Straw Returning With No‐Tillage Alleviates Microbial Metabolic Carbon Limitation and Improves Soil Multifunctionality in the Northeast Plain

ABSTRACT Straw returning has been broadly recognized as an agronomic strategy to manage soil quality and has great potential to enhance soil fertility. However, soil microbial metabolism and ecosystem multifunctionality in response to various straw returning strategies in the black soil remain poorly understood. Here, a 5‐year field trial was conducted to discover the effects of four straw management strategies (SIDP, straw incorporation by deep ploughing; SIRT, straw incorporation by rotary tillage; SM, straw mulching with no‐tillage; SR, straw removal with no‐tillage) on the soil biochemical properties in the topsoil (0–20 cm) and subsoil (20–40 cm). SM maintained soil fertility, as evidenced by increases in soil organic carbon, total nitrogen, dissolved organic carbon, and nitrogen, compared with SIDP and SR. Additionally, this strategy promoted microbial biomass. It also stimulated nutrient cycling through increased enzyme activity. Meanwhile, SM alleviated microbial carbon limitation and promoted the shift of soil microbial metabolism from P limitation to N limitation compared to other treatments, especially in the subsoil. This shift was directly influenced by soil available nutrients and microbial properties, as revealed by the partial least‐squares path modeling analysis. Besides, SM promoted soil ecosystem multifunctionality by 29%–37% in both soil layers compared to SIDP and SR. Random forest analysis indicated that soil microbial biomass and activity were the main drivers of this increase in multifunctionality. In conclusion, straw returning with no‐tillage is an optimal straw management strategy for improving the soil biochemical properties, stimulating enzyme activities, alleviating microbial carbon limitation, and increasing ecosystem multifunctionality in the Northeast Plain.