By Robert Meinen
Penn State researchers and Extension have released an updated version of the Pre-sidedress Soil Nitrate Test (PSNT) for corn. The fact sheet is available in electronic form and can be downloaded as a pdf file from this Penn State Extension webpage.
The affordable PSNT is a valuable tool that allows producers to sample soil during corn’s early growth stage and have it tested at a soil laboratory for nitrate nitrogen (NO3) concentration. The NO3-N is indicative of the N supply available in the soil from manure and other organic sources. The lab results are entered into a simple PSNT formula that provides a recommendation of sidedress nitrogen amount that is expected to provide Economic Optimum Nitrogen Rate (EONR) to the corn in the current growing season. The test can also indicate if no sidedress N is needed. Both scenarios can prove valuable considering the soil test is relatively inexpensive compared to bulk fertilizer purchases.
The updated PSNT fact sheet contains a new formula that was developed after extensive analysis of data from many field plots that reflect changes in agricultural practices that have occurred since the original PSNT was developed in the 1990s. The new PSNT reflects the widespread use of cover crops, modern manure management, and industry focus on soil health that have helped many soils attain a resilient ability to supply N to crops from existing organic matter.
Another new section of the PSNT fact sheet provides guidance for the collection of soil from fields that have received manure injection. Fields with manure injection have patterned N-concentration variability and the sampling protocol developed from research in Pennsylvania soils takes advantage of the predictable NO3-N variation to provide a PSNT laboratory result that is reflected in the new PSNT formula.
Soil sampling and laboratory protocols should be followed closely so maximum agronomic, economic, and environmental benefits of the new PSNT can be realized.
Source : psu.edu