESA) 3rd workshop, 27-30 April 1987, Arusha, Tanzania. pp. 132-145.

Mohammed-Saleem, M.A., Suleiman, H. and Otsyina, R.M. 1986. Fodder banks: For pastoralists or farmers. In: I. Haque, 5. Jutzi and P.J.H. Neate (eds). Potentials of forage legumes in Farming Systems of Sub-saharan Africa. Printed at ILCA, P. O. Box 5689, Addis Ababa, Ethiopia. pp. 420-437.

Nnadi, L.A. and Haque, I. 1986. Forage legume - cereal systems: Improvement of soil-fertility and agricultural production with special reference to sub-saharan Africa. In: I. Haque, S. Jutzi and R.J.H. Neate (eds). Potentials of Forage Legume in Farming Systems of Sub-saharan Africa. Printed at ILCA, P. O. Box 5689, Addis Ababa, Ethiopia. pp. 330-362.

Rukandema, M. 1984. Farming Systems of Semi-arid Eastern Kenya. E. Afr. Agric. For. J. Special issue Vol. 44.

Russo, S.L. 1986. The introduction of forage legumes into Gambian farming systems. In: I. Haque, J. Jutzi and P.J.H. Neate (eds). Potentials of Forage Legumes in Farming Systems in Sub-saharan Africa. Printed at ILCA, P. O. Box 5689, Addis Ababa, Ethiopia. pp. 255-264.

Tessema, S. and Emojong E.E. 1981. 1984. The influence of stocking rates and grazing management on livestock changes in cattle, sheep and goat grazing natural pasture. In: E. Afr. Agric. For. J. Special issue Vol. 44.

Tessema, S., Emojong, E.E., Wandera, F.P. and Nderito, M. 1985. Features of traditional farming systems as they affect livestock production. Field document No. 6. Dryland Farming Research and Development Project - KEN/81/011 Katumani - Kenya.

Thairu, D.H. Tessema, S. 1987. Research on animal feed resources. Medium-potential areas of Kenya: In: J.A. Kategile, A.N. Said and B.H. Dzowela (eds). Animal feed resources for small-scale livestock producers. Proceedings of the second PANESA workshop, held in nairobi, Kenya, 1115 November 1985 IDRC manuscript report Canada. pp. 125-148.

Wheeler, J.L. and Jones, R.J. 1984. Potential for forage legumes in Kenya. In: UNDP/FAO Dryland Farming Research and Developement project KEN/74/017 Katumani - Kenya.

Appendix I: List of accessions under seed multiplication.

Species

CPI/Cultivar

K No.

Origin

1. Aeschynomene americana

cv Glen

19897

Mexico

2. Alysicarpus rugosus

52351

14384

Malawi

3. Cassia rotundifolia

cv Wynn

18177

-

4. Centrosema pascuorum

cv Cavalcade

14418

-

5. Clitoria ternatea

48337

14403

Tanzania

6. Desmanthus virgatus

40071

14456

Brazil

7. Desmodium intortum

cv Greenleaf

14455

-

8. Lablab purpureus

cv Rongai

14420

Kenya

9. Macroptilium atropurpureum

cv Siratro

14348

Mexico

10. Macrotyloma africanum

24972

14348

Zambia

11. Macrotyloma axillare

cv Archer

14462

-

12. Neonotonia wightii

cv Cooper

cv Cooper

Tanzania

13. Stylosanthes guianensis

-

A. composite

Kenya

14. Stylosanthes guianensis

cv Cook

18189

Colombia

15. Stylosanthes hamata

cv Verano

14428

Venezuela

16. Stylosanthes scabra

cv Fitzroy

14431

-

17. Stylosanthes scabra

cv Seca

14430

-


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