The many promises of ammonium sulphate

Ravinder Kumar knows exactly what ammonium sulphate is. A retired railwayman in his late sixties, he farms his ancestral, five-acre land in Ghargoha, a hamlet in Bihar’s Gaya district. Even when he put in the hours at his full-time job, the farming never stopped. Few farmers or sellers in the area can describe fertilisers as precisely as he does.

The fertilisers Kumar and the farmers around him actually use are urea, potash, zinc, and sometimes, Di-Ammonium Phosphate (DAP). Ammonium sulphate is not on that list. But he knows it well enough to still feed it to the soil.

“Like urea, ammonium sulphate also has nitrogen. Just less of it,” he says over the phone in early June, taking a break from the kendu leaf harvest in the nearby Gurpa forest. “And it doesn’t hurt the yield much.”

Then, he pauses and adds, “It is expensive, though. So fewer people use it here.” He isn’t sure of the current price of ammonium sulphate; it’s been a few years since he last purchased it.

He buys his urea at Rs. 8 per kg from a shop nearby; the price is a little higher than the government rate, which stands at roughly Rs. 6. But it is the convenience of a closer shop that costs him the difference. To pay the government price at a licensed khaad bhandar or krishi kendra, he would have to travel to Paharpur or Tankuppa, more than 15 km away.

A fertiliser bag, suddenly in the spotlight

Ammonium sulphate (AS) retails, before subsidy, at Rs. 1,100 to Rs. 1,200 for a 50-kg bag (Rs. 22-24 per kg), against a subsidised 45-kg bag of urea at Rs. 266.50 (under Rs. 6 per kg). But during the kharif season of 2025, widespread urea shortage was reported from across states. Soon after, in the following rabi season (2025-26), the government, perhaps to address this scarcity, “decided to include Ammonium Sulphate (both domestic as well as imported)” under the Nutrient Based Subsidy scheme.

The government also began promoting it as a stand-in for urea. The subsidy on the main grade of ammonium sulphate (20.5 per cent nitrogen and 23 per cent sulphur) was set at Rs. 9,479 a tonne, about Rs. 474 off a 50-kg bag, pulling the retail price down to Rs. 700 per 50-kg bag (Rs. 14 per kg). Even then, it remains more than twice the price of subsidised urea, which carries 46 per cent nitrogen.

Where soils lack sulphur, studies have found ammonium sulphate can match or outperform urea and use nitrogen more efficiently.

The push became more pronounced a few months later, amid the West Asia war that began in February 2026. The Indian Council of Agricultural Research (ICAR) wrote to states in May 2026, asking them to use ammonium sulphate instead of urea for paddy in the upcoming kharif season.

In a release dated June 14, 2026, the Department of Fertilizers said it had ridden out the West Asia crisis, with its shortage of natural gas and shipping delays around the Strait of Hormuz, while keeping urea at Rs. 266.50 per bag—even as the global price climbed above Rs. 4,100. The same release noted that ammonium sulphate usage had risen by nearly 60,000 tonnes. Yet over the same years, the government has also built six new urea plants and is opening two more, expanding the supply of the very fertiliser that it is, elsewhere, asking farmers to use less of, and wean from.

But what is ammonium sulphate, and what can it do? As the name suggests, it is a compound of ammonium and sulphate, carrying about 21 per cent nitrogen and 23 per cent sulphur. In India, it is made mostly as a by-product of other industries, unlike urea, which is made from natural gas and contains 46 per cent nitrogen.

The Fertiliser Association of India’s policy record lists ammonium sulphate as a caprolactam-grade by-product of plants run by Gujarat State Fertilizers and Chemicals (GSFC) and Fertilisers And Chemicals Travancore Limited (FACT). This industrial origin might explain why it has drawn fresh attention during a gas crisis. However, it is interesting to note that in soil, urea and ammonium sulphate work similarly: urea has to break down into ammonium first. Ammonium sulphate supplies that ammonium directly. After that, soil microbes convert it into nitrate, which the plant then absorbs. But urea provides only nitrogen, while ammonium sulphate also provides sulphur.

Devi says that moving farmers off the familiar white granules has been a losing battle, “again and again.”

Academic field trials don’t crown a clear winner. Where soils lack sulphur, studies have found ammonium sulphate can match or outperform urea and use nitrogen more efficiently. Where sulphur is already adequate, the two tend to perform about the same, and in some soils, urea gives steadier results.

The push for ammonium sulphate seems to be the need of the hour. But one wonders if it can really replace urea–even in part.

Compared to his neighbours, Kumar uses less fertiliser. His fields also receive applications of cow dung. He also consumes most of what he grows, unlike many of his peers, who depend on a substantial yield because farming is their only source of income. But even so, Kumar is not willing to pay more than he must for fertiliser.

As of our conversation in early June, news of the short supply of urea had yet to reach his fields. “If farmers, including me, don’t find urea, they make do with whatever is available. What option do we really have?” he asks. Other alternatives only create a greater dent in the pocket. To him, anything other than urea is a fallback he would resort to only if he had absolutely no choice.

Also read: India’s urea usage reveals the vulnerability of its food systems

From the other side of the counter

More than 200 km away from Gurpa, in Jharkhand’s Gumla, seed and fertiliser seller Rajni Devi confirms what Kumar’s economics imply, from the other side of the counter.

In her two decades of running a licensed shop–a business she married into, and for which she earned a diploma in agri-inputs–she has watched farmers refuse to use anything but urea.

“They’ll ask from outside, ‘urea hai?’ (do you have urea?) The moment you say no, they walk off to the next shop. As a result, none of your other products gets sold either,” she says over the phone, between customers. “If they do come in, they’ll add DAP, and a few other things.”

It is worth noting that India’s fertiliser journey began with SSP and ammonium sulphate, long before urea entered the picture.I

Neither Kumar nor Devi had heard of the push for ammonium sulphate as an alternative to urea. But Devi says that moving farmers off the familiar white granules has been a losing battle, “again and again.”

It is not that the alternatives never sell. She and sellers like her have been called to government meetings, locally, about alternatives like nano urea, the liquid fertiliser that IFFCO launched in 2021 and has promoted ever since as a substitute for the conventional kind. A 500 ml bottle of nano urea is priced at around Rs 225 at cooperative societies. But she has watched those alternatives sit on her shelves.

“Some better-informed farmers do buy it. They’ve seen videos on YouTube and Instagram, and they know it might be the better option,” Devi explains. “But that number is small. Maybe two in ten.” For the rest, she says, “no method works.”

The steady decline of soil

For decades, Indian farmers have sworn by urea. And why wouldn't they? At Rs. 266.50 for a 45-kg bag (last revised in 2018), it is the cheapest fertiliser available—kept that way by a government subsidy. Over time, that has only deepened the over-dependence on it.

A comprehensive study published in Regional Environmental Change in 2025, by Tek B. Sapkota and Bijay-Singh, traces how decades of fertiliser policy in India have pushed farmers toward an unhealthy dependence on it. As per their analysis, by 2022-23, urea made up over 81 per cent of all nitrogen applied; farmers in many states such as Punjab, Haryana, western Uttar Pradesh, and Telangana are reported to be using 50-70 per cent more nitrogen than needed. Phosphorus and potassium (P and K) were being persistently under-applied because they were more expensive. For context, the recommended ratio of application of NPK to the soil is 4:2:1. An imbalance in this ratio has resulted in declining soil health and diminishing returns from fertilisers over time.

People working in the agriculture domain know this too well.

Rishi Mishra, an agricultural expert who works with small-holder farmers in the Panna region of MP, says that until about a decade-and-a-half ago, a mix of diammonium phosphate and single superphosphate was used by farmers widely. “Together, they would cover the soil’s need for nitrogen, phosphorus, sulphur and calcium,” he explains, adding that policy changes over the years made urea more lucrative, and everything else took a backseat. Even diversification itself remained urea-centric—neem-coated urea, nano urea, sulphur-coated urea gold–so that everything continues to be planned around urea. This only leaves further nutrient shortage in soils, more in some regions than others.

A 2021 study in Scientific Reports, a Nature journal, mapped the extent of nutrient shortage in India. Carried out under the ICAR’s All India Coordinated Research Project (AICRP) on Micro- and Secondary-Nutrients, the team analysed 2,42,827 soil samples from 615 districts and found 58.6 per cent of them (acute deficient + deficient + latent deficiency) to be short of sulphur, the worst shortage of any nutrient it measured.

Bihar, where Kumar farms, fared worse than the national average. More than 60 per cent of its soils came up short of sulphur. It was one of 13 states, Jharkhand and Madhya Pradesh among them, where the deficiency crossed that mark.

The best way forward is to bring a region’s own indigenous knowledge of its land back into practice, instead of leaning on any one fertiliser to do the work.

The study traces the shortage partly to the rising use of NPK fertilisers that carry little or no sulphur or micronutrients, and to the dwindling use of organic manure: nutrients taken out and not put back in in any manner.

Ammonium sulphate could help fix a part of that soil degradation problem–at least the sulphur part of it, believes soil scientist Arvind Kumar Shukla, the lead author of the 2021 paper.

Shukla is currently the Vice-Chancellor of the Rajmata Vijayaraje Scindia Krishi Vishwavidyalaya in Gwalior, Madhya Pradesh. Formerly, he was the coordinator for the AICRP-Micro and Secondary Nutrients and Pollutant Elements in Soils and Plants at Indian Council of Agricultural Research (ICAR) - Indian Institute of Soil Science, Bhopal. Shukla began the exhaustive work of figuring out sulphur deficiency back in 1998, along with other soil scientists, in the soils of Uttar Pradesh, particularly in the Indo-Gangetic plain.

“At that time, we tried to understand how sulphur deficiency came about. One of the important reasons we could attribute it to was the use of high-analysis fertilisers like urea, diammonium phosphate (DAP) and muriate of potash (MoP),” explains Shukla. Earlier, he adds, farmers were using ammonium sulphate, which automatically provided 24 per cent sulphur to the soil along with nitrogen. And for phosphorus, instead of DAP, “we were using single superphosphate (SSP), which also contains around 12 per cent sulphur.”

It is worth noting that India’s fertiliser journey began with SSP and ammonium sulphate, long before urea entered the picture. In 1906, E.I.D Parry established India's first single superphosphate plant in Ranipet, Tamil Nadu, and ammonium sulphate production as a by-product of steelmaking began in 1933. Synthetic ammonium sulphate production followed in 1941, and the Fertilisers and Chemicals Travancore (FACT) plant began producing it in 1947.

India makes only a fraction of what a real switch would demand today. The bulk of domestic ammonium sulphate is produced, as mentioned, by GSFC and FACT–and much of it is a by-product of making other chemicals. GSFC’s capacity is about 4.59 lakh tonnes a year and FACT’s about 2.25 lakh tonnes, a combined total of under seven lakh tonnes. 

According to the Department of Fertilizers’ 2023-24 annual report, FACT was already running its plant above its rated capacity, producing about 2.4 lakh tonnes. GSFC added a new line in Vadodara in early 2024; even so, the shortfall is met by imports, which have been climbing fast, growing at around 45 per cent a year between 2020 and 2024, and coming mostly from China. In April 2026, the government also floated a tender to import three lakh tonnes of ammonium sulphate. 

“Earlier, sulphur was reaching the soil inadvertently,” says Shukla. “Now, we are devoid of these fertilisers. We use high-analysis fertilisers that contain one nutrient in a very high amount. Nitrogen in urea is 46 per cent, and phosphorus in DAP is 46 per cent. And they don’t contain any sulphur. Although several sulphur-containing fertilisers, including SSP, gypsum and bentonite sulphur, are available, the quantity used is meagre,” remarks Shukla, who also thinks changing cropping patterns have aggravated the problem.

“Instead of one crop, we are now taking two or three. Moreover, we are also bringing a sizeable area under vegetable and fruit production. The expansion of intensive agriculture, including horticulture and oilseed cultivation, has increased sulphur demand and nutrient removal from soils.”

Also read: What's lurking in our food?

The doubt over paddy

Not everyone is convinced ammonium sulphate suits every crop, paddy in particular. Dr Virender Singh Lather, former principal scientist at ICAR, warned in a recent New Indian Express report that a high dose of sulphur could turn harmful in waterlogged soils, putting paddy fields at risk. 

The concern is grounded in established science. In flooded fields, soil microbes can convert sulphate into hydrogen sulphide, a gas that damages rice roots and reduces the plant’s ability to take up water and nutrients. According to the International Rice Research Institute (IRRI), the global authority on rice agronomy, this sulphide toxicity is “associated with low-Iron (Fe) soils” and can show up in sandy, degraded, acidic or poorly drained fields. Where soils hold enough iron, it locks away the sulphide harmlessly, and the danger narrows quite a bit.

Shukla is not persuaded that it is a general problem. To him, urea and ammonium sulphate end up feeding the plant in much the same way. Urea breaks down into ammonium in the soil, ammonium sulphate supplies that ammonium directly, and in both cases, soil microbes convert it into the nitrate the plant absorbs.

IRRI also notes that the problem “is not very common in rice” and tends to be of little economic significance. In other words, whether added sulphur helps or harms a paddy field depends heavily on the soil it goes into.

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Push the fertiliser, or build the system?

It is always a welcome step to diversify when it comes to fertiliser, believes Shweta Saini, an agricultural economist and the co-founder of the Delhi-based Arcus Policy Research. “But soil health should be the ideal way to identify the dosages for different geographies,” she says, underlining that policy and infrastructure should be designed with the soil as the central focus.

Mishra and Saini also agree that pushing a fertiliser is not enough on its own. The government, they argue, needs to put systems in place to ensure that inputs are matched to what each soil actually needs, rather than recommended in a blanket fashion across regions.

“Just pushing another fertiliser on paper won’t work. It has to be economically accessible,” says Saini, adding that the government has to take cognisance of and change the policy accordingly. “You cannot continue to have urea so cheap; it has to be corrected.”

Mishra goes a step further. The best way forward, he says, is to bring a region’s own indigenous knowledge of its land back into practice, instead of leaning on any one fertiliser to do the work.

For now, though, the ground reality is something else. Since June 8, as reported by The Indian Express, farmers across Punjab and Haryana have held repeated protests over a shortage of urea.

Also read: The grave personal cost of pesticide use