Tillage and Straw Returning Modulate Aggregate Stability, Root Metabolism, and Soil Biotic Interactions for Ecosystem Productivity

Against the dual pressures of global food security and climate change, sustainable management of intensive agricultural ecosystems has emerged as a core issue in balancing crop production and ecological stability. Tillage practices and straw returning, as key agronomic measures for regulating soil health and crop productivity, are widely recognized as critical approaches to enhance soil organic carbon sequestration, improve soil structure, and strengthen nutrient cycling. However, most existing studies focus on the macro-scale effects of single practices, and there remains a significant knowledge gap in understanding how tillage and straw returning drive ecosystem productivity by modulating micro-scale processes at the root-soil-microbe interface. 

To address this knowledge gap, we conducted a long-term field experiment in the Huang-Huai-Hai Plain, with three tillage regimes (plow tillage, subsoiling, rotary tillage) crossed with two straw management strategies (straw returning and no straw returning). We systematically analyzed soil physicochemical properties, root morphological and metabolic characteristics, and annual crop yields (wheat and maize) to unravel the regulatory mechanisms of tillage and straw returning on root-soil-microbe interactions and their linkage to ecosystem productivity.

Results showed that subsoiling and rotary tillage significantly improved soil water storage compared to plow tillage, with subsoiling enhancing water availability more effectively. Straw returning combined with subsoiling increased soil organic carbon (SOC) and total nitrogen (TN) storage in the 0-40 cm layer, with SOC increasing by 41.7% and TN by 23.6% compared to baseline measurements in 2002. Tillage practices reshaped soil aggregate stability: subsoiling and rotary tillage increased the proportion of water-stable aggregates (>0.25 mm) in the 0-20 cm layer, providing favorable habitats for microbial communities. Root metabolic analysis revealed that plow tillage promoted root elongation and smooth surface morphology, while rotary tillage resulted in thicker roots with fewer root hairs. Differential enrichment of key metabolic pathways, including ATP-binding cassette transporters, salicylic acid signaling, and purine metabolism, indicated that tillage practices reprogrammed root-microbe communication at the rhizosphere interface.

Subsoiling with straw returning achieved the highest grain yield (8.28 t hm⁻² for wheat and 11.83 t hm⁻² for maize), which was attributed to improved soil structure, enhanced nutrient cycling, and synergistic root-soil-microbe interactions. This study demonstrates that tillage and straw returning regulate soil interface processes, effectively bridging micro-scale root metabolism and aggregate dynamics to macro-scale ecosystem productivity. These findings provide a robust scientific basis for sustainable farming management in the Huang-Huai-Hai region and highlight the critical role of rhizosphere plant-microbial interactions in scaling ecological processes from soil habitats to ecosystem functions.