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Fluid Journal : Fall 2017
6 The Fluid Journal Fall 2017 Sidedressing Potassium and Nitrogen on Corn Evaluations made on yield effects. The Fluid Journal • Official Journal of the Fluid Fertilizer Foundation • Fall 2017 • Vol. 25, No. 4, Issue #98 Dr. Robert D. Miller Summary: Results of a Midwestern population study across five sites show optimum yields were obtained with planted corn populations of 32k-36k plants ac-1 based on 30” rows in the Midwest. Higher populations resulted in reduced number of plants with ears and lower grain yields. Side dress nitrogen (N) was site and year specific with an average response of 30 bu ac-1 to 50 lbs N ac-1 on the most responsive sites. Sidedress response to potassium (K) was limited, and the average response to sidedress applied K was 10- 12 bu ac-1 with 50 lbs K ac-1 .K source product studies showed K acetate combined with N showed significant grain yield response. Cluster analysis of corn ear leaf nutrients collected at growth stage R1-R2 from 112 grower fields from 2011 to 2016 across six states, indicate leaf K levels <1.9% are indicative of lower yields and that K deficient fields show increased magnesium (Mg) accumulation resulting in lower ear leaf K:Mg ratios. Across five years low ear leaf K clusters averaged 45.2 bu ac-1 less grain yield than those with >2.0 leaf K. Established N, K, Mg DRIS ratio norms for corn leaves are an effective tool in diagnosing corn K deficiencies, their impact on grain yield, and addressing long-term K fertility management of corn. ▼ DOWNLOAD Soil testing is the foundation for nutrient management decisions, the reliability of which is based on a representative sample, an appropriate test method, and the nutrient calibration crop response model. Agronomic corn production practices in the Midwest have advanced significantly over the past thirty years, with improved hybrid genetics, decreased tillage, increased plant populations and refined N management resulting in higher yields. Over this period, corn grain yields have increased an average of 2.5 bushels per acre per year. While N fertility management has generally kept pace with increased corn plant populations and yield, that for K has remained relatively unchanged. Increasingly, K deficiencies have been noted. A survey of ear leaves from Ceres Solutions in Indiana from 2011 to 2013 indicates K deficiencies ranged from 15.3 to 57.3 (Miller, 2014) and were significantly more than any other nutrient. Soil fertility results from a survey of Midwestern soil testing labs by the International Plant Nutrition