Iowa State University (ISU) research has evaluated corn and soybean response to preplant potassium (K) fertilizer placement methods and starter since the middle 1990s. These results have been used for developing guidelines in Extension publication PM 1688. In recent years, excessive fall and spring rainfall sometimes has precluded the normal K preplant fertilization. Therefore, growers and crop consultants have been asking if sidedressed liquid K fertilizer could alleviate deficiency or be a good complement to preplant K fertilization, as is commonly the case for nitrogen. A crop response to P sidedressing is unlikely, and preplant or starter fertilization is preferred, because sufficient P needs to be available very early for seedlings shoot and root growth and early cell multiplication to attain the hybrid and soil yield potential. This is not so much the case for K, however, which explains why very often there is corn response to starter P but only occasionally for K when soil-test K is very deficient.
Iowa State University
Mallarino, Antonio, "Sidedressed Liquid Potassium Can Partially Offset Deficient Preplant Fertilization for Corn" (2020). Integrated Crop Management News. 2634.
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