Comparative performance of conservation agriculture and current smallholder farming practices in semi-arid Zimbabwe

Conservation agriculture is promoted in sub-Saharan Africa as a means to improve water use efficiency in an region with variable or poorly distributed rainfall. However, other environmental and social factors may contribute to the success or failure of implementation and practice. The purpose of this study was to compare on-farm conservation agriculture trials of cotton and sorghum with production practices currently in place. Two experiments at multiple locations were executed. The first involved an unfertilized cotton-sorghum rotation (three consecutive seasons), while the second examined cotton production with fertilizer provided on credit (two consecutive seasons). Mulches were produced on site to further emulate conditions present for farmers of the Mid-Zambezi valley. Farmers' perceptions of the technologies involved were also studied. CA was found to have no effect on cotton yields during the first two seasons, which received average or above average rainfall, but was found to be detrimental to yields during a third season of decreased rainfall. Additionally, greater run-off was found in on-farm CA trials in coarser soils than fine-textured soils. Farmers perceived that plowing was necessary to avoid soil crusting and compaction in drier years while CA was beneficial during wetter seasons. The authors site poor mulch coverage as a factor in this result and recommend legume intercropping as part of the solution.