No-Till Corn on Corn: Tips For Handling Residue

By Jane Fyksen, Crops Editor
Thursday, April 12, 2007 11:07 AM CDT

When it comes to no-till corn, this year's planting season really started with last fall's harvest. It's turning into a cold, wet spring, and no-till residue is notorious for slowing soil warm-up.

This week, University of Nebraska's Paul Jasa, Extension engineer, and Robert Klein, cropping systems specialist, examine fall harvest and planting interactions for no-till corn on corn. Other specialists look at planting date and "cost control."

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 stalks. By getting stalks broken up and down to the soil, they're exposed to microbes and weather to speed decomposition. Too often, intermeshing snapping rolls don't let the corn stalks between them and leave stalks tall and leaning. While this catches more snowfall, it doesn't allow stalks to decompose much before planting. With Bt corn hybrids, processing the stalks with the corn head is even more important, they say.

This pair suggests running the corn head about a foot high to get most of the residue down to the ground yet leaving enough standing to keep it in place and 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. 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 catching on planters or fertilizer equipment in the spring.

All field operations should use the same traffic rows. Space combine tires between the rows to keep residue standing in all cornrows. 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.

Some producers generate extra income by renting out corn stalks for grazing or harvesting residue themselves for feed or bedding. A good plan is 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 now, plant the strips in the field where 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.

Residue mulch greatly reduces evaporation, saving 3 to 5 inches of water over the growing season. 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, Jasa and Klein say.

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

Shredding the stalks or fluffing the top layer of soil with a rotary harrow 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 planting if it's not uniformly distributed or it's too thick. In addition, if the residue is detached, it may plug up the planter. 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.

Corn on corn holds extra costs

High prices have many farmers switching their usual planting rotation of corn following soybeans to corn on corn. However, University of Nebraska soils scientist Charles Shapiro warns producers they need to keep cost in mind if making the switch.

When calculating which crop would be most profitable, figure that continuous corn yield will be 10 to 15 percent less than corn after beans, and it will take 30 to 45 pounds more nitrogen to raise that crop, at a current cost of about 48 cents a pound.

"One cannot just take the net income from soybeans and corn and compare them if the cropping sequences have changed," he says. "Other practices will change as well. It also is important to factor in timeliness of operations. Corn yields will be reduced about a bushel per day if they are planted late." As a farmer increases corn acres, there's more chance that some of them will not be planted at the optimum time, he contends.

In addition, planting corn on corn also can result in a possibility of increased corn rootworm problems, says Bob Wright, University of Nebraska field crops specialist. Rootworm beetles lay eggs in cornfields, that after overwintering, hatch in the spring. The beetles can't survive in soybeans. "The more years you have corn on corn the more populations can build up," Wright warns.

It looks like corn planting could get started later than normal. In general, corn should be planted when soil temperatures are near 50 degrees. Seed will absorb about 30 percent of its weight in water, and temperature does not affect water "imbibition" much. That's different than root and shoot growth, which is correlated with soil temperature. In cold soil conditions (below 50 degrees), seeds will readily absorb water but not initiate root or shoot growth, leading to seed rots and poor emergence if poor seedbed conditions are prolonged.

Cool soil conditions early in the season is one reason there is more variability in final stands relative to seeding rate.

Keep in mind that yields are reduced more when planting too late rather than too early. Some producers will be especially pushed this year when planting corn because of the increase in corn acreage. With more acres to plant, the possibility of having corn planted outside the optimum window is higher than other years. In general, research has shown a small yield loss with very early planting dates and larger yield losses with significantly delayed planting dates.

Yields are much more stable early in the planting season than late. Planting 10 days before the optimum window is generally a much safer practice than planting 10 days after the window. That's assuming, of course, that soil conditions are favorable.

Anhydrous placement eyed

Robert Mullen and Edwin Lentz with Ohio State University say a wetter, later spring may delay some early-season applications of anhydrous, and with more corn to plant this year, eventual warmer weather may have growers thinking more about planting then putting on that nitrogen. But should they manage that ammonia application?

Placing anhydrous too near germinating seed can kill the corn and cause stand problems, so caution is warranted. If you put anhydrous ammonia deep enough into the soil (6 to 8 inches below the surface) you can plant immediately after the application, but be certain about the depth, they warn.

What you're trying to avoid is placing seed in the ammonia "saturation zone." The liquid form injected quickly becomes a gas and expands. The amount of expansion is a function of soil moisture, and the greater the moisture level the smaller the zone will be.

Anhydrous ammonia can also be applied on the diagonal to avoid applications that kill entire rows of corn.

If the weather really works against you, wait until the corn has emerged to make an application.

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