Effects of reduced tillage with stubble remaining and nitrogen application on soil aggregation, soil organic carbon and grain yield in maize-wheat rotation system

Global climate change has threatened stable food production and soil carbon storage. Whether reduced tillage with stubble remaining (RTS) and nitrogen (N) application improve soil carbon storage and grain yield simultaneously and its impact on soil aggregation and soil organic carbon (SOC) fractions are still controversial. A 4-year experiment, including four treatments (CT, rotary tillage with stubble removing; RTS; CT+N; RTS+N), was conducted to explore the effects of RTS and N application on soil aggregates and soil organic carbon fractions, and answer whether the combination of RTS and N application can simultaneously improve soil carbon storage, crop yield and water productivity in summer maize-winter wheat rotation (MWR) system. The results showed that soil aggregates stability and SOC content of RTS+N increased by 34.9% and 9.2% due to increased proportion of large macroaggregate (LM, increased by 6.6%) and small macroaggregate (SM, increased by 6.9%), respectively, compared to CT+N at the end of the 4-year experiment. RTS significantly increased particular organic carbon (POC) content, and N application significantly increased the mineral-associated organic carbon (MAOC) content. Compared with CT, the POC, MAOC and POC/MAOC increased by 42.7%, 18.7% and 20.4% in bulk soil, increased by 19.6%, 8.5% and 10.5% in LM, increased by 33.2%, 14.2% and 17.1% in SM, increased by 25.9%, 16.8% and 8.3% in microaggregate, respectively, under RTS+N. Meanwhile, the mean grain yield, yield stability and water productivity of RTS+N increased by 33.7%, 206.4% and 43.4% for summer maize, and increased by 7.0%, 29.3% and 3.0% for winter wheat compared with CT+N. Therefore, reduced tillage with stubble remaining combined with nitrogen application in semi humid and drought-prone areas can simultaneously increase soil carbon storage, grain yield and water productivity in the MWR system.