The crucial roles of citrus branch compost in enhancing soil nutrients, optimizing microbial community structure, and improving fruit quality over its raw materials

Aims Fruit harvesting and branch pruning are key drivers of soil acidification in citrus orchards. Compost fermented from citrus waste and acid soil amendments may effectively mitigate soil acidification. At present, limited research has been conducted on the effects of compost and its raw materials on soil amelioration and fruit quality enhancement. Methods We applied chemical fertilizers (CK), citrus branch compost (CC) and its raw materials including crushed branches (CI), biochar (CB) and microbial inoculant (CM) to ameliorate acidified soil, analyzed soil quality, microbial community, citrus yield and quality, as well as their relationships. Results Applying compost enhanced the soil amelioration effect of raw materials, CC significantly increased soil pH, organic carbonfractions, and available nutrient concentrations, particularly the N, P, K, Ca, Mg, and B. Compared with CK,CC increased soil quality index and yield by 170.8% and 34.6% respectively in 2023. Furthermore, CC, CB, and CI significantly decreased the diversity and abundance of bacterial community. Notably, CC increased the number of biomarkers and gene abundance of C fixation, P cycling, and N mineralization, decreased the gene abundance of C degradation and nitrification. Conclusions A two-year trial demonstrated that compost application enhanced soil carbon, nitrogen, and phosphorus cycling functions and optimized microbial community structure, thereby improving soil quality and productivity levels in acidified citrus orchards. These findings underscore the advantages of composting lignocellulosic waste as a soil amendment and green, sustainable development strategy.