Nitrogen-based fertilisers like urea, which have been instrumental in increasing crop yields in India, are now turning into potent destroyers by polluting land and water, affecting people’s health and leading to climate change.

This was revealed by a unique 10 year study “The Indian Nitrogen Assessment “ carried out by Down To Earth, a New Delhi-based environment and health magazine, in a seminar in Amritsar on Thursday.

The Indian Nitrogen Assessment is, done by a group of scientists referred to as the Indian Nitrogen Group (ING). This is the first study of this kind in India. “According to the ING study, agriculture is the main source of nitrogen pollution in India. Within agriculture, cereals like rice and wheat, which account for the maximum cropped area, pollute the most,” says Richard Mahapatra of DTE

In the past five decades, every Indian farmer has, on an average, used up over 6,000 kg of urea. Only 33 per cent of this urea is consumed by rice and wheat crops – the remaining 67 per cent remains in the soil, water and environment, harming all irreparably. In the last 60 years, the use of urea in agriculture has increased by leaps and bounds. In 1960-61, urea used to form only 10 per cent of the total nitrogen fertilizer base in the country; by 2015-16, it had swollen to 82 per cent.

This has had a serious adverse effect on soil health leading to lower yields. A farmer interviewed by Down To Earth says: “We put in over 200 kg of urea in our fields this time, but the yields have been far lower than last year. Urea has completely messed up our lives.” How does N pollution lead to impaired soil health?

Too much nitrogen in the soil leads to reduction in carbon content of the soil and destroys the balance of nutrients in the soil.

N pollution also affects water. Nitrate (NO3)concentration in dug-well and shallow bore-well water in Punjab, Haryana and western Uttar Pradesh has been found to be above the limits prescribed by the World Health Organization (WHO). Haryana fares the worst – with 99.5 mg per litre of NO3 against the WHO norm of 50 mg per litre.

Too much nitrates in drinking water has been connected to what is called the ‘blue baby syndrome’ in children – affected children experience a dip in the oxygen levels in their blood, leading to incidences of continuous diarrhea, respiratory problems, and high blood pressure.

“Adverse impacts of N pollution are not limited only to water and soil,” says Mahapatra. Nitrogen in the form of nitrous oxide (N2O) is a greenhouse gas, and a contributor to climate change. Fertilizers are the major emitters of nitrous oxide in India, though emissions from sewage and solid wastes are quickly catching up.

N Raghuram, president of the ING, says that the scourge of N pollution can be contained, and a balance achieved between food security and the use of fertilizers. India is already moving to put a check on overuse of urea.

What is needed now is rationalization of unbalanced use of nitrogen fertilizers and a clamp-down on non-agricultural sources of nitrogen, he said.