Some wheat producers may have found that part of their new crop has turned yellow, and K-State Research and Extension crop specialist Jim Shroyer said there are several possible reasons why.
* Poor root growth. This may be due to dry soils, waterlogging, or poor seedbed conditions at planting time. If the plants have been emerged for several weeks or more, can be pulled up easily, and have only a couple of primary roots visible, then the plants are yellow because the root systems are not extensive enough to provide enough nutrients.
* Nitrogen deficiency. Nitrogen deficiency causes an overall yellowing of the plant with the lower leaves yellowing and dying from the leaf tips inward. The primary causes of nitrogen deficiency are insufficient fertilizer rates, leaching from heavy rains, and the presence of heavy amounts of crop residue, which immobilize nitrogen.
* Low temperatures. When the weather is cold as the wheat emerges, it can result in yellow banding on the leaves. If this is the cause of the yellowing, symptoms should eventually fade away.
* Leaf rust. If leaf rust infects young seedlings in the fall, the plants may turn yellowish. Fall infections of leaf rust are not common in Kansas, but can occur. Tan spot can also cause wheat to turn yellow in the fall. It rarely, if ever, pays to treat fields in the fall for leaf rust or tan spot, even if those diseases do cause yellowing. Cold weather in the winter normally cures this problem.