Optimizing straw incorporation depth as a plastic film alternative for sustainable maize production in semi-arid Eastern African Plateau

Abstract

Optimizing the depth of straw incorporation is a promising strategy to reduce reliance on plastic film while sustaining crop productivity in dryland agriculture; however, its integrative effects still remain poorly understood. A two-year field experiment was conducted on the semi-arid Eastern African Plateau (EAP) from 2024 to 2025 growing seasons. The treatments were designed as follows: conventional flat bare planting (CK-1), ridge-furrow full plastic film mulching (CK-2), and ridge-furrow straw incorporation (10 t ha-¹) at depths of 20 cm, 40 cm, and 60 cm (BR-20, BR-40, BR-60). The data indicated that full film mulching (CK-2) achieved the best crop growth performance. Among non-film treatments, straw incorporation at 40 cm (BR-40) consistently outperformed BR-20 and BR-60. A single straw application exerted evident residual effects across growing seasons and effectively alleviated water stress even under the low rainfall conditions. BR-40 yielded the highest grain output and water use efficiency among all straw-incorporation groups. Despite BR-20 achieving an optimal topsoil aggregate structure in the 0–20 cm layer, mere surface soil improvement failed to maximize crop productivity. The superior performance of BR-40 was consistent with a depth-matching mechanism, whereby straw placement at 40 cm improved soil hydrothermal conditions, C-N-P availability, and microbial activity within a soil layer likely to overlap with an active maize root zone, thereby promoting more effective coupling between residue-derived resource availability and crop uptake. Life cycle assessment indicated higher greenhouse gas emissions under film mulching, yet BR-40 had an average yield-scaled carbon emission of 175.53 kg CO₂e t−1 grain, realizing low-carbon production while reducing plastic dependence. Thus, root zone matching serves as the core mechanism driving straw incorporation efficiency, and BR-40 is a promising tillage strategy to stabilize maize yield and reduce plastic consumption in EAP.