AGRI-BRIEFS
  AGRONOMIC NEWS ITEMS
From Agronomists of the
Potash & Phosphate Institute
655 Engineering Drive, Suite 110
Norcross, Georgia 30092-2837
Phone (770) 447-0335

Fall 2002, No. 4

NUTRIENT MANAGEMENT IN STRIP-TILLAGE SYSTEMS

Strip-till and zone-till systems are gaining popularity, especially in poorly-drained soils of the Midwest, where cool, wet spring weather delays corn and soybean emergence under reduced tillage. These systems involve tilling a narrow strip of soil, and leaving the majority of the surface undisturbed. For strip-till, strips approximately 6 inches wide and 4 to 8 inches deep are tilled ahead of planting, usually in the fall. For zone-till, crop residue is removed from a band about 8 inches wide, and the soil in that area is tilled 1 to 2 inches deep with multiple fluted coulters. The shallow tillage helps avoid bringing up wet soil in the process. Different variations include vertical slits being cut with coulters 3 to 6 inches deep or thin-profile knives up to 16 inches deep.

These tillage systems all fall within the definition of no-till if they leave the field surface covered with 30 percent or more residue and disturb a maximum of one-third of the surface area, so a strip may be tilled up to 10 inches wide in a 30-inch-row system. The main advantages of these systems are that there is an opportunity to incorporate nutrients if they are applied ahead of or with the tillage operation and that the seed is planted in the loosened soil with less surface residue. Emergence and early growth are enhanced because the soil in the strip tends to be drier and warmer (often by as much as 10 degrees F), and a concentrated source of nutrients is available to provide the “starter effect” to get the crop growing earlier. Even if nutrients are broadcast applied, at least part of the total will be incorporated in the strip tillage operation. Crop yields with strip-till tend to be closer to conventional tillage systems, avoiding the yield depression sometimes associated with no-till systems.

From a nutrient management standpoint, strip systems provide an opportunity to incorporate nutrients and still comply with guidelines or requirements for maintaining residue cover, while providing most or all of the erosion control of no-till. In fact, the increased potential for water infiltration in the loosened tillage strips may further reduce erosion potential. A wider selection of nitrogen sources and manure applications can be used without as much concern for nitrogen losses if the application is made within the strips and incorporated or knife-injected.

Strip application of nutrients is sometimes used as a means of reducing total nutrient application, but that should be done with caution. Even though applied fertilizer may be more efficiently used, total crop removal must be replaced in order to maintain productivity. Energy and time savings are possible if the tillage and nutrient application can be combined with a single trip across the field. This also helps reduce compaction. Special equipment is generally required, but there are variations available that will accommodate most fertilizer materials.

In a corn-soybean rotation, with narrow-row soybeans, there may be a concern when nutrient applications are concentrated in the corn rows because the between-row areas may not provide adequate nutrients for the soybeans growing in the intermediate areas the following year. This is probably a concern only when field soil tests are low. Over a few years of the cropping cycle, there will be a tendency toward more uniform distribution, and the strip effect will be less obvious. Building soil tests across the field is usually the best approach to ensuring maximum potential yield and quality.

Other tillage variations involve a shallow crust-breaking action over the whole surface, maintaining surface residue, and often helping spread it more evenly. They help dry out the soil, but do not provide much incorporation of nutrients.


—HFR—

For more information, contact Dr. Harold F. Reetz, Jr., Midwest Director, PPI, 111 E. Washington Street, Monticello, IL 61856-1640. Phone: (217) 762-2074. E-mail: hreetz@ppi-far.org
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