Intermittent deep tillage increases soil quality and ecosystem multifunctionality in a Fluvo-aquic soil on the North China Plain

Intensive tillage operations often disrupt soil structure and accelerate the decomposition of organic matter, resulting in negative long-term impacts on soil health. Thus, identifying sustainable tillage practices is key for enhancing soil nutrient cycling and improving soil biochemical and biological properties. This study evaluated the effects of five tillage modes on soil quality and ecosystem multifunctionality (EMF) over three years in the North China Plain, where rotary tillage (RT) has degraded soil structure and hindered wheat yield increases. The treatments combined deep tillage (DT), RT, and shallow rotary tillage (SRT): (1) RT-RT-RT; (2) DT-RT-RT; (3) DT-RT-SRT; (4) DT-SRT-SRT; (5) DT-SRT-RT. Measurements included soil nutrients, microbial biomass carbon and nitrogen (C_mic and N_mic), enzyme activities, soil quality index (SQI), EMF, across 0-50 cm soil layers, as well as crop yields. We found that DT significantly improved various soil properties compared to continuous RT, thereby improving crop yield. In the first year of the cycle, DT increased available nitrogen (AN), available phosphorus (AP), potassium (K), C_mic, N_mic, enzyme activities, SQI, and EMF in the 20-40 cm soil layer. These improvements persisted in the following two years. Compared to RT-RT-RT, the largest increases in SQI (13.0%-22.2%) and EMF (11.2%-126.9%) were found in the 0-30 cm layer under DT-SRT-RT. Random forest analysis identified C_mic, AN, AP, C_org, and N_total as key EMF drivers. Meanwhile, wheat yield under DT-SRT-RT was 14.6% higher than under RT-RT-RT. These findings demonstrate that incorporating occasional DT enhances soil properties and crop yields, offering a sustainable strategy for cropping system management.