Multicultivar field evaluation of organic and inorganic fertilizer formulations for improving citrus productivity, fruit quality, root architecture, and soil fertility

Organic and inorganic fertilization (OIF) is a promising strategy for sustaining citrus productivity while improving soil fertility, but its integrated effects on citrus yield, fruit quality, root architecture, and soil quality remain insufficiently understood under field conditions, particularly across different citrus cultivars. To address this gap, this study established multi-nutrient OIF application protocols and evaluated their effects on three citrus cultivars, Ehime, Haruka, and Orah, under field conditions in Chongqing, China. Fruit, root, and soil responses were evaluated within an integrated framework. Four fertilization treatments were compared: conventional inorganic fertilization (T1), animal-derived OIF (T2), plant-derived OIF (T3), and animal-derived OIF with modified application timing and rate compared with T2 (T4). Results showed that OIF treatments enhanced citrus yield, with T2 and T4 showing relatively favorable responses in multiple tested orchard-year cases and increasing yield by 20.3%-26.7% and 16.9%-28.7%, respectively, compared with T1. T2 improved fruit quality, increasing vitamin C, total soluble solids, and total sugars by 8.4%-20.4%, 17.6%-22.3%, and 20.3%-27.1%, respectively, while reducing titratable acid by 6.6%-17.6%. OIF application increased citrus root length, root surface area, root volume, root tip number, and the proportion of fine roots. Soil analysis further showed that OIF increased soil organic matter by 17.0%-34.8% and increased soil available nitrogen, phosphorus, and potassium in the 0-20 cm and 20-40 cm soil layers. Overall, the tested OIF formulations, especially T2 and T4, improved citrus performance alongside coordinated enhancements in fruit production, root development, and soil nutrient status, supporting their potential as promising fertilization options for sustainable citrus orchard management.