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Potassium Deficiency Symptoms in Dry Bean and Soybean (08/26/21)

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Along with many other challenges associated with dry conditions this crop season, potassium (K) deficiency symptoms are being expressed in crops including dry bean and soybean. The image shows K deficiency symptoms in pinto bean from the Carrington REC dryland dry bean variety trial. The dry bean plants have been translocating K from older leaves to upper leaves and pods for seed development, and plants lacking sufficient K are displaying leaves with yellow or chlorotic edges. Extended dry soil conditions reduce K availability, with deficiency symptoms likely with soil K levels below soil test critical values and especially with soil clay chemistry having smectite-to-illite ratio greater than 3.5. In addition to the fixation/retention of K in smectitic clay interlayers, the lack of soil water forces plant roots to only encounter K through direct contact or diffusion. Both of these processes limit the volume of soil with possible plant-available K that can be taken up. In moist soils, K is released from smectitic clays and some K movement is possible with soil water to the roots.

Details on K management (soil testing and K fertilizer application) can be found in NDSU Extension circular ‘ND Fertilizer Recommendation Tables and Equations’ or specific crop plant nutrition circulars including ‘Soybean Soil Fertility’.

 

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Greg Endres

Extension Cropping Systems Specialist

NDSU Carrington Research Extension Center

 

Dave Franzen

Extension Soil Specialist