Pulses in India contribute less to global warming
greenhouse gas emission during pulse cultivation in India is much less than in developed countries because of minimal use of nitrogenous fertilizers. India has just got a proof of it.
Pulse crops are known to release nitrous oxide, a greenhouse gas, but no one had measured it. Now researchers from the Bhubaneswar-based Institute of Mineral and Materials Technology have measured nitrous oxide emitted per unit area from certain pulse farms in eastern India (India-specific emission factor).
"There are indications that Indian emission factors for nitrous oxide from pulse cultivation are lower than the ipcc (Intergovernmental Panel on Climate Change) emission factors. This is because of the minimal use of nitrogenous fertilizers in pulse cultivation in the country. But studies need to be carried out in different parts of India to arrive at a definite conclusion," said G Roy Choudhury, part of the research team. The study published in the September 10 issue of Current Science showed that the average nitrous oxide emission from cultivation of green gram, horse gram and black gram in two tribal villages of Orissa ranged between 11 and 20 microgramme () per square metre per day.
ipcc estimates nitrous oxide emission from pulses only in terms of percentage of fertilizers used. It is 0.25 to 2.25 per cent of nitrogen fertilizer applied depending on environmental conditions.
Senior scientist S N Das, who was part of the study, said since a worldwide average of nitrous oxide emission from pulses is not available, a direct comparison could not be made. Instead they used international estimations of emissions from cereals. In Britain, nitrous oxide emission from cereals ranges from 80 to 90 g/sq m/day.
Pulse cultivation emits more nitrous oxide than cereals. "This is because in cereals nitrogen assimilated only from the soil is partly converted to nitrous oxide, but in pulses nitrogen assimilated from the atmosphere is also partly emitted as nitrous oxide," said N Raghuram, biotechnologist at Guru Gobind Singh Indraprastha University, Delhi.
Leguminous plants like pulses convert atmospheric nitrogen into ammonia and nitrous oxide through nitrogen fixation and emit part of the greenhouse gas into the atmosphere.
"Nitrous oxide emissions under different environmental conditions are different, so it is important to calculate these values under different conditions to arrive at an inventory of nitrous oxide emissions in India," said Raghuram. India is a major cultivator of pulses.
T K Adhya, scientist at the Central Rice Research Institute, Bhubaneswar, doubts the accuracy of the study. "While the present paper is a good beginning...probably the most important deficiency lies in its sampling schedule. Nitrous oxide emission always comes in spurts. Thus a proper sampling of the flux at a very short interval is an urgent requirement," he said.
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