Potassium (K) Deficiency of Soybean
Potassium (K) deficiency symptoms appear as a yellowing of the leaves that begins at the tip and extends along edges or margins and continues toward the base as severity increases. These symptoms may appear as early as the V3 stage and occur in the lower to middle canopy early in the season; symptoms may also appear in the upper canopy during mid to late reproductive stages. Eventually, the yellow tissue will die and become necrotic, before falling from the plant. Plants with K deficiency are often stunted and may also exhibit premature advanced plant maturity. K deficiency often occurs in patches within a field. K is mobile in the soybean plant, which can be used to help differentiate it from other nutrient deficiency symptoms. From the edge of the field, patches of K deficient plants can be confused with soybean foliar diseases such as sudden death syndrome (SDS) or brown stem rot.
Soybean leaf showing potassium (K) deficiency symptoms.
Daren Mueller
Soybean plants with potassium (K) deficiency symptoms.
Daren Mueller
Symptoms are more likely to occur in soils with low K levels or low availability due to dry or cool soils. K deficiency may be more likely on soils with coarse textures and low cation exchange capacity. Factors that limit root growth can also result in K deficiency symptoms such as compaction, sidewall compaction, nematode infection, and nutrient stratification within the soil.
Soil testing for K is often used to determine how much fertilizer to apply, however, tissue testing is also available. Nutrient deficiency can occur without visible symptoms. Dry fertilizer application according to soil test levels is often the only economical option.
Prepared and reviewed by the Science for Success team and the Integrated Pest Management Program at Iowa State University.
Soybean leaf showing potassium (K) deficiency symptoms.
Soybean leaf showing potassium (K) deficiency symptoms.
Soybean plants with potassium (K) deficiency symptoms.
Soybean plants with potassium (K) deficiency symptoms.
Soybean field with potassium (K) deficiency symptoms.
Gallery images courtesy Daren Mueller.
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