Global warming potential (gwp) under conventional flooded rice – rice and futuristic maize – rice cropping systems in cauvery delta zone, tamil nadu, south india

On a global basis, the combined agricultural emissions of Nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4) account for about 20% of the annual increase in radiative forcing of climate change. Quantification of these gas emissions from soil is difficult because of their large spatial and temporal variability. Field experiments were carried out at Tamil Nadu, South India during 2010-2011 quantifies the green house gas (GHG) emissions from conventional flooded rice – rice and futuristic maize – rice cropping systems with minimum tillage. Futuristic system reduced seasonal methane emission in rabi rice by ten times (66.6 to 6.5 kg CH4 ha-1) as compared to conventional rice-rice system. Significant amounts of N2O emission were also observed during the early stage of the kharif rice under conventional system (9.98 kg N2O ha-1) that might probably due to nitrate accumulation from previous black gram crop. Seasonal N2O emission in maize increased from 2.47 to 8.07 kg N2O ha-1with increasing N levels from 0 to 300 Kg N ha-1. The CO2 emissions measured were only from dark respiration since opaque chambers were used. It was only in the maize plots that significant CO2 emissions were detected. The CO2 emission rates were higher at initial stage of crop growth with maximum rate of 10066 mg m-2 d-1. Overall, the annual Global Warming Potential (GWP) was found to be three times higher in conventional system (6289 CO2 equivalents ha-1 yr-1) as compared to futuristic system (1944 CO2 equivalents ha-1 yr-1). In both systems, GWP was higher in kharif season than in rabi season. Under conventional system, GWP was 4624 CO2 equivalents ha-1 in kharif and 1665 CO2 equivalents ha-1 in rabi whereas under the conventional system it was 1743 CO2 equivalents ha-1 in kharif and 201 CO2 equivalents ha-1 in rabi. System rice equivalent yield increased by around 58% under the futuristic as compared to the conventional system mainly due to better rice yields during rabi rice under the futuristic as compared with the conventional system.