Final fertility applications should be scheduled throughout the month of June with no more than 25 kg N/ha applied at one time. Flower (burr) development will begin the week after June 21 (due to the change in photoperiod to decreasing day-lengths), and main nitrogen fertility applications should be discontinued at that time to reduce excessive vegetative growth during cone development.
Currently there are no Ontario fertility recommendations for hops, however, we can learn from other jurisdictions with similar climates or soil types about the basics of hop fertility and by considering nutrient requirements for similar plant species. OMAF’s Specialty Cropportunities web database has detailed information on fertility planning for specialty crops (including hops): www.omafra.gov.on.ca/CropOp/en/general_agronomics/nutrient_management/fertility_recommendations.html (refer to Table 3 for the most similar traditional crop to specialty crop for suggested approach to fertility planning). Fertiliser requirements will vary by soil type and location, so decisions should always be based on the results of a soil test from your farm. Although nitrate-nitrogen tests are offered in Ontario, results can be extremely variable between sampling periods due to the high mobility of nitrogen ions and are therefore difficult to use for general fertility planning. Please refer to the OMAF website for a listing of accredited soil testing laboratories in Ontario: www.omafra.gov.on.ca/english/crops/resource/soillabs.htm.
Extension networks in the north-east United States, including University of Vermont Extension (UVME), suggest nitrogen application rates of approximately 66 -133 kg N/ha during the establishment years and 133-151 kg N/ha for established hop yards. More information is available on their website: www.uvm.edu/extension/cropsoil/wp-content/uploads/HopFertilityManagementNE.pdf.
Oregon State University Extension (OSUE) have noted studies based in Germany and Washington State demonstrating that phosphorus requirements for hops are low, in the range of 0-33 kg P/ha. Additionally, potassium requirements typically range between 0-150 kg K/ha (OSUE Fertilizer Guide – Hops: http://extension.oregonstate.edu/catalog/pdf/fg/fg79-e.pdf).
Fertilizer applications should begin in the spring (late April) and continue every 2-3 weeks applying split applications with no more than 25 kg N/ha at any one time until early summer (late June).
Fertility requirements can be met by applying synthetic fertilizer or by using the appropriate amount of compost or manure at specific times during the growing season. Cover crops and green manures can also be used to supply and/or reduce the loss of nutrients and organic matter to crops. A summary of the fertility value of certain solid manure types from the OMAF website is found below.
Table 1: Average Amounts of Available Nutrients for Different Types of Manure (from OMAF and MRA Publication 363: Vegetable Production Recommendations, 2010-2011). Nutrient values based on average nutrient analysis results for over 3 000 samples1. There are large variations between manures, so a manure analysis is the best guide to nutrient availability.
More information on the nutrient value of manure is available on the OMAF website at the following link: http://www.omafra.gov.on.ca/english/crops/pub811/9manure.htm#table9-8.
You can also have your manure tested to determine its nutrient composition at any of these accredited labs in Ontario: http://www.omafra.gov.on.ca/english/crops/resource/soillabs.htm.
Additionally, the fundamental methods of composting are available in the Agricultural Composting Basics Factsheet on the OMAF website. Much of this information may focus on large scale operations but is also applicable to smaller acreage specialty crop producers: http://www.omafra.gov.on.ca/english/engineer/facts/05-023.htm.
For general information on micronutrients please visit the following link on the OMAF website: http://www.omafra.gov.on.ca/english/crops/hort/news/hortmatt/2009/06hrt09a4.htm.