Impact of Open Crop Residue Burning and Alternate Options for Mitigation: A Review

Burning of crop residues in field include unavailability of labour, high cost in residue removing process and use of combined in rice-wheat cropping system especially in the Indo-Gangetic plains (IGP). Primary crop types whose residues are typically burned include rice, wheat, maize, millet, sugarcane, jute, rapeseed-mustard and groundnut. Farmers in northwest India dispose a large part of rice straw by burning in situ. The ‘rice-wheat cropping system’ is the dominant cropping system in South Asia [1]. This system involves growing rice and wheat in rotation throughout the year where rice and wheat is either grown in the same plot in the same year or in different plots in the same year or in the same plot in different years. Uttar Pradesh, Punjab, Haryana, Bihar, Madhya Pradesh and Himachal Pradesh have the largest areas under this system among the Indian states. Approximately 500-550 Mt of crop residues are produced per year in the country. With a production of 93.9 million tons (Mt) of wheat, 104.6 Mt of rice, 21.6 Mt of maize, 20.7 Mt of millets, 357.7 Mt of sugarcane, 8.1 Mt of fibre crops (jute, mesta, cotton), 17.2 Mt of pulses and 30.0 Mt of oilseeds crops, in the year 2011-12. Emission of greenhouse gases (GHGs) such as carbon dioxide, methane and nitrous oxide causing global warming, loss of plant nutrients such as N, P, K and S, adverse impacts on soil properties and wastage of valuable C and energy rich residues. Black carbon emissions are the second largest contributors to current global warming, after carbon dioxide emissions [2]. Using IPCC emission coefficients, the CH4 released from this source was found to be about 167 Gg [3]. Agricultural crop residues are burnt during the months of October and November every year in the Indo-Gangetic Plains (IGPs) in huge quantities which has a significant impact on greenhouse gas emissions and aerosol loading [4]. In the IGP region of India, 12 million hectares is accounted for rice-wheat crop rotation and harvesting of these crops with combine harvesters is very popular with the farmers of Punjab, Haryana and western Uttar Pradesh [4]. Crop residue management is one of the best options for maintaining the ecological sustainability of farms. There are several options which can be practiced such as composting, generation of energy, production of biofuel, mulching, baling, biochar production and recycling in soil to manage the residues in a productive manner. Conservation agriculture (CA) offers a good promise in using these residues for improving soil health, increasing productivity, reducing pollution and enhancing sustainability and resilience of agriculture.