Fertiliser’s true climate impact

Author(s): Dinsa Sachan

Issue: May 15, 2012
Empirical estimates of nitrous oxide levels in environment made

imageThe air samples were taken from atmospheric monitoring station in Tasmania (Courtesy: Dr David Etheridge)NITROUS oxide is a potent greenhouse gas—it is 300 times more powerful than carbon dioxide in causing global warming. Though it reaches the environment through different sources like sewage treatment, livestock, vehicles and industries, use of fertilisers in agriculture is its biggest contributor. For example, India which is predominantly an agricultural country is the second largest producer and consumer of nitrogen fertilisers in the world and the third largest emitter of nitrous oxide.

Microbes produce nitrous oxide from nitrogen fertilisers through two processes of nitrogen cycle: nitrification and denitrification. They convert nitrogen fertiliser applied to farm fields into nitrates. These nitrates are then utilised by plants. Denitrification converts nitrates into atmospheric nitrogen. Excessive fertiliser use accelerates the rate of the processes, resulting in more nitrous oxide.

While scientists have attempted to measure the levels of nitrous oxide in the atmosphere mathematically, based on assumptions, empirical estimates are not available. Now scientists at the University of California in the US have filled this gap.

Using isotopic techniques they have ascertained agriculture’s contribution to nitrous oxide in the atmosphere over the years. For the study, they obtained air samples from compacted Antarctic ice, called firn air, dating between 1940 and 2005 and from an atmospheric monitoring station at Cape Grim in Tasmania which has archived air samples since 1978. The team then studied the percentage of different isotopes of nitrogen in the air samples. Isotopes are different forms of a chemical and nitrogen has two major isotopes N-14 and N-15.

“In the presence of fertilisers, nitrous oxide produced has more N-14 relative to N-15. Our data shows that over time the atmosphere is becoming enriched with N-14,” says Kristie Boering, co-author of the study. Previous studies have shown that the contribution of nitrification to global microbial nitrous oxide production has increased from 13.5 per cent in 1750 to 231.3 per cent in 2005. “As more nitrous oxides and its isotopes measurements are made in more regions we can use this data to monitor, check, and verify nitrous oxide emissions,” she adds.

The researchers in their study have also suggested that farmers should not use fertilisers during rainy season because microbes in wet soil can fire away loads of nitrous oxide. But is it feasible for countries like India?

B S Dwivedi, head of division of soil sciences and agricultural chemistry, Indian Agricultural Research Institute, Delhi, says, “Not using fertilisers during rain is not feasible for staples like rice which are grown in this season.”

Alternative practices

Even though fertiliser use cannot be stopped completely, there are alternatives to reduce nitrous oxide emissions without losing crop productivity. Use of manure could be one option, but Dwivedi thinks it is only useful for low-yielding crops like spices.

Nitrification inhibitors are another option. Inhibitors are chemicals that slow down the process of nitrification and are being used in several parts of the world. However, Lars Bakken, group leader with the Nitrogen Group at the University of Life Sciences in Norway, says, “This is controversial for two reasons. One, you need to apply ‘poison’ to solve an environmental problem. Second, it does not work so well. Nitrification is only partly and transiently inhibited.”

O P Rupela, principal scientist at the International Crops Research Institute for the Semi-Arid Tropics in Hyderabad, says, “Much of the crop nutrient needs can be met through on-farm production of plant biomass.”

S R Gopikrishna of non-profit Greenpeace says ecological fertilisation could be the way out. “By including legume crops (which can fix atmospheric nitrogen) in the cropping system, emissions can be reduced.”

Suman Sahai, convenor of non-profit Gene Campaign that rallies for food and livelihood security, says that instead of focussing on reducing emissions from agriculture it would be better to reduce those from vehicles and industry.

Toxic legacy: Nitrate pollution in California could affect 260,000 people

Author(s): Swetha Manian

Issue: Apr 30, 2012

Nitrate contamination has grown worse in agricultural areasTHOUGH nitrogen and nitrates occur naturally, they are at levels that do not harm. But concern is increasing about high concentrations of nitrogen leaching into aquifers from synthetic fertilisers and manure applied to cropland, resulting in nitrate pollution. High-nitrate levels can cause cancer, reproductive disorders and can be lethal for infants.

Now a study has shown how nitrate contamination of groundwater in some of California’s most intensely farmed regions has grown worse in recent decades. The contamination will continue to spread, threatening the drinking water supplies of more than 260,000 people, it says. The team from UC Davis Department of Land, Air and Water Resources analysed groundwater data of Tulare Lake Basin and Salinas Valley of California. They found that more than 90 per cent of the contamination comes from farms, ranches and crops. It says that nitrate in drinking water today came from nitrates introduced decades ago. “Decades from now nitrate in water will be from today’s discharges. Nitrate contamination will be an issue for years to come,” says Thomas Harter, the lead author.

The study which was mandated by legislation in the state in 2008 also notes that removing nitrates from groundwater is costly and not feasible. It says the cost of treating drinking water would increase over time as more nitrate percolates. The study thus suggests an approach based on fertiliser management and water treatment systems. Laurel Firestone, co-executive director of Tulare County’s Community Water Centre, suggests a fertiliser fee could help control nitrate contamination.

In India, high levels of nitrate contamination have been reported from agricultural areas and have been linked to intensive use of fertilisers. A study conducted by Greenpeace India, a non-profit, in November 2009 in Punjab found an average fertiliser application rate of 322 kg nitrogen per hectare, higher than the average rate of 210 kg nitrogen per hectare, set by the Fertiliser Association of India. The Davis study found an application rate of 221 kg nitrogen per hectare in high nitrate area. “While nitrate pollution can stem from many sources, overuse is prevalent mainly in Punjab, Haryana, Uttar Pradesh and coastal peninsula, which comprise 10 per cent of all agricultural area,” says N Raghuram, associate professor at Indraprastha University, New Delhi. He adds, preventing accumulation of reactive nitrogen is the best solution. “Recycling unwanted nitrogen compounds from other sectors towards agriculture could be an option.”

Centre’s new plan to delay fertiliser subsidy phaseout

NEW DELHI: UPA-II’s plans to replace the existingfertiliser subsidy regime with direct cash transfers to farmers will be delayed as the fertiliser ministry is likely to scrap an intermediate phase where the subsidy was to be rerouted from companies to retailers this summer.

This puts paid to the fertilizer industry’s expectation that very soon it would be out of the subsidy mechanism which locks up precious working capital.

“We are rethinking the original plan. Rather than routing subsidy through retailers, we now want to pass it on directly to farmers after linking it with their Aadhaar numbers,” said a senior ministry official involved in the process.

In the original plan, formalised shortly after last year’s budget, the ministry was to extend its fertiliser management system – in order to track fertiliser flows – beyond the 30,000-odd fertiliser warehouses to all 230,000 licensed retailers in the beginning of 2012.

In the second phase, slated to start this kharif, retailers would buy fertiliser at market rates and then sms transaction details to the government which would then transfer the subsidy to their bank accounts. The third phase, cash transfers to farmers, was to be rolled out once farmers got unique identification (UID) numbers.

The ministry now thinks that deleting the second phase will expedite the switch towards cash transfers. “There is no need for phase 2. When the end beneficiary is farmer, we should transfer it directly to him preventing any leakage in this proposed three-tier system,” added another official in the ministry.

Phase-two was being opposed by both companies and retailers. “If wholesalers and retailers have to pay upfront for fertiliser and get the cash afterwards from the government, our volumes will fall.

Given the available working capital, a person buying 300 tonne will now only be able to buy 100 tonne,” a wholesaler in Karnal, where the mobile-phone based expanded fertiliser management system (mFMS) had been piloted, had told ET this January.

Also, glitches in mFMS are yet to be ironed out. In Karnal, for instance, the software was available only in English, and it was not working on all handsets.

“Farmers are the ultimate beneficiaries of subsidy. It should go to them directly. Fertilizer companies should not be involved,” said IFFCO managing director U S Awasthi.

However, this means that the government’s plans for redirecting the fertiliser subsidy away from companies will be delayed. After all, before the subsidy can be directly passed onto farmers, they need to get their UID numbers.

That said, it looks like both retailers and farmers will only get short-term relief. In his speech, Finance MinisterPranab Mukherjee said that while subsidies related to the food security act will be fully provided for, “all other subsidies would be funded to the extent… they can be borne by the economy.” In other words, farmers and retailers will gradually have to pay more for fertilisers.

This is already happening, said Himanshu, an assistant professor at JNU, “While the price of urea has more or less stayed around Rs 500 over the past 6-7 years, that of DAP, for instance, has climbed from Rs 1,050 in 2010-11 to Rs 1,500 by June 2011 and is currently at Rs 1,900. It will definitely increase further.”