The problem of air pollution from paddy stubble burning is ultimately about a simple trade-off: between more smoke and less water.
Farmers in Punjab and Haryana have been setting fire to their fields after harvesting of paddy since the 1980s. That was since the time combine machines, instead of manual labourers, started being used for harvesting and threshing their grain.
What has changed — and is causing the current environmental crisis that was described by the Supreme Court Monday as “worse than the Emergency” — is the timing of the burning. And that has significantly to do with a law passed in 2009: Punjab Preservation of Subsoil Water Act.
Before the Act came into being, farmers in Punjab were sowing paddy nurseries from mid-to-late April and transplanting the seedlings from mid-May to late-May. As a result, the paddy, including 155-day varieties such as Pusa-44, got harvested by early October — and the burning of the 50-60 cm tall standing stubble, which remained after harvesting, got over around mid-October.
The 2009 Act, however, barred any nursery sowing and transplanting of paddy before May 15 and June 15, respectively. The reason was that transplanting, during peak summer, led to massive groundwater depletion.
For the first three weeks after transplanting, the plants have to be irrigated almost daily to ensure water-logged conditions to prevent weed growth. By not permitting transplanting before June 15, the Punjab government was ensuring that a significant part of the crop’s water requirement is met from monsoon rains. Also, there would be less water loss due to evaporation after mid-June.
While the 2009 Act may have helped arrest the rapid decline in the groundwater table and aquifers, it has contributed to the unprecedented deterioration in air quality indices (AQI) in the National Capital Region now.
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“Late transplanting has meant that farmers are now setting fire to their fields mostly from the third week of October to the first week of November. This is the time just before the onset of winter, when wind movement is very slow and moisture levels in the lower atmosphere are also high. It creates a layer, due to which all the particulate matter and gases from the burnt stubble, as well as vehicles and industries, get accumulated, instead of moving away. The AQI, therefore, turns bad,” says Dr Anil Sood, senior scientist at the Ludhiana-based Punjab Remote Sensing Centre (PRSC).
Haryana and Delhi are to the south and southeast of Punjab. And according to experts, at this time of the year, winds in Punjab generally blow from the northwest to the southeast.
“These northwesterly winds have been calm with a speed of less than 2 kmph for the past several days. In several places, there is ‘air locking’, too,” said Dr Surinder Paul, Director, Indian Meteorological Department, Chandigarh office.
According to Paul, it is a coincidence that in North India, mainly Punjab and Haryana, paddy stubble is burnt at the onset of the winter season, when there is a rise in air moisture and wind speeds are slow. Smoke from stubble burning, and industrial/vehicular pollution further adds to the process of ‘air locking’, which can be broken either through rain or fast winds.
That was evident Monday when relatively high speed winds over Delhi resulted in considerable decline in AQI levels.
AQI levels in many places of Punjab are also ‘poor’, but not as severe as in Delhi, said experts. If stubble burning was only to blame, they said, then Punjab should been have more polluted than Delhi due to the high number of such fires.
This year, a total of 31,267 field fires have been recorded in Punjab since September 23. That includes the 5,953 on Monday — the highest ever any for a single day as per satellite-generated data maintained by PSRC since 2016. According to the data, there were 80,979 paddy stubble burning incidents in 2016, which fell to 43,660 in 2017 and rose to 49,987 in 2018.
The cases of crop residue burning is more in Punjab, where out of the estimated 29.66 lakh hectares (lh) paddy area this year, 24.16 lh has been under non-basmati varieties. In Haryana, the total paddy acreage is only 13.50 lh, with basmati’s share at 8.43 lh. Farmers generally resort to manual harvesting of basmati paddy, which does not lead to stubble burning.
According to Punjab agriculture department officials, more than 90 per cent of paddy harvesting in the state is already over. With only the basmati area largely left to be harvested, the total number of fires this time may still end up below last year’s, they said.
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