May 4, 2011
US spring wheat shows sulphur deficiency
US spring wheat has developed a pale yellow colour and this could be an indication of sulphur deficiency, said Dorivar Ruiz Diaz, K-State Research and Extension nutrient management specialist.
Fields with sulphur deficiency have been found recently in south central and north central Kansas, he said.
Sulphur deficiency symptoms in wheat can be similar to nitrogen deficiency, with a general chlorosis of the leaf, but there are differences, he explained.
"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 said.
The uniform nature of the yellowing on the plants is one means of diagnosing sulfur deficiency in wheat, he added.
"Sulphur deficiency often occurs first on slopes, eroded areas, on coarser soils or wherever organic matter levels are lowest. Therefore, deficiencies are usually limited to only certain areas of the field," the K-State agronomist explained.
Sulphur deficiencies are more likely to occur when soils are cold in the spring, Ruiz Diaz said. But sulphur deficiencies also can be evident during the remainder of the growing season, particularly in soils prone to sulphur deficiency, he said. During the period of residue build-up in no-tillage, sulphur mineralisation may also be limited, he added.
Including sulphur in a fertiliser programme to avoid sulphur deficiency is more efficient and less costly than correcting a sulphur deficiency once it occurs, he said.
"Typically, a soil application of 15 to 40 pounds of sulphate-sulphur per acre is sufficient to prevent sulphur deficiency. Adding ammonium thiosulfate to liquid nitrogen solutions or blending ammonium sulphate with urea is convenient and cost-effective ways to provide sulphur," Ruiz Diaz explained.
Other sources include elemental sulphur; however this source is not available to the crop immediately and should be applied in time to allow conversion to the sulphate form of sulphur, he said. Gypsum, which is calcium sulphate, also can be an economical and effective fertiliser option, he said.
