Background: Soil fertility degradation is a critical challenge in tropical lowland agricultural systems, threatening food security and sustainable crop production across South Asia. Declining soil organic matter, nutrient imbalances, and over-reliance on synthetic fertilizers have collectively diminished soil productive capacity in intensively cultivated rice-growing regions.

Objective: This study aimed to assess the soil fertility status across different land-use zones and evaluate the response of rice (Oryza sativa L.) to integrated nutrient management (INM) treatments combining chemical fertilizers, organic manures, and biofertilizers.

Method: A field survey was conducted across 24 villages covering 720 soil sampling points stratified by fertility zone. Field experiments were laid out in a randomized complete block design (RCBD) with seven INM treatments and three replications over two seasons. Soil physical, chemical, and biological parameters were analyzed using standard laboratory procedures. Data were analyzed using ANOVA and treatment means compared by DMRT at p≤0.05.

Key Results: Soil fertility varied significantly among zones, with organic carbon (4.2–11.2 g/kg), available nitrogen (82–145 kg/ha), and microbial biomass carbon (182–412 µg/g) showing the widest variation. The Integrated INM treatment (NPK + FYM + Biofertilizer) produced the highest grain yield (5.38 t/ha) and net return (INR 46,240/ha), significantly surpassing all other treatments including the sole NPK control.