Less effort for extra benefit? Evaluating the impact of conservation agriculture on resource saving and returns across regions and farming systems in Zambia.

Abstract

Conservation Agriculture (CA) is claimed to be a sustainable farming approach with potential benefits for smallholder farmers. Although evidence exists on the yield impacts of CA, its contribution to economic sustainability remains underexplored. We study how context-specific CA practices in maize (with annual soybean rotation and residue retention) in Zambia, including ox-ripping (Southern and Central), tractor-ripping (Western), and basins (Eastern), affect cost-effectiveness and resilience of returns to dry spells, compared to conventional practices. Using data from 90 on-farm trials across five seasons (2016/17 to 2020/21) and over 530 plot observations, we applied mixed-effects models to estimate treatment effects, finding that ox- and tractor-ripping reduced resource use, while application of basins increased resource use. Net benefits for CA (ox-ripping) were higher by $188/ha and $270/ha in Central and Southern regions, respectively. For basins and tractor ripping, net benefits were higher by $358/ha and $420/ha. CA improved marginal returns to inputs, reduced financial risk, and enhanced resilience to dry spells, though effectiveness varied across practices. Benefits from CA increased in later years due to resource savings and yield advantages in ripping and solely from yield advantages in basins. Our findings highlight the need for site-specific recommendations and adaptation of CA to maximize sustainability benefits in Zambia.