Managing residue and tillage this fall can be a challenge given the volume of residue due to downed corn by high winds and drought. There is a tendency to think about tillage as the first option in managing a high volume of crop residue. The impact of residue incorporation with tillage on soil health and water quality has been demonstrated to be significant. Long-term tillage and crop rotation studies for the past 16 years have shown that the input cost associated with conventional tillage was in the range of $30/acre. On the other hand, in addition to the economic input cost of tillage, the combination of tillage and residue removal in excess of 50% of after-harvest residue can cause significant soil health damages that include an increase in soil erosion, reduction in water infiltration, decrease in soil organic matter, and destruction of soil structure. Certain management considerations can be beneficial to reduce the economic and environmental impacts when managing crop residue:
- Do a good evaluation for the amount of residue on the field: Evaluating the amount of residue on the field can help determine what kind of equipment and methods you need to use to manage the residue on the field. If you have a large amount of residue on the field, tillage may not be a very good option given the challenges of incorporating a large amount of residue in the soil. Residue removal or baling can offer a better option. Generally, removing 50% of the amount of residue can provide better soil working conditions, yet will leave an amount of residue to protect the soil from potential erosion (https://store.extension.iastate.edu/Product/14049-pdf ).
- Evaluate your field layout and regional soil type: there are many factors that need to be considered when selecting a management practice for residue such as tillage system for any given field or region within the state. One of those factors is soil conditions, which include soil slope, soil drainage, topsoil depth, or the A-horizon depth, soil texture, highly erodible soil, etc. (https://crops.extension.iastate.edu/cropnews/2014/01/management-practices-considerations ). This will dictate if conventional tillage is a good choice or the use of alternative methods such as baling some of the residue would be more suitable, and leaving at least 50% of the residue, depending on the actual amount on the ground, to protect the soil from potential erosion.
- Leaving residue standing or avoiding shredding residue: Residue can play a significant role in protecting soil from any potential water erosion, especially during the off season. Keeping residue upright has significant benefits in trapping snow and slowing down water movement of the field providing more opportunity for water to penetrate deep in the soil profile. This is important, especially after the significant drought we’ve experienced, to recharge the soil profile. On the other hand, shredding and chopping residue will reduce its value and it becomes a management challenge, where residue will be washed off the field, reducing its value in protecting soil.
- Consider the switch to conservation tillage: Out of a very bad situation, something good and new can evolve. The mind set of using tillage as an answer to any soil and production challenge, needs to be reconsidered. The research in Iowa for the past 16 years showed that the use of conventional tillage agronomically and economically is less superior to conservation systems such as NT and ST. On average, conventional tillage input cost over NT and ST is approximately $30/acre. Also, the research showed that corn yield, after 5-7 years of three conventional tillage systems, ST and NT were the same. The research also documented that soybean yield, with all those tillage systems, showed no significant differences. It is an opportunity for farmers to rethink and evaluate their practices given the current grain prices on top of production challenges.