PSNT
Pre-Sidedress Soil Nitrate Testing
What is PSNT?
The Pre-Sidedress Soil Nitrate Test (PSNT) for corn measures the soil nitrate concentration, which is used to provide a recommendation for sidedress Nitrogen.
The total nitrogen (N) required for a corn crop is given by organic and inorganic N (ammonium N and nitrate N) sources. Farming practices such as regular manure application, reduced tillage and cover crops can lead to an accumulation of organic N in the soil. Ammonium N and nitrate N can be released when organic N decomposes, supplying N to crops during the growing season. However, due to the environment and soil health predicting the contributions of organic N can be difficult.
Ammonium N can be lost to volatilization if not incorporated into that soil, incorporation methods include tillage, injection or a timely rainfall. The PSNT can provide a measurement of N supply from organic sources and recovery of manure ammonium N to assist in making N fertilization decisions.
The in-season PSNT allows farmers to make fertilizer application decisions and just meet crop N recommendations. Precise management of N can lower production costs while maximizing crop production, and minimizing environmental N losses.
The importance of Nitrogen
Understanding the Nitrogen cycle helps understand how useful the PSNT is. Most of N (about 98%) is unavailable to plants because it is tied up in soil organic matter. The forms of nitrogen available to plants are ammonium N and nitrate N, these forms become available to the plant by the decomposing of N in organic matter.
Nitrogen Behavior
Partial Nitrogen Cycle
The Test
The Pre-sidedress Soil Nitrate Test (PSNT) for corn is designed to measure nitrate concentration, which can aid to in determining N supply from both manure and other organic N sources in the soil and to estimate the supply of soil N that will become available to the crop throughout the growing season.
How it Works
A soil sample is collected during the growing season, when the corn is 12 inches tall, or at least a week before sidedressing is planned to happen.
Soil samples are dried down and tested for nitrate concentration.
The nitrate levels and other information is provided into a formula to produce a sidedress recommendation.
Free PSNT at LCCD!!
New for 2025 LCCD is offering free PSNT!
*Participation in the program offers free soil sampling, testing and sidedress recommendations to agricultural operators.
Interested?
When deciding which fields to have tested keep a couple things in mind:
The PSNT test is only intended for fields that have a long-term manure application history (received manure at least 2 out of the last 5 years)
50 lbs N/acre or less should be applied as starter fertilizer
Soil sampling needs to occur when the corn is about 12 inches tall, or at least 1 week prior to expected sidedressing