Enhancing Soil Quality and Ecosystem Multifunctionality to Increase Maize Yield in Saline‐Alkali Soil: A Multisource Nitrogen Fertilization Strategy

ABSTRACT The positive effect of multisource nitrogen fertilization strategies on improving soil fertility and crop yield in saline‐alkali soil has been evaluated. However, the responses of soil quality and ecosystem functions to multisource nitrogen fertilization strategies, and their roles in regulating maize yields in saline‐alkali soils remain poorly understood. Therefore, a field experiment between 2021 and 2023 with an equal nitrogen input rate (260 kg N ha −1 ) was carried out to investigate the effects of nitrogen fertilization treatment (CK, mineral fertilizer; FS, 1:1 nitrogen from mineral fertilizer and straw; FM, 1:1 nitrogen from mineral fertilizer and manure; FSM, 1:1:1 nitrogen from mineral fertilizer, manure and straw) on soil quality index (SQI), ecosystem multifunctionality (EMF) and maize yield in saline‐alkali soil. Multisource nitrogen fertilization strategies increased SQI and EMF. The FSM treatment had the greatest benefits on soil quality and ecosystem functions at 0–10 cm topsoil due to the improvement of soil nutrients and saline‐alkali conditions. Soil organic carbon (SOC), total nitrogen (TN), available phosphorus (AP), pH, salt, sucrase, alkaline phosphatase, and microbial diversity had significant explanations for the variations in SQI and EMF, and were the important regulators of maize yields. Partial least squares path modeling further showed that multisource nitrogen fertilization strategies indirectly increased maize yield by improving SQI, which was related to the increases in SOC, TN, and AP contents. Meanwhile, dual mitigation of salinity‐alkalinity stress promoted an amelioration in EMF at 0–10 cm topsoil, contributing to increased maize yield. Additionally, FSM treatment also improved EMF of the 10–20 cm depth by increasing sucrase and bacterial diversity, indirectly contributing to increased maize yields. Overall, FSM treatment had the highest maize yield, with 24.6% and 28.7% increases relative to CK treatment in 2022 and 2023, respectively. Therefore, FSM treatment was a short‐term promising fertilization strategy to synchronously improve soil quality, functionality and productivity in saline‐alkali soil.