When farmers deliberately set fire to their fields, it’s most commonly called stubble burning or crop residue burning. In a more formal or regulatory context, it falls under the broader category of agricultural burning. The specific name depends on the purpose: burning leftover stalks after harvest is stubble burning, while clearing forested or wild land for new farming is called slash-and-burn agriculture (also known as swidden farming). When the burn is carefully planned with safety and land management goals, it’s called a prescribed burn or prescribed fire.
Stubble Burning vs. Slash-and-Burn
These two practices look similar from a distance but serve very different purposes. Stubble burning happens on land that’s already being farmed. After a crop like rice or wheat is harvested, the leftover stems and stalks (the “stubble”) remain in the field. Farmers set fire to this residue to clear the way for the next planting season quickly and cheaply. It’s a seasonal practice, repeated on the same land year after year.
Slash-and-burn, by contrast, is about converting new land into farmland. Trees, brush, and vegetation are cut down and then burned, with the ash acting as a short-term fertilizer. This method is most common in tropical regions and is sometimes practiced on a rotating basis, where farmers move to a new plot every few years and let the old one regrow. When done on this rotating cycle, it’s called swidden agriculture.
Why Farmers Burn Their Fields
The main reason is speed. In places like northern India, farmers often have only a few weeks between harvesting rice and planting wheat. Modern combine harvesters leave behind tall, tough rice stalks that are difficult to remove mechanically, and burning clears an entire field in hours. It’s also essentially free, while renting equipment to manage residue costs money and time that smallholder farmers may not have.
For prescribed burns on rangelands or grasslands in the United States, the goals are different. Land managers use fire to reduce the buildup of dead plant material that could fuel wildfires, to control invasive species, or to encourage the growth of native grasses. These burns require an approved written plan, specific weather conditions, and trained personnel on site.
What Burning Does to the Soil
Fire clears the surface, but it comes at a measurable cost to soil health. Research from South Dakota State University found that burning crop residue destroys 98 to 100% of the nitrogen in the plant material and about 21% of the phosphorus. Both are nutrients the soil needs to support the next crop. A long-term study in western Canada tracked fields where cereal residue was burned every year for 19 years and found that soil organic matter declined by 0.03 to 0.07% annually compared to fields where residue was left in place. That sounds small, but organic matter is the foundation of soil fertility, and those losses compound over decades.
The damage goes deeper than chemistry. The microbial life in soil, the fungi and bacteria responsible for breaking down organic material and recycling nutrients, is highly sensitive to fire. Research published in the journal Soil Biology and Biochemistry found that microbial functions in fire-affected soil can take 20 to 24 years to recover to the levels found in unburned soil. Fungal diversity plays a particularly important role in restoring the soil’s ability to process carbon, while bacterial diversity helps rebuild phosphorus cycling.
Air Quality and Health Risks
The smoke from burning fields is loaded with fine particulate matter, tiny particles small enough to pass through your nose and throat and settle deep in your lungs. The EPA links exposure to this type of pollution to aggravated asthma, decreased lung function, irregular heartbeat, nonfatal heart attacks, and premature death in people with existing heart or lung disease. Even healthy people can experience coughing, airway irritation, and difficulty breathing.
The scale of the problem depends on geography. In the Indo-Gangetic Plain of northern India, millions of small rice paddies are burned within the same few weeks each autumn, creating a seasonal smog crisis that blankets Delhi and surrounding cities. In parts of the American Midwest and Pacific Northwest, agricultural burns can similarly degrade local air quality, though typically on a smaller and more regulated scale.
Permits and Legal Restrictions
In the United States, agricultural burning generally requires a permit. Federal regulations under the Clean Air Act require applicants to provide the location of the burn, the type and estimated weight of material being burned, the method (pile burn, broadcast burn, windrow burn), and a description of safety measures like firebreaks and available water. Permits must be approved on the day of the burn and kept on site. State and local rules often add further restrictions based on air quality conditions and wind forecasts.
India has taken a more aggressive enforcement approach. The Commission for Air Quality Management (CAQM) has directed states to create dedicated “Parali Protection Forces” at the district and block level, made up of police officers, agriculture department officials, and administrative staff. These teams patrol fields, particularly during late evening hours, to catch and penalize farmers who burn illegally. An environmental compensation mechanism exists to fine violators, though enforcement remains inconsistent across regions.
Alternatives to Burning
The most widely discussed alternative is a machine called the Happy Seeder, which plants wheat seeds directly into standing rice stubble without any need to clear or burn the residue. The leftover stalks act as mulch, helping retain soil moisture and suppress weeds. Studies show the Happy Seeder saves farmers money on wheat production costs and reduces water use, while also improving soil health over time. It has the potential, according to researchers, to completely eliminate the practice of rice residue burning.
Adoption has been slower than expected, though. Farmers report problems with uneven seeding depth, especially on fine-textured soils, and the fields look rough and messy after planting. For farmers accustomed to the clean appearance of a freshly burned and tilled field, the visual impression alone creates doubt. The machine also struggles when rice straw is wet from rain or morning dew, causing blockages in the seed delivery system.
A competing machine called the Super Seeder addresses the appearance issue by incorporating residue into the soil with a rotary tiller, leaving the surface clean and familiar-looking. By 2020, Super Seeder purchases had actually overtaken the Happy Seeder in northwest India. However, the Super Seeder requires significantly more fuel and energy to operate, and on-farm trials across 159 fields showed that net returns from wheat were about 15% lower compared to the Happy Seeder. It also defeats the purpose of leaving residue on the surface as protective mulch.
Another option is the Super Straw Management System, an attachment that bolts onto the back of a combine harvester. It chops loose rice straw and spreads it evenly across the harvesting width as the combine moves through the field. This makes it much easier for a Happy Seeder to plant into the residue afterward, improving crop establishment and reducing the clogging problems farmers encounter with unprocessed stubble.