Integrated Soil Fertility Management Enhances Soil Properties, Yield, and Nitrogen Use Efficiency of Rice Cultivation: Influence of Fertilizer Rate, Humic Acid, and Gypsum

Integrated soil fertility management is essential to improve soil productivity, rice yield, and nitrogen use efficiency (NUE). This study evaluated the integration of chemical fertilizer rate, humic acid (HA), and flue gas desulfurization gypsum (FG) on soil chemical properties, rice yield, NUE, and nitrogen agronomic efficiency (NAE) in acidic paddy soil. This study included three factors: (1) fertilization based on farmer practices and rice requirements, (2) HA at 0 and 975 kg ha-1, and (3) FG at 0, 636, and 23 kg ha-1. Fertilization based on rice requirements reduced nitrogen (N) input by 14.5% compared to farmer practices while maintaining similar yields. Under farmer practice, HA enhanced total N, CEC, rice yield, NUE, and NAE. HA with FG at 636 kg ha-1 increased TOC, total N, and exchangeable NH4-N but decreased yield. In contrast, HA combined with FG at 23 kg ha-1 enhanced soil exchangeable Ca and S, rice yield, NUE, and NAE. This study suggests that to maintain farmer fertilization practices while improving soil properties and rice yield, HA should be applied with FG (23 kg ha-1). HA combined with FG (636 kg ha-1) should be applied with fertilization tailored to rice nutrient requirements to optimize NUE and NAE.