ENVIRONMENTAL IMPACT OF OVER-FERTILIZATION IN RICE CULTIVATION: A GIS-BASED SPATIAL RISK ANALYSIS

Abstract

Over-fertilization in rice cultivation presents a significant environmental threat, contributing to nutrient leaching, groundwater contamination, eutrophication of aquatic ecosystems, and long-term soil degradation. This study employed a GIS-based spatial risk analysis to assess the environmental impact of fertilizer overuse across major rice-growing regions. By integrating multi-source spatial data—including fertilizer application rates, soil types, topography, and hydrological proximity—we identified critical hotspot zones and quantified regional vulnerability to nutrient-driven ecological degradation. The results revealed that southern and western regions exhibit the highest fertilizer input, particularly nitrogen and phosphorus, which correlates with elevated risk indices for runoff and leaching. Soil analysis showed that sandy soils, with poor nutrient retention capacity, intensified the environmental risk in these areas. Groundwater analysis indicated that nitrate concentrations in the East and North approached or exceeded WHO safety limits, signifying acute contamination. The risk of eutrophication at the catchment level was greatest in regions C3 and C5, shown by increased phosphorus loading and chlorophyll-a levels. GIS-based hotspot mapping highlighted zones Z1 and Z3 as essential intervention locations due to their elevated composite environmental risk. A regression analysis of fertiliser input and crop output revealed diminishing returns on nitrogen application, underscoring economic inefficiencies and environmental detriment. These findings highlight the necessity for precise fertilisation, sustainable nutrient management strategies, and focused policy actions. The research illustrates the effectiveness of GIS as a decision-support instrument in pinpointing high-risk areas and directing region-specific environmental management approaches for sustainable rice farming