I’ve had a few discussions about hop fertility planning over the last few days.
One question that has come up is about the form of nitrogen to use while fertilizing hops. Typically, granular fertility applications in hop yards will use either urea (46-0-0) or ammonium nitrate (34-0-0).
So, that said, as we are currently experiencing a period of cooler temperatures and with the forecast predicting cold and wet weather across the southern part of the province for the next 7 days, is one form of nitrogen better to use than the other?
Generally speaking, if the option to use ammonium nitrate exists in the short term, it is slightly more available to plants at low temperatures than urea. However, there is no practical difference between the two forms under normal growing conditions. Therefore, even at low temperatures, the cheapest form of nitrogen may be your best option for crop profitability (OMAFRA Pub 611, Soil Fertility Handbook).
There are currently no Ontario fertility recommendations for hops. The following tables for Nitrogen, Phosphorus and Potassium applications are guidelines only and provided for reference (note: Phosphorus and Potassium should always be applied according to a soil test):