Tinkering on the periphery: Labour burden not crop productivity increased under no-till planting basins on smallholder farms in Murehwa district, Zimbabwe

Abstract

No-till planting basins are promoted using seed and fertiliser inputs as incentives for their widespread uptake in Zimbabwe. The short term effects of planting basins on crop yields and labour requirements were evaluated in an on-farm experiment over two seasons (2009/2010 and 2010/2011) in Murehwa district, Zimbabwe. The experiment was established on clay (Luvisols) and sandy soils (Lixisols), in two field types; outfields (degraded) and homefields (better managed fields). Fields closest to homesteads (homefields) typically receive most nutrients and preferential management, and are more fertile than outlying fields (outfields), with implications for crop production and nutrient use efficiencies. The fertiliser sub-treatments consisted of (a) no fertiliser (control), (b) 60kg N+3tmanureha−1, (c) 60kgNha−1+10kgPha−1 (SSP) and (d) 60kgNha−1+20kgPha−1 (SSP). In addition, a socio-economic survey was carried out to understand the diversity in resource ownership among farmers and to explore whether there was a relationship with uptake of planting basins. Results showed that field type, nutrient application and season had a significant effect on crop yields (p<0.001); there was no significant effect of tillage practice. The largest maize grain yield of 5.6tha−1 was obtained with a combination of manure (3tha−1) and 60kgNha−1 under conventional tillage; the equivalent treatment under planting basins yielded 4.6tha−1 in the 2009–2010 season. Rainfall was poorly distributed in 2010–2011 season and the same treatment gave the largest grain yield of 1.6tha−1 under conventional tillage and 1.2tha−1 under no-till planting basins. Land preparation under conventional tillage required 6mandaysha−1 while planting basins construction required 76.5mandays’ha−1 for the clay soils and 51.5mandaysha−1 for the sandy soils. Weeding in planting basins required 40% more labour compared with conventional tillage (12mandaysha−1) due to greater weed densities associated with early years of no-tillage. Planting basins did not enhance moisture conservation in a the 2010–2011 season when rainfall was poorly distributed as shown by the smaller yields. The increased labour requirements suggested a major impediment to the uptake of planting basins even for farmers without livestock. Farmers differed greatly in resource ownership; four resource groups were identified based on land size, cattle ownership, labour availability and land utilisation. However, the practice of planting basins did not relate to resource ownership due to the incentives provided by the NGOs. Given that planting basins increased the labour burden but not crop yield, and that incentives cannot go on forever, widespread adoption by smallholder farmers seems unlikely.