For those worried about the need for additional N this spring, one method in determining if additional N is needed is by doing the Late Spring Soil Nitrate Test (LSNT). This test measures the nitrate-N concentration in the top foot of soil. The measured N is a combination of nitrate residual from the prior year, mineralized N from soil organic matter, and any fall or early spring applied N that has converted to nitrate.
Corn is reaching the stage on when we want to collect soil samples for the LSNT as the test is calibrated for when corn is between 6 to 12 inches tall (measured from the ground to the center of the whorl). How soil samples are collected is very critical, especially when preplant N fertilizer or manure was injected into the soil. Check out the following video which explains more about the procedure on collecting soil samples for the LSNT.
More information on the LSNT including how to interpret the results from the test can be found in the ISU publication, CROP 3140 “Use of the Late-Spring Soil Nitrate Test in Iowa Corn Production.” Also, for more information on N considerations this growing season, check out the ICM News Article “Nitrogen Considerations for Spring 2021” for additional information.