Conservation agriculture enhances productivity, nutrient use efficiency, and environmental sustainability in rice–maize rotations

Conservation agriculture (CA), which emphasizes minimal soil disturbance, residue retention, and diversified rotations, enhances sustainability but faces adoption barriers among smallholders due to uncertainties in nutrient use efficiency (NUE). A three-year field study across various agroecological zones (AEZ) assessed NUE and greenhouse gas (GHG) emissions in rice‒maize rotations under CA (strip tillage, 30% residue retention) versus traditional agriculture (TA; conventional tillage, no residues). Both systems received full NPKZn fertilization and individual nutrient omission treatments. GHG emissions were measured using the Climate Change, Agriculture and Food Security Mitigation Options Tool (CCAFS-MOT). The maize and rice grain yields under CA were consistently approximately 5% higher than those under TA, with no significant tillage × fertilizer interaction. The partial factor productivity (PFP) increased under CA because of nutrient release from retained residues, while the agronomic efficiency of nutrients (AEn) remained unchanged. CA reduced the total global warming potential (GWP) by 20% in maize and 26% in rice, and the emission intensity (EI) by 26% and 30%, respectively, mainly through increased carbon sequestration, reduced diesel use, and higher yields. This study indicates that current fertilizer recommendations remain suitable under CA, while residue retention supplies additional nutrients, providing a simple, cost-effective strategy to enhance productivity and promote CA among smallholder farmers.