Nitrogen Management for Wheat in 2019
Dr. Edwin Ritchey — Extension Soils Specialist
Nitrogen (N) management for the 2019 wheat crop may differ from recent years for some producers. The current appearance of the 2019 wheat crop is basically determined by planting date. Wheat planted before the end of October generally looked pretty good going into winter. However, later planting dates that struggled with emergence and growth prior to cold and wet weather don’t have the same growth and overall appearance. Many years, wheat planted at the end of October or beginning of November will have adequate growth before the arrival of winter, but not this year.
Producers that split apply N should be getting ready to consider the first application when the weather breaks and growing conditions warrant. Research shows a yield advantage for split applied N (Feekes 2-3 and at Feekes 5-6) over a single N application (Feekes 4-5). The first application at Feekes 2-3 typically occurs between mid-February to early March, depending on environmental conditions. The N rates used should be based on tiller counts and overall stand appearance. Nitro-gen rates for the first application are generally recommended between 30 to 50 lb N/A as deter-mined by tiller counts. Tiller counts above 70 tillers per square foot would receive the lower N rate and the higher N rate would benefit wheat with tiller counts less than 70 per square foot.
Some late planted wheat is currently very small and has a very small root system. Smaller root systems might not be capable of taking up the same amount of nutrients as larger plants. One caveat to N fertilization by tiller counts is due to this very small wheat and subsequent root systems. It might benefit producers with very small wheat to apply the lower end of the recommended N rate so that wheat can utilize the applied N and benefit, but not leaving excess N available for loss-es. Once the wheat utilizes that N and grows, the remainder of the total N rate can be adjusted with the second N application at Feekes 5-6.
A short stint of unseasonably warm weather may have encouraged some wheat growth the last few days. Wheat will likely utilize the majority of the N applied by those producers that made their first application recently. The weather is predicted to turn cold again, stopping wheat growth and nutrient uptake. The remaining N not utilized by the wheat during this time will be subjected to N loss mechanisms such as denitrification and leaching.
Adequate N rates do encourage tillering, but excessive N rates make the plant more susceptible to lodging, diseases, and freeze damage. Proximal crop canopy sensors such as Greenseeker detect a combination of plant biomass and crop “greenness”. There is not enough biomass present at the first application to adequately sense greenness and is not recommended to make the first N application.
Timely planted wheat typically grew off well in the fall and went into the winter in pretty good shape, while late planted wheat is further behind. Nitrogen recommendations should be based on overall vigor and tiller counts at Feekes 2-3 if making a split N application. For more information, please consult AGR-1: Lime and Fertilizer Recommendations, ID-125: A Comprehensive Guide to Wheat Management in Kentucky, or your local county agricultural extension agent.