Keeping an eye on wheat plants may pay off this spring. Specifically, a pale-yellow hue could signal a sulfur deficiency, says Dorivar Ruiz Diaz, Kansas State University research and Extension crop nutrient management specialist. Fields with sulfur deficiency are surfacing in south central and north central Kansas
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 the yellowing on the 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. Therefore, deficiencies are usually limited to only certain areas of the field,” he explains.
Sulfur deficiencies are more likely to occur when soils are cold in the spring. But deficiencies also can be evident during the remainder of the growing season, particularly in soils prone to sulfur deficiency. During the period of residue buildup in no-tillage, sulfur mineralization may also be limited, Ruiz Diaz says.
Including sulfur in a fertilizer program to avoid sulfur deficiency is more efficient and less costly than correcting a sulfur deficiency once it occurs.
“Typically, a soil application of 15 to 40 pounds of sulfate-sulfur per 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,” he notes.
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. Gypsum, which is calcium sulfate, also can be an economical and effective fertilizer option, Ruiz Diaz says.
For more information on sulfur, see Kansas State Research and Extension publication MF-2264, “Sulphur in Kansas: Plant, Soil and Fertilizer Considerations” at your local county extension office, or online. http://www.ksre.ksu.edu/library/CRPSL2/mf2264.pdf.
Source: Kansas State University