Wheat that has developed a pale yellow color this spring may have sulfur deficiency, says Dorivar Ruiz Diaz, Kansas State University Research and Extension nutrient management specialist. Fields with sulfur deficiency have been found recently in south-central and north-central Kansas, he says.
Sulfur deficiency symptoms in wheat can be similar to nitrogen deficiency, with a general chlorosis of the leaf, but there are differences. “With sulfur deficiency, the whole plant is pale, with a greater degree of chlorosis in the young leaves. Sulfur is not mobile in the plant like nitrogen, so lower leaves do not show more severe deficiency symptoms than the upper leaves. That is just the opposite of the pattern with nitrogen deficiency,” Ruiz Diaz says.
The uniform nature of yellowing on plants is one means of diagnosing sulfur deficiency in wheat. “Sulfur deficiency often occurs first on slopes, eroded areas, on coarser soils or wherever organic matter levels are lowest,” he says. “Therefore, deficiencies are usually limited to only certain areas of the field.”
Sulfur deficiencies are more likely to occur when soils are cold in the spring. But sulfur deficiencies also can be evident during the remainder of the growing season, particularly in soils prone to sulfur deficiency, Ruiz Diaz says. During the period of residue buildup in no-tillage, sulfur mineralization may also be limited. Including sulfur in a fertilizer program to avoid sulfur deficiency is more efficient and less costly than correcting a sulfur deficiency once it occurs, he says.
“Typically, a soil application of 15-40 lbs. of sulfate-sulfur/acre is sufficient to prevent sulfur deficiency. Adding ammonium thiosulfate to liquid nitrogen solutions or blending ammonium sulfate with urea are convenient and cost-effective ways to provide sulfur,” Ruiz Diaz says.
Other sources include elemental sulfur; however, this source is not available to the crop immediately and should be applied in time to allow conversion to the sulfate form of sulfur, he says. Gypsum, which is calcium sulfate, also can be an economical and effective fertilizer option.