Geoclimatic modeling and assessment of pesticide dynamics in Indian soil.

Although pesticides can protect crops from pests and diseases, their extensive use poses significant environmental risks through soil quality degradation and groundwater contamination. Pesticide dynamics in soil are influenced by geoclimatic factors. The aim of this study was to evaluate local variability in pesticide dynamics based on geoclimatic variation across India at the individual farm level and to identify emerging patterns of pesticide residue accumulation in the soil. Using a bioreactive transport simulator, biogeochemical models from 19,573 farms were evaluated to study the dynamics of 46 pesticides across India by incorporating farm-level data on soil and climatic conditions. Hotspots of pesticide leaching and residue accumulation were identified by analyzing several parameters, including soil texture, organic carbon content, pH, and rainfall. This study highlighted the variability in pesticide residue accumulation at the topsoil and leaching rates from topsoil to below root zone across three dimensions-time, location, and pesticide species. It also explored the statistical patterns of pesticide leaching. The average leaching ratio was estimated to be 5% of the applied pesticide mass, which aligns with previous studies reporting approximately 7%. In this study, we evaluated for the first time spatial variations of pesticide dynamics in soil by simulating geoclimatic data at the farm level, which is the smallest unit of agriculture. This opens up the possibility of data-driven pesticide management at both farm and regional levels. This research provides actionable insights for policymakers to optimize pesticide application rates across regions and for farmers to select pesticides with minimal environmental impact based on specific local conditions.