ISSUE 4 June 4, 2009
Several calls have come in lately concerning yellow areas in small grain fields or the ability to see areas where the sulfur fertilizer ran out during application. The weather since the fall has been ideal for sulfur deficiencies to appear. The fall and spring were wet. Yellow areas where a soluble sulfur fertilizer was not applied would be most pronounced on low organic matter hilltops and slopes, especially in sandier soils. If N was applied and these areas are still yellow, you should suspect S deficiency. If elemental forms of S were applied and these areas are yellow, you should also suspect S deficiency. Sulfur deficiency can be a problem in all crops, even legumes. Therefore, growers should be alert for sulfur deficiency to show during the next few weeks. Sulfur deficiency is usually not a problem in depressional landscape higher organic matter soils.
Sulfur deficiency symptoms in spring wheat.
Newer leaves are more yellow than older leaves.
Deficiency was corrected with a dry broadcast
ammonium sulfate application.
Sulfur deficiency will usually appear on newer leaves, while older leaves remain green. Nitrogen on the other hand will usually show on older leaves and the newer leaves will be green. If the plants are both N and S deficient, the symptoms will be more like N deficiency, as S will be translocated to newer tissues along with the N, leaving older leaves more affected.
Treatment for S deficiency is to apply a soluble sulfate/thiosulfate fertilizer as soon as practical. Streambar liquid forms, or broadcast dry ammonium sulfate in small grains. Gypsum could also be used, but solubility is lower than ammonium sulfate and higher rates might need to be used and rainfall to activate gypsum may need to be higher.
In row crops, directing a liquid stream towards the base of the plant on the soil may be the best option.
NDSU Extension Soil Specialist