Connecting Soil Parameters With Variable Seeding Rates For Corn.

The capability to use variable seeding rates has increased dramatically in recent years. Farmers and agronomists frequently collect and analyze soil samples to determine nutrient needs for subsequent crop production. Our objective was to identify the linkage between soil parameters and seeding rates to optimize corn grain yield. Treatments for this research included five seeding rates (61,750; 74,100; 86,450; 98,800; and 111,150 seeds ha^-1) in a randomized complete block experimental design with five replications at 3 locations in central Iowa. Total cropped area used for the three studies was approximately 35.2 ha (16.3 ha, 10.3 ha, and 8.6 ha at the individual sites). Soil samples at the 16.3 ha site, the site presented in this poster, were collected from 23 points within each seeding rate plot. Soil samples were analyzed for soil P, K, pH, organic matter, CEC, and texture. Elevation data were collected using the RTK-GPS signal at the time of grain harvest. Additional data collection included spring and fall stand counts at each point as well as lodging counts. Grain yield and moisture were measured using the combine’s yield monitor. Since 2012 was abnormally dry, we expected that elevation and percent sand would have a negative correlation with grain yield for all seeding rates, and in general this was true. Other soil parameters generally had positive but very low correlations (less than 0.1) with grain yield.