Subsoiling with straw return optimizes the maize root system and water productivity

Long-term conventional tillage exacerbates subsoil compaction, restricting root penetration and water and nutrient uptake. Although subsoiling is known to mitigate plough pan formation, the interactive effects of tillage and straw return on root system architecture (RSA) and water productivity (WP) in maize remain poorly understood. Based on a long-term field experiment, this study evaluated three tillage methods (plough tillage, PT; subsoiling tillage, ST; and rotary tillage, RT) and two straw management practices (no return and all straw return). We investigated effects of tillage and straw management on soil hydro-physical properties, maize RSA, and their consequent impacts on grain yield and WP. ST significantly reduced soil bulk density by 5.4 % and increased porosity by 6.4 % in the 0–40 cm soil compared to PT. The integration of subsoiling with straw return (STA) was particularly effective, enhancing subsoil fertility and promoting a deeper, coarser root system. STA increased root length density by 33 %, root weight density by 28 %, and root diameter by 41 % in the subsoil (40–60 cm soil). This optimized RSA improved access to deep soil water and nutrients, resulting in a 4.7 % increase in grain yield and a 3.8 % increase in WP compared to plough tillage with straw return. Subsoiling tillage-straw synergy reshapes RSA by alleviating mechanical impedance and enhancing subsoil fertility, offering a scalable strategy to improve crop resilience and resource efficiency.