Since the times of prohibition, hop (Humulus lupulus) production has been regionally concentrated in the Northwestern U.S. However, consumer and industry interest in locally grown crops has presented an opportunity for Nebraska hop production. Nebraska produced 34,000 barrels of craft beer in 2014, yet there is limited commercial hop production. The increase in local beer manufacturing is ideal for the U.S. craft beer industry and specialty crop growers alike. With research in cultivar selection and breeding, sustainable management practices and harvest and drying methods, the Nebraska Hops Project is turning this vision of sustainable, locally grown hops into reality.
Hop is a perennial herbaceous crop grown on a trellis system. It grows rapidly and has relatively high nitrogen requirements (150 to 200 lbs/acre). Because hop is a specialty crop, there are few herbicides registered for use, and organic or non-chemical approaches are typically limited to mulching, tillage, and hand-weeding. The combined challenges of providing sufficient crop nitrogen and managing weeds in hops, suggest there may be an opportunity for integrated weed and nutrient management using organic amendments like corn gluten meal and soybean meal. Both corn gluten meal (CGM) and soybean meal are labelled as organic fertilizers, and both have shown allelopathic effects on weed germination and growth at relatively low application rates. However, our recent research in annual vegetable crops suggests that relatively high rates of these organic seed meals (>25 lbs/acre) applied at the surface may inhibit weed seedling emergence via temporary ammonium toxicity without injuring the crop.
The objective of this project is to test the potential for an organic seed meal to concurrently displace synthetic nitrogen fertilizer needs and reduce weed seedling emergence in hop production systems. To accomplish this objective, we will leverage an existing experimental commercial hop production facility at the University of Nebraska – a resource of the Nebraska Hops Project – where we will compare corn gluten meal with a weedy and weed-free control. We will collect data on soil nitrogen availability, weed emergence and biomass, and hop yield and quality. Results will be disseminated via extension and the Nebraska Hops Project team. Outcomes of this project include increased stakeholder awareness of hop production in Nebraska and increased efficiency and sustainability of hop production throughout the North Central Region through integrated weed and nutrient management using organic amendments.
The purpose of this research is to determine the capacity for integrated nutrient and weed management using organic amendments in hop production systems. Learning outcomes will be achieved through outreach with farmers and growers at a variety of scales ranging from commercial to small acreage market gardeners. Each stakeholder will increase his or her knowledge of sustainable agriculture through organic amendment application. The action outcomes of this project are that growers will apply this new knowledge into their own cropping systems. Growers who take action on this new knowledge will experience increased efficiency through the use of organic amendments as multi-functional inputs with fertilizer and weed control properties. This change in behavior will include changes in fertilizer source and application strategy and in approaches to weed management.
Specifically, growers will be less dependent on synthetic fertilizer, tillage, hand-weeding, and herbicides.
Design: Randomized complete block design with three replications.
- CGM = corn gluten meal (applied at rate of 941 g/4.5 sq. ft. plot, which is 251 lbs N/acre)
- WF = weed free control + synthetic fertilizer to meet crop demand (125 lbs N/acre)
- WD = weedy control + synthetic fertilizer to meet crop demand (125 lbs N/acre)
- Flag and stake plots. Each plot is one plant, 3 x 1.5 ft (4.5 sq. ft area). *Include one buffer plant between plots to prevent crossover of corn gluten meal or synthetic fertilizer on adjacent plants.
- Count and bag 50 velvetleaf (Abutilon theophrasti) seed and 50 shattercane (Sorghum bicolor) seed per planting hole using average seed weights.
- Broadcast plant weed seeds in each plot and cover with a uniform volume of top soil to simulate field conditions and prevent CGM from direct contact with the seeds. *Treatments should be applied within 24 hours of planting weed seeds as CGM is a pre-emergent herbicide.
- Irrigate within 48 hours of CGM application if it has not rained, and be sure that amendments are thoroughly wetted to activate herbicidal properties.
- Insert Plant Root Simulator (PRS) probes in all plots within 48 hours of applying CGM. Two sets of probes (4 probes in total) per plot are evenly distributed throughout the area (two on each side of the plant). Probes will be buried for 2 weeks, removed, and then replaced by a new set of probes within the same hole for subsequent 2 week burial periods for a total of 8 weeks (four incubation intervals). Probes should be cleaned within 24 hours of removal from the field, and shipped to WesternAg as outlined on their website. PRS probes have ion-exchange resin membranes that capture anion and cation exchange in the soil. These probes will be analyzed by WesternAg labs for total nitrogen, ammonium (NH4+) and nitrate (NO3-) content.
- Take leaf tissue samples in each plot for complete nutritional analysis one time during the season (e.g., just prior to flowering).
- Manage crops with irrigation and pest management as necessary. Do not remove any weeds, except from the WF control (which should be weeded weekly).
- Record weed emergence weekly from each planting hole in all plots until weed emergence slows/stalls.
- Record leaf chlorophyll content bi-weekly (SPAD meter).
- Measure weed biomass in each plot before weeds begin to senesce.
- Harvest hop cones from each plot and record fresh weights to determine treatment effects on yield.
Corn gluten meal application showed up to 75% reduction of weed emergence compared to the weedy control.
Corn gluten meal application did not have a significant affect on leaf chlorophyll content (measured with SPAD meter) for the first year of application. Ongoing tests on long-term leaf chlorophyll content, leaf tissue nutrient analysis, and yield are in progress and will be reported on in 2019.
Educational & Outreach Activities
- Field day/on-farm demonstration of hops harvesting in fall 2019.
- Poster presentation at Great Plains Growers Conference 2019.
- Presentation at 2019 Nebraska Hops Growers and Brewers Conference.
Being able to present at the Nebraska Hops Growers and Brewers conference has been the most important factor for my project to affect future sustainability. I met with 3 different growers who were very interested in learning more about my project and how it could help their operation grow. My project has the potential to help growers,
- Economically through reduced labor costs for hand weeding and fertilizer application
- Environmentally through less synthetic fertilizer use
- Socially through the interactions we had, and will continue to have, bringing researchers and growers together to help each other. I was able to introduce a grower to an extension agent in their area that has working knowledge of my experiment and could help them implement these sustainable practices. It is mutually beneficial relationships like this that I think are so important to all of us.
Before beginning this project, my knowledge of sustainable practices in hops production was nonexistent. Throughout researching for and implementing this project, my knowledge and skills about sustainable agriculture have increased . Additionally, my skills in applying sustainable agriculture has changed substantially. I have had a lot of hands-on experience and learned so much from experienced researchers and growers specifically because of this project.