Tropical Grasslands (2007) Volume 41, 84–91 84 Utilisation of ley legumes as livestock feed in Zimbabwe C. MAPIYE1, M. MWALE1, J.F. MUPANGWA1, subsistence basis and is severely limited by, inter P. H. MUGABE2, X. POSHIWA3 AND alia, a shortage of inputs, recurrent droughts, lack N. CHIKUMBA3 of draught power and inherent poor soil fertility. 1 Department of Agriculture, Bindura University Ruminant livestock are grazed largely on native of Science Education, Bindura pasture, that is usually in short supply and of poor 2 Department of Animal Science, University of nutritive value during the prolonged dry season Zimbabwe, Mount Pleasant, Harare (Muchadeyi 1998). Crop stovers make up the 3 Grasslands Research Station, Marondera, bulk of livestock feed during this time. Increasing Zimbabwe rural resettlement has led to a rapid and general decline in the areas of grazing lands available to smallholder farmers (Nyoka et al. 2004). There- Abstract fore, the need to intensify and optimise both live- stock and crop production is the major challenge Rural communities in Zimbabwe rely heavily on being faced by smallholder farmers. integration between crop and livestock activities Technologies aiming at increasing productivity at farm level. This form of agriculture is under of crops and livestock, while enhancing well-being increasing pressure because of land degradation, of farmers and minimising resource degradation, recurrent droughts and increasing human pop- must be developed. One such technology is cul- ulation. Tech nologies aimed at achieving a bal- tivation of ley legumes, which has the potential ance, whereby crop and livestock can increase in to improve sustainability and productivity of the productivity, while resource degradation is min- smallholder mixed-farming systems by providing imised, must be developed. Cultivation of ley high-quality feed that can boost crop and live- legumes has the potential to improve the sustain- stock production in Zimbabwe. By providing soil ability and produc tivity of the smallholder mixed- cover, ley legumes reduce soil erosion and runoff, farming systems by providing high-quality feed improve soil organic matter content and compete that can boost crop and livestock production. This with weeds (Foppes 1993). Successful utilisa- paper reviews selection, utilisation and adoption tion of ley legumes depends on the selection of of major ley legumes, and highlights research locally adapted (climate and edaphic) species that gaps, constraints and opportunities for ley legume produce reasonable quantities of quality forage. research in Zimbabwe. This paper reviews research on screening, eval- uation, agronomy, conservation, utilisation and adoption of major ley legumes for the past two Introduction decades and highlights research gaps, constraints to and opportunities for ley legume research in Rural communities in Zimbabwe and Africa, Zimbabwe. in general, rely heavily for their survival on integrated crop and livestock activities at farm level. This form of agriculture is under Screening and evaluation of ley legumes increasing pressure because of land degradation and expanding human population (Francis et al. Screening and evaluation research in Zimbabwe 1997). Crop production is most commonly on a during the past two decades aimed to identify new ley legume varieties that could improve Correspondence: C. Mapiye, Department of Agricul- productivity in crop-livestock farming systems. ture, Bindura University of Science Education, P Bag 1020, Researchers concentrated on identifying ley Bindura, Zimbabwe. E-mail: [email protected] 006_07_2_Mapiye.indd6_07_2_Mapiye.indd 8844 44/6/07/6/07 55:19:34:19:34 PPMM Utilisation of ley legumes in Zimbabwe 85 legumes that would be ideal for cereal-legume digestibility, in vivo degradability and effects on intercropping systems. Substantial evidence milk yield, reproduction and growth rates. has been accumulated to show that ley farming Grasslands Research Station in Marondera is both feasible and potentially very benefi cial identifi ed Lablab purpureus cvv. Rongai and for Zimbabwe (Muchadeyi 1998; Jiri 2003; Highworth and ILCA Acc. 11642 as appropriate Maasdorp et al. 2004). However, there are few legumes for intercropping in the high- potential examples of legume-based ley farming systems agro-ecological communal areas of Zimbabwe that have been readily adopted by farmers in (Manyawu et al. 1993; Manyawu 1998). Grown Zimbabwe. Three species, namely: Lablab pur- alone, Rongai and Jhansi gave the highest forage pureus (lablab), Mucuna pruriens (velvet bean) yields (5.9 and 5.85 t/ha DM) and were ideal and Vigna unguiculata (cowpea), have been suc- for use as annual or bi-annual fodder banks cessfully established, mainly to feed dairy cattle (Manyawu et al. 1993; Jingura et al. 2001). How- under different climatic and management con- ever, Highworth produced the highest grain and ditions (Majee and Chikumba 1995; Muchadeyi forage yields in semi-arid agro-ecological zones 1998; Nyoka et al. 2004) (Table 1). Crotalaria of Zimbabwe (Mutisi et al. 1994). In order to juncea (sunnhemp), Glycine max (soybean) realise full benefi ts from lablab, there is a need to Vicia sativa (vetch), Pisum sativum (pea) and control diseases and pests (aphids and cutworms) Lupinus albus (white lupin) have been used to (Manyawu et al. 1993). Therefore, it is important a lesser extent, and research on these species to select lablab accessions for resistance to not in Zimbabwe is limited. Despite little attention only bacterial and fungal diseases but also pest being given to the afore-mentioned species, they attack. have shown a lot of potential in other tropical Preliminary fi ndings from on-farm research in countries (Muchadeyi 1998). Hence, there is need Chihota communal lands and Makaholi Research to broaden the research agenda to include selec- Station indicated that Mucuna pruriens and Vigna tion of these species, especially in smallholder unguiculata produced high yields in warmer and areas of low agricultural potential. medium-high rainfall areas with poor soil fer- The following attributes were used for tility in Zimbabwe (Majee and Chikumba 1995; screen ing and evaluation: ease of establishment Jiri 2003) (Table 1). Vigna unguiculata accession (high seed-production potential); ease of re- 121688 gave the highest forage dry matter yield establishment (high soil-seed-reserve potential, (2.38 t/ha) after one season’s growth in studies hardseededness); longevity; ease of control during conducted in Hwedza (Manyawu 1998; Muring- the crop phase; high nitrogen-fi xation potential (a weni et al. 2004). function of plant productivity and soil adaptation); Selection of tropical legumes for leys has con- drought tolerance; tolerance of diseases and pests; centrated largely on the three above-mentioned chemical composition; and animal production (a species rather than on systematic screening of function of plant production and nutritive value) large germplasm collections for suitability as (Clatworthy and Madakadze 1988; Mutisi et al. leys. Thus, it is suggested that screening and 1994). The selection criteria should be extended evaluation programs should be expanded to to include important parameters such as: nutrient include accessions/cultivars of legumes that are uptake effi ciency; species complementarity (asso- more effi cient and require fewer establishment ciative ability); economics of ley legume produc- and management inputs than existing species and tion; and animal production factors such as in vivo cultivars. Different germplasm options should Table 1. Climatic and edaphic attributes of common ley legume species and cultivars used in crop-livestock systems in Zimbabwe. Species Common name Common cultivars Soil type Rainfall (mm) Temperature (°C) Lablab purpureus Lablab Rongai, Highworth Deep sands to heavy clays <500 18–30 and Jhansi Mucuna pruriens Velvet bean Utilis Well drained, medium to <600 19–27 high fertility soils Vigna unguiculata Cowpea — Sandy to heavy soils <500 25–35 Source: Majee and Chikumba 1995; Muchadeyi 1998; Nyoka et al. 2004. 006_07_2_Mapiye.indd6_07_2_Mapiye.indd 8855 44/6/07/6/07 55:19:34:19:34 PPMM 86 C. Mapiye et al. be considered, including those developed for that it is best to harvest lablab once (May–June) different environments in terms of soil, climate for optimum herbage yield (Manyawu 1998). and production systems. In addition to a wider Results of intercropping research over the past species range, evaluation of legumes should be two decades favoured the simultaneous planting based on an intra-specifi c variability as broad as of ley legumes (velvet bean, cowpea and lablab) possible. with maize, napier/bana grass, millet or sorghum, Longevity of the species is another important except where the legume can be too vigorous for consideration. Although the concept of a short- the companion crop (Muchadeyi 1998; Nyoka term ley almost implies that the respective legume et al. 2004). Intercropping with legumes increased is short-lived, persistent legume banks or mixed herbage yield by 40–60%, although the cereal pastures with high legume content should also be grain yields were depressed by up to 20%. When considered. In comparison with annuals, longer- velvet bean is mixed with grasses or cereals, the lived legumes will have an important advantage yield of cereals is naturally depressed to below during the dry season. In this context, a potential 10 t/ha. However, the total yields depend on plant option that should be researched is that of mix-