Using the Spring Wheat Nitrogen Fertilizer Calculator

Palouse wheat fields.

Spring wheat planting is upon us, and fertilizer management is critical for profitable production, especially given fertilizer and wheat market prices. A good soil sample is the first and very important step in fertilizer management, however, the interpretation of a soil sample is also key to making valuable fertilizer recommendations, especially regarding nitrogen application.

WSU Extension has a Dryland Wheat Nitrogen Fertilizer Calculator that is designed to help growers realistically evaluate nitrogen fertilizer applications based on previous crop production and soil sample data. In this example, Joe Farmer is in a reduced tillage annual cropping system in the 17-20” annual rainfall zone. He is planning on planting DNS wheat on the North 40 field that is coming off of 92 bu/acre winter wheat, and he estimates his yield will be 65 bu/acre. His soil sample results show 10.3 inches of available moisture in the profile, and he annually receives 5.8 inches of precipitation from mid-April through mid-July. His soil sample results show organic matter at 3.1%, 7 lbs/acre ammonium-nitrogen and 87 lbs/acre of nitrate nitrogen in the top 4 feet.

Screenshot of the nitrogen fertilizer calculator with inputs as described in the article.

When Joe Farmer enters these data into the calculator, it shows he has a net soil nitrogen supply of 103 lbs/acre. For Joe’s estimated yield of 65 bu/acre, DNS wheat requires 234 lbs/acre (65*3.6) total nitrogen, so he would have to apply 131 lbs/acre. Yield based on soil moisture and expected precipitation is 73 bu/acre of DNS wheat, and it would require 261 lbs/acre total nitrogen. Joe would need to apply 158 lbs/acre.

A total nitrogen fertilizer application between 130 to 160 lbs/acre for 65-73 bu/acre DNS wheat is recommended.

Nitrogen is not the only nutrient needed for profitable production. Other nutrient recommendations can be found in Extension Bulletin WSU EB1987E.

Aaron Esser

For questions or comments, contact Aaron Esser via email at