Organic fertilizer made from food waste improves nitrogen mineralization by altering aggregate-associated microbial biomass and enzyme activities in Chinese paddy soil

Purpose Fertilization can affect soil microbial biomass and enzyme activities, as well as the nitrogen (N) transformation process. The effect of organic fertilizer derived from food waste on soil aggregate-associated N mineralization, microbial biomass, and enzyme activities remains unclear. The goals of this study were to investigate how the substitution of organic fertilizer from food waste to chemical N affects N mineralization, microbial biomass, and enzyme activities in paddy soil in Eastern China. Materials and methods We ran a 148-day rice pot experiment to see how organic N affected N mineralization, enzyme activity, and microbial biomass in soil aggregates when chemical N was replaced with organic N. In this experiment, four treatments were established: no fertilizer (CK), chemical fertilizer (CF), organic fertilizer (OF), and chemical fertilizer (50% N) plus organic fertilizer (50% N) (CO). Furthermore, bulk soil was classified into three aggregate-size fractions: > 2-mm large macro-aggregates, 2–0.25-mm small macro-aggregates, and 2-mm large macro-aggregates, and the values of mean weight diameter (MWD) and geometric mean diameter (GMD) of soil aggregates, (2) increased N mineralization accumulation and the average net N mineralization rate across soil aggregate fractions, and (3) increased microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) contents but decreased MBC/MBN ratio and increased the activities of urease, protease, and arylamidase. Furthermore, when comopared to soil aggregate-size fractions, fertilization explained the most variation in soil N mineralization, microbial biomass, and enzyme activities, and N mineralization in soil aggregates was driven by microbial biomass and enzyme activities. Conclusions Our findings indicated that organic fertilizer from food waste could increase soil N mineralization by regulating aggregate-associated microbial biomass and enzyme activities, providing a promising reference for food waste recycling, sustainable agricultural practices, and paddy soil N management.