Nutrient deficiencies are a major source of yield and income loss in winter wheat. Winter wheat is generally in the field for eight months and planted in well drained soils so the chance of losing nutrients due to leaching is high.
Wheat is very sensitive to insufficient macro nutrients, secondary nutrients and micro nutrients. Nitrogen is the most common deficiency in wheat.
Nitrogen leaches easily and is required in relatively large amounts by the wheat crop. It is likely that nitrogen is the most common nutrient deficiency in areas with predominantly sandy soils.
Symptoms vary with the time of occurrence. Fall deficiencies generally result in slow growth, fewer tillers and a general yellow cast to the field. Spring deficiencies can produce stunted pale plants that cut out earlier and produce less grain per plant.
Sulfur deficiencies are very similar in appearance to nitrogen. If observed early enough they will be spotted higher in the plant than nitrogen deficiencies. Soils with low amounts of clay in the subsoil are more likely to have problems holding sulfur. To be safe, sulfur should be applied in both the fall and spring.
Phosphorus needs should be supplied at or before planting. High yielding winter wheat depends on fall tillers, and fall tillering is severely limited when phosphorus is deficient. Wheat fields often appear to be lacking in phosphorus when spring temperatures fluctuate wildly.
Imbalances in nutrient ratios result in the characteristic purpling of wheat plants. However, fields fertilized properly in the fall rarely need additional phosphates in the spring.
Calcium and boron deficiencies can easily be confused. Smaller, poorly formed plants are common in both cases. Death of tissue at the terminal end of plants is common in all boron deficient plants. Boron deficient wheat plants are not as widespread where previous crops received boron even though it leaches easily.
Manganese and magnesium both cause chlorosis, but with just a little practice the two are easily distinguishable. Lack of manganese causes chlorotic spots while magnesium problems result in chlorotic stripes. Manganese problems are more often associated with high pH and magnesium problems are most often associated with poor liming and low soil pH.
One nutrient deficiency that is often overlooked is copper. Copper is relatively inexpensive and consistently produces a yield response when applied to very sandy fields and organic soils. Early symptoms in the fall include tip burn of small plants that is very similar to frost injury. Spring symptoms include partial head emergence. Various studies show response to copper treatments is most effective when fall applied to winter wheat.
Potassium deficiency is expressed as dead edges sometimes referred to as the margin burn. Smaller, weaker stalks are also common when potassium is lacking.
In addition to direct losses, deficiencies also cause indirect losses due to lowered disease resistance and harvest losses. Tissue samples are the best tools for preventing losses because potential yield has been lowered once symptoms are obvious.
WENDELL COOPER checks nutrient levels in cotton in a Virginia field.