Post harvest nitrate testing (PHNT) is basically a report card on how much of the N you applied is left over to leach out at the end of the growing season. It makes use of the Agri and Agri-Food Canada’s nitrogen model developed for use in our raspberry industry. In this model, a fall nitrate test is combined in a formula with other field parameters such as whether manure was used and whether a fall cover crop was planted. It provides a more accurate recommendation for nitrogen fertilizer in the following spring. A high level of soil nitrate in fall may indicate:
- Poor plant health not allowing roots to uptake the fertilizer applied.
- Too much nitrogen fertilizer or manure applied.
Excess nitrogen of course will leach to the ground water, possibly polluting the aquifer. This will be an increasingly important issue in coming years. The PHNT will be in the nutrient section of Environmental Farm Planning. It can be considered a Good Agricultural Practice (GAP). The cost of a nitrate test is very low with at our Plant Science Lab. Testing is an inexpensive way for you to know exactly how much nitrogen you have in your raspberry field in the fall.