Improving soil quality and wheat yield through diversified crop rotations in the North China Plain

Continuous wheat-maize rotation (WM) has caused soil degradation and yield reduction in the North China Plain (NCP). To explore sustainable crop systems, four diversified rotations were conducted over three 2-year cycles from 2015 to 2021: (i) Maize-* WM, spring maize-WM; (ii) Millet-* WM, spring millet-WM; (iii) Peanut-* WM, spring peanut-WM; and (iv) Soybean-* WM, spring soybean-WM. During the third rotation cycle (2019-2021), we investigated variations in soil nutrients and enzyme activities in the 0-40 cm layer throughout wheat growth stages (sowing, regreening, jointing, anthesis, and maturity stage) among different rotations and assessed their impacts on wheat production and soil quality. Results indicate that diversified 2-year rotations reduced nitrogen loss by lowering soil mineral nitrogen during wheat growth stages compared to WM. The heightened activities of nutrient-acquisition (carbon, nitrogen, and phosphorus) enzymes in diversified 2-year rotations contributed to an improvement in soil quality index (SQI) by 4.1 %-8.7 % ( P < 0.05) and 9.8 %-18.9 % in the 0-20 cm and 20-40 cm soil layers, respectively, compared to WM. However, the SQI in the 0-20 cm was significantly lower in Peanut-* WM compared to Soybean-* WM. Diversified 2-year rotations also increased wheat yield by 45.7 %66.4 % ( P < 0.05) compared to WM. The stoichiometry of enzymes revealed that diversified 2-year rotations exacerbated soil microbial carbon limitation during wheat growth stages. This issue, however, was effectively addressed by increasing dissolved organic carbon to fulfill the crop's carbon requirements. The findings highlight the potential of incorporating diverse spring crop species, whether leguminous or non-leguminous, into wheatmaize rotation as a promising crop pattern to enhance soil quality and increase wheat yield in the NCP.