April 6, 2007

Tips for No-tilling Corn on Corn

Run the combine cornhead about a foot high at harvest to get most of the residue down to the ground yet leave enough residue standing to keep it in place and to catch snowfall. Knife-to-knife or tapered snapping rolls do a good job of processing the residue to make no-tilling into corn residue easier.

1. Process the residue with the cornhead. Corn stalks and leaves must be processed down through the snapping rolls at harvest to make no-tilling corn on corn easier. Knife-to-knife or tapered snapping rolls are more aggressive to lacerate and crush the stalks. By getting the stalks broken up and down to the soil, they are exposed to microbes and the weather to speed decomposition. Too often, intermeshing snapping rolls don't let the corn stalks between them and leave the stalks tall and leaning. While this catches more snowfall, it doesn't allow the stalks to decompose much before planting. With Bt corn hybrids, processing the stalks with the cornhead is even more important.

2. Leave some of the corn stalk standing at harvest. A 10- to 12-inch tall corn stalk anchored and upright after harvest helps keep the residue in place, reducing residue movement by wind and water. It also catches snowfall and reduces wind erosion. The standing residue allows good air movement down to the soil surface, encouraging faster breakdown of the residue. Matted or flattened residue doesn't let the surface soil dry as quickly and may delay planting in wet springs. Leaving taller stalks at harvest may create problems when catching on planters or fertilizer equipment the next spring.

3. Use controlled traffic if possible. All field operations should use the same traffic rows. Space the combine tires between the rows to keep the residue standing in all the corn rows. With uniform stalk heights, a more even winter snow catch across the field will result in more uniform soil moisture and temperature conditions at planting time. When planting down the old row or immediately next to it, the new seedlings won't be in a compacted wheel track. Consider putting narrow depth gauge wheels on the planter to allow planting closer to the old row and to leave more residue standing in no-till. With controlled traffic, the firmed soil in the wheel tracks provides better traction and often more timely field operations. Potential compaction problems are greatly reduced as the remaining row middles aren't driven on. Consider Auto Steer to help maintain controlled traffic driving patterns.

4. Consider grazing the corn stalks to reduce residue levels and clean up volunteer corn. Some producers generate extra income by renting out the corn stalks for grazing or by harvesting the residue for feed or bedding. While this decreases the amount of residue, not all of the residue should be removed and it shouldn't be done every year. If mechanically removing residue, leave 8, 12, 16 or 24 rows standing every 48 rows to reduce wind erosion and trap snowfall. This may create some problems with planting since the soil and residue conditions will not be uniform.

A better plan would be to remove the residue from 24 rows and leave 24 rows standing; or another number of rows to fit multiple widths of the planter. In the spring, plant the strips in the field where the residue was removed first. Then stop and make adjustments on the planter to handle the residue and plant the rest of the field. Controlled traffic, ridge-planting, light bars or Auto Steer make planting in strips easier.

5. Realize the value of leaving residue in the field. Residue should be left in the field as it protects the soil to reduce erosion and conserve water, critical in dryland production. The residue mulch greatly reduces evaporation, saving three to five inches of water over the growing season (see Residue reduces soil moisture evaporation in the April 21, 2006 issue of CropWatch).

The nutrients in the removed residue will need to be replaced with increased fertilizer rates. Estimates are that for every ton of corn grain produced there is a ton of stover produced. With 200 bushel corn, there would be 11,200 pounds of corn grain, or 5.6 tons of grain, and 5.6 tons of stover. Each ton of stover contains about 12.25 pounds of nitrogen and about 3.25 pounds of phosphorus which needs to be replaced if the residue is removed. Removing too much residue over a period of years will lead to a decrease in organic matter as the carbon in the residue isn't returning to the soil.

6. Expand the use of cover crops. The humidity in the growing cover crop canopy helps decompose the residue after corn harvest. In addition, cover crops can help dry poorly drained soils to aid soil warming in the spring. The added roots helps stabilize the soil and build soil structure. However, the cover crop must be controlled in a timely manner so that it doesn't over dry the soil or create too much additional residue.

7. Leave residue anchored and attached, standing upright. Shredding the stalks or fluffing the top layer of soil with a rotary harrow or similar tool may aid in residue decomposition, but it detaches the residue or flattens it. The residue mat formed makes it more difficult for the soil surface to dry and may interfere with the planting process if it's not uniformly distributed or if it's too thick. In addition, if the residue is detached, it may plug up the planter or move with wind or water. Any residue that's standing upright doesn't have to be cut with the planter or fertilizer equipment and helps keep the wind and sun off the soil surface.

Paul Jasa
Extension Engineer
Robert Klein
Cropping Systems Specialist