Understanding Crop Residue Decomposition
With great yields, come great residue opportunities or challenges. Although this statement may not be entirely accurate for all crops or every season, it represents the idea that crop residue left in the field should be properly managed to ensure next year’s crop will not be hindered by excessive, uneven residue.
Compared to corn stover, soybean residue is not a major problem since it is less in quantity and easily decomposable. Why is there more corn residue? Some of the reasons include improved genetic packages, better gene traits, higher populations, increased overall plant nutrient programs and fungicide use, just to name a few. Another primary reason for more residue is reduced tillage practices which result in less residue breakdown. In these fields, growers must manage corn residue properly or they will risk the possibility of stand establishment issues as shown in the images below.
This is especially important in a corn-on-corn rotation, as corn is less tolerant of residue than soybeans. Residue reflects sunlight and insulates the soil, reducing both warming and drying of fields in the spring. This may prevent early planting or result in reduced or non-uniform emergence. Uniform emergence is critical to optimizing yield potential in corn. Plants that emerge later than their neighbors may be competing throughout their development, and yield may be reduced proportionately to their delay.
When planting corn-on-corn, issues arise in the small seed establishment zone or row. These issues can result in some of the following challenges:
- Residue can be pushed into the seed furrow with the planter disc openers or coulters which may interfere with proper seed placement, reduce seed-to-soil contact and delay germination.
- Excessive residue over the row may reduce soil temperature and delay germination, or it may present a physical barrier to planting or emergence. Root growth and nutrient uptake is also reduced by cool soils.
- Corn residue that is in contact with corn seedling roots may have an allelopathic (toxic) effect, resulting in stunted growth and delayed development.
- Later emerging or slower developing "runt" plants may acts as weeds, competing for sunlight, water and nutrients but contributing very little to grain yield.
- Excess corn residue increases the risk of pest infestations, including insects, diseases and rodents, and it may intercept and tie up herbicides and nitrogen (N).
Is there something that can be done to accelerate corn residue breakdown? Try a fall/winter application of N and liquid Hydra-Hume® to corn stalks? If weather permits, an application of 3-4 gal of UAN + 1 gal of Hydra-Hume @ 12-15 gal/ac will provide a readily available food source for the biological decomposition of corn residue. This process will be very limited in the cold, winter months; however, once warmer springtime temperatures return, the breakdown of residue will be enhanced. As mentioned above, making the residue easier to plant through for even seed placement and emergence is a good management practice that usually pays dividends with extra bushels during the next harvest. To learn more, find a Helena location near you.
- Sam N. Bartee, CCA/CAC, West Central Division Agronomist