Abstract
Since the Green Revolution in the mid-1960s, a widespread transition to a rice–wheat rotation in the Indian state of Punjab has led to steady increases in crop yield and production. After harvest of the summer monsoon rice crop, the burning of excess crop residue in Punjab from October to November allows for rapid preparation of fields for sowing of the winter wheat crop. Here we use daily satellite remote sensing data to show that the timing of peak post-monsoon fire activity in Punjab and regional aerosol optical depth (AOD) has shifted later by approximately two weeks in Punjab from 2003 to 2016. This shift is consistent with delays of 11–15 d in the timing of maximum greenness of the monsoon crop and smaller delays of 4–6 d in the timing of minimum greenness during the monsoon-to-winter crop transition period. The resulting compression of the harvest-to-sowing period coincides with a 42% increase in total burning and 55% increase in regional AOD. Potential drivers of these trends include agricultural intensification and a recent groundwater policy that delays sowing of the monsoon crop. The delay and amplification of burning into the late post-monsoon season suggest greater air quality degradation and public health consequences across the densely populated Indo-Gangetic Plain.
Highlights
Rapid increases in mechanized harvesting in the Indo-Gangetic Plain (IGP) since the mid-1980s, together with steady increases in crop production, have led many farmers to burn the abundant residue left behind by this practice (Badarinath et al 2006)
In contrast to the shift in maximum Normalized Burn Ratio (NBR) and Normalized Difference Vegetation Index (NDVI), we find a smaller delay of 4-6 days in the timing of the minimum values of these indices during post-monsoon (Figure 3c-d, Table S5), indicating that the shift in the monsoon growing season is greater than the corresponding shift in the timing of the earliest date when fields are ready for winter wheat sowing
We further demonstrate the viability and applicability of using daily Moderate Resolution Imaging Spectroradiometer (MODIS) surface reflectance to characterize crop cycles and the utility of NBR as a useful complement to NDVI for quantifying these vegetation changes
Summary
Rapid increases in mechanized harvesting in the Indo-Gangetic Plain (IGP) since the mid-1980s, together with steady increases in crop production, have led many farmers to burn the abundant residue left behind by this practice (Badarinath et al 2006). We use daily satellite remote sensing data to quantify the temporal shift toward later burning in the state of Punjab, the “breadbasket” of India. Such a shift would have implications for air quality degradation, since peak burning is more likely to coincide with meteorological conditions that are favorable in amplifying persistent haze, such as weak winds, low mixing layer heights, temperature inversions, and high relative humidity (Ojha et al 2020)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
