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Explained: From humble fungi, the promise of cleaner air in New Delhi this winter

IARI has developed 'decomposer' capsules, which when mixed in a water solution and sprayed on land, gets to work on paddy stubble, softening and decomposing it to the extent it can mix with soil and act as compost. Theoretically at least, it does away with the reason farmers set fire to fields ahead of the rabi sowing.

Written by Shivam Patel , Edited by Explained Desk | New Delhi |
Updated: October 10, 2020 2:10:52 pm
Punjab, Punjab stubble burning, Punjab AQI, Punjab air pollution, Delhi NCR pollution, Indian ExpressA labourer burns the wheat stubble in his field in Ludhiana. (Express Photo: Gurmeet Singh)

Paddy stubble-burning season is here, and satellite remote sensing data from the Indian Agriculture Research Institute (IARI) show a five-fold increase in the number of farm fires in Punjab, Haryana, and Uttar Pradesh during the first six days of October compared to the corresponding dates in 2019.

While this initial spike might flatten in the coming days, the SAFAR-India short-range forecast on Thursday (October 8) said the overall AQI in Delhi was in the “higher end moderate category”, and was forecast “at the higher end of moderate to the poor category” for October 9.

The burning of paddy stubble left in the fields after harvest has been a cause of concern for the past several years as it contributes to air pollution in the northern Gangetic plains and its already polluted cities like Delhi.

It is a common practice in October and November across North West India, but primarily in Punjab, Haryana, and Uttar Pradesh to quickly clear crop residue from their fields before planting the rabi wheat crop.

Several solutions have been proposed over the years to tackle the issue. The most recent one, which has been billed as a game-changer if found successful, is the ‘Pusa Decomposer’ capsule developed by IARI.

What is the ‘Pusa Decomposer’?

It is essentially a fungi-based liquid solution that can soften hard stubble to the extent that it can be easily mixed with soil in the field to act as compost.

This would then rule out the need to burn the stubble, and also help in retaining the essential microbes and nutrients in soil that are otherwise damaged when the residue is burned.


Impact on Delhi's air

Farmers in Punjab and Haryana burn paddy stubble around this time before they prepare the soil for the rabi crop. Smoke from burning crop stubble contributes to air pollution over the national capital and large parts of the Indo-Gangetic plain every winter.

How long does it take for the decomposer to work?

The window of time required for the solution to work, which is currently the main concern of farmers, is around 20 to 25 days, as per the IARI.

Farmers argue that this window is too long for them, as they ideally wait about a week or 10 days after harvesting the non-basmati variety of rice — which leaves hard stubble — to sow the wheat crop.

IARI scientists, however, say that farmers do not necessarily have to plant the next crop in a rush — and that 20-25 days is enough waiting time.

These seven strains of fungi are packed into four capsules, which cost about Rs 20 per pack of four.

How is the decomposer to be used by farmers?

There are seven strains of fungi that IARI has identified after research which help in rapid breakdown of hard stubble.

These seven strains of fungi are packed into four capsules, which cost about Rs 20 per pack of four. But there is a process for developing the liquid solution from these capsules which can take about four to five days.

It starts with boiling 25 litres of water mixed with 150 grams of jaggery, which scientists say has properties that help in multiplication of fungi.

After this mix has cooled, 50 grams of besan (or gram flour) is added to it along with four ‘Pusa Decomposer’ capsules.

This solution is then covered with a thin piece of cloth and left in a dark room for four days. On the fourth day, a thick growth of fungi will be seen on top of the solution. This has to be mixed well, and thereafter the solution is ready for use.

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What is the ‘dose’ of decomposer that has to be used?

A 25-litre solution is advisable for use in one hectare of land after being mixed with 500 litres of water. It can be sprayed over the field and left to do its work.

IARI scientists explained that the decomposer will work even in fields where stubble has not been finely chopped with a Super Straw Management System (Super SMS) machine.

The Super SMS is attached with a combine harvester machine to cut paddy stubble into small pieces and spread it uniformly in the field.

This in itself is a stubble management process, as chopped stubble can be removed from the field or wheat can be sowed in the field even without removing the chopped stubble, however, not all farmers currently have this machine, which is offered on 50% subsidy to individual farmers.

About the decomposer, IARI scientists have also said that farmers do not necessarily have to wait for the entire 20-25 day window before getting to work on the field. They can start ploughing and preparing the land 10-15 days after spraying the decomposer.

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How is this technology being used?

Union Environment Minister Prakash Javadekar has said that the decomposer will be used on a trial basis this year in Punjab, Haryana, Uttar Pradesh and Delhi.

Ministry officials said the technology would be used over 100 hectares of land in Punjab and Haryana, 800 hectares in Delhi and 10,000 hectares in Uttar Pradesh, which they said has been experimenting with a similar technology for the last three years.

IARI has been conducting experiments for a year-and-a-half on the decomposer. The technology was licensed for commercial use to four companies in 2019, and to two other companies in 2020.

Delhi has started preparing the solution with help from IARI and would begin spraying it over fields October 11 onwards.

Chief Minister Arvind Kejriwal has said the technology is inexpensive, as the whole process — from development, transport and spraying of decomposer — is costing the government only Rs 20 lakh.

The results from trials this year would give an answer to the effectiveness of the technology and decide whether its use would be scaled up in the future.

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