By Nutifafa Adotey, Assistant Professor & Soil and Nutr. Magt Specialist, Forbes R Walker, Professor & Envt. Soil Specialist, and Frank Yin, Professor & Cropping System Scientist, University of Tennessee

Poultry litter has become readily available to producers in Tennessee. However, poultry litter cannot supply all the nitrogen needed for corn and thus supplemental N is required to obtain optimal yield. The amount of supplemental N can be estimated using the Pre-Sidedress Nitrate Test. The Pre-Sidedress Nitrate Test is recommended only for corn producers using animal manure, poultry litter or biosolids, who want to estimate and fine-tune their sidedress N fertilizer applications following manure/poultry litter application. This article provides a guide for Tennessee corn producers using poultry litter on how to estimate sidedress N rate using the Pre-Sidedress Nitrate Test.

An accurate interpretation of the PSNT depends on when and how the soil samples are collected from the field. Information on the sampling time, depth, approach/method, and processing is shown in the figure below. Detailed information on sample collection and processing procedure are described in the UT publication, “The Pre-Sidedress Nitrate-N Soil Test (PSNT) For Nitrogen Management in Corn Production Systems of Tennessee” available at https://soillab.tennessee.edu/wp-content/uploads/sites/129/2020/07/FactsheetPSNTCinfosheet105.pdf

There are two key considerations when interpreting the results for the PSNT in Tennessee: soil nitrate test level and yield potential of the field. Based on this test, soil nitrate is categorized into three soil test levels; Low, medium, and high indicating that corn response to additional N will be assured, possible or unlikely, respectively. The levels vary depending on the yield potential of the field. For the PSNT, yield potential is characterized into two groups: (1) 125 to 175 Bu/acre and (2) > 175 Bu/acre. The soil nitrate test levels for each yield potential is shown below.

Sidedress N recommendations for corn based on the PSNT are made for only the low and medium soil nitrate test level regardless of the yield potential. The current recommended sidedress N rates for corn based on soil nitrate is presented in the table below.

The PSNT offer farmers a reliable tool for producers to estimate Sidedress N fertilizer recommendations

Further reading

Hubert J. Savoy. The pre-sidedress nitrate-n soil test (PSNT) for nitrogen management in corn production systems of Tennessee. Biosystems Engineering & Soil Science BESS #105. https://soillab.tennessee.edu/wp-content/uploads/sites/129/2020/07/FactsheetPSNTCinfosheet105.pdf