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Drought Induced Potassium Deficiency in Soybeans

Yellowing symptoms in soybeans impacted from K deficiency
Yellowing symptoms in soybeans impacted from K deficiency

Yellowing of soybean leaves could occur for many reasons, such as disease presence, low fertility or management factors. In growing seasons with drought conditions, potassium (K) deficiency in soybeans may cause the discoloration. Even when symptoms of deficiency are present, actual soil tests may show that soil is in the normal range for potassium. This indicates that the plant is unable to access and uptake K due to limiting factors such as drought or compaction. Potassium deficiency is more common and well understood at early growth stages, but less understood in late reproductive stages where the middle and upper leaves are impacted. Soybeans demand a high amount of K during the R1-R5 growth stages, as 75% of the total K uptake occurs during this time. Potassium is very mobile within the plant and much is remobilized from roots and stems right before seed fill is initiated.

What Are the Signs of Potassium Deficiency?

  • Yellowing along soybean leaf margins is visible in middle and upper leaves later in season and on lower leaves early in season. Impacted leaves may fall off.
  • Leaf margins may become brown or necrotic with prolonged deficiency.
  • K deficiency may advance soybean maturation, along with other nutrient deficiencies and excessively wet or dry soil.

Yellowing around soybean leaf margins

Advanced K deficiency symptoms

What Causes K Deficiency in Soybeans

  • Drought: K is made available in the soil solution, and in drought conditions the diffusion of K to the roots is slowed, so soils with marginal K levels will likely show even more symptoms with low soil moisture.
  • Inadequate K levels: soils can become depleted of K, as soybeans are a high-removal crop.

K Deficiency Treatment

  • Test soil and leaf samples for K in normal and affected areas to help determine K levels.
  • Prevention is the best treatment – apply K fertilizer as recommended before the next crop.
  • Prevent soil compaction or limitations to root development.

Contact your local Golden Harvest Seed Advisor with questions or to help identify potassium deficiency in soybeans.

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