I’m Nathan Slaton with the University of Arkansas Division of Agriculture. Fertilization of soybeans is often required to produce maximum yields and maintain soil productivity here in Arkansas. Potassium is one of the nutrients that soybeans tend to be very responsive to. And as such, potassium deficiency tends to be one of the more common nutrient problems that we see in soybeans every year. Potassium deficiencies tend to occur either in very early growing season conditions or, as [in] a field we’re standing in today, when soybeans reach the early reproductive and later reproductive stages. Early in the growing season when the plants are small and have a small root system, a lot of times just adverse environmental conditions like very hot and dry weather can reduce potassium uptake, or it can certainly cause plants to show deficiency symptoms to the point that it is a reflection of the overall soil fertility. But either way, early in the growing season, a good soil test and perhaps tissue analysis may help determine what the problem is. So you can see that the plants I’m holding up now are starting to bloom and the deficiency that we see is a yellowing along the margin of the leaf, towards the tip of the leaf, and as the deficiency or the severity of the deficiency progresses and becomes more severe, a greater portion of the plant leaf will turn yellow. So, [the] last question is, how do we prevent this from happening? The first component is to get into a good soil sampling program. And that means that, No. 1, we want the most recent soil test results, but we’re also interested in the history of soil test results, so that we can monitor the trend and say soil test potassium over a five- or six-year period.
So if you need more help in diagnosing potassium deficiency or reviewing your fertilization program, find us at ueax.edu or your local county extension office.