Conservation farming strategies in East and Southern Africa: Yields and rain water productivity from on-farm action research

Conservation farming for smallholders has been primarily applied and researched in humid and sub-humid regions, where it has shown significant improvements in agricultural productivity. In these regions, water generally is not a limiting constraint on plant growth and CF methods emphasize no-till or minimal tillage and mulch cover. However, in semi-arid and arid regions, rainfall variability and scarcity are significant constraints to productivity, the potential for attaining substantial mulch coverage is low, and no-tillage contributes to a soil crust that further decreases water infiltration. This study develops a CF approach focused on non-inversion tillage methods, adapted to the needs of arid and semi-arid agriculture. Using a participatory approach with local farmers and extension agents, trials comparing CF and conventional farming, with and without fertilization, were conducted in Tanzania, Kenya, Ethiopia, and Zambia. Neither CF tillage methods nor fertilization alone showed a significant improvement, but CF methods with fertilization improved both yields and water productivity (amount of water required per unit of crop). The improvements of CF over conventional farming methods were especially pronounced in seasons with the lowest rainfall, suggesting that CF could be a valuable water harvesting method in water-scarce regions.