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Potassium Deficiency in-Season Diagnosis and Correction in Corn (07/11/19)

Potassium deficiency in corn is a relatively new problem for most of North Dakota outside of the highly eroded, deep sandy soils on the western edge of the Red River Valley where K deficiency has been common for decades.

Potassium deficiency in corn is a relatively new problem for most of North Dakota outside of the highly eroded, deep sandy soils on the western edge of the Red River Valley where K deficiency has been common for decades. Potassium deficiency symptoms at V6 to V8 growth stages look similar to the image below.

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A full diagnosis to confirm the K deficiency can be made using a paired plant sample analysis from a ‘good’ area compared with a ‘not-so-good’ area. There is an NDSU Extension circular available explaining the updated K recommendations for North Dakota, which are related to clay chemistry.

Link to SF 1881, North Dakota Clay Mineralogy Impacts Crop Potassium Nutrition and Tillage Systems

The corn in the field shown is in an area of the state where the critical level defined by the clay chemistry map in the circular is 150 ppm, but the area where the deficiency is located tested 170 ppm. Obviously, the corn is telling the farmer that the critical value should be 200 ppm, not 150 ppm. Although 145 soil samples were taken within the state to develop the clay chemistry maps, including at least 2-3 in each county, there are probably areas of some size not represented in the survey that require the higher critical K value. If a field is in a condition as shown, and the field was not fertilized with K because the field was in the lower critical K area and the soil test was between 150 and 200 ppm, then for the future, please note that the field should be fertilized based on the 200 ppm critical value, and not the lower value indicated in the general clay chemistry map.

A field, or a part of a field, showing K deficiency at this stage of growth, or even a few leaves more mature, can be rescued by applying a broadcast application of 0-0-60 at 100 pounds per acre. With a little rain shower following application, the corn should come back to normal. If left to nature, the yield reduction in our research was generally 20-30 bushels per acre less than corn adequately fertilized with K. A row-type applicator mounted with a dry fertilizer box would be the preferred application, since 100 pounds per acre is a lot for an airplane to deal with. Potassium thiosulfate liquid would also be a possibility if dribbled between the rows, but the rate of K would need to be similar to the dry K recommendation and would likely be more expensive.

 

Dave Franzen

Extension Soil Specialist

701-799-2565

This site is supported in part by the Crop Protection and Pest Management Program [grant no. 2017-70006-27144/accession 1013592] from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed are those of the website author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

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