By: Ken Panchuk, PAg. Provincial Specialist Soils, Crops and Irrigation Branch
The southern U.S. wheat harvest is underway, with early Kansas wheat showing lower-than-ideal protein levels. This may result in increased demand for higher protein wheat that could translate into higher protein premiums for our bread wheat classes. To ensure high protein levels, producers can top dress additional nitrogen in the form of liquid nitrogen, with or without a urease inhibitor (if needed).
The rate of nitrogen needed will depend on the yield and protein potential in a particular crop. In general, top-up nitrogen rates range from 20 to 40 pounds of actual nitrogen per acre applied with drop tubes or split nozzles. This application method minimizes leaf burn as large drops roll off the leaves and fall to the soil surface. If there is no rain in the forecast for a couple of days, then use a urease inhibitor to protect the urea part of the liquid nitrogen fertilizer while waiting for a rain to move the nitrogen into the soil for access by the crop. About half an inch of rain is needed to move the nitrogen into the soil. Application of nitrogen at an early growth stage, before elongation in wheat, can provide both yield and protein increases. However, this assumes normal precipitation during critical times for the rest of the growing season. Application of nitrogen at later growth stages contributes more to protein.
Several tools are available for crop scouting to determine whether additional nitrogen is needed. Tissue testing from good and pale green areas within a field gives an indication of nitrogen levels within crop tissues to aid decision making. Today, there is a move to use electronic real time sensors such as a hand-held Greenseeker. A Greenseeker, or other optical sensors whether hand-held or on a drone, require a nitrogen-rich check strip of the same crop variety to compare to other areas of the field. GPS tracking helps identify the areas of the field during the field operation. Some producers have optical sensors on their high-clearance applicator, which enables automatic, on-the-go sensing of nitrogen needs. Satellite images, in real time, are also available to assist in identifying areas that may need additional nitrogen. However, field scouting is still a necessary step to determine if the pale green areas that appear to need more nitrogen are not caused by other issues such as problem soils, and root or leaf diseases.