Burning Stalks – What does it Really Cost?

After harvest, you face management decisions that may have profound effect on future productivity as you begin preparing fields for next year’s crop. Following a corn crop, you may face substantial shock because corn produces far more crop residue than our traditional Mississippi staples – cotton and soybeans. Historically, many perceive this residue as “trash” or a problem which should be removed by fire or tillage. However, crop residue generated in crop rotation systems can produce substantial long-term benefits which are likely to far outweigh any short-term savings accomplished by destroying residue, particularly since our Mississippi soils are naturally low in organic matter. Kip Cullers, a Missouri farmer who was a recent world record holder for soybean yield (160.6 bu/a) and National Corn Growers Association yield contest winner says when asked about burning corn residue, “My opinion is that the soil benefits from the return of both root tissue and above-ground crop residues. We rarely use field burning in our high-yield fields. We do everything we can to maintain or increase the amount of organic matter in our soils.”

Crop residue has substantial long-term benefits when recycled in our cropping systems.

Burning crop residue eliminates a precious opportunity to improve soil organic matter content and potentially can lead to substantial nutrient loss. Nearly all nitrogen and at least 75% of sulfur contained in plant residues will be lost upon combustion. These nutrients could be particularly beneficial for a wheat crop planted following corn harvest. Although phosphorus and potash are not theoretically lost due to residue combustion, considerable loss will realistically occur from smoke and ash that are not recoverable or recycled into the soil. Some of this will occur during the burn event when ash floats out of your field. Substantial loss may also occur thereafter from wind and subsequent rainfall displacing ash. Therefore, if you don’t immediately perform a tillage operation capable of incorporating the ash in the soil, additional nutrients contained in the ash will likely be lost from your field. This can cause considerable fertility limitations in the future and seriously deplete nutrient levels over the long-term. The associated nutrient replacement cost could be $150 per acre or more for phosphate and potash loss alone, from losing the residue of a high-yielding corn crop.

While plants can grow on soils with little organic matter, we face far more issues with fertility, water availability, soil compaction, poor plant health, and erosion on such soils. Furthermore, we will spend considerably more time, management efforts and expenses to overcome these shortcomings arising from low organic matter. So why is organic matter so important? Crop residues and resultant higher soil organic matter improve essentially all soil properties and ultimately enhance crop productivity. In fact, some studies have shown each 1% improvement in soil organic matter improves crop yield potential more than 10%. Additional organic matter affects soils by:

• Improving soil tilth
• Improving soil water holding capability
• Improving water infiltration
• Improving nutrient availability
• Reducing evaporation
• Improving raised bed stability
• Reducing soil erosion

These properties improve plant root development and greatly enhance plant health, particularly during droughty periods. In other words, residue recycling can better accomplish many of the same goals we annually attempt to temporarily fix using deep and/or intensive tillage.

Building soil organic matter level is a long-term process, which should be a primary management goal for southern producers. Our warm, moist environment inherently limits native soil organic matter levels in our region, because it encourages rapid organic decomposition. Tillage also accelerates decomposition, which restricts soil organic matter improvement. Since corn generally produces much more plant residue than traditional crops, you have an exceptional opportunity to improve your soil properties and crop productivity in coming years.

Equipment manufacturers now produce improved planters and planter residue managers specifically designed for use in heavy corn residue. These equipment improvements have facilitated widespread adoption of reduced tillage systems, allowing more opportunity to realize the benefits crop residue offer.  Therefore, we encourage you to try new methods and/or minimal tillage on some acres, and let mother-nature decompose those stalks over the winter, rather than burning diesel or valuable stalks.