Soil Nutrient management
Sulfur
Forms of Sulfur Taken up by Plants
The sulfate (SO4¯) ion is the available form of sulfur to plants. The sulfate ion is subject to leaching too but not as much as nitrate. The main sources of sulfate in the soil are sulfur-containing minerals and organic matter. Most sulfur, 60 to 90 percent, in soils comes from organic matter, which upon mineralization releases available sulfate slowly. Sulfur is, therefore, concentrated in the topsoil or plow layer.
Sulfur Deficiency in Plants
Deficiency symptoms of sulfur are typically exhibited as yellow or pale green leaves and slow growth. Sulfur deficiency is sometimes mistaken for a shortage of nitrogen. Both nutrients have critical roles in synthesis of protein and chlorophyll and in photosynthesis. Although the deficiency symptoms are similar, sulfur deficiency is expressed most clearly on younger leaves, whereas nitrogen deficiency is most prominent on older leaves.
Sulfur Toxicity in Plants
Sulfur toxicity for practical purposes should be considered as non-existent. Excess sulfate (SO4¯) can reduce the uptake of some anions such as nitrate (NO3¯) and molybdate (MoO4¯).
Management of Soil Sulfur
Sandy soils may require annual applications of sulfate forms of sulfur because the sulfate leaches through these soils more rapidly than loamy soils. Fine-textured soils may test low in sulfate-sulfur but they may not show an increase in crop yield when sulfur fertilizer is applied.
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