AEN-131

NO-TILL CORN CAN WORK

ISU Extension Pub # AEN-131
Authors: Dr. Greg Brenneman, ISU Extension Field Specialist -
Agricultural Engineering, and Mr. Jim Fawcett, ISU Field Specialist - Crop Production
Revised January 1992
Content reviewed 4/95 by Dr. Mark Hanna, ISU Department of
Agricultural and Biosystems Engineering

Over the past 10 to 15 years, most of the no-till acreage has been in planting corn. This has included corn no-tilled into sod, soybean stubble and into cornstalks. While this has been the place many producers first tried no-till, more are now finding that success comes easier with no-till soybeans. With corn, better management has been required to overcome problems of early corn growth, maintaining yields and handling fertility. In this issue of No-till Notes, we will look at management tips for successfully no-tilling corn.

Yield Results

In most cases, yield results for corn following soybeans have been very similar between tillage systems. In situations where no-till corn after soybean yields have been lower, often the problem has been previous soil compaction or excess soybean pods and fines windrowed by the combine. When the fines coming off the combine sieves are not spread out, they can create a thick mat that keeps the soil significantly wetter and cooler which slows corns early growth. While row cleaners on the planter can move some of this residue aside, a better solution is a chaff spreader on the combine to get the fines and pods spread out the width of the combine. If compaction has been a problem as evidenced by poor root growth, some remedial tillage may be needed. Some producers are having good results with a deep tillage operation in the fall and then "no-tilling" the following spring. Usually this only needs to be done when first starting into no-till and is not needed every year.

The place where more difficulty has been experienced in maintaining yields, has been in no-till corn after corn. Regardless of tillage system, corn after corn yields usually average 10% less than corn grown in a rotation. With no-till corn on corn, there is often heavy residue cover even when it is spread uniformly. On some light textured soils, this residue cover is beneficial in holding moisture for the new corn seedling. On finer textured soils with a higher clay content, this moisture holding and insulating effect may be detrimental to the corn seedling. While there is some concern that there is a toxic or allelopathic affect of corn residue on new corn seedlings, it appears that residue keeping the soil cool is more important in slowing early corn growth. By removing some of the corn residue over the row and allowing sun light to warm the row area, the delayed early growth is minimized. As mentioned earlier, compaction can also be a problem when starting to no-till corn after corn. If this is a problem, deep tillage in the fall before starting to no-till should be considered.

Weed Control

While there have been few new developments in no-till weed control for corn, there are number of weed control programs that have proven very successful. One in particular is the use of an early preplant (EPP) application followed by a preemergence or post emergence herbicide application. This type of program has resulted in very consistent weed control under a wide range of weather conditions. Since the EPP application goes on in early April before many weeds have emerged, a burndown herbicide is not needed. Also, there is a high probability of receiving rainfall to incorporate the herbicide. This herbicide activation, along with a follow-up herbicide application, has resulted in very consistent weed control. Herbicides that have worked well for EPP applications include Bladex, atrazine, Dual and Lasso. The triazines (Bladex, atrazine or combinations) have worked especially well because they provide control of annual grass and broadleaf weeds. They also burndown winter annual broadleaf weeds and other early emerging weeds such as giant ragweed. These weeds may be up in an early spring or if the EPP application is a little latter than planned. Usually, only 1/2 to 2/3 of a normal rate is used with the EPP application. The rest of the herbicide is then applied preemergence or early postemergence. This covers any soil disturbance done during planting and helps provide season long weed control. If cultivation is planned on, a good option is to apply a broadcast EPP application and then band a PRE treatment over the row.

For those who are planting in mid April, the advantages of the EPP treatment are less. With the early planting, often just a PRE treatment will work well Since most weeds up at this time are primarily small broadleaf weeds, Bladex or atrazine as a part of the PRE treatment will do a good job of burning these weeds down.

Fertility

While more concern has been expressed in the past on how to apply P and K in no-till, it appears that method of N application may be more important. If soil tests for P or K are low or very low, incorporation, deep banding, or planter applications of P and K are recommended. If soil tests are medium or above, the P and K can be surface applied or put on with the planter. With no-till corn, some fertilizer application with the planter is suggested. If fertilizer is not being applied with the planter, putting 15-30 lb of N on with the herbicide can help with the early growth of the corn.

Research data from around the Midwest has shown a yield advantage in no-till corn when the nitrogen is incorporated into the soil. Applications of anhydrous ammonia can be done in both corn and soybean residue. Good results have come in using a coulter in front of a thin blade applicator knife. While liquid N can be broadcast alone or with herbicides, there is potential for loss because of urea volatilization unless timely rainfall is received. More consistent yields have been achieved when most of the liquid N is placed in the soil. This can be done with a coulter and thin knife applicator or applied during cultivation. Recently, some applicators have come on the
market that use a straight stream spray nozzle behind a coulter. These also
seem to be working well.

Operating Advice

More equipment specifics will be covered in the fourth issue of this newsletter. With no-till corn after corn, it is a good idea to clear some of the residue away from the row using double disk row cleaners or multiple coulters. Double disk row cleaners should be set to run just at or slightly above the soil surface. If coulters are being used, plan to run them at or just above planting depth. In most conditions, no-till corn should be planted at a depth of 1.5 to 2 inches.

There is considerable difference of opinion on whether to plant in the row middle, right on the old row, just to the side of the old row, or wherever the rows happen to fall. This is primarily a concern with corn after corn and will depend some on planter setup and condition of the residue. In general, planting right on or just off to one side of the old corn row will keep wheel traffic confined to row middle areas. Some experimentation will be needed for individual situations.

Getting Ready For This Spring

To get ready to no-till corn this spring, evaluate the following items:

Is your planter equipped with coulters or cleaning disks if you are going to no-till into cornstalks?
Can you put some fertilizer on close to the row with the planter?
How will the nitrogen be applied?
What will be your weed control program? Will you be putting on an EPP application? If so, be prepared to go as soon as the soils are fit in early April.

Be flexible as you head into each new season. Also, be patient and don't push the field work before soils have dried and are fit to plant.