Microbial decomposers don’t avert straw burning; they only give leaders publicity
The Delhi and Union governments may be touting microbial decomposers as the solution to stubble-burning and the resultant pollution, but a study has found these to be ineffective
Microbial decomposers, including one which Delhi Chief Minister Arvind Kejriwal touted as a quick fix for the burning of paddy stubble, have been found in a study to be ineffective, underscoring why premature claims made for political advantage sow confusion in farmers, and deflect from the serious effort of tackling a dire health issue.
Punjab Agricultural University (PAU) began trials of two microbial decomposers of paddy straw for two years from 2015 to 2016. In 2017-18, it added another two. In 2018-19 and 2019-20, it tested six microbial decomposers, including two of its own and four from the market. Among those tested was Pusa Decomposer of the Pusa Institute, or the Indian Agricultural Research Institute (IARI), Delhi.
The study published mid-November in a journal on recycling of organic waste in agriculture found that the decomposition of lignin, which is the toughest part of paddy straw, was the least when no microbial sprays were applied. It was in the range of 2.11% and 13.57%. With microbial cultures, the degradation varied from 7.51% to 35.79%. This shows that the sprays do hasten the decomposition of paddy straw.
There was significant variation in straw degradation between the four locations: Ladhowal, Ludhiana, Sangrur, and Kapurthala. This may be due to different field conditions such as soil type, moisture, straw load, and so on. But the degradation was not sufficient for the straw to be considered practically decomposed.
Difference in lab and field results
Ajmer Singh Dhatt, PAU’s Director, Research, said the decomposition in controlled laboratory conditions was a “bit faster” but in field conditions, it was “not encouraging.” The straw did not decompose within the timeframe required for wheat sowing, which is four weeks or less, depending on paddy varieties (early or late maturing) being harvested. It took 35 to 40 days to make straw retained on field surfaces brittle, Dhatt said. That is because the straw on field surfaces is exposed to air and dries up. Day temperatures are also lower than required for the microbes to work.
Both IARI and PAU began work on microbial decomposition of paddy straw in 2015 when alternatives to burning were not available. IARI launched the Pusa Decomposer in October 2020, which it said could make paddy straw and stubble soft within about three weeks and completely degrade it in about seven weeks when mixed with soil with machines and lightly irrigated.
The PAU study noted that decomposition was faster when the straw was mixed with soil. This would have happened even without external application of microbes. “Our studies show the soil microflora is sufficient to decompose, and addition of any decomposer has no statistical advantage in degrading in paddy straw,” Gurvinder Singh Kocher, the head of PAU’s Department of Microbiology, said in an emailed reply to questions.
Publicity from political leaders
“I slightly differ,” said AK Singh, Director, IARI. “Decomposer will only accelerate the process of decomposition, and it is always useful to use it” on straw, he said.
Of all the decomposers in the market, Pusa’s has received most publicity. The reputation of IARI as the country’s premier agricultural research institute has lent credibility to its product. Kejriwal has been Pusa Decomposer’s forceful champion. He has projected it as a low-cost solution to the city’s air pollution aggravated by soot and smoke from burning paddy straw.
Kejriwal has also used the fungal mix to flatter his image as a leader who cares for the capital city. News Laundry, a website that tracks news reported by media, reported in May that the Delhi government spent Rs 68 lakh on the concoction and Rs 23 crore on advertising it.
The Centre has also been plugging it. In reply to a question in the Lok Sabha in August 2021, Union Agriculture Minister Narendra Singh Tomar said the amount of the fungal culture it had made available would cover 5,730 hectares. That included 3,700 ha in UP, 200 ha in Punjab, and 800 ha in Delhi. IARI’s YouTube Channel Pusa Samachar regularly ran a programme on Pusa Decomposer technology, he said.
The Punjab and Delhi government announced in September that Pusa Decomposer would be tried out on 5,000 acres as a cost-effective solution to stubble burning.
Farmers take the easy way out
The decomposer is a mix of seven fungi that produce enzymes to break down lignin, cellulose, and pectin in paddy straw. They are supplied in four capsules. The starter culture is made by adding the fungi to 50 grams of besan and 150 grams of jaggery in five litres of boiled and cooled water. Every two days, the starter must be fed with jaggery mixed in five litres of water. Twenty litres of the broth diluted to 500 litres is sufficient for one hectare, it said. According to the Press Information Bureau, IARI has transferred the technology to 12 companies, including UPL, a large pesticide producer.
Punjab grew rice on about 31 lakh hectares this year, according to the ministry of agriculture. Each hectare produces about 6.5 tonnes of straw. That is about 20 million tonnes, which combine what harvesters leave in fields after threshing the grain. The ideal time for sowing wheat is between the last week of October and the first fortnight of November. To get the fields ready for sowing in that short time, farmers take the easy way out by lighting the straw, though there are alternatives to manage it without burning or shifting off the field.
Going by the PAU study, decomposers add to the cost of cultivation but not to value. Producing enough solution to cover vast swathes of paddy fields, spraying them with machines and churning the soil are additional expenses. They also result in tractor emissions.
There is a tried and tested method, called no-till farming, by which paddy straw is retained on field surfaces to degrade over time and wheat is sown with minimal disturbance of soil. It’s basically sowing without ploughing, and is the trend in advanced agricultural countries.
In August 2019, the then Director-General of the Indian Council of Agricultural Research, Trilochan Mohapatra, took credit for popularising no-till wheat sowing while releasing a joint study of five national and international research institutions that was published in the journal, Science. Scientists should stay on the message that no-till wheat sowing is the best method. They should work to improve it rather than stray from it.