A Cover Cropping System to Enhance Small Scale Production of Hops on the Colorado

Front Range

Dana Hayward Master’s Candidate Colorado State University Department of Agriculture

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Abstract: A cover cropping method for use in small-scale hop yards on the Colorado Front Range is suggested, discussed, and evaluated. An overview of hop plant biology is provided, as is a discussion of cultivation methods specific to organic growth situations. The benefits and challenges to growing hops organically are reviewed and market dynamics are briefly examined. Disease and pest risk information is offered, and management techniques are discussed. Benefits and drawbacks to cover cropping systems are put forth, and the importance of their fitting into a whole farm plan is emphasized. The suggested red clover-triticale fall planted cover crop seed mix was designed specifically for use on a small-scale market farm operation in Boulder County Colorado referred to herein as Black Kettle Farm*. This particular mix was chosen based on the values, goals, and objectives of farm ownership in conjunction with agronomic traits and feasibility of growth in the Front Range climate zone. The cropping system discussed may be applicable on other farms with similar production situations, business goals, soils, and climatic characteristics although cover cropping systems and the benefits and challenges they present are always farm specific. Cultivated Hops (Humulus lupulus)

The herbaceous woody perennial Humulus lupulus is a member of the Cannabaceae family, which also includes hemp and cannabis (Filmer 5). Grown primarily for the production of flowering cones for brewing, the plants are native to northern temperate climates and grow best at latitudes between 30º and 55º North and South, although they prosper best between 45º and 50º (Turner, Benedict and Darby 1645-1646) (Hieronymus 93). Hops are dioecious plants and can reproduce by seed, cutting, or rhizome (Kneen 11). Although distinctive male and female plants exist, only female plants produce cones that contain oils and resins valuable for brewing. Male plants, which produce large amounts of pollen, have only 10 to 15 resin glands in their flowers compared to over 10,000 in female flowers. Seeds resulting from pollination add unwanted weight to the cones, can result in unwanted breeding crosses, and furthermore lack any benefit to the brewing process. For these reasons, producers not actively breeding

new plant varieties work hard to exclude male plants from their hop yards (Kneen 11). Hops have a vertical growth habit and their bines climb upward and clockwise, able to reach heights near to 30 feet, with the use of tiny hairs called trichomes (Turner, Benedict and Darby 1647). Cultivated hops develop perennial rootstock that can grow up to 12 feet deep in the soil. A root mass, called the crown, includes both fleshy rhizomes and true roots. The true roots grow deep into the ground, become very woody as they mature, and don’t have reproductive buds. Rhizomes, which grow horizontally outward just below the soil surface, have buds and rootlets that can spout into new above ground growth (Kneen 10). During their first year of growth, young plants use the majority of their energy developing this extensive root system and produce only a minimal 6 feet of above ground growth (Kneen 10). As they mature, the plants use their deep roots to obtain and store water and nutrients used to fuel more above ground growth, which dies back to the crown in the fall each year. The

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extensive root system developed early on overwinters yearly, allowing a healthy plant to live over 20 years (Filmer 5). As they are photoperiodic plants, day length and light play a large role in determining when and at what rate hop plants grow and produce flowers (Hieronymus 93). Early each spring after winter dormancy, buds emerge from underground rhizomes and bines begin rapid vegetative growth, climbing up to a foot each day. This quick growth is primarily vertical, but after reaching the top of trellises, usually between 16 and 24 feet high depending on growing practice, the plants grow horizontal flowering branches that originate from the axils of main leaves (Kneen 10) (Hieronymus 94,97). In mid-summer, these horizontal branches produce clusters of burrs prompted by decreasing day length after the summer solstice (Turner, Benedict and Darby 1647). If there are male plants present, pollination occurs during the burr stage (Kneen 10). Pollinated or not, burrs then fall off the plant as florets grow into petals or bracts that form large cones around a central stem or strig on the female plant (Kneen 11). Within the cones are bracteoles, small petal shaped resin glands attached directly to the strig. At the base of each bracteole are small yellow lupulin glands, filled with resin made up of oils and alpha and beta acids valuable to brewing (Kneen 11). Alpha acids add bitterness to beer, while beta acids are responsible for preservative qualities. Hop oils flavor beer and provide aroma (Filmer 5). Each horizontal branch supports multiple clusters of cones that generally grow in groups of three. The cones mature later in the summer and can be harvested at most latitudes in late August and September when lupulin is

bright yellow and abundant (Kneen 10) (Hieronymus 125). Cones should be harvested when lupulin is fragrant and sticky and cones are just beginning to dry out. Mature cones will be pale green in color with light gold bottom bracts and will feel light and papery but buoyant when squeezed (Kneen 28). Healthy plants generally produce between 1 and 2 pounds of wet cones a season, although yield varies depending on plant variety. The bines of cultivated hops are generally cut back shortly after harvest, but enough photosynthetic material is left so the plants can continue to build energy reserves in preparation for dormancy. Just before the first frost, bines are cut back to just above the crown (Kneen 10). The first recorded use of hops describes leaves and shoots being eaten as salad greens in the first century A.D. and the first record of cultivation dates to the 8th century A.D., when European monks grew them for medicinal purposes. It wasn’t until the 12th century that cultivated hops were used in brewing, after which hop cones became a critical component for flavoring, clarifying, and preserving beer (Turner, Benedict and Darby 1645). Since the first colonists arrived on the North American continent, hop cultivation has been a part of American agricultural production. Primarily grown in the northeast starting in the 1600’s, cultivation moved west until the majority of hop farms were in the Washington territory and northern California by the late 1800’s. Today the majority of production in the United States still occurs in Washington, Oregon, and Idaho (Turner, Benedict and Darby 1645). Although there is still some production in the northeast, the comparatively drier climate and well-

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drained soils of the northwest are more conducive to hop growth and reduce the incidence of fungal and viral diseases that can plague the plants (Hieronymus 90). As such, provided an adequate water source, the arid Colorado climate provides similar advantages for hop production. In addition, certain varieties fare better in certain climates and prove more disease resistant. The hundreds of varieties and numerous selectively propagated cultivars of Humulus lupulus are sorted based both on agronomic and brewing characteristics (Kneen 12). Bittering varieties are higher in alpha acids and store for longer periods of time without losing quality characteristics. On the other hand, aroma varieties have lower alpha acid content, higher proportions of hop oils, and do not age as well as bittering hops. In addition to these two categories, a third category of noble hops exists. These hops are characterized based on the European region in which they are grown and contain high levels of humulene, a specific hop oil (Kneen 12). In addition to their use in brewing, hops and hop byproducts are also utilized in sugar processing, as a preservative in ethanol production, for medicinal purposes, as antimicrobials in animal feed, and for making fibers among other uses (Turner, Benedict and Darby 1652). Although different varieties are better adapted to certain environments, their size mandates that most all types utilize large amounts of solar energy, water, and nutrients (Kneen 10) (Lipecki and Berbec 177). Due to their photoperiodic growth pattern, hops grow best in regions that receive about 15 hours of sunlight daily. A period of seasonal dormancy where temperatures are consistently below 40ºF for between 6 and 8 weeks is also necessary for

optimal growth. If necessary, the extensive root system can survive temperatures as cold as -13ºF if insulated by snow and soil (Turner, Benedict and Darby 1646). Despite this tolerance, at least 120 frost free days are necessary for cone production and the best hop producing regions have fairly dry climates and long, bright days with adequate water availability (Hieronymus 89) (Kneen 14). Grown outside of these conditions, hop yields are likely to be low if cones are produced at all. Although there is no ideal soil type for growth, hops grow most successfully in well-drained soils, as excessive wetness inhibits root growth and increases disease risk (Hieronymus 95) (Kneen 13). Despite the need for drainage, plants utilize large amounts of water, especially in the spring in conjunction with rapid growth. Foliage and crowns should be kept fairly dry and if possible water should be delivered directly to roots where it will be readily absorbed. These conditions make drip irrigation ideal for growing hops (Kneen 14). Soil should also have good structure supported by active biology. Superior soil will have a loamy surface, sandy or gravelly depths, and be mildly acidic (Hieronymus 89) (Lipecki and Berbec 177). Adequate amounts of nitrogen and other macronutrients should also be available for times of rapid growth in June and July, as this is when demands are highest (Turner, Benedict and Darby 1647). As long as the soil is fertile and well drained, plants will establish themselves and become productive, leaving room to improve soil qualities if necessary. Proper hop yard placement and infrastructure is also critical to growing a successful crop. Based on the planned size of the yard, an area with appropriate

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soil characteristics, sun exposure, airflow, water availability, and ease of accessibility should be selected (Kneen 20). If soil is not optimal for hop growth, it should be amended before planting. Although air flow is crucial to keeping plants dry and disease free, wind exposure should be considered when selecting the site for a hop yard as high winds can damage cones late in the growing season. The yard should be oriented so that wind funnels through climbing bines and keeps them dry with minimal cone damage (Kneen 20). Once a site is selected, a trellis system is built using poles and cables and irrigation is set up to work with the trellis. Modern trellis systems have 18 foot high poles and support cables that run the length of the yard. Early in the growing season each year, strings are run from the tops of these cables down to the crowns of plants so they can begin climbing. The trellis system has to be strong and well anchored as mature plants can weigh up to 20 pounds each (Hieronymus 89). The most important part of designing hop yard infrastructure is planning plant spacing correctly. As the crowns of mature plants can grow to be 4 feet across, plants should be spaced at least 4 to 5 feet apart in a row and rows should be spaced 8 to 10 feet apart, forming a series of access aisles in the yard (Kneen 21). Spacing is also important because crowded above ground growth prevents proper airflow and increases disease risk (Tomlan 57). Once hop yard infrastructure is set up, rhizomes or immature plants can be introduced. Rhizomes and plants should be obtained from a disease free source and planted by mounding early in the spring. Mounding between 6 inches and a foot of dirt on top of the rhizomes will increase drainage and insulation.

Once in the ground, new plants should be watered frequently for short amounts of time so they do not dry out or become water logged (Kneen 25). Each successive year, established plants need to be dressed and pruned in the spring. During the process, winter mulch should be removed and the crown should be pruned to remove excess rhizomatous runners. At this time, rhizomes can be harvested from mature plants for propagation (Kneen 25). Young buds that are left should then be covered with manure (Tomlan 51). A few weeks after this dressing process, young shoots will emerge. The strongest shoots growing from stocky, close jointed bines are chosen to train on string connected to the cable at the top of the trellis (Tomlan 54). Bines are trained carefully around the string, 3 bines per string, in a clockwise direction. If the growing tip of a bine is broken, another should be selected for training, as it will take a long time for a new shoot to develop (Kneen 26). Training is also an appropriate time to add soil nutrients if necessary (Hieronymus 89). The bulk of the summer consists of additional shoot pruning, watering, weed control, monitoring plant health, and watching for harmful insects and signs of disease. New shoots should be pruned so they don’t compete for nutrients with selected bines, although pruning should stop just before harvest when plants begin producing rhizomes for the next spring (Kneen 27). Harvest in most hop yards begins in late August or early September when lupulin is at its most fragrant and the cones are beginning to dry. Harvest timing is critical as cones are easily damaged by wind, hail and frost and can also become too dry to pick and package. As a result, cones must be picked from bines, cleaned and dried as

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soon as they have ripened (Tomlan 62). In order to most efficiently remove cones, bines are cut from the trellis, leaving a small amount of above ground growth so the plants can store energy to overwinter (Hieronymus 90). Cones must be dried immediately after harvest as the acids and oils in lupulin oxidize and lose their desirable characteristics quickly if not properly stored (Hieronymus 119). After harvest and at or after the first frost, remaining above ground growth should be removed and the crowns should be covered with mulch to insulate them during the winter (Hieronymus 90). Winter green manures and cover crops should also be planted between harvest and the first frost. In the spring, mulch will be removed and pruning will resume again (Kneen 34). Diseases, Pests and Beneficial Insects

Pressure from weeds, pests, and pathogens can decrease both the quantity and quality of harvested hops. In order to manage these problems, they must be monitored and evaluated in the context of the entire hop farm (Oregon State University et al. 1). To design a pest and disease management regime for a hop yard, it is important to first be familiar with the pests and diseases that pose the greatest threat to hop production.

As hop plants need large amounts of water, nutrients, and light to be productive, competition from weeds for these resources can greatly decrease crop yield. Weeds can also cause problems if they serve as host to pathogens and destructive insects when hops aren’t actively growing or if they otherwise interfere with field operations (Oregon State University et al. 69). The perennial nature of hops also means that both annual and perennial weeds can cause problems for hop production year

round. New hop yards should be well prepared and as weed free as possible because competition can severely cripple the growth of young plants (Kneen 13). Weeds can be managed in hop yards before planting and in established yards through the use of herbicides, planting of competitive cover crops or practice of mechanical control (Kneen 13). When designing a new yard, it is also important to consider plant spacing and irrigation methods for ease of weed control. These are important details to consider as weed seed germination is triggered by a combination of moisture, light exposure, and optimal temperatures and once they begin growth they compete fiercely with cash crops (Oregon State University et al. 70). Although it is difficult to keep weed seeds out of a hop yard, cleaning equipment that has been used elsewhere and mowing weeds around the perimeter can reduce the potential for weed seed to be carried into the hop yard (Oregon State University et al. 70). Weeds that do appear in the hop yard should be diligently controlled before they produce seed, as many weed seeds can lay dormant in the soil for extended periods of time until conditions are optimal for germination. For example, only about 26% of kochia and 3% of lambsquarter seeds in the soil germinate each year (Oregon State University et al. 70). Summer annual weeds such as prickly lettuce, lambsquarter, kochia, redroot pigweed, purslane, and puncture vine are often found growing within the hop yard competing with plants for resources. Even harder to control, perennial weeds such as thistle and field bindweed compete fiercely with hops during the summer growing season (Oregon State University et al. 69). Although winter annual weeds don’t directly compete with hops, they can still cause problems

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by depleting soil moisture and interfering with early spring cultivation activities (Oregon State University et al. 69). One effective management practice to control both winter annual weeds and reduce spring emergence of perennials and summer annuals is to plant a fall cover crop in the hop yard. Although a useful tool, cover cropping is most effective when combined with other management practices (Oregon State University et al. 72).

Diseases, viruses, and nutrient deficiencies can also become problematic for hop production if not carefully monitored. Powdery mildew and downy mildew are two fungal diseases that can severely affect the quality and quantity of hops as well as the health of the plants. Although certain varieties of hops are more resistant to mildew infection than others, growers cannot always produce these varieties if sufficient market demand does not exist (Turner, Benedict and Darby 1649). Both powdery and downy mildew overwinter in infected roots, rhizomes and buds, so they appear early in the growing season when bines first appear (Hieronymus 90-91). Both mildews are most prolific during cloudy conditions when accompanied by high humidity and mild temperatures (Oregon State University et al. 18). Powdery mildew appears as white patches and thin fungal threads on young bines and can infect leaves and cones with spores later in the season. Infected plants will produce deformed, reddish cones if they produce cones at all (Kneen 14). Signs of downy mildew include stunted bines covered with thick clusters of pale, curled leaves called basal spikes. Young leaves of affected plants have a silvery upper surface and black mold spores on their underside (Kneen 15). Mold spores

are formed mostly at night when temperatures are greater than 43ºF and humidity is greater than 90%. Spores are then released in mid morning and grow into zoospores that enter other plants through open stomata. Because of this cycle, downy mildew infection is most likely to spread during the day when plants are damp (Oregon State University et al. 11). Infected leaves of mature plants will display dark, angular splotches of spores and infected cones will be covered with dark vertical stripes before turning completely brown (Kneen 15). Proper sanitation and pruning is important for the control of both types of mildew. Pruning low leaves that are likely to get wet and stay moist is important, as is maintaining proper airflow in the hop yard. Avoiding over application of nitrogen fertilizer can also decrease the likelihood of infection (Turner, Benedict and Darby 1649). Infected shoots and bines should be pruned early, removed from the hop yard and burned (Oregon State University et al. 18) (Kneen 15). Fungal diseases are less of a problem when arid growing conditions persist. Verticillium wilt is another fungus that ails hop plants, but signs of infection don’t appear until later in the growing season. Like the mildews, this pathogen overwinters in the soil, first invades roots, and then later moves to above ground plant tissue (Oregon State University et al. 25). Unlike the mildews, there are numerous related strains of verticillium wilt fungi that can cause mild to severe symptoms of infection (Oregon State University et al. 25). Of the two most common strains that infect hops, one is lethal and one is not. The more common non-lethal fungus causes yellowing and curling of leaves as well as swelling and darkening or browning of bines (Oregon State

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University et al. 25). Comparatively, the lethal fungus causes rapid wilt and death of plant leaves and reproductive side arms (Hieronymus 91). Browning associated with this disease should not be confused with normal browning and thickening of bines low on plants as they grow (Kneen 16). In addition to living in the soil, verticillium wilt pathogens can survive on weeds commonly found in hop yards such as lambsquarter and redroot pigweed, so weed control can greatly minimize chances of infection. Again, pruning, sanitation, and removal of infected material from the hop yard are important to controlling this disease (Oregon State University et al. 26). Although other diseases such as apple mosaic virus, hop stunt viroid, and hop latent virus can infect hops, they are less common and will not be discussed.

Unlike disease symptoms, signs of particular nutrient deficiencies can be difficult to diagnose as different shortages can produce similar symptoms and a lack of specific nutrients can produce varied symptoms depending on plant variety and growing environment. Nonetheless, nutrient deficiencies and less common instances of toxicities can significantly impact hop yield and cone quality (Oregon State University et al. 79). Along with nitrogen, phosphorus and potassium, hops require certain levels of other nutrients including boron, calcium, iron, magnesium, manganese, molybdenum, sulfur and zinc to grow and successfully produce cones (Oregon State University et al. 79-80). Deficiencies of many of these nutrients cause yellowing of leaves and reduced plant vigor, while high levels of certain nutrients often interfere with the uptake of others (Oregon State University et al. 79). Differences in existing soil nutrient levels and soil pH as well as climatic

conditions will dictate recommended fertilization levels. Prolific insect pests in the hop yard can directly damage plants and reduce cone quality and yield through feeding and breeding behaviors and cause injury by facilitating the spread of disease. The two most common pests found in hop yards are hop aphids and two spotted spider mites (Oregon State University et al. 38-42). Although hop aphid eggs overwinter in the Prunus tree, hops are the summer host to mature aphids that feed on leaves, stems and cones (Turner, Benedict and Darby 1649). The aphids are small pale white or yellow insects when wingless and darker green or brown when winged (Oregon State University et al. 38). In addition to removing water, nutrients and vascular tissue from all parts of the plant other than the roots, aphids secrete sugary honeydew that can transmit plant viruses and encourage the growth of black sooty mold that covers leaves and destroys the inside of cones (Oregon State University et al. 38) (Hieronymus 92). Severe aphid infestations can be avoided by applying nitrogen fertilizer conservatively to avoid excessive vegetative growth in the early spring. Infestations can be managed through the introduction of natural predators, planting of trap crops and insecticide application (Oregon State University et al. 38) (Kneen 17). The two-spotted spider mite thrives in hot, dry and dusty conditions (Turner, Benedict and Darby 1647). Red female mites overwinter in the soil and feed on the undersides of new leaves in the spring while they make delicate white webs. After they mature, the mites turn a greenish yellow color with dark spots on their backs (Kneen 17). Mature mites feed both on leaves and cones leaving webbing

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behind, causing leaves and cones to bronze, and reducing plant vigor (Oregon State University et al. 46). The mites most easily infest plants during periods of hot dry weather when dust is prevalent. Excessive nitrogen fertilization can also exacerbate mite problems (Hieronymus 92) (Oregon State University et al. 46). Mites are easiest to control as they emerge in the spring by pruning surplus bines and excess vegetative growth. Encouragement or introduction of predatory insects, planting cover crops to reduce dust, and application of insecticides are also options for controlling mites (Oregon State University et al. 48). In addition to these two pests, hop loopers, armyworms, hop flea beetles, California prionus beetles and cucumber beetles can attack growing hop plants (Oregon State University et al. 42-51). These insects are less numerous and will not be discussed. Conserving and increasing populations of predatory insects and parasites is one way to reduce harmful insect pressure in the hop yard. Providing a hospitable environment with supplemental food and habitat for these organisms allows them to play a large role in pest management, reducing the need for other management actions. If properly encouraged and managed, beneficial organisms are capable of partially or even completely controlling spider mite and aphid populations (Oregon State University et al. 52) (Grasswitz and James 211) (Silva, Franco and Vasconcelos 489). Lady beetles are common predatory insects that prey on aphids and spider mites, their preferred prey depending on beetle variety. Although adult beetles consume many aphids, larvae more ravenously

feed on prey (Oregon State University et al. 54-57). Predatory mites also feed on spider mites and occasionally on aphids and other insect pests. Beneficial mites complete their life cycles faster than pest mites, but eggs require high humidity to hatch and survive. After hatching, the mites are active predators as larva, nymphs, and adults (Oregon State University et al. 52). In addition to these two predators, a host of predatory and parasitic insects that feed on multiple species of prey at various stages of maturity may be present in the hop yard. These insects include minute pirate bugs, big-eyed bugs, predatory mirids, assassin bugs, damsel bugs, predatory thrips, parasitic wasps, many predatory flies, lacewings, and spiders (Oregon State University et al. 58-68). If identified and encouraged, each of these species can play an important role in hop yard pest management. Regular monitoring and continual education about environmental conditions conducive to insect growth and reproduction, and pest and predator biology is critical to the development, implementation and monitoring of a successful, multifaceted pest management program for a hop yard (Oregon State University et al. 2). Organic Hop Cultivation Hops are difficult to produce organically on a commercial scale because of high nutrient requirements and weed, pest, and disease pressure that can reduce yield and quality (Turner, Benedict and Darby 1645). As a result, certain disease and pest resistant varieties are more suited to organic production. The consequential lack of organic hop varieties in the marketplace makes it difficult for small breweries, the primary buyers of organic and whole cone hops, to produce a wide range of

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unique and competitive products (Kneen 8). In addition, organic producers can have a hard time finding reliable buyers and may need to sell organically produced hops for a loss at non-organic prices (Turner, Benedict and Darby 1646). Because of these problems, hops were placed on the ‘allowed and prohibited’ substances list by the USDA National Organic Standards Board (NOSB) in 2007, allowing brewers to produce certified organic beer without the use of certified organic hops in brewing (Turner, Benedict and Darby 1646). This change helped brewers to meet consumer demand for organic beers that had increased at an average rate of almost 11% annually between 1998 and 2003 (Turner, Benedict and Darby 1646). Starting in 2007, the American Organic Hops Growers Association (AOHGA) petitioned the NOSB to remove hops from the exemption list. Petitioning made sense as the supply of organic hops continued to rise due to improved agronomic practices, plant breeding, and ever increasing demand for organically produced beverage products (Turner, Benedict and Darby 1646) (Kneen 3) (Hieronymus 96). After some protest, hops were removed from the organic exemption list in late 2010 and beginning January 2013, all value added organic products made with hops must use certified organic hops (Turner, Benedict and Darby 1646). Due to this change, market demand for organic hops increased dramatically, encouraging farmers to work at growing a product that can be priced up to three times higher than conventional hops despite added production risk and consistently lower yields (Kneen 9) (Greenaway). The lure of selling directly to brewers also made organic production more

attractive for small growers as direct sales mean larger capital returns for producers and the opportunity to form meaningful business relationships (Kneen 7-9). These relationships also allow smaller producers to adapt to changing brewer demands for unique and specific plant varieties (Kneen 7) (Hieronymus 88). As a result, the number of producers and acreage of organic hop production in the United States have doubled, and the selection of varieties produced organically has increased (Hieronymus 96). In fact, the AOHGA reports that 218,000 pounds of organic hops were produced in the United States in 2012, triple the 70,000 pounds produced in 2011 (Greenaway). Most new producers are small and competing in the market based on the added value of organic production practices and not as much on price (Hieronymus 108) (Turner, Benedict and Darby 1646). Organic hop production has increased in response to a sudden and significant increase in demand. As this portion of the industry continues to flourish, more research and experimentation will help growers use effective cultural and agronomic practices that align with business goals to grow hops organically (Turner, Benedict and Darby 1647). As described above, organic hop production is challenging due to greater difficulties in pest and disease control, weed management, and fertility and irrigation planning (Turner, Benedict and Darby 1645). If not managed carefully, these challenges often lead to low yields and high production costs (Hieronymus 96). Diseases and pests are problematic in all hop yards as they often contain many genetically similar, if not identical plants resulting from propagation by cutting rhizomes.

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Genetic uniformity of this perennial crop greatly increases disease and pest susceptibility (Turner, Benedict and Darby 1647). Although this causes issues in all hop yards, organic growers have to be more creative with pest and disease management solutions than conventional growers that use pesticides and herbicides not approved for organic use (Turner, Benedict and Darby 1647) (Hieronymus 96). Although it will not eliminate problems that arise later, growers should obtain pest and disease free plants and rhizomes at the start of production (Kneen 3). Breeding efforts to produce disease resistant hop varieties is very important to the organic industry. New growers should also be sure to design hop yards well considering airflow, plant spacing, and sanitation practices. In addition, growers can reduce disease and pest risk by alternating varieties to decrease the number of genetically identical plants in their hop yard, although this involves more labor (Turner, Benedict and Darby 1649). Weed management is another cultivation challenge exacerbated in organic production. Although weed management does not imply the elimination of weeds, they must be controlled to effectively limit their ability to compete with the hops for water, nutrients, and light (Linares, Scholberg and Boote 27) (Blackman, Rees and Glendinning 635). If not properly managed, weed pressure and competition can become a big issue in organic systems as hops need large amounts of water and nutrients during periods of rapid growth. This problem is compounded by the struggle organic producers are faced with to provide enough nitrogen and other nutrients to bines during rapid growth without the use of chemical fertilizers used in

conventional production (Hieronymus 96). Instead of using unapproved herbicides, organic growers have the option to use tillage, irrigation control, mulches, cultivation, burning, cover crops, mowing, and some organic herbicides to control weeds. The strategy used by each producer will be multilayered and based on individualized need (Turner, Benedict and Darby 1648) (Blackman, Rees and Glendinning 635) (Granatstein and Mullinix 45). Although it can cause problems in any system, mismanaged fertility and irrigation can severely affect organic production. Hops are irrigated from mid spring in most regions until shortly before harvest, but if irrigation is not properly managed, it increases plant susceptibility to diseases and also poses the threat of increasing weed pressure. Despite high initial cost, drip irrigation systems efficiently deliver water to plants with little waste and can also be used to directly deliver nutrients (Turner, Benedict and Darby 1650). Nitrogen needs are especially difficult to meet in an organic growing situation, and the high nitrogen demand of fast growing plants necessitates the development of innovative and cost effective fertility strategies. In order to add and retain nitrogen in soil, many organic producers manage legume or grass-legume mixed cover crops in aisles and less commonly in rows of hop yards (Turner, Benedict and Darby 1647). This technique increases soil nitrogen while building and stabilizing soil. If managed properly, cover crops can supply a large portion of nitrogen required by growing hop plants (Turner, Benedict and Darby 1647). A variety of methods and techniques are used to manage and overcome the difficulties associated with

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producing hops in organic systems. Individual methods are often combined to effectively manage diseases, pests, weeds, and plant nutrition and are tailored to serve the needs of specific hop yards. These methods include mechanical, biological and chemical control (Oregon State University et al. 3). Mechanical solutions including tillage, mowing, and handwork in hop yards are most often used to aerate roots and to control weeds and soil water content (Lipecki and Berbec 177). Tillage methods may also be utilized to reduce pest habitat, increase available soil nutrients, and promote sanitation, therefore reducing disease risk (Turner, Benedict and Darby 1648). Due to ease and efficiency, tillage is commonly used as a method of weed control in hop yards, although it can greatly compromise soil quality due to agitation, loss of organic matter and compaction. In fact, experiments done in orchards have demonstrated that fruit yield increases by up to 50 percent over time with the use of soil protecting management techniques such as cover cropping, residue mulching and no-till practices (Montanaro, Celano and Dichio 132). Additionally, mechanical practices utilize fossil fuels and can be harmful to hop roots (Granatstein, Wiman and Kirby 115). Although there are drawbacks, tillage practices are a good option for controlling weeds in hop yard aisles if proper implements are used and timing is well planned and executed (Lipecki and Berbec 178). Although mowing has fewer negative effects on soil, it can still cause compaction and is even more time sensitive than tillage. If weeds are allowed to go to seed before being mowed, this is an ineffective form of weed management (Oregon State University et al. 3). Although hand-

pulling weeds can be an effective method of control, it is very labor intensive. Biological management techniques including management of cover crops, mulching, and introduction or encouragement and retention of organisms that compete with or prey on pest species can also be useful in the hop yard (Oregon State University et al. 3). A non-cash cover crop can be grown in aisles between hop rows and occasionally within rows (University of California 3). Cultivating cover crops involves the use of chosen plants to improve physical characteristics and fertility of soils in addition to discouraging weed growth, increasing soil water holding potential, possibly breaking pest life cycles, and providing needed resources to beneficial insects (Kneen 18) (Turner, Benedict and Darby 1648). Covering the soil with a chosen cover crop can be done seasonally or year round and fits well into hop cultivation because of the wide, uncultivated aisles left between plants. So they don’t become a management issue themselves and will best benefit the hop yard, cover crops are mowed or tilled under at specified times based on a planned management regime (Kneen 19). Planting such a crop might be unattractive due to increased management activity, concerns that the crops themselves might become weeds and compete with the hops, and nutrient, water, and seasonal constraints (USDA Soil Conservation Service 7). Cover crops may also provide inconsistent weed suppression depending on weather and available water and nutrients (Granatstein, Wiman and Kirby 115). Managing time is the most difficult aspect of managing a cover crop because mowing or tilling must be performed at specific intervals based on desired

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results. For example, if plant residue is to be used to increase soil fertility, plant break down and soil nitrogen availability must be carefully timed so growing hops can meet their nutritional needs in the spring (Turner, Benedict and Darby 1647). Finally, while they often invite and harbor beneficial species, cover crops can also provide habitat for insect and rodent pests that can wreak havoc in a hop yard. In spite of these drawbacks, the use of cover crops in hop yards has the potential to improve soil quality by conserving, recycling, and adding nutrients and by improving soil structure. Cover crops are also an environmentally sound alternative to weed management (Linares, Scholberg and Boote 27). They can also be used to increase water infiltration and retention in soils, decrease dust and control erosion, and moderate soil temperatures, thus playing an important role in an integrated pest management regime (USDA Soil Conservation Service 5) (Kneen 18) (Silva, Franco and Vasconcelos 490). If chosen and managed properly in conjunction with other problem targeting strategies, cover crops can be beneficial to hop producers in both organic and non-organic situations. Mulching, a practice often associated with cover cropping, is another method of biological weed control that also provides added benefits of increased water infiltration and soil insulation. Leaving cover crop residue on top of soil or only partially integrating it can supply these benefits, as can adding a paper, wood, or straw mulch to the hop yard (Turner, Benedict and Darby 1648). When mulching hops, especially in winter, the crown should be surrounded by mulch but not directly covered to decrease the chances of the crown becoming too wet (Kneen 18).

Although a less direct method to biologically manipulate hop yield and quality, plant breeding is another important aspect of hop production. Plants are bred both for their brewing characteristics and agronomic qualities and certain varieties have been bred in a way that allows them to be more productive in organic growing conditions due to disease and pest resistance, growth habit, or ability to more efficiently accumulate and utilize soil nutrients (Turner, Benedict and Darby 1651). If breeding science can continue to produce a myriad of hop varieties that grow well in organic systems, organic production will continue to increase, as will the purchase and use of organic hops by brewers. Chemical control of weeds, pests, and diseases and chemical augmentation of soil nutrients is the final way that organic producers can manage challenging production situations (Oregon State University et al. 3). Although most organic growers strive to avoid the use of even organically approved pesticides, herbicides, and fungicides, these substances can play an important role in an integrated management regime. Even if used infrequently, chemical tools may be necessary to control an especially vigorous disease or pest outbreak or to provide nutrients quickly to deficient plants (Turner, Benedict and Darby 1649) (Granatstein, Wiman and Kirby 115). Application can include synthetic or natural pesticides or fertilizers. Selective substances that control harmful insects, diseases, and weeds while leaving beneficial organisms unharmed are the most favorable (Oregon State University et al. 3). Chemical management tools should seldom be

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used in isolation from or in the place of other effective management tools. Whatever combination of management tools is chosen, it must be tailored specifically both to the needs of the hop yard and to the goals and needs of the producer. No technique is right for a farm if management actions and results do not align with the goals and values of the business. More often than not, organic producers, and especially small-scale organic producers with diversified farming operations, place great consequence on environmental impacts, managing ecosystems, and sustainable practices (Kneen 6) (Granatstein, Wiman and Kirby 115). Additionally, all farms, organic or not, must be managed so they are economically viable, environmentally sound, and socially acceptable (Granatstein, Wiman and Kirby 115). If a farm fails in any one of these areas, the producer is unable to cultivate the land so it may perform the functions associated with the other two necessary conditions (Granatstein, Wiman and Kirby 115). For example, an environmentally sound cover cropping system designed to manage weeds and add nutrients to the soil is ineffective if it is not economically viable. As many new hop producers are farmers adding hop production to an existing operation or farmers starting a diversified operation to sell a variety of cash crops, any management regime designed for the hop yard must fit into the context of the larger operation and business (Kneen 6). This will be a common issue as organic hop production increases because, despite all of the options, finding and utilizing reliable methods of pest, disease, weed, and nutrient control is challenging. This difficulty in fact makes organic hop production more

suited to small scale operations where producers and workers have more time to spend observing and managing issues that might arise and affect hop yield and quality (Turner, Benedict and Darby 1652). Regardless of production scale, hop farmers must evaluate the economic viability, environmental influence, and social impacts of management regimes in order to develop systems that will best serve the needs of their operation. Cover Crops in Hop Cultivation A cover crop is a non-cash crop made up of densely planted annual, biennial or perennial grasses, legumes and/or broadleaf plants that cover the soil surface (Card 1). Often grown to improve soil conditions, these crops serve as a source of organic material for soil building and amendment as well as a functional system to cycle and conserve soil nutrients and water (Natural Capitalism Solutions 64) (Kneen 18) (Gomez, Guzman and Giroldez 137). These functions are especially important to organic growers as USDA national organic standards require growers to at least maintain, but preferably improve soil quality, a goal that is difficult to achieve while producing a cash crop that utilizes significant amounts of soil resources (Granatstein and Mullinix 45). If chosen and managed correctly, cover crops can help producers improve soil by adding new nutrients and valuable soil binding compounds that remain in the soil because of active biology and improved soil structure achieved through decomposition of organic material (Card 3). Both actively growing crops and spent residues also play a vital role in reducing the impacts of wind and water erosion on soil that removes soil nutrients (NRCS Soil Quality Institute 1). Different types of crops help achieve

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these goals. With more fibrous root systems, grasses bind to soil, reducing erosion and increasing water infiltration while legumes are able to symbiotically fix atmospheric nitrogen, making it available as a soil nutrient. The residues of both legumes and grasses add valuable organic matter and carbon to the soil although legume debris breaks down much more quickly than grass debris (USDA Soil Conservation Service 12). All of these soil-improving measures are significant because good soil condition is paramount to the functioning and availability of other agricultural resources for production (NRCS Soil Quality Institute 1). In addition to being instrumental in soil improvement, cover crops are an invaluable tool for weed and pest management for hops (Turner, Benedict and Darby 1648). Cover crops can be planted in the spring or fall; seasonal planting should be based on cash crop production schedules, climate, intended crop management, and desired results. A good cover crop achieves desired results by fitting into a broader scale farm management and production plan (USDA Soil Conservation Service 12). Although spring planted cover crops can be utilized in hop yard systems, the focus of this discussion will be on annual fall planted crops as timing of their growth and management does not directly overlap with the primary hop growing season. Fall planted crops are often a mix of cereal grain and legume, seeded each year to be mowed or tilled the following spring (University of California 6). Depending on regional climate, these crops are sown sometime in mid-fall after hop harvest is complete. Mid October is probably the latest that any fall cover crop should be planted as

the crop must have ample time to establish and store nutrients before overwintering (Card 3). Crops used as fall cover should be fairly winter hardy and able to establish provided the water, nutrient, and light resources available in the fall. Primary advantages to fall cover crops include weed suppression, increased soil biological activity, improved water infiltration, increased soil organic matter, soil nutrient retention and cycling, and fixation of atmospheric nitrogen if legumes are utilized. Secondary benefits of a fall cover crop system may include reduced dust, compaction, soil erosion and insect pest pressure the following season (University of California 6). Depending on the crops chosen, these benefits can be captured under good monitoring and management without competing for nutrients, light, water or labor resources with a hop crop during the main growing season (Grubinger) (Lipecki and Berbec 169). Depending on the chosen fall crops, target benefits can be realized in a well planned and managed cover cropping system. The easiest way to plant a cover crop in a hop yard is to utilize uncultivated aisle space between plant rows to establish and grow crops that can then be used as a soil amendment or mulch the following spring (SARE 13). This plan utilizes otherwise idle space to contribute positively to the hop yard agricultural system. Before choosing any crop, it is important to understand how a cover cropping system will fit into a whole farm plan and to define and prioritize the desired benefits of the system. Identifying needs and prioritizing desired benefits, along with an evaluation of restrictions and potential challenges, will aid in the selection of

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crops that will best achieve desired results within a specified time frame (SARE 12-14). This is important as different crops are better suited to achieving certain goals such as adding nitrogen to soil, improving soil structure, and fighting weeds, pests and erosion (SARE 8). Identifying cover cropping goals and needs should be done in conjunction with a cropping feasibility analysis within the context of specific operations. A feasibility analysis must include financial analysis, climate and weather considerations, resource availability, timing concerns, and residue management planning (SARE 12) (Oregon State University et al. 2). After considerable planning, a cover cropping system can be devised and cropping species chosen. If a mix of species is desirable, each type of seed chosen must have a specific and measurable purpose (Linares, Scholberg and Boote 31). Of possible challenges associated with cover cropping methods, proper timing of seeding, mowing or tilling, and residue management activities can make a cover cropping system valuable, while improper timing can render the system almost useless (SARE 50). If crops can’t germinate properly or are managed in the spring too early or too late, the cropping system can turn out to be a waste of resources or become a new management problem. Fall cover crops planted too late in the season may not germinate or overwinter well, defeating the purpose of planting in the first place. Another common issue is cover crops being managed too late in the spring allowing for reseeding, resulting in them having to be managed differently than originally planned, and not generating desired results (SARE 52). Poor time management can also result in undesirable spring nitrogen tie up as

microorganisms work to decompose cereal grains or grasses (NRCS Soil Quality Institute 2). This can be an issue in hop yards, as plants require large amounts of soil nitrogen during periods of rapid vegetative growth. To avoid this problem, cover crops should be managed and killed a few weeks prior to the beginning of rapid spring growth in the hop yard. Despite similar challenges and goals, each hop yard is different. Therefore, individual producers will identify and prioritize unique goals to be achieved via an individualized cover cropping system (SARE 12). If planned, managed, and monitored properly, a fall cover cropping system can greatly benefit organic hop production through improvement of growing conditions and resources. One of the primary benefits of cover cropping systems is the ability to enhance and manage soil nutrient availability and cycling. This advantage can reduce fertilizer costs and increase hop yield and quality by improving soil health and moisture content (SARE 9). Additionally, building and maintaining healthy soil is an investment in sustainability and quality production for the future (SARE 16). Legume crops are primarily used to increase soil nitrogen content, as they are able to fix atmospheric nitrogen through symbiosis with rhizobia bacteria, although they can also provide other soil improving benefits. Grasses on the other hand, are often used to scavenge and conserve soil nutrients, stabilize soils, reduce compaction, and increase water infiltration (SARE 9). Both legumes and grasses provide a habitat and food source for beneficial soil organisms that play a large role in break down of organic matter, nutrient cycling, and maintenance of soil structure (SARE

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16). The addition of organic matter in the form of cover crop residue in the spring can increase both water infiltration and soil water holding capacity while also enhancing both short-term and long-term soil nutrient availability and storage (SARE 17). Organic matter is broken down by microorganisms at different rates based on soil and climatic conditions as well as the carbon to nitrogen ratio of the material. Generally, microorganisms need to consume a diet of organic matter with a C:N ratio of 24:1 in order to grow and fulfill their ecological niche (USDA NRCS). Crop residues with C:N ratios lower than this are decomposed very quickly resulting in mineralization that makes nitrogen immediately available to cash crops (USDA NRCS) (SARE 46). In contrast, crop residues with C:N ratios higher than 24:1 result in the tie up of soil nitrogen as microorganisms utilize it as they consume and decompose excess carbon (USDA NRCS). Active fractions of organic matter, such as leafy legume debris, decompose quickly as they are primarily composed of simple sugars and nitrogen rich proteins. These types of residues have comparatively low carbon to nitrogen ratios (Godin). Due to quick break down and utilization by microorganisms, this type of organic matter doesn’t contribute much to lasting soil organic matter content (SARE 17). Despite this fact, active organic matter is crucial to the health of soil biological communities that then work to break down stable fractions of organic matter that do contribute to soil organic matter content, thereby increasing water holding capacity and nutrient storage. Stable fractions of organic matter generally have higher C:N ratios and organic carbons greatly contribute to improved soil structure (Godin)

(Montanaro, Celano and Dichio 132). In cover cropping systems, grasses as well as legume stems and roots provide the majority of the stable fraction of soil organic matter (SARE 17). Deceased soil microbes themselves also decompose and become quickly available valuable soil nutrients, while the stable fraction of organic matter that they work to break down releases nutrients slowly, building soil organic matter and enhancing the physical properties of soil (SARE 17) (Montanaro, Celano and Dichio 134). In the process of decomposing all materials, microbes also add polysaccharide sugars to soil that aggregate soil particles together, improving soil tilth (SARE 17). The break down of both active and stable fractions of organic matter is crucial to achieving improved soil structure and health (Godin). Grass and legume mixed cover crops provide both active and stable fraction organic matter. Mixed crops can be managed to mitigate nitrogen immobilization that results from stable fraction decomposition as they often have intermediate C:N ratios. As such, cover cropping systems that combine both grasses and legumes in order to balance decomposition and nutrient cycling are the most effective for achieving this goal. Addition of fixed nitrogen to soil is an important function of legume crops. When paired symbiotically with the correct rhizobia bacteria, legumes are able to convert atmospheric nitrogen into usable organic forms, but the extent to which legumes are able to perform this function is dependent on other soil resources. In order for legumes to fix nitrogen to their full potential, the soil has to be nitrogen deficient enough to warrant fixation; at the same time it must

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be fertile and damp enough to support legume growth (SARE 20) (Natural Capitalism Solutions 68). Soils that support nitrogen fixation also have pHs no lower than 5 and allow for air filtration, which delivers atmospheric nitrogen to legume roots (SARE 20). It is also important to note that in order to begin fixing nitrogen, legume crops must first utilize available soil nitrogen for growth, meaning there is an immediate energy expense for the production and addition of soil nitrogen later (SARE 20). If conditions are right, legumes utilize fixed nitrogen to manufacture proteins, chlorophyll, and other substances in stems and leaves as well as to produce seeds. As such, the nitrogen will be unavailable to other crops until the legumes are killed by tilling or mowing and decompose (SARE 20) (Card 1). Timing of legume management should be based on these facts as legume nitrogen content will peak in blossom stage and nitrogen availability will increase significantly once a legume crop begins to decompose (SARE 20). To best meet the needs of rapidly growing hop plants in the spring and early summer, timing of mowing or tilling legume crops should be calculated so that available nitrogen resulting from decomposition aligns with the nitrogen demands of the plants in late May, June and July when they may utilize up to 1.82 kilograms of nitrogen per acre per day (Turner, Benedict and Darby 1647). Nitrogen used by hops supports both vegetative and reproductive growth and mature cones contain approximately 32 percent of above ground plant nitrogen (Turner, Benedict and Darby 1647). Although it can be difficult to meet nitrogen demands in an organic hop growing system, a well-managed legume crop can supply a large portion of

needed nitrogen. Legume and grass mixed cover crops are also very useful for nitrogen cycling management as grasses scavenge and conserve nitrogen at different points in the growing season while legumes contribute fixed nitrogen to the soil that is more readily available to a hop crop (SARE 47). Additionally, this method of nitrogen delivery is used to balance nitrogen needs and inputs and is unlikely to result in excessive fertilization that can contribute to increased disease and pest risk in a hop yard (Oregon State University et al. 80) (Kneen 13) (Xiloyannis, Dichio and Montanaro 421). Cover crops also help with the conservation and management of other important nutrients and compounds such as potassium, calcium and phosphorus. Fall planted grass crops are often utilized as nutrient catch crops to immobilize soil nutrients and prevent them from leaving the soil via water or wind transport. These same crops then supply large amounts of carbon to soil microbes in the spring. Increased levels of soil organic carbon resulting from managed residue decomposition greatly improve nutrient uptake and retention in soils (Xiloyannis, Dichio and Montanaro 421). As such, the way the soil microbial communities are utilized and manipulated in conjunction with cover crop residue greatly affects soil nutrient cycling and availability (Paszkowski and Dwornikiewicz 1162). Management of fall planted cover crops can therefore improve the quantity and quality of hop yields by enhancing overall soil health. Tillage methods are another variable that affects the rate of cover crop residue breakdown and therefore cover crop utility. Conventional tillage is a commonly used method for organic matter incorporation in both organic and

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non-organic growing systems as it speeds decomposition, making nutrients more immediately available to growing crops. Tillage accomplishes this by mechanically breaking down and mixing in organic matter, making it more accessible to soil microbes (SARE 18-22). This can be a boon if nutrients are needed quickly, but can be dangerous as soil nitrogen must be stored in organic form to remain for longer periods of time in the soil (SARE 22). Excessive tillage may expedite the break down of proteins in organic matter so much so that soil nitrogen becomes susceptible to loss through runoff and leeching and subsequent tilling can exacerbate this problem (SARE 22) (University of California 7). Tillage can also cause other soil and cropping problems including compaction, reduction of water holding capacity, increased erosion potential, increased weed seed germination and injury to microbial communities due to disturbance (SARE 18,49). In contrast, conservation tillage systems leave at least 30% of killed or mowed cover crop residue on the soil surface and no-till systems leave all crop residues on the soil surface (Natural Capitalism Solutions 59) (SARE 44) (USDA Soil Conservation Service 9). If cover crop management is timed properly and the dynamics of organic matter break down are well understood, these systems can greatly enhance the long-term benefits of cover crops in a hop yard (SARE 18). Benefits to leaving more organic matter on the soil surface include reduced soil erosion, increased water infiltration and holding capacity, reduced organic matter volitization, increased soil aggregation, weed suppression, and decreased energy input (Natural Capitalism Solutions 59). Although it slows decomposition,

leaving at least some cover crop biomass on the soil surface also improves nutrient cycling and supports and even increases soil biological activity and organism diversity that supports nutrient cycling and helps in the management of soil borne pests and diseases (SARE 44). In order to reap these benefits, cover crops must be managed in a timely manner based on desired results. For example, early spring kill of a fall planted cover crop will increase soil warming, decrease potentially negative allelopathic effects of cover crops on successive crops, allow for the replenishment of soil water, and speed residue decomposition and mineralization of nitrogen from crops with low C:N ratios (SARE 53). In contrast, later killing of a fall planted cover crop will allow for more biomass build up and soil water retention in addition to increased potential nitrogen contribution from legumes and superior weed control. Late killing of fall planted cover crops also gives a producer the option of letting annual crops reseed if desired (SARE 54). Although there are many advantages to no-till and conservation tillage practices, there are some drawbacks and limitations to these systems. First, it is important to remember that nitrogen volitization and loss still occurs in alternative tillage systems albeit at a decreased rate. In conservation tillage and no-till systems, organic nitrogen can still be converted to ammonia and lost as gas, or nitrate that can be lost to leeching before plants utilize it (SARE 24). Additionally, they require more management and attention than conventional tillage, a resource that may not be available to all growers, especially if they manage larger operations. In addition, these tillage systems can limit soil nitrogen

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availability at critical growing times due to slower decomposition and may require specialized equipment such as roller crimpers and no-till drills (University of California 9) (SARE 54). They also allow for more weed growth than traditional tillage despite weed suppression (Natural Capitalism Solutions 60). Finally, the value of these systems is greatly limited by cropping restrictions that dictate potential benefits of residue management (Natural Capitalism Solutions 60). Cover crops can also be utilized in integrated weed, pest, and disease management systems. Weeds can be an especially large problem in organic hop production situations as they are more difficult to control using organic methods and compete with hop plants for soil nutrients, light, and moisture, potentially reducing the quality and quantity of hop cones produced (Turner, Benedict and Darby 1648) (Granatstein and Mullinix 45). Furthermore, weeds can interfere with irrigation management and hop harvest as well as increase labor demands (Linares, Scholberg and Boote 27). Common hop yard weeds include field bindweed, kochia, redroot pigweed, purslane, thistle and lambsquarter among others. Weed management involves the control, rather than eradication of these weed species that compete with a hop crop for valuable resources (Blackman, Rees and Glendinning 635). As tools for weed control, living cover crops as well as residues reduce herbicide use by helping to suppress both annual and perennial weeds. Living crops compete with weeds for water and nutrients, while residue blocks solar energy and can alter soil surface temperatures to be unfavorable for weed germination and growth (SARE 9). Cover crops may also alter soil biology in ways that decrease

weed seedling vigor (Linares, Scholberg and Boote 27). In the long term, effectively controlling weeds by preventing them from going to seed, thus depleting weed seed banks, is the best approach; however this type of long-term management requires producer knowledge of weed life cycles (SARE 33). Weed suppression using cover crops is also connected to pest and disease management as weeds can serve as hosts to these organisms (Linares, Scholberg and Boote 27). Efficiency of weed control by cover cropping systems largely depends on timing, cover crop type, and stand density (Oregon State University et al. 75). For example, annual cover crops are often more effective at suppressing weeds as they generally establish more quickly than perennials and expediently produce more biomass (Linares, Scholberg and Boote 32). If plant species compliment each other well, fall planted grass and legume mixes can be effective spring weed suppressors (Linares, Scholberg and Boote 32). In this case, growing biomass suppresses weeds early in the spring season and longer lasting grass residue functions to suppress them later on. Longer lasting weed control can also be achieved by mowing, rather than entirely killing a cover crop in the spring (SARE 32). Utilization of fall cover crops like cereal rye that have known allelopathic effects can be useful in weed suppression, but should be managed carefully and killed a couple of weeks before rapid hop growth begins to reduce the chances that allelochemicals might negatively affect the crop (NRCS Soil Quality Institute 3). Other management challenges to using cover crops for weed control include additional costs, water allocation to establish and grow cover crops, excessively low soil temperatures

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associated with both growing covers and residues that could delay hop growth, the potential for crops and mulches to protect young weed seedlings from other management efforts, and the potential for mismanaged crops to become weeds themselves (SARE 49) (Blackman, Rees and Glendinning 635) (Lashbrook) (University of California 4). In general, cover crops should not serve as a stand-alone weed management tool in a hop yard, but should be combined with mechanical or chemical means of control for maximum effectiveness (Oregon State University et al. 75). Insect and disease management is another less understood function of cover cropping systems. Of all the cover crop functions discussed, this is the most variable function from farm to farm as surrounding geography and ecosystems differ greatly, thereby affecting pest and disease prevalence. Additionally, the role that certain cover crops can play in management of beneficial insects, pests and diseases by serving as an ecosystem tool is not thoroughly understood (Silva, Franco and Vasconcelos 490). Using cover crops as a part of an integrated pest management plan involves introducing or inviting beneficial insects including pollinators to the hop yard and then maintaining their populations by providing habitat and food resources (Silva, Franco and Vasconcelos 490) (Grasswitz and James 211). In theory, increased cropping diversity will attract a large diversity of beneficial insets that will then regulate harmful hop yard pests like aphids and spider mites (Silva, Franco and Vasconcelos 490) (Grubinger). Although managing a cover crop in orchards and hop yards has been shown to increase the number of beneficial insects within the cover cropped zone and somewhat in the lower

part of the hop yard, it is still unclear whether or not beneficial insects attracted by cover crops regulate pests effectively in the hop yard canopy. Of course, in order for this cropping strategy to be an effective part of integrated pest management, beneficial insects must move frequently between the cover crop and hop cash crop (Silva, Franco and Vasconcelos 494) (Grasswitz and James 218). Although these relationships are not fully understood among cover crops, it has been shown that planting any cover crop in a hop yard or orchard does increase densities of beneficial insects above those associated with bare soil in aisles (Silva, Franco and Vasconcelos 498). As such, creating habitat areas for beneficial insects is a way to mimic natural systems and possibly utilize ecosystem services to manage harmful insect pressure in hop yards (SARE 28). In addition, cover crops that interrupt the life cycles of pests may be planted, although this can be difficult in a hop yard due to the perennial nature of the cash crop (Kneen 18). Based on specific farm needs, generalist predators, parasitic beneficials, more specific predators, and pollinators are all beneficial insect populations a hop producer might aim to enhance (SARE 28). However, crops must be chosen based on specific insect management needs in order to effectively have natural systems work to achieve farming goals (Lashbrook). Feasibility also plays a role in the ability of cover crops to aid in pest management as crops that might be the best habitat for beneficial insects may not be suited to the climate or able to grow successfully provided the available resources on a particular farm (Lashbrook). The cost to plant and manage a cover crop for pest

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management purposes may not be justified when compared to the cash value of crop loss or damage from pests (Oregon State University et al. 2). Another barrier to the use of cover crops for pest management may be limited knowledge of pest life cycles and predator-prey interactions that should be well understood before endeavoring to manage beneficial insect habitat in order to manipulate pest populations (SARE 47). Knowledge and consideration of larger ecosystem interactions is also important as cover crops can invite new pests such as rodents, different undesirable insects, and even diseases into a hop yard (Oregon State University et al. 1) (USDA Soil Conservation Service 7) (Granatstein and Mullinix 45) (Granatstein, Wiman and Kirby 117). Pest management using cover crops is closely associated with disease prevention and management. Depending on soil and climatic conditions, cover crops can serve as a host to beneficial soil microbes as well as beneficial insects above ground. These microbes can reduce the chances that soil borne pathogens might infect the hop yard. Microbes achieve this by competing with pathogens for nutrients and creating debilitating biofilms (SARE 24). Crops may also alter soil chemistry to be less hospitable to pathogens as well as create and excrete soil compounds that can reduce densities of nematode pests and encourage beneficial nematode species (SARE 10). Generally, more diverse cropping systems enhance these beneficial functions (Paszkowski and Dwornikiewicz 1159). In spite of potential benefits of cover cropping for disease control, systems should be well researched and planned before being implemented in a hop yard as cover crops can also serve as hosts to harmful

soil nematodes and create habitats that are hospitable to certain diseases and pathogens (Lashbrook). As with other uses of cover crops, they should not be used as a stand alone pest management tool, but instead play an integral role in a larger integrated pest management plan that functions within a farm system level management and production plan. A working understanding of potential benefits and challenges of cover cropping in a hop yard and defined priorities and goals to be accomplished by the system are necessary prerequisites for implementation of a cover cropping system. After these steps, a cover cropping system should be devised and evaluated for feasibility. A cover crop may achieve delineated goals, but is not an effective farm management tool if it costs more money than it saves or if it invites new social or environmental difficulties (Natural Capitalism Solutions 64). Direct costs of cover cropping include seeds, water, energy, and nutrient requirements. Common indirect costs are increased labor demands associated with establishment and management, loss of intended benefits if the crop doesn’t perform well, potential hindrance of hop growth resulting from resource competition, and possible yield damage resulting from unexpected diseases or pests (Natural Capitalism Solutions 65). Extensive planning for how and when to manage a cover crop within the hop yard is critical. In this planning, hop producers should consider soil area to be planted, water resources for stand establishment, hop yard air circulation, nutrient availability and limitations for both the cover crop and hop cash crop, and labor demands among other details (USDA Soil Conservation Service 8). All of these

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considerations should be made and evaluated within the context of a comprehensive farm production plan (Silva, Franco and Vasconcelos 497). Therefore, the choice to utilize cover crops as a management tool in a hop yard as well as the choice of cover crops to be used should be individualized and situationally based for every farm. Example Hops Farm: Boulder County The information in this section was obtained via extensive interviews with the owners and operators of Black Kettle Farm* and took place in the spring of 2013 (Witman and Dent). Additional information provided comes from the work experience of the researcher.

Black Kettle Farm is a small market farm located on the Colorado Front Range near Niwot in Boulder County. Situated on approximately six acres along Left Hand Creek, not all of which are in cultivation, the farm intensively produces vegetables, herbs and flowers to be sold to local restaurants, grocery stores, and markets (Witman and Dent). In addition to growing these crops, Black Kettle Farm produces organically grown hops on half an acre, which are sold to breweries, restaurants, home brew stores and through direct on-farm and internet sales. The current production schedule is fairly new. The oldest part of the business is honey production, which began in 2005 as one partner’s hobby business, but continues today as part of the overall farm business (Witman and Dent). Before 2009, the northern most section of what is now the hop yard was a personal garden. Starting in 2009, a third-party grower leased land on the southern part of the Black Kettle Farm property, and continued to lease through

2012, although the hop yard was constructed and planted in 2010. In 2012, the business expanded from just hop production to market vegetables, herbs and flowers and the business was named Black Kettle Farm (Witman and Dent). In the beginning of 2013, the owners stopped leasing to the third-party grower in order to take over field management and to allow for expansion of their own business (Witman and Dent). Although neither partner had commercial agricultural experience before starting Black Kettle Farm, both had many years of growing knowledge and did a significant amount of research before starting the hops operation and before expanding production to other market crops. Black Kettle Farm currently operates as an LLC with two partners who live on and manage the property performing all business functions. One of the two partners is employed full time off-farm, while the other has a part time source of off-farm income (Witman and Dent). The partner with a full time job is directly responsible for hop yard infrastructure maintenance as well as harvest, packaging and management of sales. To supplement these efforts, the second partner serves as the field manager, directing every day activities both in the hop yard and on other parts of the farm. Both partners serve as events coordinators for farm events. As a team, both partners contribute generally to field management and planning, bookkeeping and recordkeeping, sales and marketing, budgeting and financing, and product development (Witman and Dent). The management team also holds weekly, monthly and quarterly meetings and communicates discussion items to employees regularly.

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The owners of Black Kettle Farm have delineated specific business goals and objectives in a business plan. In addition to this set of goals, an evolving set of goals is perpetually considered, explored, and tested on the farm. The guiding principles behind all farm goals and the daily activities that help to achieve them are the three pillars of sustainability: economic, social and environmental (Witman and Dent). Upon writing a business plan, the owners of Black Kettle Farm agreed that their goal was not to become a large commercial operation and they are not. Instead, as the production space at Black Kettle Farm is fairly small, the owners seek to manage unique fields and growing systems in a way that optimizes market yield in small spaces. In practice, this means growing efficiently by choosing crops that are suited to climatic and soil conditions of the area and well received and supported by the Boulder County community (Witman and Dent). The size of the farm, importance of local business relationships, and values of the owners also dictate that production emphasis is on quality before quantity. Farm ownership is also committed to conserving the important resources that allow them to grow such a wide variety of quality specialty products on the farm and is unanimously committed to perpetual stewardship of land, water, soil, biodiversity and habitat. As such, production optimization goals fit into a larger context that includes organic production practices, crop rotation, companion planting, annual soil monitoring, and soil amendment as important aspects of whole farm management (Witman and Dent).

At the outset, the owners of Black Kettle Farm made the goal to

break even on their hop yard investment in five years, and although they are on the right track, this goal has yet to be achieved after three years of hop production. In order to meet this goal more easily, a quarter acre was added to the south portion of the hop yard in 2013 as additional production space and the owners are working ceaselessly to improve the efficiency of all management systems in the hop yard and otherwise (Witman and Dent). Another financial goal was to double farm based income every year for the first five years of production starting in 2010. As a result of hard work to build strong business relationships and exploring and fulfilling unique market niches, Black Kettle Farm has successfully tripled farm income each successive year, although infrastructure, labor, and production expenses still bar the farm from creating value as profitable income. Aiming to maintain the socially and environmentally sustainable practices on the farm, the owners are still working to achieve the third economic pillar of sustainability (Witman and Dent). Although one partners’ full time off-farm income is currently helping to fund production, the farm owners would like their agricultural endeavors to eventually be self sustaining. The fact that one business partner has a full time off-farm job also puts a strain on valuable time and labor resources on the farm. As they are just getting started in agricultural production, the owners of the farm intend to grow somewhat and continue to explore new markets including those for value added products, which they know will be an important aspect of economic sustainability for the farm, especially in the off season (Witman and Dent). As the business grows, more employees and volunteers will be invited

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to help with field management, product processing, marketing and sales. It is important to note, however, that farm resources are limited due to size and financial resources. As a result, the majority of hop yard plant and infrastructure maintenance is done by hand with basic tools as well as with a small lawn tractor with tiller attachment, a power mower, and a weed-whacker. All farming activities necessitating heavier machinery or equipment are done using rented equipment or via contracted help which somewhat restricts timing of these activities (Witman and Dent).

The context in which production occurs at Black Kettle Farm is important as the climate, weather, soil conditions, water availability, access to ecosystem services, and farm resources all affect the quality and quantity of agricultural products. Black Kettle Farm is located at approximately 40º North latitude, making it a good spot for hop production due to day length during the growing season. Other aspects of the climate in Boulder County are supportive of hops production, while some pose significant challenges. The climate of the Colorado Front Range is characterized by low annual precipitation, dry winters, sunny days, periodic drought, and fairly extreme temperature fluctuations ranging from -15ºF to 115ºF over the course of a year (Natural Capitalism Solutions 9-10). Daily temperature variations are also significant. The region also experiences intermittent snowstorms, hailstorms, and thunderstorms in addition to varied winds with gusts that can reach over 75 miles per hour (Natural Capitalism Solutions 10). The majority of high-powered wind occurs in the winter months, not during the main growing

season for hops and other crops, which saves crop damage, but can still cause significant top soil loss and wind erosion (Natural Capitalism Solutions 55). The Rocky Mountains to the west are the defining topographic feature in the area and contribute greatly to the aridity of the Front Range via the rain shadow effect. As winds in Colorado are primarily westerlies, the majority of precipitation carried by storms falls on the western slope or in the mountains as moist air rises, cools, and condenses in the process of moving over the mountains (Natural Capitalism Solutions 9-10). This effect, in combination with other climatic forces, creates the semi-arid high plains region occupied by Boulder County. Rainfall in the area ranges from 15-18 inches annually, with the majority falling during thunderstorms from April to September (Natural Capitalism Solutions 9). Each year, and especially in very dry years, agriculture in Boulder County is largely dependent on snow melt from the Rockies that feeds ditches, lakes, rivers and reservoirs (Natural Capitalism Solutions 9). Aridity can also affect agriculture due to high levels of evapotranspiration expedited by high levels of solar radiation resulting from cloudless days and high altitude (Natural Capitalism Solutions 10). The growing season in the county averages 140 frost-free days generally occurring between the first week of May and the first week of October (Natural Capitalism Solutions 10). Please see appendix A for more detailed climate data for Boulder County.

The owners of Black Kettle Farm monitor their soil closely and work to maintain active soil biology and a balance of water, nutrients and organic material in the soil (Witman and Dent).

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Ultimately, soil promotes the health of the crops grown on the property and therefore, maintaining healthy soil chemistry, biology and structure is paramount to intensive production on this small market farm (Natural Capitalism Solutions 55). Maintaining healthy soil is especially important for growing hops due to high water and nutrient demands as well as the perennial growth habit of the plants. The well-drained soils of the hop yard and farm in general are primarily sandy loam, while a small southern portion of the hop yard and the entire southern portion of the farm is classified as sandy clay loam (Witman and Dent) (USDA NRCS). A layer of hardpan exists beneath the entire hop yard. These soils have fairly active biology, but the north end of the hop yard has noticeably more diverse soil biology and better soil structure than the south end of the yard (Witman and Dent). These soils are ideal for hops production due to their drainage qualities, but production would not be possible in this area without reliable irrigation. For soil maps of the Black Kettle Farm property, please see appendix B. The soil in the hop yard is slightly basic, with soil tests from 2012 revealing a pH of 7.8 in the hop aisles and a pH of 7.4 in hop rows (Witman and Dent). Hop yard soils also have high potassium content compared to phosphorus and the owners have amended the soil by adding rock phosphate in the past. Dairy compost and fish emulsion are also used in the hop yard as sources of both phosphorus and nitrogen (Witman and Dent). The compost is applied in the fall in hop rows, while fish emulsion is generally applied as a foliar spray. The owners would welcome a local, organic approved source of chicken manure for

soil nitrogen additions. Calcium has also been added to the hop yard soil in the form of ground limestone, and elemental sulfur and gypsum have also been used as amendments (Witman and Dent). This year, ownership decided to apply an Organic Materials Review Institute (OMRI) approved 5-10-5 fertilizer as a foliar spray twice during the growing season spraying at 1.5 pounds nitrogen, 0.5 pounds zinc, and 0.25 pounds boron per acre each time. This foliar spray contained 0.02% boron, 0.05% zinc and 0.05% manganese (Witman and Dent). Boron is also applied as a foliar spray using dissolved dry product in a hand sprayer; in 2013 Solubar product will be used for this purpose. Boron is an important element in hop yards as adequate levels can boost cone yields late in the growing season (Witman and Dent). Soil tests from 2012 indicated that phosphorus and potassium levels in the hop yard were high based on soil samples collected in September of 2012. Regardless, hops plants have very high nutrient demands and soil nutrient and water availability should be closely monitored in hop yards. Please see soil test data and results in appendix C. Also important to note, the water table on the Black Kettle Farm property is fairly high, but not so high that hop roots are in danger of being water logged (Witman and Dent). The farm is adjacent to the Left Hand Creek riparian corridor as well as open wetlands and these habitats contribute to the diversity of birds, insects, reptiles, and amphibians that make up the above ground biological community in the hop yard (Witman and Dent).

The current hop yard at Black Kettle Farm occupies 1/2 acre and the rows are oriented north and south. Approximately 500 plants of three

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different varieties, Chinook, Cascade, and Crystal occupy this area (Witman and Dent). Cascade comprises 300 of the plants, while there are 100 of each of the other two varieties. In 2013, an additional ¼ acre was added to the south end of the hop yard making room for an additional 98 plants purchased from Summit Plant Laboratories in Fort Collins, CO; 84 of these plants are Chinook and 14 are CTZ, a newer high alpha (15.5-16.5%) bittering variety (Witman and Dent). Crystal hops, bred by the USDA, are the lowest alpha acid hop grown at Black Kettle Farm ranging between 3.5 and 5.5%, followed by Cascade another aroma hop developed by the USDA breeding program at 4.5% to 7% alpha acid, and finally Chinook, a bittering variety with alpha acid between 12 and 14% (Hop Growers of America 3,8,10,12). Primarily used as aroma hops, Cascade and Crystal varieties have poor storability; Chinook hops store much better (Hieronymus 143-146). Of the three varieties, Chinook is the best performer in the hop yard, maturing the earliest and producing the highest average cone weight per plant. Cascade generally matures second, followed by Crystal (Witman and Dent). Although maturity dates vary, all varieties sell equally well at harvest time. The existing ½ acre hop yard infrastructure, which took approximately one month to construct, consists of 70, 16 foot untreated pine poles that support wire rope held in place by ground anchors. Originally, poles were 12 feet high, but 4-foot extensions were added in 2012 to increase Chinook and Crystal yields. The 14 hop rows occupying this ½ acre are 8 feet apart and the poles within the rows are 30 feet apart. The plants within each row are approximately 3.5 feet apart and are trained to climb two

lengths of untreated sisal twine strung from wire ropes above each year (Witman and Dent). Before plants were very large, each was trained first up one string and next up two strings in a “V” shape; plants in the new ¼ acre hop yard addition will be trained this way until they are larger (Witman and Dent). A 1/2 inch drip irrigation line is suspended by light-gage wire approximately 1.5 feet above the ground in hop rows with one emitter above each plant capable of delivering 2 gallons of water per hour. A drip irrigation water delivery system was chosen to allow for precise control of water delivery and water use efficiency (Witman and Dent). All of the water used in the hop yard comes from a municipal source and no fertilizer is currently delivered via irrigation although the drip system does allow for this possibility. The line is elevated to allow for easier hop yard weeding, and irrigation repair (Witman and Dent).

The hops at Black Kettle Farm produce approximately two pounds of cones per plant depending on the variety and yearly growing conditions. This yield indicates that the plants are fairly healthy and receiving adequate amounts of water, nutrients and sunlight (Witman and Dent). A petiole test from June of 2013 indicates that magnesium and sulfur levels in the plants were slightly low, as were zinc and nitrogen (Witman and Dent). Provided these test results, fertilizer was applied in the form of a foliar spray as described above. Please see petiole test results in appendix D. Comparatively, plants in the south and especially the southwest portion of the hop yard are less productive and vigorous than those in the north end. The reason for this is still unknown although the soil is sandy clay loam as opposed to sandy loam in this part of the

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yard (Witman and Dent). In addition, these plants are exposed to more westerly winds and have been exposed to more severe weed pressure than plants in the north end of the field. Plants in the southern part of the field may also have been too heavily pruned in the spring of 2012, resulting in stunted growth and low yields (Witman and Dent). All of the plants occupying the southwest portion of the field are the Cascade variety. A dairy cow and goats followed by a personal garden previously occupied the north end of the field, perhaps adding to soil nutrients that now allow the hops in this portion of the field to be more productive (Witman and Dent). Rows 10 and 11 are also of interest as plants experienced strong dry winds during transplant and have been less productive than other rows. As needed, some plants may be replaced if they continue to under produce (Witman and Dent).

Challenges to organic production in the whole hop yard include weed pressure, pests, and water and nutrient availability. When the hop yard was established in 2010, the owners of the farm decided to leave pasture grass in the aisles between hop rows in order to maintain soil moisture, avoid disturbing soil biology, and for ease of management through mowing. This decision has in fact turned out to be a management issue, as the rhizomatous pasture grass competes for moisture and nutrients with the hop plants in addition to spreading aggressively into the hop rows (Witman and Dent). Another perennial weed that significantly affects the hops is field bindweed, which climbs up plants and infrastructure competing for nutrients, water and light while also posing challenges during maintenance and harvest activities (Witman and

Dent). Tilling and other mechanical control of these and other weeds must be timed properly based on the life cycle of the weed species and on weather conditions as disturbing soil and creating dust can attract spider mites. Management is currently exploring other ways to suppress and control these competitive weeds including planting winter cover crops in hop aisles (Witman and Dent).

Overall, the hop yard at Black Kettle Farm has not had severe pest problems, although the northwest corner of the hop yard experienced an aphid infestation in 2011, likely perpetuated by over application of nitrogen fertilizer that encouraged excessive vegetative growth that attracts aphids. Aphid infestations are especially a concern with higher alpha acid plants like Chinook and CTZ, as they notoriously attract the pests more than low alpha acid plants (Witman and Dent). Proper pruning, careful application of nitrogen, and encouragement of healthy populations of predator insects are three methods used to control aphid activity on the farm (Witman and Dent). Provided the dry climate, two spotted spider mites could potentially be a large problem; cultivation practices that help producers avoid attracting these insects are of paramount importance. Tilling, weeding, and other soil disrupting activities should not be done in the hop yard when it is dry as spider mites are attracted to dust on plant leaves (Witman and Dent). Thrips have been a bit of an issue in the hop yard since 2012 and due to a lack of knowledge of thrip life cycles combined with inaction, the pest has infested parts of the yard causing plant damage. Thus far, the thrips are not known to be carriers of Fusarium or Verticillium wilts that could severely

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damage the plants. The owners intend to introduce beneficial nematodes in the spring of 2014 to help control the thrip population (Witman and Dent). Current pest management practices include companion planting to maintain habitat for beneficial predator insects as well as working to understand the life cycles of pest species so management practices can be carried out at the most effective times (Witman and Dent). Winter cover cropping in hop aisles could potentially play a role in habitat based pest management already practiced on the farm. Continual observation of pest and beneficial insect species is an important farm practice.

Nutrient and water availabilities also challenge production at Black Kettle Farm. Although soil nutrients and fertilization were discussed above, management is also interested in composting spent bines and returning nitrogen-rich composted material back to the hop yard. This practice will require additional labor as twine cannot be put through a standard chipping machine and the bines need to be cut into approximately one-foot lengths while still green (Witman and Dent). This poses a problem at harvest time when staff is already exhausted from long harvest hours. Additionally, a front-end loader needs to be purchased in order to successfully carry out windrow and composting efforts. Another barrier to beginning this practice is the fact that much of the hops harvest is done using an off-site picking machine shared with others. Although this is an economical solution to harvest, albeit a bit of a locational inconvenience, there is no way to control what insects or bine bits might be taken back to the windrow on the farm (Witman and Dent). Planting a winter grass and legume mixed cover

crop could help the owners of the farm achieve a similar mulching goal without having to make large investments in machinery or worry about introducing new pests to their farm. Crop establishment would however, require additional labor after hop harvest in the fall. A municipal supply of irrigation water is available from early to mid May through mid or late October each year when the system is shut off and drained in preparation for winter (Witman and Dent). Although irrigation water is available for most of the growing season, hops, especially young plants, are not drought tolerant. The small size of the hop yard has allowed the owners to hand water with a frost-free hydrant in months when irrigation water is unavailable (Witman and Dent). Although this is a time consuming practice, it has proven to be a useful method for off-season watering when necessary.

Rhizome harvest at the farm begins in mid-March when the ground becomes soft enough and continues through April. Harvested rhizomes are then sold to homebrew stores and via direct sale. Some of the harvested rhizomes are also planted and starter plants are sold in the same markets. Generally, rhizomes should be planted in April, as should transplants. If ambient and soil temperatures are warmer than normal in the spring, emergence of dormant shoots will occur earlier and rhizomes may be harvested earlier (Witman and Dent). Both should be protected from strong wind, hot sun, and frost for about two weeks. Depending on the hop variety, pruning and training will likely begin in mid to late May. After summer long maintenance, plants produce cones that are harvested mid-August through mid-September.

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Different plant varieties as well as plants of the same variety in different parts of the hop yard mature and produce cones at different rates (Witman and Dent). Climate trends and weather events also affect hop yield and quality from year to year. Drying, packaging and storing happen immediately after harvest if the hops aren’t sold and delivered for use immediately (Witman and Dent). Although the farm currently utilizes off-site solar dryers to process the hops, management would like to build an on-farm solar dryer and picker. This would be a great investment that could save large amounts of time and energy spent transporting bines and product on and off farm during harvest. The solar dryer could also be utilized to process other farm products in addition to hops (Witman and Dent). Although Black Kettle Farm does not currently have the resources to purchase or construct these items, management seeks to do so in the near future. After harvest and just before or after the first frost, any remaining above ground vegetation is removed and the plants begin to overwinter. Fall Planted Cover Crop System In 2011, the aisles in the hop yard were tilled at Black Kettle Farm for the first time. Tilling was performed in an attempt to control the bindweed and pasture grasses in the hop yard that were competing with the hops for water, nutrients, and light (Witman and Dent). In addition to mechanical control of the weeds, the owners of the farm wished to utilize a cover crop to suppress the weeds. Other desired cover cropping characteristics included improved soil nutrient cycling and availability, shade tolerance, durability, and ease of management. After some research, they

chose White Dutch Clover for spring planting and broadcast into the tilled hop yard aisles at 50 pounds an acre and lightly incorporated by raking (Witman and Dent). To encourage seed germination, the clover was irrigated via overhead tripod sprayers with municipal water at 15 psi. This system did not cover the entire seeded area at once and the tripods required rotation for successful watering of the entire clover seed bed (Witman and Dent). Compared to the cool wet spring of the previous year, the early spring of 2011 was warm and dry, unwelcome conditions for legume establishment. Ultimately, the spring cover crop attempt with Dutch clover was unsuccessful mainly due to uneven and untimely distribution of irrigation water. Overhead irrigation also aided in the germination of bindweed in the hop yard, perpetuating rather than controlling the weed problem (Witman and Dent). Another cover cropping attempt has not been made in the hop yard at Black Kettle Farm since this time. Mechanical weed control in the hop yard aisles was performed by tilling three times between March and June of 2013 and will be performed more as the season continues. Additional weed control is done using hoes and by hand a couple of times a week (Witman and Dent). All mechanical weed control is performed when soil is moist, so as not to stir up dust and attract spider mites. The amount of mechanical weed management currently required in the hop yard is seen as unsustainable for soil health and labor reasons by farm management. In order to effectively manage weeds while enhancing soil health and reducing constant labor demands in the coming years, farm management is interested in another

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cover cropping attempt beginning in the fall of 2013 (Witman and Dent). A fall cropping system is desired as the attempted spring crop required a lot of additional management during a time of high activity in the hop yard; establishment, growth, and management of a fall planted cover crop fits much better with the growing season of hops plants. Timing is still very important however; fall planted crops should be established by November because of frost and winter hop yard preparations, and need to be managed in a timely manner in the spring in order to maximize desired results (Witman and Dent). Utilization of a fall planted cover crop will provide early season weed suppression during growth as well as later season weed suppression via mowed residue on the soil surface. As hops require large amounts of soil nitrogen during rapid growth periods, management wishes to include legumes in a fall planted cover crop mix although they are unsure about other elements (Witman and Dent). The owners of Black Kettle Farm intend to run soil tests in both the hop lanes and rows before and after the first season of fall cover cropping to measure impacts on soil nutrient levels. Just as in previous years, dairy compost will be applied around hop crowns sometime around the first frost and elemental sulfur and gypsum will be added in the hop yard as soil amendments (Witman and Dent). Although the owners of Black Kettle Farm consider the nutrient cycling, weed suppression, and soil building benefits of growing a fall cover crop to be worth additional labor needed to manage the crop, time constraints are still a concern in the fall as the farm team is often strained by harvest, sales, storage, and

preparation of value added products for winter markets (Witman and Dent). As recognized by the owners, the cover crop mix chosen for use in the hop aisles at Black Kettle Farm must fit into the big picture production schedule at the farm (SARE 1) (USDA Soil Conservation Service 9) (Godin). As such, a fall planted cover crop is ideal as the main growing season for the hop cash crop is the spring and summer (Godin). The cropping mix must also be a viable choice based on the climate in Boulder County, irrigation capacity on the farm, soil characteristics of the hop yard, disease potential of the crops, accessible equipment, and management resources available (USDA Soil Conservation Service 12). Shade tolerance of plants will not be a significant consideration as the cover crop will be grown in the fall when hops are not actively growing above ground (University of California 8). Any cropping mix chosen has to be site specific (Lashbrook). In order for the cropping system to align with the goals and objectives of the farm business, it must fit into the current production schedule that mainly involves spring, summer, and fall work in the hop yard and other farm production areas. A fall cover crop is a better choice than a spring crop for this reason. The cropping mix chosen also must be manageable with the time and labor available as well as help to achieve delineated goals that align with the sustainability and land stewardship-based values of the farm owners. In addition, the system must add value to the farm by improving soil, conserving water, helping control weeds, attracting beneficial insects, and ultimately improving yields (SARE 12). Value must be added with minimum risk that

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exceeds the cost of adding that value (SARE 12). The primary reasons for designing a new cover cropping system for the hop aisles at Black Kettle Farm* are to improve soil nutrient content and cycling, improve soil structure, suppress weeds, and to attract beneficial insects. Each species in the seed mix must have the capacity to achieve one of these primary goals (Witman and Dent).

As discussed above, planting mixtures of grasses and legumes in a cover crop system allows producers to reap the benefits of both crops. Cover crop mixtures are therefore often more successful at achieving desired results than single crops (SARE 117) (Gibson, Singer and Barnhart 2). For example, one of the main benefits of mixing grasses and legumes is the ability of stands to adjust to available soil nitrogen; in nitrogen rich soils, grasses will dominate, while nitrogen fixing legumes will dominate nitrogen poor soils (SARE 117). Balancing utilization of soil nitrogen also carries over into cover crop residue situations as legume residue provides immediately available nitrogen needed by soil microorganisms to aid in the break down of grass residue. Another important advantage to planting a mixed species crop is that it increases utilization of solar radiation by increasing ground cover (SARE 117). Deciding to plant a mixture also increases cropping options. Potential disadvantages of a cover crop mix compared to a single species can be increased seeding costs associated with successful establishment of mixed seed, excessive residue production, and more complex management (SARE 117). Planting a mixed fall cover crop in hop aisles will require measuring the desired growth area based on closeness to hop rows and on ability to mow, till, and

manage crop residue (USDA Soil Conservation Service 8). Irrigation infrastructure will also have to be built and crops selected that can become established and grow using a drip system with occasional supplemental water (University of California 7). Based on desired results, crops should be mowed and used as mulch and only lightly tilled in the spring as excessive tilling can undesirably speed up nutrient cycling and negatively impact soil structure and biology (SARE 13, 44). This should be done a few weeks prior to rapid bine growth in late spring and early summer to avoid nitrogen tie up (Godin). Practicing conservation tillage in the spring after planting a fall cover crop will also reduce soil erosion, increase water infiltration, and keep soil temperatures cooler during the growing season while residue sits on the soil surface (SARE 44). Therefore, this practice will maximize soil condition and fertility benefits (University of California 7). The chosen winter hardy mix should be seeded ideally in mid September just after hop harvest, although seeding might be slightly delayed due to important hop preservation activities that have to occur directly after harvest (Card 3). The chosen grass and legume mix will likely need to be seeded each fall, although with some experimentation with timing, the varieties chosen could be allowed to reseed (University of California 6). Based on the broad business goals and values of Black Kettle Farm as well as specific cover cropping goals defined by ownership, a fall planted grass-legume mixture of winter triticale and Mammoth red clover could help to achieve desired results in the hop yard. The mixture should be tested in a plot outside the hop yard or in a small portion of the hop yard

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before being planted in the entire production area (SARE 12).

Legumes like red clover are used in cover crop mixes primarily for their nitrogen fixing abilities although they also reduce erosion, add organic matter to the soil and attract beneficial insects. Utilized as winter cover crops, legumes will establish in the fall, overwinter, and produce the majority of their biomass in the spring (SARE 116) (Sattell, Dick and Hemphill). Red clover, Trifolium pratense is a short-lived herbaceous perennial legume that can be treated as a biennial or winter annual based on management practices (SARE 159) (Sattell, Dick and Hemphill). Starting at a thick root crown, it bears erect leafy stems reaching up to two feet in height that eventually terminate in purple or magenta flowers (Sattell, Dick and Hemphill). Two general types of red clover, Medium and Mammoth, can be utilized as part of a fall planted cover crop mix depending on cover cropping goals and limitations. Medium red clover recovers quickly after mowing and can be cut multiple times in a season provided a long growing season, although seed is often expensive (SARE 161) (Sattell, Dick and Hemphill). Mammoth red clover produces more biomass than Medium and a functionally equivalent amount of fixed nitrogen if inoculated with the correct rhizobia bacteria (SARE 161) (Sattell, Dick and Hemphill). Healthy red clover nitrogen contributions in Colorado can range from 1.6 to 3.4 pounds per thousand square feet or between 70 and 150 pounds of nitrogen per acre (Card 2) (SARE 66). Provided these amounts, 50 to 75 percent of this nitrogen will mineralize and become available to crops during the following growing season (SARE 162) (Gibson, Singer and

Barnhart 2). These nitrogen additions can decrease the need for fertilizer applications and increase hop yard yields if managed properly. Yearly precipitation, temperature, and available soil nutrients will affect the amount of nitrogen fixed and contributed to soil by clover each year (Gibson, Singer and Barnhart 6). A later flowering variety that is less tolerant of cutting, Mammoth clover is the suggested variety for use on Black Kettle Farm* as it grows better in areas with a shorter growing season due to increased winter hardiness (Sattell, Dick and Hemphill). Overwintering red clover can survive winter temperatures as low as -30ºF and thrive in cooler conditions (Sattell, Dick and Hemphill). In addition, red clover grows best in well-drained sandy loams and sandy clay loams, the two soil types that occupy the hop yard (Sattell, Dick and Hemphill). This clover is also a good choice as it thrives in soils with a pH between 6.6 and 7.6, but will tolerate soils with a pH between 4.5 and 8.2, a good trait as measured pH in hop yard aisles at Black Kettle Farm* have been just slightly basic (Sattell, Dick and Hemphill). Residues from the significant biomass produced by Mammoth red clover can supply significant amounts of nitrogen to growing crops and a well developed tap root helps to loosen dense, compacted soils like the hard pans in the hop yard and to cycle nutrients deeper in the profile back to the soil surface (Sattell, Dick and Hemphill) (SARE 18, 160). Although not a common practice, if planted properly and closely monitored, fall planted red clover could likely establish on a well-designed drip irrigation system (Kneen 19). Red clover residue will also provide quickly available nitrogen to soil microorganisms that will assist in the

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break down of mowed and tilled triticale residues enhancing soil nutrient cycling and helping to enhance soil structure through the addition and break down of organic matter. (SARE 16) (Gibson, Singer and Barnhart 6). Clover residue will decompose quickly after mechanical killing and be released as available soil nitrogen within a month (Gibson, Singer and Barnhart 6). Although it will not contribute as much to soil organic carbon content and therefore soil structure enhancement as triticale, red clover still produces between 2000 and 5000 pounds of dry matter per acre and can contribute somewhat to improving soil tilth (Gibson, Singer and Barnhart 2). Compared to other legumes, red clover is also a good weed suppressor both while growing and as residue (SARE 67). The preference for this clover to grow in cool conditions allows it to compete with common hop yard weeds as it will begin spring growth early, while soil temperatures are still too cold for weed seeds to germinate (SARE 160) (Sattell, Dick and Hemphill). In the spring, red clover flowers and vegetation will also attract beneficial insects as pollen and habitat become available. The red clover will be especially useful to apiary operations on Black Kettle Farm* (Witman and Dent). Residues left on the soil surface in a conservation tillage system all help increase soil water infiltration and water holding capacity (Gibson, Singer and Barnhart 6). Mechanical killing of red clover should be performed after blooming begins in the spring so that benefits of blossoms are still reaped and nitrogen contribution is greater due to more growing time (SARE 162). Planted alone, Mammoth red clover should be drill seeded into a prepared seedbed at ½ inch deep and between 15

and 25 pounds to the acre. Irrigation should be immediately available, as the clover will not establish well if conditions are too dry (Gibson, Singer and Barnhart 5). Planting in mid to late September will allow for best establishment before winter (Sattell, Dick and Hemphill). Seeding rates should be increased if the seedbed is rough or if the seed is to be broadcast (Sattell, Dick and Hemphill). This seeding rate as well as seeding time will be altered when planted in combination with winter triticale (Syngenta). Organic Mammoth red clover seed and the proper inoculant are available from Johnny’s Seeds at $162 plus shipping for 25 pounds plus $5 for the inoculant (Johnny's Selected Seeds). Provided that the hop yard is half of an acre and soon to be ¾ of an acre, there is no need to purchase more seed than this amount. Other seed sources could also be explored. Only certified seed should be purchased as it will perform more reliably than uncertified seed and contain less unwanted weed seeds (Grubinger).

Triticale, Triticosecale X, is a winter hardy wheat and cereal rye hybrid small grain. With an upright growth habit, this disease resistant winter annual can reach up to five feet at maturity (University of California 16) (Lashbrook). As a hybrid, this plant possesses growth qualities of both wheat and rye. It is as cold hardy if not more so than winter wheat but not as much so as winter rye. It should be planted earlier in the fall than rye as it takes longer to harden off and prepare to overwinter, and similarly to red clover, a planting time in late September or early October would be ideal in Colorado (Government of Alberta) (Sattell, Dick and Karow). Planted and established in

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the fall, triticale will scavenge unused nitrogen and other soil nutrients that might otherwise be lost over the winter via a deep fibrous root system (Sattell, Dick and Karow) (Lashbrook) (SARE 18). Triticale also protects the soil surface from erosion and increases soil water infiltration and holding capacity both while it is growing and as a crop residue (Sattell, Dick and Karow). As it grows well in cooler temperatures, this plant also suppresses weeds early in the spring growing season and continues to suppress them as residue after being spring killed (Sattell, Dick and Karow). Due to a high C:N ratio, triticale residue will break down slowly compared to red clover in the spring, but nitrogen from the red clover will be utilized by soil microorganisms to break down triticale residues that will contribute significant amounts of soil organic carbon and improve soil structure (Sattell, Dick and Karow) (SARE 16) (Gibson, Singer and Barnhart 2). Triticale also works well in a cropping system with red clover as it serves as a nurse crop in the fall, protecting the clover as it germinates, and functions as structural support for the clover in the spring (Sattell, Dick and Karow). Planted alone, triticale seed should be drilled into a well-prepared seed bed at between 70 and 90 pounds per acre and one to one-and-a-half inches deep (Sattell, Dick and Karow) (Syngenta). Triticale will establish best in well-drained soils like those at Black Kettle Farm (Gibson, Singer and Barnhart 3). Seeding rate should be increased if the seed is broadcast or to enhance the effectiveness of weed smothering (Sattell, Dick and Karow). Irrigation is necessary in the fall for establishment and in the spring to encourage the rapid growth that produces significant amounts of biomass

and outcompetes weeds (Kneen 19). As drill seeding should be done in rows 8 inches or less apart, drip lines should be configured to correspond to these rows (Gibson, Singer and Barnhart 3). Triticale should be killed and incorporated into the soil about three weeks before hops experience fast vegetative growth to avoid tie up of soil nitrogen. Mowing alone will not usually kill triticale unless it is very near to maturity; however mowing can be used to manage triticale as mowed residues can suppress weeds within hop rows while standing stubble continues to suppress them in hop aisles (Sattell, Dick and Karow). Another benefit of triticale is that it is less likely than winter rye to become a weed if not mowed or plowed exactly on time the following spring, although timely management is still key to receiving desired cover cropping results (Sattell, Dick and Karow). This seeding rate should be decreased when planted in combination with red clover. As triticale is a cereal grain, available varieties are usually those typically used for grain production and specialty varieties ideal for cover cropping can be difficult to purchase without significant foresight (Sattell, Dick and Karow). Organic fall triticale seed is available from Albert Lea Seed at $22 for a 50-pound bag plus $29 shipping (Albert Lea Seed). Other seed sources could also be explored.

Provided the desired cover cropping results in the hop yard at Black Kettle Farm, a seed mix of 30% Mammoth red clover and 70% fall triticale should be planted using a seed drill in the last half of September or the first week of October. This mix is intended to be planted in the hop yard aisles only, and should leave 1 foot of space on either side of each hop row,

36

meaning a 6 foot width of aisle space will be planted in each of the 14 aisles; planted this way, the crop will cover 7,020 square feet in the hop yard. The cover crop mix will not be planted around the perimeter of the field as this space is utilized for other crops that already play a role in integrated pest management and farm production (Witman and Dent). It is important to leave a foot of room on either side of the hop aisles to allow room for spring growth and for ease of spring pruning. This seeding schedule will coincide nicely will the end of hop harvest, which usually finishes in mid-September on Black Kettle Farm, and the slight flexibility in planting date will allow time to process and sell the hop crop in a timely manner after harvest (Witman and Dent). These dates should allow both the triticale and the clover enough time to establish before the first frost, although earlier planting in September will increase these chances (Sattell, Dick and Karow) (Card 3). As the farm does not own a drill, the owners will have to rent one or contract someone to seed the hop yard aisles. The use of a drill will improve germination rates compared to broadcast seeding due to more precise planting depth and better seed to soil contact (SARE 56). If there is a significant amount of residue left on the soil surface from the hop harvest, this can be removed by raking, or using a row cleaner. A no-till drill could also be used for seeding if hop residue was prevalent and one was available (SARE 56). If a drill is unavailable, the red clover-triticale mix can be broadcast seeded and incorporated with hoes and a rake, although seeding rates must be increased due to a predictably lower germination rate (SARE 51). Given that red clover and triticale seeds need to be

planted at different depths, the drill would have to make two passes, or triticale seed could be drilled followed by a broadcast seeding of red clover at an adjusted seeding rate. If drilling both the red clover and the triticale, the clover should be seeded at 2/3 its normal seeding rate and triticale should be seeded at ½ its normal seeding rate (Sattell, Dick and Hemphill). As with any fall planted cover crop, it will be important to choose dates for spring management so that biomass production of the triticale and red clover and nitrogen capture by the red clover is maximized, but soil moisture and nutrients are available to the growing hop crop when needed (University of California 9) (NRCS Soil Quality Institute 2). This mixed cover crop should be managed about three weeks before the hops begin rapid vegetative growth in the late spring, which allows enough time for the cool weather crops to mature. Given this time, the red clover-triticale crop will enhance soil nutrient cycling, suppress early spring weeds, and invite beneficial insects and pollinators into the hop yard. Spring management of the crop is also unlikely to interfere with spring pruning or rhizome harvest since it is planted only in the aisles. After spring management, likely by mowing the crop will contribute to soil nutrient availability, enhance soil structure, and continue to suppress weeds as residue (Sattell, Dick and Karow) (SARE 51). If the clover persists, it should be mowed during the growing season. Peak nitrogen contribution will come from red clover if killed mid bloom (SARE 162). A later spring kill date that allows the cover crop to mature this way should not cause set backs in hop growth due to cold soil temperatures as the hops emerge early in

37

the spring and can endure early cold snaps (SARE 51) (University of California 6). If the owners of Black Kettle Farm decide they want to let the crop reseed, it should not be mowed or killed until after seed set, although this is not recommended (USDA Soil Conservation Service 9). In a conservation tillage system like that to be used at Black Kettle Farm, the red clover-triticale cover crop should be mowed and mulched and then partially incorporated with a tiller into the hop aisle soil (SARE 55). The tilling will not negatively affect the hop plants as underground rhizomes extending into the aisles are pruned yearly anyhow. Each year at different times in hop growth and cover crop management, soil samples should be taken and analyzed in order to track and monitor the impacts the cover crop is having on soil nutrient availability and structure (Witman and Dent). Degree of weed suppression and attraction of beneficial insects should be monitored through field notes and daily observation. Although engineered specifically to meet needs of Black Kettle Farm, the red clover and triticale cover cropping system could be very useful in a similar hop production or orchard situation on the Colorado Front Range. However, this system, like any other cropping system will present new challenges and tradeoffs to farm managers and owners. As with any cover crop, timely management is key. If the crop is planted too late or winter frost comes too early, it is unlikely that the crop will establish or overwinter well, resulting in decreased spring benefits (SARE 50). In addition, if reseeding is undesirable and the crop isn’t mowed and tilled in a timely manner, both crops have the potential to become weeds that compete

with hop plants within the rows (Kneen 18). Untimely spring management can also result in the tie up of nitrogen and other nutrients that the hops need to grow and produce a good yield (Blackman, Rees and Glendinning 636). Reduced cash crop yields would effectively devalue the cover cropping system, until at a certain point, managing the system, albeit improperly, would no longer be worthwhile (Natural Capitalism Solutions 64). Poor cover crop stand establishment could also occur in a very wet year if the soil somehow became water logged, although this situation would also adversely affect the hops. Soil pH in the hop yard at Black Kettle Farm should also be closely monitored to ensure it doesn’t become too basic, which would reduce the seedling vigor and growth of the red clover and triticale (Sattell, Dick and Hemphill). Adverse fall or spring weather conditions could also reduce the effectiveness of this cover cropping system. Cost and equipment availability will be other challenges on Black Kettle Farm* (Witman and Dent). In addition to seed cost, growing this crop will demand increased water utilization, which will increase both irrigation infrastructure material costs and the municipal water bill in the spring and fall (University of California 4). The farm owners will also incur both time and money costs associated with seedbed preparation, seeding, and yearly spring management (University of California 13). Monitoring of cover cropping results and measuring how well they help meet designated goals is important, because if the cost of working towards or achieving defined goals exceeds the value created by doing so, the cover cropping system is unsuccessful. Depending on how well

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management at Black Kettle Farm is able to manage and allocate resources, a fall planted red clover-triticale cover cropping system could play an instrumental role in achieving the soil

enhancement, weed suppression, and pest management goals for the hop yard, ultimately contributing to increased hop yield and quality.

Works  Cited  Albert Lea Seed. Other Organic Winter Grains. 2013. 2 July 2013 <http://www.alseed.com/Pages/CropCategoryListing.aspx?categoryID=33>. Blackman, J.D., L. Rees and P.J. Glendinning. "The Effect of Alternative to Soil Residual Herbicides on Weed Control,Yield, and Quality of Hops." Journal of Horticultural Science 71.4 (1996): 629-638. Card, Adrian. "CSU Extension." 2009. Colorado Master Gardener Program. 15 June 2013 <http://www.ext.colostate.edu/mg/Gardennotes/244.html>. Filmer, Richard. Hops and Hop Picking. Oxford: Shire Publishing, 1982. Gibson, Lance, et al. Intercropping Winter Cereal Grains and Red Clover. Manual. Iowa State University. Ames: Iowa State University Extension, 2006. Godin, Ron. Soil Fertility Management: Cover Crops and Green Manures. Power Point. Delta, February 2013. Gomez, Jose A., et al. "The Influence of Cover Crops and Tillage on Water and Sediment Yield and on Nutrient and Organic Matter Losses in an Olive Orchard on a Sandy Loam Soil." Soil and Tillage Research 160 (2009): 137-144. Government of Alberta. Triticale. 2013. 2 July 2013 <http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex127>. Granatstein, D., et al. "Sustainability Trade-offs in Organic Orchard Floor Management." Acta Horticulture 873 (2010): 115-122. Granatstein, David and Kent Mullinix. "Mulching Options for North-West Organic and Conventional Orchards." Horticultural Science 43.1 (2008): 45-50. Grasswitz, T.R. and D.G. James. "Influence of Hop Yard Ground Flora on Invertebrate Pests of Hops and Their Natural Enemies." Journal of Applied Entomology 133 (2009): 210-221. Greenaway, Twilight. "Your Certified Organic Beer Just Got More Organic." Take Part. Take Part LLC. 11 June 2013.

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Grubinger, Vern. "Vegetable and Berry." University of Vermont Extension. 14 May 2013 <http://www.uvm.edu/vtvegandberry/factsheets/covercrops.html>. Hieronymus, Stan. For the Love of Hops: A Practical Guide to Aroma, Bitterness and the Culture of Hops. Georgetown: Brewers Publications, 2012. Hop Growers of America. "USA Hops." March 2011. USA Hops. 4 June 2013 <http://www.usahops.org/userfiles/file/HGA%20BCI%20Reports/HGA%20Variety%20Manual%20-%20English%20(updated%20March%202011).pdf>. Johnny's Selected Seeds. Mammoth Red Clover (OG). 2013. 26 June 2013 <http://www.johnnyseeds.com/p-6765-mammoth-red-clover-og.aspx>. Kneen, Rebecca. "Small Scale and Organic Hops Production." Manual. Left Fields BC, n.d. Lashbrook, Cindy. Cover Crops for Orchards and Vineyards. Power Point. Prod. CCOF Foundation. Linares, Jose, et al. "Use of Cover crop Weed Index to Evaluate Weed Suppression by Cover Crops in Organic Citrus Orchards." Horticultural Science 43.1 (2008): 27-34. Lipecki, J. and S. Berbec. "Soil Management in Perennial Crops: Orchards and Hop Gardens." Soil and Tillage Research 43 (1997): 169-184. Montanaro, G., et al. "Effects of Soil-Protecting Agricultural Practices on Soil Organic Carbon and Productivity in Fruit Tree Orchards." Land Degredation and Development 21 (2010): 132-138. Natural Capitalism Solutions. Sustainable Agriculture Literature Review. Prod. Natural Capitalism Solutions. Boulder, March 2011. NRCS Soil Quality Institute. Soil Quality - Agronomy Technical Note no.1. Technical Note. Auburn: USDA, 1996. Oregon State University et al. Field Guide for Integrated Pest Management in Hops. Ed. David H. Gent, et al. Washington Hop Commission, 2009. Paszkowski, Wojciech L. and Jerzy Dwornikiewicz. "Effect of Green Manure on the Incidence of Cyanogenic Pseudomonas Strains in Hop Garden Soils." Journal of Chemical Ecology 29.5 (2003): 1159-1165. SARE. Managing Cover Crops Profitably. 3rd Edition. St. Paul: SARE, 2007. Sattell, R. , et al. Barley, Oats, Triticale, Wheat. Manual. Oregon State University. Corvallis: Oregon State University Extension, 1998.

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Sattell, R., et al. Red Clover (Trifolium pratense). Manual. Oregon State University . Corvallis: Oregon State University Extension, 1998. Silva, E.B., et al. "Effect of ground Cover Vegetation on the Abundance and Diversity of Beneficial Arthropods in Citrus Orchards." Bulletin of Entomological Research 100 (2010): 489-499. Syngenta. Triticale: Your Best Choice for Fall Planted Forage. Agripro. Berthoud, 2012. Tomlan, Michael A. Tinged With Gold: Hop Culture in the United States. Athens: University of Georgia Press, 1992. Turner, Samuel F., et al. "Challenges and Opportunities for Organic Hop Produciton in the United States." Agronomy Journal 103.6 (2011): 1645-1654. University of California. Cover Crops for Walnut Orchards. publication. University of California. Oakland: University of California, n.d. USDA NRCS. Carbon to Nitrogen Ratios in Cropping Systems. Greensboro: USDA NRCS, 2011. Web Soil Survey. 17 February 2012. 22 May 2013 <http://websoilsurvey.nrcs.usda.gov/app/HomePage.htm>. USDA Soil Conservation Service. Cover Crops in California Orchards and Vineyards. Davis: USDA Soil Conservation Service, 1983. Witman, Will and Lisa Dent. The Situation at Black Kettle Farm* Dana Hayward. 5-25 May 2013. Xiloyannis, C., B. Dichio and G. Montanaro. "Sustainable Apricot Orchard Management to Improve Soil Fertility and Water Use Efficiency." Acta Horticulture 862 (2010): 419-424.

 

                                                                                                                                                                                                                                                                     

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Appendix  A.

Source: NOAA Earth System Research Laboratory Physical Sciences Division. Accessed June 20, 2013. http://www.wrcc.dri.edu/pcpn/co.gif

Source: NOAA Earth System Research Laboratory Physical Sciences Division. Accessed June 20, 2013. http://www.esrl.noaa.gov/psd/boulder/images/precip.mm.GIF

42

Source: NOAA Earth System Research Laboratory Physical Sciences Division. Accessed June 20, 2013. http://www.esrl.noaa.gov/psd/boulder/dailyrecords/images/daily.tmp.GIF

Source: Boulder County Nature Association. Accessed June 20, 2013. http://www.bcna.org/winds.html

43

Source: Boulder County Nature Association. Accessed June 20, 2013. http://www.bcna.org/winds.html

44

B.

45

Source: Web Soil Survey. Accessed June 25, 2013. http://websoilsurvey.nrcs.usda.gov/app/HomePage.htm C.

Boulder County Area, Colorado (CO643)

Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI

CaB Calkins sandy loam, 1 to 3 percent slopes 2.1 26.8%

MdB Manter sandy loam, 1 to 3 percent slopes 2.9 36.6%

NnA Nunn sandy clay loam, 0 to 1 percent slopes 2.9 36.6%

Totals for Area of Interest 7.8 100.0%

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47

Source: All soil analyses provided by owners of Black Kettle Farm

48

D.

Source: Provided by owners of Black Kettle Farm *Name changed for proprietary reasons

49