Recalibrating the Pennsylvania pre‐sidedress soil nitrate test recommendations for modern corn production

Abstract

The pre‐sidedress soil nitrate test (PSNT) was developed over 30 years ago to determine sidedress N fertilizer recommendations for corn (Zea mays L.). Since the original PSNT calibrations were developed, changes in production practices such as no‐till and cover cropping and increases in corn yields and N use efficiency could affect the accuracy of PSNT recommendations. To update the PSNT recommendations in Pennsylvania and demonstrate the test's efficacy, we compiled a dataset of 32 calibration sites and 13 demonstration sites where the PSNT was conducted and the economically optimum N rate (EONR) for corn was determined from an N fertilizer yield response curve. We recalibrated the PSNT recommendation algorithm and compared its accuracy to the original calibration. The new calibration resulted in a single long‐term manure history factor that interacted with the PSNT result to adjust the sidedress N recommendation (‐5.7 kg N ha−1 (mg NO3‐N kg−1)−1). The new calibration also included a term for a mixed species cover crop, which increased the sidedress N recommendation 56.2 kg N ha−1. Finally, the coefficient that scales the N fertilizer recommendation based on yield goal decreased by 29% from the original calibration to 12.9 kg N Mg−1 grain. The new algorithm for predicting EONR reduced the error of the sidedress N recommendation by one‐half compared to the original calibration. The new PSNT calibration will allow users to accurately determine sidedress N recommendations in sites with a long‐term manure history and underscores the importance of updating soil fertility recommendation algorithms with modern data.This article is protected by copyright. All rights reserved

Improving a nitrogen mineralization model for predicting unfertilized corn yield

“…The N mineralization model was developed to predict unfertilized corn yield as part of a nitrogen decision support tool for corn in Pennsylvania that is based on inputs that can be measured through commercial lab services (White et al., 2023). This tool allows users to visualize the corn yield credits from decomposing cover crop residues (Equation ) and SOM (Equation ) under current conditions and possible future scenarios.…”

“…A variety of approaches have been used to estimate the N contributions of SOM and cover crops to the following cash crop. Some of these include empirical equations based on laboratory incubations (Quemada & Cabrera, 1995; Sullivan et al., 2019; Franzluebbers et al., 2022), the pre‐sidedress soil nitrate test (White et al., 2023), and detailed crop‐soil simulation models (Thapa et al., 2022; Woodruff et al., 2018). Here we focus on improving an N mineralization model (White et al., 2020) that uses simple biogeochemical equations to explicitly represent microbial decomposition and mineral‐associated SOM.…”

Effect of soil sample handling and storage on inorganic nitrogen determination: Implications for the presidedress nitrate test

“…The resulting soil test value, NO 3 − -N reported in mg kg −1 (or parts per million), is then entered into an algorithm to provide an N rate recommendation, normally alongside additional information such as yield goal and/or field history. PSNT-based algorithms are calibrated regionally and are currently used by farmers in North America, including Ontario (OMAFRA, 2017), Wisconsin (Bundy, 2007), Pennsylvania (White et al, 2023), Western Minnesota (Kaiser et al, 2023), Massachusetts (Hashemi et al, 2019), and Iowa (Sawyer & Mallarino, 2017). In other regions, the PSNT test does not recommend an N rate but identifies economically responsive fields by comparing the PSNT value to a critical cutoff value (e.g., Brouder & Mengel, 2003;Coale et al, 2010).…”