Optimizing Corn Seeding Rates Using a Field's Corn Suitability Rating

Abstract

The response of corn (Zea mays L.) grain yield (GY) to plant population or seeding rate is well studied. Population recommendations have been previously made by amassing numerous data points to find the optimum plant population. However, the response has not yet been linked with the corn suitability rating (CSR), a measure of soil productivity. We evaluated the effect of seeding rate with respect to the CSR system on corn GY. The study was performed across 33 site‐years in Iowa from 2006 to 2009. Seeding rates ranged from 49,400 to 118,560 seeds ha−1. Two versions of CSR were examined—the original CSR and the revised CSR2. Averaged across all site‐years, corn GY showed a quadratic response to the seeding rate. Predicted corn GY was maximized at 13.4 Mg ha−1 with the seeding rate of 96,000 ha−1. Corn GY plateaued for the highest CSR class, had significant quadratic responses to second and third CSR classes, but did not respond to seeding rate at the lowest CSR class. However, corn GY did not plateau for the highest CSR2 class as in the CSR. Although all three lower CSR2 classes responded quadratically, there was no clear pattern. Generally, the predicted corn GY also responded quadratically to seeding rate with respect to the parameters used for calculating CSR2 values. Because the original CSR values incorporate climatic conditions and predicted more realistic corn GY responses to seeding rate in this study, we recommend using CSR values when estimating the optimum seeding rate to maximize corn GY.