Developing Soil Tests to Predict Nitrogen Availability to Corn in Ohio.

Predicting nitrogen (N) supply using soil-based testing has been a goal of soil fertility research for decades, however, identifying simple and affordable methods that predict soil N availability to corn continues to elude researchers. The objective of this study was to evaluate the ability of indices of soil N availability to predict corn N response and productivity in Ohio. Fifty site-years, from 2015 and 2016, were used to evaluate the surface (0-20 cm) soil concentration of permanganate-oxidizable carbon (POXC), mineralizable C, and soil protein N in relation to leaf tissue N concentration and grain yield. Preliminary results indicate that POXC ranged from 291 to 835 mg kg^-1 soil, mineralizable C ranged from 29 to 668 mg kg^-1 soil, and soil protein N exhibited a range of 3411 to 7073 mg kg soil^-1 for the 2015 growing season. Results from 2016 show that POXC values were 309 to 761 mg kg soil^-1, mineralizable C ranged from 11 to 55 mg kg^-1 soil, and soil protein N ranged from 3350 to 5655 mg kg^-1 soil. In 2015, leaf tissue N of unfertilized (0 kg N ha^-1) corn ranged from 0.89 to 2.2% and grain yield ranged from 1.1 to 10.4 Mg ha^-1. Whereas in 2016, leaf tissue N of unfertilized corn ranged from 1.4 to 3.5% and grain yield exhibited a range of 3.0 to 12.4 Mg ha^-1. Preliminary results also revealed several linear relationships between the soil tests evaluated in this study and corn N status and productivity during the 2015 and 2016 growing seasons.