Niveta Jain

Methane production, oxidation and mitigation: A mechanistic understanding and comprehensive evaluation of influencing factors.

Methane is one of the critical greenhouse gases, which absorb long wavelength radiation, affects the chemistry of atmosphere and contributes to global climate change. Rice ecosystem is one of the major anthropogenic sources of methane. The anaerobic waterlogged soil in rice field provides an ideal environment to methanogens for methanogenesis. However, the rate of methanogenesis differs according to rice cultivation regions due to a number of biological, environmental and physical factors like carbon sources, pH, Eh, temperature etc. The interplay between the different conditions and factors may also convert the rice fields into sink from source temporarily. Mechanistic understanding and comprehensive evaluation of these variations and responsible factors are urgently required for designing new mitigation options and evaluation of reported option in different climatic conditions. The objective of this review paper is to develop conclusive understanding on the methane production, oxidation, and emission and methane measurement techniques from rice field along with its mitigation/abatement mechanism to explore the possible reduction techniques from rice ecosystem.

Greenhouse gases emission from soils under major crops in Northwest India.

Quantification of greenhouse gases (GHGs) emissions from agriculture is necessary to prepare the national inventories and to develop the mitigation strategies. Field experiments were conducted during 2008-2010 at the experimental farm of the Indian Agricultural Research Institute, New Delhi, India to quantify nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2) emissions from soils under cereals, pulses, millets, and oilseed crops. Total cumulative N2O emissions were significantly different (P>0.05) among the crop types. Emission of N2O as percentage of applied N was the highest in pulses (0.67%) followed by oilseeds (0.55%), millets (0.43%) and cereals (0.40%). The emission increased with increasing rate of N application (r(2)=0.74, P<0.05). The cumulative flux of CH4 from the rice crop was 28.64±4.40 kg ha(-1), while the mean seasonal integrated flux of CO2 from soils ranged from 3058±236 to 3616±157 kg CO2 ha(-1) under different crops. The global warming potential (GWP) of crops varied between 3053 kg CO2 eq. ha(-1) (pigeon pea) and 3968 kg CO2 eq. ha(-1) (wheat). The carbon equivalent emission (CEE) was least in pigeon pea (833 kg C ha(-1)) and largest in wheat (1042 kg C ha(-1)). The GWP per unit of economic yield was the highest in pulses and the lowest in cereal crops. The uncertainties in emission values varied from 4.6 to 22.0%. These emission values will be useful in updating the GHGs emission inventory of Indian agriculture.

NITROUS OXIDE AND CARBON DIOXIDE EMISSION FROM MAIZE ( Zea mays L.) UNDER FERTILISER APPLICATION AND ELEVATED CARBON DIOXIDE IN NORTHWEST INDIA

A field experiment was carried out at the farm of Indian Agricultural Research Institute, New Delhi to quantify the effect of elevated carbon dioxide (CO 2 ) and different levels of N fertiliser application on nitrous oxide (N 2 O) and carbon dioxide (CO 2 ) emissions from soil under maize. The experiment included five treatments: 60 kg N ha −1 under ambient CO 2 (385 ppm) in open plots, 120 kg N ha −1 under ambient CO 2 (385 ppm) in open plots, 160 kg N ha −1 under ambient CO 2 (385 ppm) in open plots, 120 kg N ha −1 under ambient CO 2 (385 ppm) in open top chambers (OTC) and 120 kg N ha −1 under elevated CO 2 (500 ± 50 ppm) in the OTC. Peaks of N 2 O flux were observed after every dose of N application. Cumulative N 2 O emission was 13% lower under ambient CO 2 as compared to the elevated CO 2 concentrations. There was an increase in CO 2 emissions with application of N from 60 kg ha −1 to 160 kg ha −1 . Higher yield and root biomass was observed under higher N treatment (160 kg N ha −1 ). There was no significant increase in maize yield under elevated CO 2 as compared to ambient CO 2 . The carbon emitted was more than the carbon fixed under elevated CO 2 as compared to ambient CO 2 levels. The carbon efficiency ratio (C fixed/C emitted) was highest in ambient CO 2 treatment in the OTC.