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3/31/2008 - 4/6/2008

Managing Residue for a Good Stand

By Mahdi Al-Kaisi, Department of Agronomy and Mark Hanna, Department of Agricultural and Biosystems Engineering

Managing corn residue, particularly with no-till system in highly productive and wet soils present a significant challenge to establish corn stands in such environment. One of the biggest advantages of this system is that it leaves significant amounts of crop residue on the soil surface, which protects the soil from water erosion and improves soil tilth. Conversely, these significant amounts of residue pose a challenge of their own: Managing residue as a part of a no-till system.

No-till soybean field
Corn residue in soybeans

To ensure the success of no-till, farmers need to use a system approach in the management of residue. This involves the integration of planting, nutrient application and harvesting processes. While each of these components is important, this article will focus on two ways to manage crop residue in a no-till system: cutting residue after harvest and adjusting the combine to ensure uniform height, volume and distribution of residue during harvest.

Overcoming the challenges associated with managing crop residue during planting season starts at harvest time. The way residue is managed on the field after harvest is very critical to the success of providing a good soil seedbed environment for planting. Operating the cornhead as high as practical (e.g., 12 inches or more) will provide a better residue orientation for trapping snow and uniform distribution of it across the field.

Many farmers have gotten into the habit of chopping corn stalks after harvest. This can present a significant management problem as well as other potential production problems that are associated with low soil temperature early in the spring, potential soil diseases, and early germination problems just to name a few. Chopping residue also can reduce the effectiveness of it in protecting the soil surface from potential water erosion, especially during high intensity rainfall events, where residue will be washed away with the surface runoff. Chopped residue is no longer anchored into the soil and is more prone to plugging tillage implements or planters used in subsequent operations.

Other alternative in managing corn residue with minimum soil disturbance is the use of strip-tillage or residue cleaners/mangers attachment prior or during planting. The use of strip-tillage is an excellent choice in areas where wet soil conditions are dominant during early spring and during planting and relatively flat soil surface. The removal of residue with residue cleaners or strip-tilling 8 inches zone can improve soil temperature in the top 2 inches by as much as 2 degrees F. This task can be accomplished with very shallow soil disturbance or just residue removal with residue cleaners to speed warm-up the seedbed early in the spring by exposing the soil surface to direct solar radiation. One caution, however, if anhydrous will be involved with strip-tillage in the spring; the tilled zone must be 6-8 inches deep to prevent nitrogen losses and other potential effects on seed germination.

By Mahdi Al-Kaisi is an associate professor in agronomy with research and extension responsibilities in soil management and environmental soil science and Mark Hanna is an extension agricultural engineer in agricultural and biosystems engineering with responsibilities in field machinery.

Spring Sampling OK for Two Corn Nematode Species

By Greg Tylka, Department of Plant Pathology

Plant-parasitic nematodes can damage corn. Each year, several instances of this are discovered in Iowa. More frequent cropping of corn following corn and less frequent use of soil-applied insecticides that might have provided some nematode control may result in more instances of nematode damage to corn this growing season. Also, nematodes are more damaging to corn (and other crops) during hot, dry conditions, so if a drought occurs in Iowa in 2008, damage to corn from nematode feeding may be more common.

Assessing whether nematodes are damaging corn requires determining what species are present in a field and what their population densities (numbers) are when the numbers are at their highest. For most plant-parasitic nematodes that feed on corn, numbers increase through the first half of the growing season. So samples should be collected mid season, when nematode numbers likely are greatest, and then the numbers can be compared to damage thresholds established for corn. Spring sampling is not recommended for most corn nematode species.

Corn plants damaged by nematodes
Corn seedlings damaged by needle nematode in southeast Iowa (photo Tom Hillyer).

However, Iowa fields with 70 percent or more sand content might be infested with the needle and/or the sting nematode (both species are restricted to sandy soils), and these nematodes migrate down into the soil in the middle of summer, when soils are warmest. So if damage from needle or sting nematode is suspected in a sandy field, samples should be collected in the spring or fall, not in the summer. Needle and sting nematode could be missed in mid-season samples.

To test for needle or sting nematode, collect 20 or more 12-inch-deep soil cores in the spring.  Sampling can be done prior to planting. If sampling is done after crop emergence and damage to the young crop is seen, collect the soil cores from the root zone of corn plants within the area being damaged.

Soil cores should be mixed well, then placed in a moisture-proof bag and submitted for processing as soon as possible. Root tissue, which is required for an accurate diagnosis of corn nematodes in mid season, is not needed when sampling specifically for needle and/or sting nematode in the spring.

Samples for nematode diagnosis can be sent to the ISU Plant and Insect Diagnostic Clinic, 327 Bessey Hall, Iowa State University, Ames, IA 50011. The test for all corn nematodes, including needle and sting nematodes, is called a complete nematode count. Samples sent to ISU should be accompanied by a completed Plant Nematode Sample Submission Form (ISU Extension publication PD 32), and a check for the $30 per sample processing fee.

For more information about corn nematodes, an ISU Extension publication titled Nematodes That Attack Corn in Iowa (PM 1027)  is available online.

Greg Tylka is a professor of plant pathology with extension and research responsibilities in management of plant-parasitic nematodes.

This article was published originally on 4/7/2008 The information contained within the article may or may not be up to date depending on when you are accessing the information.

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