Long-term conservation agriculture improves water properties and crop productivity in a Lixisol

Abstract Climate variability increasingly affects smallholder farmers in southern Africa. Conservation Agriculture (CA) practices have been proposed to improve the resilience of farming systems against the adversities of climate, specifically moisture stress. However, lack of detailed field data on soil water and chemical dynamics leads to over-reliance on simulation models without concrete evidence and ground-truthing of results. Here, we test the effects of different CA and conventional tillage (CP) practices on soil moisture content and water infiltration rate over a 14-year trial period. We also report soil chemical properties measured over 10 years from 0 to 30 cm soil depth. As study object, we used a CA long-term trial at the Monze Farmer Training Centre in Southern Zambia as it included different cropping systems and had parallel infiltration, soil moisture, soil chemical and crop yield measurements. Our results showed significant differences in average soil moisture in the first 60 cm among the cropping systems in different years with the basins plus mulching system having highest moisture content in most of the years. The interaction of cropping systems and years significantly affected water infiltration rate with highest final infiltration rates averaging 48.5 mm h−1 in the CA-based systems and the lowest in CP which averaged 12.6 mm h−1. Soil chemical properties did not significantly differ across the systems but across seasons and depths or their interaction. For crop yield, a direct seeded maize-cotton rotation (DS-MC) consistently had the highest grain yields across most of the years as compared to the CP practice. Maize grain yield significantly differed among the years with a strong influence from the rainfall. Regression analysis revealed significant effect of seasonal rainfall on both soil moisture content and crop yield. The DS-MC system showed high responses of grain yield to rainfall and moisture. This was caused by increased available water and a greater buffering capacity against water stress in the cotton rotation. Systems that conserve moisture, increase infiltration and yield are of paramount importance in environments of variable rainfall. CA-based systems may therefore have the potential to buffer the effects of climate variability and may provide greater resilience.