Hops need both macro and micronutrients to carry out the necessary plant functions to produce their cones each season. Nitrogen is one of the most, if not the most, important nutrient in order for it to reach the top wire and support the biomass the plants build as it matures each growing season. Hop variety, application timing, the type of nitrogen applied and the soil type in which your hops are grown are factors to consider when developing a fertilization plan for optimized growth.
From the moment hops break dormancy, nitrogen is required. This is because at that time, they are using carbohydrate reserves from the previous season until photosynthesis resumes in the new season1. The total nitrogen applied each season is “the amount needed to replace what has been taken up by the plant biomass for fully-grown bines, is approximately 110 lbs/ac/year (cones-45 lbs/ac, crop residue-65 lbs/ac)2.” Depending on soil and varying management practices, hops have a nitrogen use efficiency of about 65%, suggesting that 35% of nitrogen applied is lost to the environment through leaching, etc. If hops need 110 lbs N/ac/yr, but are only taking up 35% of that applied, then about 170 lbs N/ac/yr should actually be applied. (Nitrogen fixing, compost and other additions should be subtracted from that amount.) When comparing one spring banded application to many fertigation applications through May and June, a greater loss is anticipated from the former scenario. Similarly, when growing hops in regions of sandy soils, higher rates of nitrogen are recommended to be applied. Upon reaching the end of June, when hop plants transition from vegetative growth to reproductive growth, a grower should have added about 150 lbs N/ac cumulatively. Growers with varieties that perform less vigorously may benefit from addition nitrogen, whereas more vigorous varieties may need less nitrogen. Baby hops, or first year plants, require about 80 lbs N/ac in total.
To gain a better understanding of overall season nitrogen applications, view a graph “weekly and cumulative nitrogen application for hops in Michigan” on page 15 in the 2018 Michigan Hop Management Guide. While the onset of the spring hop season is delayed in Michigan compared to Nebraska, the bulk of nitrogen should be applied in the 1st-3rd weeks in June. Due to the amount of biomass that hop plants continue to put on as they flower and develop cones, nitrogen applications should continue, but taper significantly in amounts applied.
One way to gauge your plants’ response to nitrogen applications is to measure internode length near the end of June. If internode lengths are greater than 8 inches, nitrogen applications should be reduced. Similarly, if the internode length is less than 8 inches, then a grower should increase their nitrogen applications. Signs of nitrogen deficiency include stunting, yellowing leaves, reduced growth, and poor cone development.
Growers who notice small leaves emerging from their cones close to or during harvest are seeing a symptom called “angels wings,” which occurs when too much nitrogen is added too late in the season. Keep in mind too that excessive applications of nitrogen can lead to disease and insect issues.
A hop cone with “angel wings.”
- Gingrich, G., J. Hart, and N. Christensen. 2000. Fertilizer Guide: Hops. FG 79. Oregon State University, Corvallis, OR.
- Lizotte, E. and R. Sirrine. 2018. Michigan Hop Management Guide. Michigan State University, East Lansing, MI.