Optimizing soil quality and rhizosphere ecology to enhance Annona squamosa yield and quality through water-fertilizer-mulching synergy

To address the decline in Annona squamosa yield and quality in Yunnan Province resulting from inadequate irrigation and excessive fertilization, this study was focused on the interaction mechanism between rhizosphere micro ecology and fruit production of Annona squamosa, aiming to explore schemes to improve soil health and realize sustainable management of fruit trees. Based on field experiments conducted in 2022-2023, a three-factor, three-level orthogonal experimental design was developed (Irrigation: W1/W2/W3 for field water holding capacity is 55/75/85%; fertilization: F1/F2/F3 is 1666/2083/2500 kg·ha-1; mulching: A1/A2/A3 is no mulching/grass/straw mulching). The results indicated that irrigation and fertilization methods combined with mulching significantly influenced soil nutrient levels, and W2F3A1 treatment showed higher nutrient content at multiple growth stages. The activity of soil urease, phosphatase and catalase in soil reached its highest level under the W2F2A3 method. Analysis of microbial communities revealed that different treatments significantly affected the population size and diversity, with the highest microbial abundance observed under the W3F3A2 treatment. In terms of fruit quality, W2F2A3 treatment significantly increased the weight and yield of single fruit, and also stood out for soluble solids, soluble sugars, vitamin C content, and sugar-to-acid ratio. A close correlation was observed among soil nutrients, enzyme function and microbial community structure, on the one hand, and indicators of the quality of Annona squamosa fruit, on the other. Additionally a water-fertilizer-mulching evaluation algorithm based on PCA-GRA confirmed that W2F2A3 was the optimal solution. This study revealed the mechanism by which water, fertilizer, and mulching in orchards synergistically drive the regulation and optimization of rhizosphere micro ecology, clarified the key pathways through which straw mulching promotes nutrient cycling by regulating enzyme activity and microbial functions, and proposed the W2F2A3 optimization scheme, which provided a practical model for ecological restoration and economic benefits in green fruit tree cultivation.