Safe Burning of Crop Residues
In a White Paper posted on this website, guidelines for burning crop residues to destroy weed seeds were presented. Results from research cited in that paper provide evidence that burning crop residues that are concentrated into narrow windrows by a specially designed chute at the rear of the combine can be an effective method for destroying weed seeds that are dispensed from the combine during crop harvest.
It is doubtful that this tool for weed management/control has been/is being used on a wide-scale basis in the Midsouth. However, with the increase in problematic herbicide-resistant (HR) weeds such as Palmer amaranth in soybean, it is reasonable to assume that alternative methods such as residue burning may become more commonplace. It is with that thought in mind that the following is presented.
In a recent Arkansas Row Crops blog article titled “Managing Row Crop Residue Burns” by Dr. Jarrod Hardke of the Univ. of Arkansas, a link is provided to a publication titled “Arkansas Voluntary Smoke Management Guidelines for Row Crop Burning” that was compiled by a task force comprised of members from several Arkansas agricultural organizations. Major points from that publication follow.
• When burning crop residue for any purpose, smoke management techniques will minimize the impact of the smoke on roadways and facilities in the surrounding area.
• For a more effective burn, an optimum waiting period of four days (assumes no rain) should be observed to ensure low fuel moisture.
• In Arkansas, medium grain/seed yields for corn (180 bu/acre), soybean (48 bu/acre), and rice (163 bu/acre) will result in available fuel in the order of corn (4.7 tons/acre), soybean (4.3 tons/acre), and rice (3.7 tons/acre). A soybean yield of 64 bu/acre (common for irrigated soybean) will result in 5.7 tons/acre of available fuel. An estimate of the tons of fuel available for the burn is an important component in planning a burn.
• Identify the nearest smoke-sensitive area, and burn so smoke does not go in that direction. The above guide gives 5 criteria to use for determining how to keep smoke from moving to identified sensitive areas.
• Determine the burn category day based on the presented guidelines used for a 1 to 5 scale, with 1 being poor and 5 being excellent for smoke dispersal. Inversion periods are to be avoided.
• Do not burn if 1) winds exceed 15 mph, 2) humidity is below 20%, or 3) the wind direction could send smoke directly onto roadways or into populated communities.
• And finally, consult the complete Arkansas guide for details about the above major points and additional information about burning row crop residues.
A publication titled “Windrow burning–tips from the experts” from the Government of Western Australia, Dept. Of Primary Industries and Regional Development, presents many helpful tips for windrow burning. It provides links to video resources about the process, including how to construct a combine-attached chute that will create narrow windrows, or windrows where most or all of the residue from the combine will be concentrated. Such narrow windrows are considered necessary for effective burning of most residues, including weed seeds. And a concentration of soybean residue into such narrow windrows will be a necessity since the entire soybean plant will go through the combine during harvest–i.e., there will be little or no remaining soybean stubble to aid in the burning process.
Even though the above smoke management publication is from Arkansas, its contents can be applied to burn management in other Midsouth states that do not have published burn/smoke management guidelines for agricultural producers. Also, note the word “voluntary” in the title of the Arkansas publication. Thus, the contents of the publication can be considered advisory. However, agricultural producers are advised that their due diligence in managing smoke that emanates from agricultural burning should be done according to these voluntary guidelines so that mandatory restrictions will not be forthcoming. This will be especially important if/when windrow burning becomes a much-used practice in the fight against HR weeds.
Composed by Larry G. Heatherly, Oct. 2020, larryheatherly@bellsouth.net