Fields on fire: Alternatives to crop residue burning in India
Although intentional use of fires to transform land has decreased globally (1, 2), particularly among highly capitalized countries through regulatory and market-oriented approaches and moral suasion, regulatory strategies have been less effective in southern and eastern Asia (see table S21). Some densely populated agricultural regions in China and India buck the global trend, showing increases in agricultural fires (2). This is particularly true in northwestern India, where rice residue burning makes a substantial contribution to air pollution and short-lived climate pollutants (3, 4). Regulations are in place to reduce agricultural fires, but burning continues because of uncertainty regarding policy implementation and regarding access and returns to alternative technologies. With the field burning season soon upon us, we synthesize emerging evidence on alternatives to burning, clarify the business case for alternative practices, identify remaining uncertainties, and discuss approaches to increase their widespread adoption. Often, there are difficult trade-offs between environmental improvement and profitable economic opportunities. The case of crop residue management in northwestern India does not appear to fit this pattern and provides lessons that may be useful elsewhere. Some of the least healthy air in the world is in India (5), where polluted air is the second-highest health risk factor (6). Seasonal smog imposes enormous costs, such as major transportation disruptions and the closure of 4000 schools in Delhi in November 2017 (7). The risks peak during October and November with the burning of rice crop residues in agricultural areas (8, 9). During this period, crop residue burning contributes to major particulate pollution in Delhi and northern India (9–11). Eighty percent of agriculture in northwestern India's Indo-Gangetic plains is based on a rice-wheat cropping system (∼4.1 million ha). Concerns over groundwater withdrawals have led to a planting cycle that allows the rice crop to benefit from monsoon rains. This cycle creates a short period (∼10 to 20 days) to harvest rice, manage rice crop residue, and plant wheat. Many of the 2.5 million farmers in northwestern India prepare for wheat planting by burning an estimated 23 million metric tons of rice residue in their fields (12). India's national government recognizes both the air pollution risks and the crucial role of crop residue burning. Despite federal and state regulations since 2014 and related advisories and bans, directives against burning have been only partially enforced. The reluctance to enforce existing policies arises, in part, from the belief that profitable alternatives to burning crop residue do not exist. Any alternative to crop residue burning must be feasible, affordable, and capable of scaling to adoption by thousands of farmers. Burning could be avoided by changing the overall cropping system (e.g., growing different crops) or by adopting different rice-wheat management practices. The focus to date has been on these latter options, which we include in the scope of this study. After mechanical harvesting of rice, farmers in northwestern India have different options for sowing wheat. All options include some combination of rice residue treatments (mulching by cutting and on-field distribution, baling and removal from the field, incorporation by tilling into the field, and on-field burning), land preparation (no additional preparation, rotavate, disc and tine harrow, and plank), and seeding of wheat (using Happy Seeders, conventional seeders, other zero-till seeders, and rotaseeders). Not all combinations of these options are regularly used in northwestern India, and we focus on 10 combinations that are commonly practiced or are viewed as potentially scalable (fig. S1). The majority of farmers currently choose to burn rice straw, plow fields, and sow wheat using conventional seeders. Given variation in practices, we evaluate the public and private costs and benefits and potential scalability of 10 alternative farming options, three of which result in residue burning.