IITGN Study: Targeting Nitrogen, Not Water, Could Ease India's Farm Pollution

A new study by researchers at the Indian Institute of Technology Gandhinagar (IITGN) and Germany's Helmholtz Centre for Environmental Research (UFZ) has found that redesigning India's cereal cultivation patterns around nitrogen management, rather than water conservation, could sharply reduce environmental damage while maintaining calorie production. The study was published in Nature Communications.

The researchers, led by Dr. Shekhar Sharan Goyal and Professor Udit Bhatia of IITGN with Dr. Rohini Kumar of UFZ in Leipzig, argue that nitrogen surplus, the portion of applied fertilizer that crops do not absorb and that leaches into wells, rivers and the atmosphere as greenhouse gases, should be the primary policy target instead of water saved. Optimizing a model to minimize nitrogen surplus across India's cereal-growing districts cut water use by 18.6% as a side effect, saving an estimated 86.8 billion cubic meters a year; optimizing for water alone yielded nitrogen gains roughly 4.6 times smaller. The nitrogen-led path was estimated to avert about $1.19 billion, roughly Rs 10,000 crore, in damage annually.

The model reallocated existing cereal cropland across 664 districts among rice, wheat, maize, sorghum, pearl millet and finger millet, while requiring that no state's calorie production or the cereal sector's net returns fall below 2017 levels. In the recommended pattern, rice area contracts by 8.8% and wheat by 12.1%, with the freed land taken up by maize and the three traditional millets, whose combined share of cereal cropland rises from about a quarter to nearly a third. The study does not call for eliminating rice or wheat, only reallocating land at the margin.

The researchers found the shift would cut agricultural greenhouse gas emissions by 8.7%, reduce fertilizer pollution by 13.4%, and cut nitrogen leaching by 11.3% nationally, while requiring new interstate trade links to move coarse cereals to states that currently import mostly rice and wheat.