2005 Year in Review

Winter Wheat Crop

It will soon be time for wheat producers in northern Illinois to evaluate the condition of the winter wheat crop and to make decisions regarding spring application of nitrogen.

As a general guide, when home lawns begin to show green color, winter wheat should be “breaking” dormancy and starting to grow. A stand of 25 to 30 plants per square foot is generally considered optimum. 15 to 20 plants per square foot is the minimum population needed to keep a field in the spring. One should take stand counts at several locations across the field so a representative sampling is obtained. A stand count can be determined by throwing a hoop or square of known diameter into the field and counting the plants within it.

As one makes a plant count, also check the condition of the crown. The crown of the plant needs to be ¾ - to 1-inch below for the soil surface and can be killed at temperatures less than 15 degrees F. The crown is the source of carbohydrate storage, and as long as it is alive, the plant can put out new leaves.

How much nitrogen is needed? University of Illinois nitrogen recommendations for wheat depend upon soil organic matter and the presence of a legume underseeding. For example, with moderately dark-colored soils with 2 to 3 percent organic matter and without a legume underseeding, the suggested application range is 70 to 90 pounds per acre. With a legume underseeding, drop the nitrogen rate by 20 pounds. Be sure to give credit for any nitrogen that may have been applied last fall with phosphorus and potassium fertilizer. 10 pounds of nitrogen credit can be realized when wheat follows soybean.

The best time to apply nitrogen is in the early spring, when growth is resuming. Stands that are to be kept should be treated with nitrogen as soon as they begin to green. University of Illinois research has not shown a consistent advantage for splitting nitrogen application in the spring. Applying all of the nitrogen in the fall increases risk of loss, but it is a common recommendation to apply some nitrogen in the fall, at least 20 pounds per acre but no more than 40 pounds per acre. Uniformity of nitrogen application is important.

A 3-year study by The Ohio State University indicated that yields decrease substantially when nitrogen is applied after early stem elongation (Feekes growth stage 6, or when the first node is visible). At this stage, wheat begins a period of rapid nitrogen uptake.

Further information is found in the Illinois Agronomy Handbook available at Extension offices.

by  Editor, theCity1.com
March 10, 2005