Early seeded wheat is looking pretty good in eastern ND and Northern MN, but there are some fields that have yellow areas starting to show up. Some agronomists have called with questions about these yellow areas, thinking they are related to soil fertility. Soil and tissue analysis are tools that you can use together to “Trouble Shoot” or “diagnose” if a nutrient deficiency is causing the yellowing and if so, which nutrient is the problem.
One field I drive by on the way to work each day started getting some yellowing in patches last week (see picture below). All of the other wheat fields in the area have a nice green color so this field really sticks out. While sulfur deficiency is supposed to show up first on the upper new leaves and nitrogen deficiency should show up first on the lower older leaves, symptoms in the field don’t always look obvious like they do in text books.
To try and figure out which nutrient is causing the wheat to yellow, I collected soil and tissue samples from an area with yellow wheat and an adjacent area with green wheat. When I was collecting the soil samples, I noticed a change in the soil texture from the yellow wheat area to the green wheat area. The soil where the wheat was yellow had more sand and had a thin layer of topsoil. Where the wheat was green, the soil had more clay and more inches of dark topsoil. It is important when you are trouble shooting problem areas in fields to be aware of everything you see (soil texture, topsoil depth, soil moisture, amount of crop residue etc.)
The tissue and soil samples from the yellow wheat area tested much lower in sulfur than the adjacent green wheat, while the nitrogen level in both areas was very high in the tissue and in the soil (see tables below). The soil and tissue tests confirmed that sulfur is the nutrient causing the yellowing and not nitrogen.
In this wheat field, it is early enough in the season to broadcast some ammonium sulfate fertilizer on the yellow areas and correct the sulfur deficiency before large yield losses occur. This is just one example of using tissue and soil analysis together early in the season to “Trouble shoot” issues that may be related to soil fertility.
As row crops progress in this region, we will put together another example of trouble shooting nutrient deficiencies in corn and soybeans using soil and tissue analysis together! Please give one of our Soil Scientists or agronomists a call if you have any questions on how to use soil and tissue diagnose suspected nutrient deficiencies in your fields.