If you are guilty of complaining about the recent heat and humidity, stop and think. Just a few weeks ago we were all talking about the unseasonably cool May temperatures and the gray, rainy weather. Aside from our personal comfort, there are other issues to consider.

As we approach the point in the growing season when producers sidedress nitrogen on their corn crop, they may have concerns about nitrogen that was applied earlier in the season. The rainy weather that we experienced in May sets us up for major nitrogen losses in the soil caused by leaching and/or denitrification.

According to Penn State University agronomy professor Douglas Beegle, the dynamic nature of nitrogen in the soil and the specific nature of nitrogen behavior make it impossible to determine the status of soil nitrogen on a statewide basis.

Beegle recommends a Pre-sidedress Soil Nitrate Test to determine the nitrogen availability status for corn crops just prior to the period of peak demand for nitrogen by the crop. For optimum nitrogen nutrition for corn, the PSNT should be above 21 ppm when the corn is 12 inches tall or around leaf stage 6. If the test shows that the available nitrogen is below this critical level then sidedressing additional nitrogen is recommended, even if adequate nitrogen was applied earlier in the season.

Agronomy Fact Sheet #17 "Pre-sidedress Soil Nitrate Test for Corn" provides all of the details on the PSNT, including sampling procedures and recommendations based on the results of the test. The fact sheet can be found on the internet at http://cropsoil.psu.edu/extension/facts/agfact17.pdf or you may obtain a copy by contacting the Butler County Extension Office at 724-287-4761.

The fact sheet includes several important points to keep in mind when using the PSNT:

n Wait until the corn is 12" tall. Sampling too early can provide misleading results.

n Do not sample immediately following heavy rains. Wait two to three days.

n Take a 12" deep soil sample.

n Dry the soil sample the same day it is taken.

n Use a quick test kit or send the dry sample to a soil testing lab for NO3-N analysis.

Because of the narrow window of opportunity for sidedressing, the Penn State Ag Analytical Services Lab will provide one day turnaround once the samples have been received for the PSNT.

According to Beegle, sampling several fields that are representative of different nitrogen management strategies on your farm can be very helpful in making a decision about whether additional sidedress nitrogen is needed. Nitrogen is too expensive to apply to the soil "just in case". Sidedress nitrogen recommendations based on the PSNT are, on average, twice as accurate as recommendations made without the PSNT.

This material is submitted by Donna Zang, Extension director, and the staff of the Penn State Extension office at the Sunnyview Home complex.