This is the third article in a series of blog articles that will focus on some fundamental information on UT fertilizer recommendations for corn, with a different nutrient featured in each article. Commonly recommended nutrients for use in corn production in TN include nitrogen (N), phosphorus (P), potassium (K), sulfur (S), and zinc (Zn). Each nutrient will be discussed in terms of the relevant soil test that may be used or used in recommendation; recommended preplant, starter, sidedress, and foliar fertilizer applications; and plant/tissue analysis. Today’s blog will focus on UT potassium recommendations for optimal corn productivity under conditions in TN. Potassium is a macronutrient that plays important functions in the plant including protein and starch formation in the grain, movement of water, nutrients, and carbohydrate within the plant, stomata closure, cell wall and stalk strength. Thus, corn plants with inadequate K are susceptible to drought stress, diseases and insects, and greater risk of lodging after maturity. Additionally, K-deficient corn plants may have shorter ear length and narrower ear diameter.
Soil test for potassium
Potassium fertilizer application rate should be based on soil test. In TN, K fertilizer recommendations are based on Mehlich I extraction procedure because it correlates well with the soils in Tennessee. Detailed information on how UT recommendations were developed is addressed in UT Publication W795, University of Tennessee Fertilizer Recommendation Development. Recently, a calibration for Mehlich III was established for west TN soils and ranges of sufficiency for soil K using Mehlich III testing are described in the UT Publication, UT Fertility Recommendations for Tennessee Row Crops.