Influence of basin-based conservation agriculture on selected soil quality parameters under smallholder farming in Zimbabwe

The research was carried out to determine the effect of basin-based conservation agriculture (CA) on selected soil quality parameters. Paired plots (0.01ha) of CA and conventional tillage based on the animal-drawn mouldboard plough (CONV) were established between 2004 and 2007 on farm fields on soils with either low (12-18% - sandy loams and sandy clay loams) or high clay levels (>18-46% - sandy clays and clays) as part of an ongoing project promoting CA in six districts in the smallholder farming areas of Zimbabwe. We hypothesized that CA would improve soil organic carbon (SOC), bulk density, aggregate stability, soil moisture retention and infiltration rate. Soil samples for SOC and aggregate stability were taken from 0 to 15cm depth and for bulk density and soil moisture retention from 0 to 5, 5 to 10 and 10 to 15cm depths in 2011 from maize plots. Larger SOC contents, SOC stocks and improved aggregate stability, decreased bulk density, increased pore volume and moisture retention were observed in CA treatments. Results were consistent with the hypothesis, and we conclude that CA improves soil quality under smallholder farming. Benefits were, however, greater in high clay soils, which is relevant to the targeting of practices on smallholder farming areas of sub-Saharan Africa.