Winter Wheat Spring Nitrogen Applications
Cristie Preston, Ph.D.
Agriculture has always been an integral part of Dr. Cristie Preston’s life. She grew up in southwest Virginia and had interest in crop and animal agriculture since an early age. Once she began college, she initially chose to study animal science but switched to soil science. Dr. Preston attributes her decision partly to an influential professor who told her, “You can’t understand animals until you understand what they eat.” She received a Bachelor of Science degree in animal science and a Master of Science degree in crop and soil environmental science from Virginia Tech. Dr. Preston holds a Ph.D. in agronomy, focusing on soil fertility from Kansas State University. While completing her advanced degrees, Dr. Preston conducted more than six years of field and lab research. Dr. Preston has experience in laboratory research measuring volatility loss from urea-based fertilizers. Her field research has focused on phosphorus availability and the interactions with tillage and placement. She also has extensive experience in working with large data sets and analysis. Her main priority is helping growers to identify yield-limiting factors and fix those issues as cost efficiently as possible.
As winter wheat begins to green-up (break dormancy) in the spring, plant nitrogen requirements increase as biomass increases. It is critical that adequate nitrogen levels are supplied prior to jointing (first hollow stem). Adequate nitrogen levels promote tillering and large head size. Nitrogen is also the primary factor determining the protein level of the grain at harvest. By matching nitrogen applications with timing of uptake, farmers can potentially increase their nitrogen use efficiency (NUE) and decrease the chances of losses.
Topdressing wheat at green-up can be done using urea or urea-ammonium nitrate (UAN) solution. Regardless of the source, the main goal is to get the nitrogen below any residue present and into the root zone for plant uptake. Nitrogen loss, as ammonia volatilization, can increase when ammonium based fertilizers are applied to the soil surface without incorporation and without penetrating the canopy.
Check out the Nebraska guide for Estimating Winter Wheat Grain Yields at various growth stages.