CHIANG RAI, (Thailand): Rice farmers Siriporn and Amnat Taidee used to burn their paddy fields between plantings – a common method of clearing crop residue partly blamed for toxic smog that blankets much of Thailand every spring.
A quick and affordable way to prepare for a new growing cycle, the practice has long been seen as the only feasible option for millions of Thai rice farmers.
But for the couple from Chiang Rai, abandoning what Amnat called “the old way of doing things” for new microbial solutions has been a boon.
Thanks to the hungry bacteria that chew up post-harvest leftovers – their soil is softer, their yields are up and their fertiliser bills are down.
“My life has changed,” said Siriporn, 63, as she sloshed through a verdant paddy field in Chiang Rai. “I’m so happy... we don’t have to burn anymore.”
Every year between January and April, smoke from crop residue, forest fires and industrial emissions – compounded by smog drifting over from neighbouring countries – pushes Thailand’s air quality to dangerous levels.
Bangkok has restricted burning for years, but a recent crackdown has put government environmental goals on a collision course with traditional agricultural practices.
The threat of heavy fines and even prison has frightened farmers – but many feel they still have no alternative.
“It simply pushes the burden onto farmers,” environmental economist Witsanu Attavanich at Kasetsart University said of the ban on open burning.
The price of change
The Taidees were early converts, using a product called Soil Digest developed by a Thai scientist using five strains of Bacillus bacteria – one of which is derived from traditional fermented soybeans.
Siriporn said the solution decomposed the “terrible” stubble on the fields in a matter of days and helped restore the soil.
“The rice is coming in great and the soil is healthy,” she says. “This microbial stuff is a game-changer.”
In 2025, the authorities in Chiang Rai – one of Thailand’s main rice-growing provinces – began encouraging local farmers to try microbial solutions.
So far, around 2,000 have made the switch – a fraction of the province’s 100,000 rice farmers, but a start.
“If we are to stop the burning, we must provide them with multiple alternatives,” said provincial agricultural official Orracha Wongsaroj.
Microbial products have long been used in Thai agriculture, but demand for newer formulations targeting straw decomposition has grown sharply since the burning crackdown intensified a few years ago.
The Thai government promotes free access to microbial products for farmers – but officials told AFP that stocks had run out and they were struggling to scale up supply.
For those who cannot access government supplies, private market alternatives can be pricey.
In Pathum Thani, a rice-growing province in central Thailand, farmer Samart Atthong spent 1,200 baht ($48) hiring an agricultural drone to spray Soil Digest over his fields.
“People may only see the extra cost of the microbes, but they should look in the long run,” Samart said.
“Once the soil heals, we won’t need nearly as much fertiliser,” he said. “Where I live, burning has dropped to nearly zero.”
Making microbes work
Striding through air thick with dust from yeast, retired professor Wichien Yongmanitchai watches the whirring machines producing his microbial concoction.
He started by isolating local bacterial strains, convinced that native ones would work best in Thailand’s tropical environment.
He hopes his invention – sold as Soil Digest – will fix Thailand’s annual air crisis for good.
Without microbial treatment, rice straw takes around 30 days to soften enough to till – his solution works in five to seven days.
Early trials show yield increases of up to 20 per cent.
Dr Wichien also said the bacteria can reduce methane emissions from paddy fields by at least 20 per cent, helping Thailand meet its climate commitments.
“This is one of the biggest benefits to make (for achieving) carbon neutrality in the rice field.”
But Dr Wichien knows his small operation cannot reach Thailand’s 20 million farmers alone. And without government and corporate backing, the gap may prove too wide.
Independent experts agree the technology shows promise – but warn the system around it must change.
“The government wants to reduce straw burning – but there is no one-size-fits-all solution,” agricultural policy expert Nipon Poapongsakorn at the Thailand Development Research Institute said.
To start with, he suggests conditional subsidies tied to a no-burn commitment, combined with machinery access and farmer education.
Dr Wichien is already thinking beyond Thailand to paddy fields across South-east Asia and ultimately Africa.
“I don’t want anything else. I just want to make it work.” - AFP
