Editor’s note: The following was written by Mahdi Al-Kaisi, professor of agronomy and Extension soil and water specialist at Iowa State University, for the Extension Integrated Crop Management website Feb. 26.
The amount of snow received and potential spring rain events can be challenging to an early start to the growing season.
Approaching field operations for nitrogen applications, tillage, weed control, etc. need to be weighed against potential soil compaction and successful seed germination. Two of the greatest concerns during spring are excess soil moisture and cold soil temperature and their impacts on seed germination, especially in areas with poorly drained soils.
Areas with poorly drained soils can be managed with less tillage to ensure suitable soil conditions for plant growth. Tillage systems that manage residue and help warm the top-2 inches of soil for seed placement to ensure successful seed germination may be considered.
The most suitable system to achieve this is strip tillage. Narrow-width tilled strips are traditionally created in the fall. They can increase early-spring soil evaporation and soil temperature in the top-2 inches. That’s particularly effective in poorly drained wet soils, where slightly raised soil strips are created by normally available farm equipment such as anhydrous knives, disks, coulters, tool bars or manure-injection equipment.
Another practice that can be equally effective in improving wet and cold soil conditions early in the spring is the use of cover crops. Cover crops can serve as a mechanism to extract excess water from the topsoil, providing drier conditions that can contribute to the increase in soil temperature.
Results from a recent study of tillage and cover crops — winter rye — demonstrate the impact of cover crops on increasing soil temperature and reducing moisture. That’s especially true with no-till — soil temperature increased 2.1 degrees.
But cover crops have less effect with a chisel plow on the top-2 inches. The effect of both no-till and cover crops in improving soil porosity and thus water infiltration and soil aeration is a contributing factor as compared to a chisel plow, where lack of soil permeability can limit cover crop effects on soil moisture.
Soil temperature is greatly influenced by soil-moisture conditions. Any practice that removes excess moisture, especially early in the spring, can improve crop establishment and potentially reduce the effect of soil-borne diseases driven by cold temperatures. The best combination of tillage and cover crops appears to be when no-till and cover crops are used to enhance the inherent best soil functions and properties provided by no-till systems.
The challenges of wet conditions that may exceed field capacity may require a comprehensive-residue and other field-management-practices plan.
- Consider residue management that ensures uniform residue distribution during harvest.
- Manage residue cutting height by setting the combine to leave corn stalks at 12 inches high.
- Avoid residue shredding to provide better aeration and soil-moisture evaporation.
- Use minimum tillage alternatives such as strip tillage, especially in the fall.
- Equip planter with residue cleaners or fluted clutters to help warm the top few inches of soil.
- Include a well-designed field-drainage system to help remove excess water.
- Incorporate perennial grasses within buffer strips and marginal areas to help extract excess moisture.
- Include a no-till system to improve soil structure, soil porosity and removal of excess water.
- Incorporate cover crops as a mechanism to extract soil moisture as well as to improve soil organic carbon and soil porosity, and contribute to warming the top soil depth.