Post-Harvest Crop Residue Management
After harvest, you face management decisions as you begin preparing fields for next yearâ€™s crop. Following a corn crop, many Mississippi growers face substantial shock because corn produces far more crop residue than the traditional staples – cotton and soybeans. Historically, growers perceive this residue as â€œtrashâ€ or a problem which must be destroyed 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 is the current 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, â€œMy 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.â€
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. 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 donâ€™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. The nutrient replacement cost associated could be as much as $150 per acre for phosphate and potash loss alone, from losing the residue of a high-yielding corn crop.
Crop residues and resultant higher soil organic matter improve many soil properties which may considerably enhance crop productivity. Additional organic matter affects soils by:
- Improving soil tilth
- Improving soil water holding capability
- Improving water infiltration
- Improving nutrient availability
- Reducing evaporation
- 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 â€“ let mother-nature decompose those stalks over the winter, rather than burning diesel or stalks.