Burning crop residue eliminates a precious opportunity to improve 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. This can result from wind and subsequent rainfall. Therefore, if you don’t perform a tillage operation for several weeks after burning a field, the nutrients contained in the ash will likely be displaced from or redistributed in your field. This can cause considerable fertility limitations with the next crop and serious long-term issues. The nutrient replacement cost associated 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 crop 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.