Application of Straw-Decomposing Microbial Inoculant JN01 Modifies Soil Microbial Communities, Enhances Nutrient Availability, and Improves Growth in a Pot-Based Early- and Late-Season Rice System with Straw Retention

Abstract

Purpose: The temporal effectiveness of double-cropping rice systems in southern China is limited by the slow natural decomposition rate of straw, which represents a crucial ecological bottleneck. This study reports on two consecutive pot experiments—one conducted in the 2019 late-rice season (cultivar: Tianyou Huazhan) and the other in the 2020 early-rice season (cultivar: Taiyou 98)—to investigate how the straw-decomposing microbial inoculant JN01 influences rice growth, microbial community traits, and soil biochemical properties under equal-nutrient straw incorporation. Methods: This study conducted pot experiments from 2019 to 2020 using the self-developed straw-decomposing microbial agent JN01 (J) as the test material. Under the condition of equal nutrients, the experiment of conventional chemical fertilization (CK) and straw returning to field (SF) was set up. Results: The application of JN01 significantly boosted the soil’s capacity to transform nutrients, as indicated by the increases of 77.50% and 69.16% in soil alkali-hydrolyzable nitrogen throughout the tillering and heading stages, respectively. It aided in the conversion of organic phosphorus in straw to effective phosphorus in soil, significantly increasing soil fungi (241.87%) and actinobacteria (93.10%) at maturity, optimizing the fungi/bacteria ratio, promoting the microbial community transition from bacterial to fungal dominance, improving soil cellulose degradation ability, and improving nitrogen transformation capability. Conclusions: This pot study clarifies the regulating mechanism of JN01 on soil microenvironment and offers theoretical support for the use of straw resources in southern double-cropping rice systems. Under controlled pot circumstances, the inoculant demonstrated potential to optimize straw-related nutrient transformation and coordinate rice yield components; nevertheless, field verification is necessary for large-scale practical implementation.