By Rob Sirrine
This article follows the Michigan State University Extension article Post-harvest hopyard management but focuses specifically on post-harvest irrigation and fertility. On the topic of irrigation, experts offer several tips for proper maintenance. In general, the best method is to put the time and effort into designing the appropriate system for your particular situation ahead of time. MSU Extension has developed an excellent fact sheet entitled Checklist for Planning Irrigation Systems (Kelley, 2011) that covers key irrigation considerations. It is also very important to have a solid understanding of irrigation water quality because it can impact crop productivity. Testing water for potential hazards such as salinity, sodium, alkalinity, pH and potentially hazardous ions is recommended. The Irrigation Water Quality Criteria fact sheet (Bauder et al., 2014) offers a nice overview of water quality criteria and acceptable levels of potential hazards. Interpreting Irrigation Water Quality Reports (Park et al., 2014) also offers a comprehensive overview of irrigation water issues as well as corrective management strategies.
While the vast majority of hop irrigation and fertility needs are from May to August, depending upon weather conditions, soil type, water holding capacity and other factors, it is important to ensure that hops go into dormancy with reserves built up for the following growing season. Although fall precipitation may be adequate in most years, in years with drier fall conditions, irrigation and fertilizer may be necessary. In addition to meeting plant water needs, some hop producers apply phosphorus, potassium and micronutrients at this time. Nitrogen is generally not applied in the fall as the plant heads into dormancy. For those interested in fertigation and nutrient management, Dr. Ron Goldy, Michigan State University Extension educator, provides a thorough overview in an online PowerPoint. Downy mildew should also be taken into consideration; producers should refrain from overwatering, which leads to soil saturation, or creating conditions conducive for downy mildew. Michigan State University Enviro-weather may be a useful tool for determining crop water needs throughout the season. For more specific information on irrigation, please visit the MSU Extension Irrigation page.
Irrigating Hops in the Midwest Great Lakes Region (Lattak, 2014) offers in-depth, hop-specific irrigation information. In terms of irrigation maintenance, Lattak suggests periodic line cleaning applications that are determined based upon the issue in question and severity (for example, bicarbonate or iron). There are many different applications available for line cleaning, but an application may have potentially negative consequences. For example, while chlorine applications will rid the lines of algae, it can also kill beneficial soil microbes, so producers should fully research products prior to application. According to Lattak, producers have had success with products such as Oxcide® or Lineblaster. In addition to periodic cleaning, producers should also regularly inspect filters and end-flush line tubes monthly. At the end of the season, for smaller scale systems, Lattak suggests that blowing out lines with an air compressor is advisable, especially if the system is on lighter soils where the underground is only a couple of feet deep. Lattak will be presenting at the 2017 Great Lakes Hop and Barley Conference in Detroit from March 2 to 3. Lyndon Kelley, MSU water quantity educator, is another excellent resource for irrigation matters. Kelley provides a general overview in his article End of season irrigation decisions.