Green manuring with balanced fertilization improves soil ecosystem multifunctionality by enhancing soil quality and enzyme activities in a smooth vetch-maize rotation system

Abstract

The use of green manure-cereal rotation has been shown to improve soil fertility, reduce land-use intensity, and mitigate adverse environmental effects. However, there have been few studies on the nutrient demands of the green manure itself and the effects of incorporating green manure with fertilizers on the soil quality index (SQI) and ecosystem multifunctionality (EMF). Therefore, this study analyzed soil parameters after different fertilization strategies in a smooth vetch-maize rotation system (i.e., optimized fertilization) based on the annual nutrient equivalence principle. The effects of five fertilization strategies, namely, fallow (CF), no fertilization (CK), nitrogen fertilizer (NF), phosphorus fertilizer (PF), and nitrogen-phosphorus fertilizer (NPF) on the SQI, microbial metabolic limitation, and EMF were evaluated to establish the optimal fertilization strategy for achieving sustainable agricultural development. The results showed that NPF increased the SQI in the smooth vetch-maize rotation system by 64.7–86.9 % compared to CF and by 22.0–48.8 % compared to CK. Fertilization alleviated microbial N limitation in the smooth-vetch phase, while the incorporation of green manure mitigated the microbial carbon (C) limitation in the maize phase. In addition, NF, PF, and NPF improved the soil EMF by 141.2–213.0 %, 124.0–226.7 %, and 199.9–247.4 %, respectively, in the smooth vetch-maize rotation system compared to CK. Notably, the improvement in soil EMF in the maize phase by NFP was 2.20–6.16 times that of PF. Random forest analysis showed that soil organic C, SQI, and the activities of enzymes involved in C and P acquisition were the main drivers of soil EMF. In addition, soil biochemical properties indirectly promoted soil EMF by increasing the activities of enzymes associated with C, N, and P acquisition as well as the SQI. In conclusion, these findings provide important guidance for a sustainable practice of reallocating part of the N and P fertilizer from the maize phase to the green manure phase to enhance soil quality and ecosystem multifunctionality in green manure-crop rotation systems.