Based on the number of calls coming in, a combination of1) applying N inearly February (especially liquid N) and 2) continued wet weather has led to N deficiencysymptoms showing up in some wheat fields.
Variations in green color within a field can be due to application method as well as weather or soil conditions.
Typical N deficiency symptoms are: bright yellow green color with yellow lower leaves and poor tillering. A plant tissue test will help to confirm N deficiency and separate it from yellowing caused by low sulfur or low pH.
Widespread N deficiencythat is visible after all N has been applied — particularly where early N was applied —may require some additional N in some fields.
What rate to apply?
The goal is to apply a modest amount of ‘corrective’ fertilizer without going too high this late in the season, especially where rates above 100 pounds of N/A have already been applied.
Too much N this late could cause lodging and potentially more diseases in the crop.
A modest rate would be 30 pounds of N/A applied as dribbled UAN or granular N flown on the field.
Spraying UAN broadcast is risky and on a hot, sunny day could cause tremendous leaf burn, which we do not need this late in the season.
Corrective N must be applied before the flag leaf is fully visible. The closer to flag leaf N is applied, the less effective it will be in turning a crop around.
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