Straw Return and Tillage Management Strategies Reshape Soil Functionality and Enhance Maize Productivity

Abstract

Long-term intensive maize cultivation under subtropical double-cropping systems has resulted in increased compaction and declining fertility. Although conservation tillage and straw return have been widely adopted to improve soil quality, their combined effects on soil physicochemical properties, biological functions across the 0–40 cm soil profile, and maize yield performance remain poorly understood. A six-year field experiment was conducted to evaluate the combined effects of straw management (CK: conventional practice; SR: straw return) and tillage systems (NT: no-tillage; RT: rotary tillage; SS: subsoiling; SS+RT: subsoiling combined with rotary tillage) on the soil physicochemical properties, enzyme activities, microbial biomass carbon (MBC), and maize yield. The integrated SR+SS+RT treatment significantly reduced soil bulk density by 2.57% while increasing soil water content by up to 12.20%. Compared with traditional seeding, straw return increased soil organic carbon (SOC) and total nitrogen (TN) by 8.38% and 13.52%, respectively. Enhanced soil biological activity was also evident, with MBC increasing by 7.70% and substantial enhancements in soil enzyme activities, particularly cellulase (+12.08%) and acid phosphatase (+15.80%). Moreover, the combined SS+RT treatment was associated with a more even vertical distribution of carbon and nitrogen, thereby alleviating nutrient stratification within the soil profile. The grain yield was strongly and positively correlated with sucrase (r = 0.773) and cellulase (r = 0.738) activities, indicating significant associations between selected soil biological indicators and maize yields. Consequently, the SR+SS+RT treatment produced the highest spring and autumn grain yield (9405 and 8696 kg ha−1), compared with SR+NT. Integrating straw return with subsoiling and rotary tillage provides a synergistic strategy for alleviating soil compaction, improving soil physicochemical and biological properties throughout the root zone, and enhancing maize productivity. This integrated management practice offers a sustainable approach for restoring soil fertility and maintaining high crop yields in intensive subtropical agricultural systems.