Although mandatory burns are effective in preparing fields after harvest, the waiver saves farmers money on expensive fertilizers and helps minimize environmental pollution, state agriculture experts say.
Farmers burn crop residues as a management tool in the fall after harvesting rice, soybeans, corn and cotton. Burning helps them prepare fields for the next growing season and rids fields of pests and diseases that could affect the next crop.
Burning allows for no-till or reduced seeding in the next growing season and more efficient field preparation, said rice agronomist Jarrod Hardke of the University of Arkansas Systems Division of Agriculture Cooperative Extension.
“Burning, when conditions permit, allows for a quick and efficient reduction in the amount of disruptive residue left on the field. Like any option, it has its pros and cons,” Hardke said.
About 40% of the residue is actually incinerated in most cases, but it can be as high as 80%, Hardke said.
“Burning can result in some nutrient loss and smoke. However, it can drastically reduce the amount of tillage and fuel used to manage the residue if only one tillage can be done.”
Tillage is an agricultural practice to aerate the soil to let in moisture and air, creating an environment that promotes plant growth, controls weeds, and introduces fertilizer into the soil. Tillage can also adversely affect soil quality over time.
“There are definitely benefits to burning crops, and we can’t ignore that,” said Kris Brye, professor of applied soil physics and soil science at the University of Arkansas Agricultural Experiment Station. Brye has been studying soil health in Arkansas for more than two decades.
“There is a convenience factor in handling really thick residue at the end of a given crop; Rice is a high biomass producing crop and we have some pretty unpredictable weather conditions that have evolved and are likely to evolve,” Brye said.
“Anything that can be done so that a field at the end of a season can be prepared for the next season or the following year, to get a go-ahead to sow their crop, we need to have the flexibility to be able to do that. but there are downsides that we cannot ignore,” he said.
Burning crop stubble can come at the cost of losing soil nutrients and organic matter that makes the soil healthy.
When crop residues are burned, the carbon trapped in the residues is also released as carbon dioxide, a greenhouse gas.
Agriculture accounted for 11% of total US greenhouse gas emissions in 2020; Emissions from agriculture in the US have also increased by 6% since 1990, according to a recent US Environmental Protection Agency report.
While there are benefits to burning crop residues, Brye says farmers should consider the health of the soil in their fields.
“When you put that organic matter back in place, there are many tangential indirect benefits of being able to do that,” Brye said.
It can also be costly to replace nutrients. Fertilizer prices have skyrocketed over the past year, contributing to the overall above-average production costs for agriculture.
Trenton Roberts, professor of soil fertility at the University of Arkansas System Division of Agriculture and soil specialist for the Cooperative Extension Service, calculated at current fertilizer prices, a high-yielding rice or corn crop produces about five tons of residues that contain nutrients such as nitrogen, phosphorus, potassium and sulfur are worth about $275 per acre, according to recent reports from the university’s Cooperative Extension Service.
An estimated 1.15 million acres of rice were planted that year, and burning crop residue could result in a loss of about $316 million in soil nutrients, according to Roberts calculations.
“How do you replace the nutrients lost through burning?” asked Bry. “Well, that means you have to buy more fertilizer, and when you’re talking hundreds of dollars per acre in potential replacement costs for nutrients from fertilizers to make up for what’s lost when crop residue is burned, that should get some people’s attention.” .”
Warm, dry periods of fall are the best time for prescribed burns for post-harvest crops because it can be done quickly and efficiently, Hardke said.
‘Farmers are always at the mercy of environmental conditions and our decisions about what is best practice at any given time are determined by those conditions,’ he said.
If burning isn’t an option for farmers, tillage and winter flooding are the other primary choices, Hardke said, adding that this also has its own concerns about greenhouse gas emissions.
“We recognize that we can lose some nutrients through burns, but it’s a trade-off between fertilizer and fuel costs and the efficiencies of being able to plant earlier the following season,” Hardke said.
