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1	Estimation of economically optimal potassium rates for soybean production in Mississippi: comparing different yield response functions Akakpo, Felix 06 August 2021 (has links) (PDF) This study estimated soybean yield responses to K fertilizer using trials data from 18 sites in Mississippi from 2011-2016. Eight response functions were fitted, including linear, linear plateau, quadratic, quadratic-plateau, square root quadratic, spherical plateau, exponential, and exponential-plateau functions. The ratio of high responsive, low responsive, and no responsive sites to K rates is 3:3:12 respectively. The response functions led to different predicted optimal K rates, and the best response function for each site was determined by the Vuong closeness test and economic loss analysis. The predicted economically optimal K rates are 157, 73, and 0 lb/acre for high, low, and no response sites respectively, and the average optimal K rate is 55 lb/acre. Compared to the currently used regional uniform K fertilizer rate of 80 lb/acre, the response-based K rates are expected to generate soybean production gain of about $14 per acre for Mississippi soybean producers. Economic return Models Comparison Models' Selection Criteria Best Model Optimal K Rate for Individual site Optimal K Rate for Group Sites Linear Response Quadratic Response Linear Response Plateau Quadratic Response Plateau Square Root Quadratic Spherical Plateau Exponential and Exponential Plateau