The Pre-sidedress soil nitrate test (PSNT) provides a means of estimating soil nitrogen supply, and can aid in fine-tuning nitrogen application rates for corn. One drawback of current soil nitrate tests is that they are only calibrated for situations where all of the nitrogen being measured has come from soil mineralization, such that cores need to be taken in soil that has not received any nitrogen fertilizer. When soil nitrate samples are pulled, a 30cm (12”) deep core is used to extrapolate the total N supply in the rooting profile based on past research which suggests that the soil nitrate in the top 12” of soil, under most conditions, represents approximately 60% of the total N in the rooting profile.

Read the entire report here: Verifying a Pre-Sidedress Soil Nitrate Threshold Test for Evaluating Nitrogen Top-Up Requirements