Phosphorus (P) Deficiency of Soybean
Phosphorus (P) deficiency symptoms in soybean include dark green leaves or a blue/purple discoloration first appearing on older leaves with extreme deficiency. Leaves may also exhibit necrotic spots and cupping. Plants are stunted with small leaves.
Symptoms occur in soils with low P levels, such as those with low pH and compaction, or those that are cold and wet, which can inhibit P uptake. Periods of rapid growth where root systems have been compromised due to soil conditions, disease, or insects can also promote P deficiency development.
As P moves slowly in soil, management for P deficiency should be performed prior to or early during the growing season. Soil testing for both P and pH level should be conducted during this same time period. Regular fertilization applications in these stages can help to improve future plant conditions.
Prepared and reviewed by the Science for Success team and the Integrated Pest Management Program at Iowa State University.
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