A sample of well water should be taken prior to irrigation if there is concern over nitrate levels in the water.
Nitrate can be a contributing source of nitrogen fertilizer and may offset agronomic rates.
The formula for calculating lbs N applied to crop from irrigation water: 0.244 x ppm NO3-N in irrigation water x inches irrigation water applied.
Example. 0.224 x 15 ppm NO3-N x 18 inches irrigation = 60.5 lbs N per acre
The sample can be taken directly from the well or at various points during irrigation. Collect the sample into a sterile container, store in a cool place, and send to the lab within 24 hours of sampling.
See the document guidelines for Collecting Water Samples for Fecal Coliform Analysis (8/28/2018 Nichole Embertson).