Integrated Crop Management News

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Since early August, soybean in several fields began showing typical potassium (K)deficiency symptoms on leaves located in the middle to upper canopy. This is notsurprising in fields or portions of fields with soil-test values in the very low or low K soil-test interpretation categories that did not receive adequate preplant K fertilization.Potassium deficiency symptoms are well-known and very common in older leaves duringearly growth stages. Due to poorly understood reasons, during the last couple of decades Kdeficiency symptoms in upper soybean leaves also have become common at middle to latereproductive stages. Moreover, K deficiency symptoms can develop in upper leaves in well-fertilized soybean when no deficiency was observed at early stages, mainly when droughtconditions develop during late spring or summer.

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Iowa State University



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