IIT Gandhinagar Study Finds Nitrogen Management Could Cut Fertiliser Pollution and Groundwater Use

A new study by the Indian Institute of Technology Gandhinagar (IITGN) and the Helmholtz Centre for Environmental Research (UFZ), Leipzig, has identified nitrogen management as a potential strategy to address some of India's major agricultural challenges, including fertiliser pollution, groundwater stress and greenhouse gas emissions.

Published in Nature Communications, the study finds that restructuring India's cereal cultivation around nitrogen surplus could reduce environmental damage while maintaining overall calorie production. The modelling exercise suggests that a nitrogen-focused approach could reduce water use by 18.6%, equivalent to around 86.8 billion cubic metres of water annually.

The study estimates that the approach could also avoid around $1.19 billion, or approximately ₹10,000 crore, in pollution-related damage each year.

Why Nitrogen Surplus Matters

Nitrogen surplus refers to the portion of nitrogen applied through fertilisers that is not absorbed by crops. Excess nitrogen can enter groundwater and rivers through leaching and can also contribute to atmospheric pollution and greenhouse gas emissions.

The researchers argue that nitrogen deserves greater attention in agricultural planning because excess nitrogen can affect soil, water and the atmosphere simultaneously.

The study was conducted by Dr Shekhar Sharan Goyal and Prof Udit Bhatia of IIT Gandhinagar, along with Dr Rohini Kumar of UFZ.

According to Prof Bhatia, focusing on nitrogen surplus could provide simultaneous benefits for both fertiliser pollution and water use, rather than treating the two problems separately.

Rice and Wheat Area Could Make Way for Other Cereals

The researchers developed an optimisation model covering 664 districts and six cereal crops: rice, wheat, maize, sorghum (jowar), pearl millet (bajra) and finger millet (ragi).

The model operated under constraints designed to maintain food and economic security. No state was allowed to fall below its 2017 calorie production, while the cereal sector's net returns were required to remain at 2017 levels. Crops could also expand only in districts where they had a documented cultivation history.

Under the recommended scenario, rice cultivation area declined by 8.8%, while wheat area fell by 12.1%. Some of the freed-up area was reallocated to maize and traditional millets including jowar, bajra and ragi.

The combined share of these coarse cereals increased from around one-quarter to nearly one-third of cereal cropland in the model.

Water Savings as a Co-Benefit

One of the study's key findings is that reducing nitrogen surplus could produce significant water savings without making water conservation the primary optimisation target.

The model estimates an 18.6% reduction in water use, or approximately 86.8 billion cubic metres annually.

The researchers found that the water benefit from a nitrogen-led strategy was substantially greater than the nitrogen benefit obtained by focusing primarily on water savings.

This is particularly relevant for regions facing severe groundwater depletion, including parts of northwestern India where water-intensive cereal cultivation has placed increasing pressure on groundwater resources.

Potential Reduction in Agricultural Emissions

The proposed crop restructuring could also reduce agricultural greenhouse gas emissions.

The study estimates an 8.7% reduction in agricultural greenhouse gas emissions, reflecting reductions in both methane associated with rice cultivation and nitrous oxide emissions associated with nitrogen use.

The model also projects:

• 13.4% reduction in fertiliser pollution

• 11.3% reduction in nitrogen leaching

• 13.9% reduction in reactive nitrogen emissions

• 18.6% reduction in agricultural water use

The findings suggest that crop planning based on nitrogen management could contribute simultaneously to water conservation, pollution reduction and climate goals.

Why Millets Feature in the Model

Millets such as jowar, bajra and ragi play an important role in the proposed crop diversification because they can be cultivated in areas where expanding rice or wheat production may create greater environmental pressure.

The study does not recommend completely replacing rice or wheat. Instead, it proposes marginal changes in cropping patterns, allowing crops to be grown in locations where they are better suited while preserving existing food production.

The approach also broadly aligns with India's policy efforts to promote millets, including the government's focus on Shree Anna and nutri-cereals.

Markets Will Be Critical for Farmers

The researchers caution that changing crop patterns cannot be achieved through agricultural planning alone.

If farmers are to move from rice and wheat towards maize or millets, they need reliable markets, procurement systems, storage facilities, logistics and appropriate price support.

The study's proposed crop redistribution would also change India's interstate cereal trade. As rice and wheat production shifts, greater movement of maize, jowar, bajra and ragi between states could become necessary.

The researchers therefore emphasise that market readiness will be essential if the model's recommendations are to be translated into real-world agricultural policy.

What the Study Does Not Claim

The researchers have stressed that this is a modelling study and not an implementation plan.

The analysis focuses on cereal-to-cereal crop changes and does not include pulses and legumes, which could offer additional benefits for nitrogen management.

The model also preserves calorie production rather than measuring the full nutritional quality of diets. In addition, the economic calculations use state-level benchmarks rather than individual farm-level returns.

Consumer demand is another important factor. Greater production of millets would need to be accompanied by sufficient demand from consumers and effective procurement systems.

Implications for India's Agricultural Policy

The study comes amid growing concerns over declining groundwater levels, fertiliser use, agricultural emissions and the sustainability of India's cereal-based food system.

Rather than advocating a blanket shift away from rice or wheat, the researchers propose a more targeted approach based on growing the right crop in the right location.

The central message is that nitrogen surplus could serve as a strategic policy lever capable of addressing several environmental pressures simultaneously.

The researchers believe the findings could contribute to broader discussions on sustainable agriculture, particularly as India seeks to balance food security, farmer incomes, water conservation and climate objectives.

Key Findings at a Glance

Indicator	Modelled Impact
Agricultural water use	18.6% reduction
Annual water savings	86.8 billion cubic metres
Agricultural greenhouse gas emissions	8.7% reduction
Fertiliser pollution	13.4% reduction
Nitrogen leaching	11.3% reduction
Reactive nitrogen emissions	13.9% reduction
Estimated avoided pollution damage	$1.19 billion / ₹10,000 crore annually
Rice cultivation area	8.8% reduction
Wheat cultivation area	12.1% reduction

FAQs

Q1. What is the main finding of the IIT Gandhinagar study?
The study suggests that optimising cereal cultivation around nitrogen surplus could simultaneously reduce fertiliser pollution, groundwater use and agricultural greenhouse gas emissions while maintaining calorie production.

Q2. How much water could potentially be saved?
The model estimates an 18.6% reduction in agricultural water use, equivalent to approximately 86.8 billion cubic metres annually.

Q3. Does the study recommend completely replacing rice and wheat?
No. The researchers propose marginal changes in cropping patterns rather than eliminating rice or wheat, with greater cultivation of crops such as maize and millets in suitable areas.

Q4. Which crops could gain cultivation area?
The model reallocates some land towards maize, jowar, bajra and ragi, while rice and wheat areas decline.

Q5. Is this an immediate policy recommendation?
No. The researchers describe it as a modelling study, not an implementation plan. Real-world adoption would require appropriate markets, procurement, storage, logistics and farmer support.

Q6. Why is nitrogen surplus important?
Excess nitrogen from fertilisers can leach into groundwater and waterways and contribute to atmospheric pollution and greenhouse gas emissions. Managing nitrogen therefore has potential benefits across multiple environmental areas.

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