A micro-level assessment of carbon equivalent greenhouse gas emission and energy budgeting of rice cultivation in India

Identification of efficient rice growing regions in terms of carbon and energy consumption per unit area of cultivation is need of the hour to develop an appropriate strategy for achieving higher productivity. In the present study, we assessed the different inputs utilization pattern to know their contribution towards carbon and energy input for rice cultivation in different districts of Karnataka, an Indian state. Details on the input's consumption pattern, viz., fertilizers, chemicals, seeds, irrigation, labour, machinery, fuel etc., were collected prior to the study and quantified respective input and output data for all districts. Further with input and output data, different carbon and energy indices were worked out individually for each district. Overall, Karnataka has shown a carbon sustainability index (CSI) and carbon efficiency ratio (CER) of 1.94 and 2.94, respectively, with methane (48%) and fertilizers (23%) being significant contributors to the carbon input. Out of 30 districts, 17 districts have shown higher (1.94–3.40 and 2.94 to 4.40) and 13 districts have shown lower (−0.21 to 1.92 and 0.79 to 2.92) CSI and CER, respectively than the state average with highest in Bangalore urban followed by Chamarajanagara. With respect to energy budgeting, the average energy use efficiency, energy profitability, nutrient energy ratio and human energy profitability in Karnataka ranged from 0.54 to 3.36, −0.46 to 2.36, 1.8 to 12.9 and 14.4 to 114.2, respectively. Indirect (69%) and non-renewable energy (61%) sources were identified as major energy inputs to the total input energy in rice cultivation. However, Bidar, Dharwad and Haveri were found most carbon and energy inefficient districts in the state. Among the regions, coastal Karnataka followed by south interior Karnataka were identified as more efficient regions both in terms of carbon and energy. Thus, our research aids policymakers in developing region/district specific carbon and energy efficient management practices for increasing rice productivity while maximising the use of limited resources.