Defining relative yield for soil test correlation and calibration trials in the Fertilizer Recommendation Support Tool

Abstract The Fertilizer Recommendation Support Tool (FRST) will perform correlations between soil nutrient concentrations and crop response to fertilization from user‐selected datasets in the FRST national database. Yield for of interest a particular site‐year is presented as relative yield (RY), ratio unfertilized maximum attainable ( A ). Several methods exist literature estimating calculating RY but effect method choice on test correlation outcomes undocumented. We used six published calculate data five datasets, fit generalized linear plateau (LP) model each. critical value (at LP join point) intercept coefficients were not significantly affected by any was only one dataset. top options after robust group discussions so‐called MAX FITMAX methods. selected method, which defines numerically highest treatment mean, most appropriate because represents maximal responsive sites, inclusive trial having range numbers, limits 100% (which allows transforming data), simpler implement than FITMAX, requires decision tree diverse trials.