India’s air pollution debate may be overlooking a source that begins far beyond the city boundary: nitrogen fertiliser used on farms. In an interview with Deccan Chronicle, journalist and author Jacob Koshy argues that ammonia released from fertiliser can combine with emissions from vehicles and coal plants to form particulate matter, including PM2.5, the fine pollution associated with serious health risks.
The argument places agriculture inside a problem that is usually framed as urban. Cities are commonly discussed through the visible sources around them—traffic, construction, industry, power generation and waste burning—while fertiliser is treated primarily as an input essential to food production. Koshy’s book, The Nitrogen Bomb, examines how these two systems are connected and why India has not yet developed a sufficiently detailed account of reactive nitrogen emissions.
That connection matters because air does not recognise administrative boundaries. Fertiliser may be applied in agricultural areas, but the chemical compounds released into the atmosphere can interact with pollutants from urban and industrial activity. The result, as described in the interview, is a pollution pathway that is difficult to understand through city-level source lists alone.
Koshy does not argue that nitrogen fertiliser can simply be removed from Indian agriculture. He describes chemical nitrogenous fertiliser as essential to modern high-yield food systems and links its rapid expansion in India to the Green Revolution of the mid-1960s and early 1970s. The same agricultural transformation that helped increase food production also created a dependence on fertiliser use whose environmental costs are now becoming harder to ignore.
The central issue, therefore, is not whether nitrogen fertiliser is useful. It is how much is used, where it is lost, and what happens to the nitrogen that crops do not absorb. Koshy says unchecked use of ammonia, the main nitrogenous fertiliser identified in the interview, allows it to volatilise into the air. It can then combine with fossil-fuel emissions to form particulate matter.
The interview also makes clear that the exact scale of this contribution remains insufficiently established. Koshy points to a paucity of scientific investigation into the extent to which fertiliser emissions contribute to PM2.5 pollution in India. He says only a handful of Indian scientists are working to quantify the problem. This means that the broad connection is being discussed, but the precise contribution of agricultural ammonia to pollution in particular cities or regions cannot be established from the supplied material.
That uncertainty has direct implications for the way cities design clean-air interventions. If urban pollution inventories do not adequately account for reactive nitrogen, authorities may be working with an incomplete picture of the chemical processes that produce particulate pollution. This does not mean that existing efforts aimed at vehicles, coal plants or other fossil-fuel sources are misplaced. Rather, the interview suggests that they may not explain the entire pollution system.
Koshy says scientists interviewed for his book remain uncertain about whether reducing ammonia alone, or reducing ammonia alongside fossil-pollution sources, would produce a measurable fall in particulate matter. That qualification is important. It prevents the nitrogen question from becoming another simplistic claim that identifies one source as the answer to a complex air-quality crisis.
The policy difficulty is even greater because fertiliser use is tied to farm economics and political choices. Government advisories have encouraged farmers to use fertiliser judiciously, Koshy says, but subsidies help keep fertilisers cheap. Those subsidies are connected to the cost of cultivation and food production, making any effort to alter fertiliser use a question of political economy as much as environmental management.
This is why Koshy describes the challenge as overwhelmingly political, even though it also requires better science. Technologies exist to reduce or slow the leakage of ammonia from soil, and alternatives for nitrogen fertiliser are being examined. But the interview says these tools have limited effectiveness on their own. A meaningful reduction would require what Koshy calls intelligent and conscious control of the system.
The comparison with stubble burning is revealing. The practice is now widely discussed as a contributor to severe winter pollution in north India, linking an agricultural activity to the air breathed in urban areas. Koshy argues that fertiliser-related emissions should similarly be framed as an environmental pollution issue rather than left inside a narrow agricultural policy conversation.
Yet the two issues are not identical. Stubble burning is a visible, episodic practice that can be observed and linked to seasonal pollution spikes. Ammonia emissions from fertiliser use are more dispersed and are part of the routine operation of the food system. Measuring them requires detailed scientific inventories and a better understanding of how they interact with emissions from transport, power generation and other sources.
The numbers available in the interview are limited but significant in what they reveal. Chemical fertiliser use accelerated in India during the mid-1960s and early 1970s. The country has only a handful of scientists, according to Koshy, attempting to quantify the relationship between fertiliser emissions and PM2.5. And while carbon emissions are routinely counted and inventoried, reactive nitrogen emissions do not yet receive comparable treatment in the account described by the author.
That accounting gap is an institutional problem. Carbon has become the organising measure for a large part of climate policy, while air-pollution management often focuses on directly emitted particles and familiar combustion sources. Reactive nitrogen cuts across these categories. It is connected to agriculture, soil management, food security, atmospheric chemistry, public health and urban air quality. No single department can address the entire chain without coordination between agricultural, environmental, scientific and urban authorities.
The policy choices also involve trade-offs. India must protect food production while reducing pollution and limiting wasteful use of fertiliser. Koshy says Indian agriculture has long used more fertiliser than necessary for a certain level of yield. He identifies increased pulse production and improved nitrogen-use efficiency as possible approaches that, in theory, could reduce wastage without necessarily increasing prices. The supplied interview does not establish how widely such approaches are currently used or what measurable impact they have had.
This distinction between possibility and evidence is essential. The interview identifies a direction for policy discussion, but it does not provide a national emissions inventory, city-level PM2.5 attribution, cost estimates or an assessment of specific government programmes. Those gaps are not peripheral. They determine whether a proposed intervention can reduce pollution without weakening farm incomes or food security.
The larger urban question is whether cities can manage air pollution while treating the city as the only relevant unit of analysis. Urban residents experience the health effects of polluted air, but some of the chemical processes that shape that pollution may originate in peri-urban and rural areas. A municipal clean-air plan that ignores those connections may be limited not because its individual measures are ineffective, but because its map of the problem is incomplete.
Koshy’s argument ultimately calls for nitrogen emissions to be counted with the same seriousness that India applies to carbon emissions. The evidence presented in the interview confirms a policy and research gap, not a settled estimate of how much urban PM2.5 comes from fertiliser use. The next stage therefore depends on better measurement: identifying emissions, tracing their atmospheric interactions and determining which reductions produce measurable improvements while protecting food production. Until that work is done, India’s clean-air strategy will continue to operate with an incomplete account of the nitrogen moving through its farms, atmosphere and cities.
