Integrated Nutrient Management, Soil Biological Functions, and their Linkages with Fruit Quality in Mango (Mangifera indica L.) under Medium-Density Planting

Integrated nutrient management (INM) using reduced recommended doses of fertilizers (RDF) as well as soil and/or foliar micronutrients is now widely advocated for the maintenance of soil health and fruit quality in intensive tropical orchards. Two years of field investigation (2023-2024) were undertaken to evaluate the impacts of ten INM treatments on soil biochemical properties, microbial communities, enzymatic action, leaf & fruit nutrition, and fruit quality in a medium-density (5 × 5 m) mango ( Mangifera indica L. cv. Dashehari) orchard. Treatments included 100 %, 75 %, 50 %, and 25 % RDF with or without soil micronutrients and 1-2 foliar micronutrient sprays in a randomized block arrangement with three replications. Both reduced RDF + foliar micronutrients (T ₈ : 75 % RDF + two foliar sprays and T ₉ : 50 % RDF + two foliar sprays) enhanced post-harvest soil pH, organic carbon, available N, K, and micronutrients (Fe, Zn, Cu, B, Ca). These treatments also increased AMF spore density (>3-fold greater than 100 % RDF control), bacterial count, and key enzyme activities (dehydrogenase, urease, acid, and alkaline phosphatases). Multivariate analysis (PCA, RDA, Pearson correlation, & Regression model) also verified strong positive correlations between microbial/enzymatic factors and soil-plant nutrient pools. As a result, leaf micronutrient and chlorophyll contents, fruit TSS (up to 20.78 °Brix), sugars, ascorbic acid, carotenoids, shelf life, flavonoids, total phenols, and antioxidant enzyme activities significantly increased, with the greatest value always obtained in the T ₈ and T ₉ . The findings show that prudent reduction of macronutrient fertilizers along with foliar micronutrients recovers biological functions of soil, promotes plant-microbe feedbacks, and yields superior fruit nutritional and phytochemical quality. The INM approach is a feasible and sustainable approach to tropical perennial agroecosystems.