Tropical forage and ley-legume technology for sustainable grazing and cropping systems in southern Africa

South Africa, Zimbabwe

Dr Bruce Pengelly
Phone: 07 3214 2348
Fax: 07 3214 2308
Email: Bruce.Pengelly@csiro.au

• Department of Agricultural Technical and Extension Services, Zimbabwe
• University of the North, South Africa
• Towoomba Research Station, South Africa
• Queensland Department of Primary Industries, Australia
• University of Zimbabwe, Zimbabwe
• Department of Research and Specialist Services, Zimbabwe
• Agricultural Research Council, South Africa

$1,164,970

01/01/1999 - 31/12/2002

01/01/2003 - 31/12/2003

Dr Bill Winter

In much of southern Africa, cropping and livestock enterprises suffer because of land degradation. There is a widespread deficiency in soil nitrogen, communally grazed areas have often lost the better grass species and annuals have replaced them, and thorny trees and shrubs have invaded some grazing lands. The poor quality and quantity of forage restrict animal production. There is substantial economic impact in both cropping and livestock enterprises from the nitrogen (and hence protein) deficiency.
With increases in human population there has been in an increase in demand for arable land but, despite the soil nutrient deficiencies, most farmers have not adopted fertilisers. When crop yields decline the area of land used for cropping expands in an effort to produce more food. This project sought to improve soil nutrient status and reduce soil erosion by using more appropriate forage plants, with the intention of developing sustainable grazing systems for the communities concerned.

The overall aim was to develop suitable sustainable farming systems and practices to reverse the deterioration in communal grazing land and arable land in southern Africa.

The project team carried out the research in cooperation with local farmers, thereby enhancing the chance of adoption of the new technology and introduced plants. The project was managed through principles of Participative Action Research, with benchmarking to ensure continuous improvement in practices and performance throughout the life of the project and beyond.
The work was divided into five subprojects. The first involved workshops and discussions with rural communities to define the problems and priorities of the farmers and the nature of their production systems. In the second subproject the researchers benchmarked farming systems in selected communities, to provide a baseline from which to measure the impact of the project.
The third subproject consisted of on-farm research. The team identified legumes suitable for rotation with crops or inter-sown with them, in order to improve the nitrogen status of soils. Germplasm from CSIRO Tropical Agriculture was introduced into South Africa and Zimbabwe. The project team also evaluated management strategies for cropping systems, dairy farming and degraded grasslands. A particular focus was the selection of forage plants for introduction into the degraded grasslands of northern South Africa, Zimbabwe and Mozambique to improve animal production systems.
The fourth subproject continued the on-farm research by examining the effect of forage technology on cereal and livestock production. This involved recording the yields and the quality of legume and maize, as well as measuring the concentration of nitrogen and organic matter in soils. The team also conducted experiments to test the efficacy of phosphorus fertiliser.
Subproject 5 focused on socioeconomic factors. Researchers measured the extent of adoption of new techniques by farmers and the degree of involvement of the community. The project also examined promising legumes to identify species suited to the southern speargrass region of southeast Queensland.

Evaluation of germplasm identified well-adapted forage legumes to boost crop production systems of Southern Africa and augment native pasture systems in Australia, South Africa and Zimbabwe. The research gained new insights into forage legume adaptation and productivity, soil nitrogen and soil organic matter dynamics, and the impact of forage or dual-purpose legumes on cereal and animal production. In many instances Zimbabwe smallholder farmers, especially those focused on semi-intensive dairy and beef fattening enterprises, started to adopt the recommended methods.
The relationship between the Zimbabwe research team and the farmers greatly contributed to the rapid acceptance and uptake of legumes into the farming systems in the area. Field trials over the first two years revealed that the legumes first trialled in Australia grew with similar success in Zimbabwe, which helped narrow down recommendations for the best legumes to plant. The farmers themselves started to produce seeds of their favourite lines, for their own use and to sell or donate to neighbours.
Most smallholder farmers in Limpopo Province in South Africa focus on production of maize and other crops and have little significant animal production in their farming system. Low nitrogen is a major constraint in most of these cropping systems. The project tested various rates and timings of nitrogen fertilizer application, and sought opportunities for better integration of appropriate legumes into these systems. The project found that N fertilizer, or significant N input from legumes, were needed to obtain grain yields in excess of 1 t/ha. Some dual-purpose legumes have special attraction in these systems, providing human food as a vegetable or pulse crop and feeds for the small number of animals present.
In other experiments a number of cowpea cultivars were successfully intercropped with maize in alternate single 90-cm rows without sacrificing grain yields of either cowpea or maize. Trials revealed that decline in maize yield could be avoided by sowing legumes after maize establishment - in the case of lablab a 28-day delay avoided maize yield depression.
In Zimbabwe and southeast Queensland velvet bean and lablab both provided considerable benefits to farmers via increases to subsequent maize yields, especially if the legumes were incorporated as a green manure. Removal of the legumes for animal feed reduced the benefits to crops, but the legume hay then provided a viable substitute for high-cost feed concentrates which are typically fed by dairy and beef-finishing farmers. In dairy production systems gross margins were 120% higher with velvet bean-based rations and 76% higher with lablab-based diets than those using commercial rations. These results induced a large number of farmers in Zimbabwe to switch to these legume-based feed systems.
Analysis of the adoption of velvet bean in the communities in Zimbabwe showed that for some farmers its use as a feed source was constrained by labour availability but that the most resource-poor farmers saw velvet bean seed production as a new opportunity for cash income..
Experimental and modelling studies in southeast Queensland showed that annual legumes used as a multiple-year pasture phase of a rotation increased soil nitrate levels by up to 100 kg/N/ha. This led to increased yields of subsequent sorghum crops for up to three years, so that sorghum yields in excess of 3 tonnes/ha could be expected in this region of Queensland in 80% of years. Beef production from the legume-based pasture was up to 0.86 kg/head/day and 200 kg/ha/year.
The project provided formal and informal training of research and extension professionals and initiated new career opportunities for several of the African project team members. Project activities exposed all team members to a wider range of biophysical and social issues and environments, developed better understanding of the farming systems, and formed a basis for long-standing professional relationships.