Understanding the current role of legumes and their significance for Biological Nitrogen Fixation (BNF) in smallholder farming systems of Zimbabwe

Submitted by marcel.lubbers on
Brenda T. Manenji
Zimbabwe, farming systems, farming system, farm types, typology, resource endowment, cropping system, farm characterization, farm characterisation, productivity, soil



One of the major challenges faced by small holder farmers in Southern Africa and Zimbabwe in particular is poor soil fertility. Use of synthetic fertilizers is limited due to its high costs and this has led to a drastic decrease in productivity. Alternatively, farmers can incorporate legumes in their cropping systems thus improving soil fertility through biological nitrogen fixation. However, legumes are still grown at a very low scale. In order to understand the cropping patterns of legumes relative to cereals a study was carried out in Murehwa and Mudzi districts. The two areas are located in two contrasting agro ecological regions. In each district, twenty farmers were selected and based on their resource endowment, they were divided into four resource groups (RG); RG1 being the richest and RG4 being the poorest farmers. Data was collected through structured questionnaires. Comparisons of legume productivity in the different resource groups were made by evaluating areas under legumes and yields attained. These results were compared with those for maize, the major cereal crop in Zimbabwe. Constraints faced by farmers in legume production were also evaluated. In the research, analysis was also made of the agronomic practices used by farmers in different RGs to grow legumes compared to maize. The agronomic practices included labour and input allocation to different fields within the farms and legume residue use. Soil structure and fertility status for the different fields of the target farmers were determined. Total nitrogen content in different legumes was also analyzed. The marketing of the different legumes was evaluated. Results indicated that groundnut, cowpea and Bambara nut were commonly grown in the two districts while common bean and soybean were exclusively grown in Murehwa. Larger proportions of land, fertilizers and labour were allocated to maize relative to legumes. Mudzi had average areas of 0.89 ha per farm under maize, 0.09 ha per farm under Bambara nut and 0.25 ha per farm under groundnut while Murehwa had on average 1.84 ha per farm, 0.19 ha per farm and 0.15 ha per farm under the respective crops. Higher yields of both legumes and cereals were attained in Murehwa compared to Mudzi. Cereals were mostly grown in the fertile home fields while legumes were grown in mid and outfields by most farmers. The majority of the farmers applied more fertilizers to the home fields while outfields are given less attention. There were no significant differences in the quantities of fertilizers used by farmers in different resource groups in both districts. Farmers indicated that they get more profits from selling legumes than from cereals. There were no significant differences in soil structure among the different farms in the different resource groups within each district. There were no significant differences in pH, soil available N, Ca, organic carbon between the different plot types. However, the proportions of most cations decreased in the pattern; Plot type 1 >Plot type 2 > Plot type 3. There is need to promote optimal agronomic practices so as increase productivity of legumes by smallholder farmers in the two districts. Differences in input resource management on the various fields within a farm result in variation in fertility and hence differences in productivity within the fields.