Iron power

Nitrogen is the most important nutrient in the rice-wheat cropping pattern predominantly practised in the Indo-Gangetic plain.

Dinesh Kumar, one of the scientists involved in the study, says the use of iron pyrite is both viable and affordable as the country has vast reserves of the ore (350 million tonnes containing 22 per cent sulphur) as sedimentary deposits in Amjhore in Rohtas district of Bihar.

"This is a new study and (pyrite) could be an important suppressing agent for stopping av," says G Narayanswami, a professor in iari 's department of soil science and agricultural chemistry.

He says av occurs commonly in fields where the p h is 7.5 and more, which is a common feature of farm soil in the country. When urea is applied to such a soil under moist conditions, the fertiliser hydrolyses (combines with water) to form ammonium carbonate, which then breaks down into carbon dioxide, ammonia and water.

But the addition of iron pyrite leads to formation of sulphate ions (following the action of the bacteria Thiobacillus ferroxidans) which reduce the p h and thereby the av losses.

Kumar says the use of iron pyrite has a dual benefit: it not only increases nitrogen use efficiency but also helps reclaim alkaline (sodic) soils.