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No doubt about it, for many new growers hops are a difficult crop to grow well. Fast growing hop plants require lots of balanced nutrients and water with critical timing of applications; making hops a real challenge to keep up with when compared to most other crops. Getting the hops to climb to the top trellis wire and produce fully developed side arms with lots of cones seems to be an unattainable goal sometimes. There always seems to be a guy named Murphy lurking around, ready to throw a wrench in the works; despite a hop grower’s best efforts. Wind, rain, drought, and pestilence... yet there are lots of pretty pictures of hopyards and recorded harvest yields to show it is more than a dream.
It is common to find in many instances, less experienced hop growers do not fully understand many integrated hopyard management practices and how plant nutrient availability and growth is affected. This following discussion covers a few of the issues that have been identified as potentially holding back hop growth and yields. These issues are gleaned from talking to, and working with hundreds of new hop growers and the challenges they have experienced.
These observations and field notes are intended to educate and provoke deeper, more in-depth discussions amongst hop growers and grower groups.
- Soil compaction, drainage issues
- Improper soil pH, corrective actions
- Drip irrigation, poor water quality
- Understanding the importance of complete soil testing
- Selecting the right fertilizers
- Replacing depleted nutrients in the hop root zone
- Removing underground rhizome growth
- Weed control issues
- Glyphosate use in a hopyard
- Using black weed barrier fabric in a commercial hopyard
- Tilling & cultivation schedules
- Fungicide interactions with nutrients
- Out-of-balance soil nutrients
- Selection /management of cover crops
- Scouting for pests and diseases
- Checking for and controlling nematodes
- Better knowledge of pests and hop pathogens and their controls
- Protecting hop crowns and buds exposed to harsh winter conditions
- Proper hopyard site selection
- Mulches and compost application
- Timing and depth of crowning, carping and bine mowing prior to training
Soil Compaction (Back To Top)
Hops are the second fastest growing plant in the world and have to develop a massive feeder root system each season to support the amazing bine growth rate. A critical part of this hop root system is a fine fibrous root mat that forms each spring in the top 6 inches of nutrient rich topsoil and spreads outward as the season progresses. Its function is to collect all the nutrients available and transport them up the plant with lots of available water. Poor root mat development and management equals poor hop growth.
Roots can only collect nutrients and water that come in contact with them. Fewer roots means less nutrient uptake. Most nutrient- collecting roots grow in the top 6 to 8 inches of soil because that’s where the microbes, nutrients, and oxygen are located. Nutrient uptake grinds to a halt if soil oxygen levels and exchange rates with the atmosphere are limited by soil compaction. It doesn’t matter if the soil test says all the soil nutrients are present and accounted for – the plant can’t take them up in sufficient quantities without the soil oxygen being present. The perfect rooting conditions are nutrient rich, well-aerated soils with adequate moisture present. Also, hard compacted dense soil physically blocks feeder root development and outward spread of the fine roots through the soil during the growing season. This is a simple case of restricted root system equals little plant.
How should a compacted soil be corrected? First identify the ALL possible factors causing the compaction; then the best actions to correct it.
- First, determine the soil type - Clay soils are notably finer than sandy soil and have limited air pore space between the smaller soil particles compared to sandy soil types. Clays also have a strong bond between soil particles caused by high levels of magnesium. The more clay content in a soil; the higher the probability of compaction. Annual freezing frosts naturally aid in reducing compaction in northern regions. Many growers will also hill their hop rows in stages throughout the growing season; adding a fresh layer of nutrient-rich aerated loose soil on top of the rooting zone. Very similar to hilling potatoes.
In many cases, compacted clay soil’s air pore space can be improved with a calcium amendment. This loosens soils with high magnesium levels. Lime (calcium carbonate) and gypsum (calcium sulfate) are the two most common sources of calcium. Lime will raise the soil pH; while gypsum is pH neutral. Sometimes a blend of the two is required to keep the other nutrients in balance.
- Physical Compaction – Usually caused by tractors and other equipment in the yard or working soils when they are too wet or dry. Note that most hopyard rows are spaced to accommodate tractor tire widths; so the most compaction occurs right alongside the hop rows. This is the equivalent of building impervious underground walls on both sides of the hop rows.
The best time to work clay-content soils is when the soil crumbles in your hand. If it balls up or chalks out, it is best to stay out of the yard with the tillage equipment. Working hopyard soils at the wrong time has a compounding long term effect of reducing pore space > reducing oxygen> reducing microbial activity> reducing organic decomposition rates> reducing the production of soil organic acids> reducing the amount of nutrient availability> reducing plant growth rates.
Hopyards in particular, need to have compaction removed by tillage done early in the season; before the shallow feeder root mat begins to form. If wet springtime conditions are common in your area, consider moving these deep tillage operations to the fall season when soil conditions may be more favorable.
Adding organic matter to mineral-based soils helps raise levels of complex organic compounds, enzymes, and acids that release nutrients that are tightly bound to soil particles available to plants.
- Striated soil pH – a condition found commonly in soils used in the past to grow other crops. This is simply a huge variation of pH levels from the topsoil to subsoil regions. Hops have both deep permanent roots and shallow annual root mat systems and huge differences in soil pH in each root zone can cause a seasonal stunting effect as the hop shifts from the deep root system to the shallow feeder root system. It results in stalled growth in severe cases and resembles transplant shock.
Ideally, this soil pH issue is identified prior to establishing a hopyard and deep subsoil tillage can be done to break up the different layers. If the problem is identified after hopyard establishment, then a deep rooted annual cover crop like daikon radish can be utilized.
- Hardpan- is a compacted soil condition that form 12 to 18 inches below the soil surface from years of shallow tillage for other crops. It stops hop roots from penetrating deep into the soil and limits root mass. Restricted root equals little plant effect. The cures are the same as for striated pH above. (See why deep subsoil tillage prior to planting most hopyards is recommended?)
Improper Soil pH (Back To Top)
- Raising soil pH - Is not as easy as dropping some lime on it. Rates have to be calculated and a soil specialist should be consulted. Different rates of lime and/or gypsum may be required (or a mix of both) to keep the levels of calcium, magnesium, and sodium balanced. Too much lime/ gymsum applied at once or over time can cause deficiencies of other nutrients like magnesium, potassium, boron, zinc, and copper. Gypsum is more pH neutral will leach downward in a soil more quickly than common lime. Ground limestone only moves downward about 1 inch per year; so it is best to incorporate it into the soil with tillage equipment. Hydrated lime is very reactive compared to regular ground field lime and should be used with precaution.
- Lowering soil pH - is accomplished with sulfur applications. It is important to know that sulfur applications can be very hard on fine root tips and hair feeder roots. It would be best advised to avoid heavy sulfur soil applications during periods of active new root growth. Applying sulfur may be best done post-harvest or in multiple small applications versus a single large application. If elemental sulfur is used as a foliar fungicide, it contributes to the plants sulfur requirement much more than affecting soil chemistry.
Irrigation Issues (Back To Top)
- Mismatched drip lines to water supply pressures and gallons delivered per hour by the water source. If the pump or well cannot support the flow rate required by the drip lines and row lengths, then drip line pressures are compromised and water delivery is uneven. A common visual symptom is that the hops get smaller the farther they are from the water source.
- Wrong dripper gallons per hour drip line selected. Sandy soils should use 1 gallon per hour(gpm) drip line emitters, while heavier clay-based soils should use ½ gpm emitters. One gpm emitters on clay soils will cause wasted runoff into the aisles, while ½ gpm emitters will create too small of a wet spot on sandy soil (the water goes straight down past the feeder root zone and takes the fertilizer with it). Either way, the fertilizer and water is not being delivered where the hops can use it.
- Wrong dripper spacing. Emitter spacing on the drip tube should be matched to create two wet zones for each plant; ideally on each side of the plant. So hops planted 36 inches apart should use drip tube with emitters spaced every 18 inches. Hops plant at 48 inches should use 24 inch emitter spacing. Mismatched drip emitter spacing delivers more water to some plants than the others and results in uneven growth in the hopyard rows.
- Using the same irrigation times for different hop cultivars or placing different hops on the same watering zone. Know your cultivars. A big hop like Chinook takes a lot more water than a hop like Centennial. If the Chinook is watered adequately, the Centennial will drown and rot.
- Setting and forgetting the irrigation control system. This means watering the same amount every day on the same schedule whether the plants require it or not. Day in and day out, a sure recipe for disaster. Times and cycles should be varied to prevent waste salt buildups, and watering should be reduced if the soil moisture levels are adequate. If fertigation systems with injectors are used, this includes checking the injectors, filters, and tanks frequently to be sure they are calibrated and functioning properly.
- Checking for clogged in-line water filters. These are often installed when using a surface water source like a pond or stream. The pump pressure gauge may indicate everything is OK when it is otherwise. Install a pressure gauge after the filter to see how plugged or restricted it is.
- Operating drip lines during the hottest part of the day. Water moves slowly thru drip lines and the lines are usually black. On a sunny day the water temperature in a black drip line can exceed 120 degrees. This hot water will cook any feeder roots it contacts. Try to schedule watering cycles early in the day to prep the hops for the hottest part of the day.
- Operating irrigation into the evening and night hours. This is like putting a baby to bed with a wet diaper. Expect a lot of rash in the morning. The high overnight humidity and moisture levels encourage rapid and severe disease development. Again, water early so the soil surface and humidity have a chance to reduce before nightfall. If you irrigation system is undersized and you have to water around the clock, you should check into expanding the capacity of your watering system or be applying good disease prevention controls rigorously during these periods of use.
- Keeping the soil continuously wet – 24/7. Many hop pathogens are dependent of saturated soil conditions to thrive and spread. Don’t help them. Through watering followed by a dry down period is far better than continuous water applications.
- Running the yard too dry during critical high growth phases. Conversely to being constantly wet, being too dry at times is equally bad. During the high growth climbing and coning phases the hops require a lot of water to move all the nutrients required to push that kind of growth. If the shallow feeder root system goes too dry during these periods, the hops will stall growth and shock; often turning yellow from the bottom up.
- Installing drip emitters right over the crown of the hop plant. Bad idea because 1.) The roots are not located there - 2. The continuous wet conditions around the crown will create the perfect conditions for crown rots and water molds like downy mildews. Lay drip lines alongside the crowns instead.
- Not knowing the water source and quality of it. Some water sources can be contaminated, full of plant pathogens, or have excessive levels of sodium, chlorides, selenium, iron, etc. Highly alkaline water sources may need to be acidified to make them useable. In short, get your water source tested so you know what you are using. Water sourced from ponds and streams will often need to be filtered to prevent organic algae and particulates from plugging drip emitters.
Complete Soil Testing (Back To Top)
- Hops require different levels and balances of nutrients at different growth stages during the season. For example: Phosphorus is critically important in early spring for new root development; at burr onset; and rebuilding energy going into winter. Nitrogen is essential during the climbing and side arm development stage; but not during cone maturation or during preparation for winter dormancy. Extra zinc and boron are specifically required at burr initiation.
- Spring testing: Shows what the general levels are of all nutrients and soil pH going into the season. Do this test before the first major round of spring hopyard cultivation. This allows time to incorporate amendments like lime, sulfur, or phosphate.
- Mid-season testing: do this test just prior to bine side arm initiation. The goal is to identify if the nutrients potassium, zinc, and boron are present in sufficient quantities to set burrs and cones for maximum yields. If the tests show deficiencies there is still time for quick corrective amendments or foliar fed nutrients.
- Post-harvest testing: Shows what was removed, what’s left, and what needs to be replaced going into winter dormancy. Specifically check the levels of phosphorus, potassium, and organic matter. If soil pH or compactions are identified as issues, early fall is a good time to apply corrective amendments like phosphate, potassium, lime, and gypsum.
Fertilizer Issues (Back To Top)
- Surface application of nutrients vs. deep spring tillage with incorporation of new nutrients. Applying replacement nutrients year-after-year to the soil surface without tilling / incorporation creates a very shallow root system. (In hopyards using weed control mat, the root system can actually be right at the soil surface.) Early spring deep soil cultivation done as the hops emerge to ensure a deeper nutrient-rich rooting bed. Hops with deeper root systems can handle adverse growing conditions such as heat-stress and drought far better than shallow rooted plants. Deep tilling on either side of the hop row has to be done early in the season, before the new shallow feeder roots form. Deep tilling after the hops are 4 to 5 feet tall is counter-productive because of the amount of damage to the feeder root system forming around each plant.
- Selecting the wrong nitrogen source for the time of the season. Most fertilizers containing nitrogen are formulated with two types: nitrate and/or urea. Both are water soluble sources of nitrogen but nitrates can be used directly by the plants, while urea has to be converted by microbes first. Either nitrogen source over-applied can cause disease out breaks and inhibit uptake of other nutrients like zinc and copper. Synthetic nitrogen fertilizers also lower and burn out existing soil microbes and can increase soil compaction. Urea applied early in the season before the hop feeder roots form is often of little use to the hop plants because - 1.) High leaching rates and 2.) The soil microbes that convert urea are relatively inactive in the cold soil conditions. It is better to wait and apply urea formulated fertilizers after the soil temps rise into the 60’s and the soil biology is more active. A better set of choices is A.) To first apply a low level of an organic fertilizer or manure to increase microbial soil activity that can then break down the later-applied urea more efficiently – and /or B.) Apply limited nitrate-based fertilizer that can leach down into the soil profile where deeper permanent hop roots can absorb it. Emerging spring hop growth primarily utilizes energy stored as sugars and carbohydrates in the overwintering deep roots until the hops reach a height of about 6 to 8 feet. At the point where the stored energy has been depleted, the newly formed shallow feeder root system takes over collection of new nutrients to push bine growth up the string to the top. This transition from one root system to another is what makes the difference between hops that reach the top wire and hops that stall growth at 10 to 12 feet.
- Selecting the wrong N-P-K and micronutrient package in the fertilizer formulation. Selecting the right mix of nutrients can only be done after analyzing a complete soil test that includes organic matter and the micro elements. Examples: Applying a calcium-based fertilizer when soil Ca levels are already high and magnesium levels are low. Or - having too much or too little Boron. See the GLH soil fertility blog for more info about interpreting soil tests or consult a good soils specialist in your area.
- Applying a fertilizer directly to the hop crown. A recipe for a disease outbreak. The roots are not located there. Always apply fertilizers around the hop plant. Having high excess nitrogen levels in the hop crown region any time of the year is a bad cultural practice.
- Not matching the quantity and type of fertilizer with the right phase of growth. Emerging hops do not require near the level of fertilization as when they are climbing aggressively and producing sidearms and cones. Many growers add a supplemental side dress of granular fertilizer as a booster during these critical high growth phases. Being too low during these periods will stall growth and shocked plants will turn yellow from the bottom up.
- Urea plus high growing temperatures equal stretched soft growth. Nitrate nitrogen tends to make shorter stockier plants. Growers can alternate nitrogen sources to effectively control plant habit and internode length (the stem length between leaf sets).
- Feeding excess nitrogen after the cones have half formed. Hops find it easier to make chlorophyll than oils and resins when extra nitrogen is available. Chlorophyll tastes like grass. Beer that tastes like grass doesn’t sell well. Period. Best alpha and oil levels are achieved by leaning out the nitrogen at this cone development stage. Too early a cut and sidearm length is reduced with fewer cones. Too late equals grass. Seeing a few yellow leaves at the bottom of the hops is a good sign at this stage. Clay soil types can cut back nitrogen levels harder than sandy soil types. Do not cut back on the potassium or other micronutrients. The hops need all these nutrients to max out the resins and oils --just not the nitrogen.
- Fertigating at the same time and frequency. Water soluble fertilizers that are applied through a drip irrigation system for the same daily time period can create high levels of concentrated waste salts. Example: potassium chloride is a fertilizer source of potassium. The plant takes up the potassium and leaves the chloride salt behind. These salts accumulate at the edges of the wet zone created by the drip emitter. It resembles an underground pot with walls of concentrated salt. The salts effectively burn off any roots trying to cross it to reach the water and nutrients inside the wet spot. The effect is that the hop plant cannot take up the interior water or nutrients adequately and the hop plant will stall growth and shock. It is important to break up this concentrated salt zone by clear water flushing for longer times during the weekly watering schedule; especially during hot periods coupled with high growth rates and little rainfall.
Annual Nutrient Replacement (Back To Top)
Replacement of nutrients is not a onetime application but rather, a year around continuous effort. The goal is three fold - 1.)To replace the depleted nutrients with balanced long term sources. 2.) To increase the nutrient holding capacity of the soil. (CEC) 3.) To rebuild soil organic matter and increase soil microbial activity to improve nutrient conversion and efficiency.
Many soil and plant processes are interdependent on the balance of nutrients in the soil and plant. Too much of one nutrient blocks uptake of another. Too little of another will stop a complex conversion process. It is easy to mess this balance up. Here are a few things to avoid.
- Do not only feed hops with synthetic fertilizers – granular and / or water soluble. It is well documented that using only synthetic fertilizers will reduce and destroy the soil microbe levels necessary to efficiently convert nutrients to forms usable by plants. Hop growers are stuck with having to use high levels of synthetic fertilizers during high growth stages to get maximum yields or choose organic-type fertilizers with lower levels of nitrogen and get reduced yields. This creates a situation where often very high relative levels of synthetic fertilizers are being applied continuously long term to a hopyard soil during peak growth periods. The potential for soil organic matter burn out and reduced microbial activity is large. This leads to soil compaction and reduced nutrient availability problems.
- Over-applying fertilizers, composts, and manures in one big shot. Soil microbes can only handle just so much at a time and large excess quantities can slow, block, or even damage soil processes and nutrient availability. Large percentages of nutrients are lost to leaching and volatilization. Plants can use nutrients far more efficiently if they are applied in multiple applications.
- Using the wrong fertilizer placement. Some nutrients like phosphates and lime do not percolate down into the soil and need to be incorporated to be available and effective. Granular fertilizers containing urea should be incorporated immediately after application or large amounts are lost to volatilization. Never apply fertilizers directly over the hop crowns. High excess nitrogen levels in the hop crown can encourage disease outbreaks. Always apply fertilizers around or alongside the hop crowns.
Since most of the soil nutrient depletion occurs in the hop row, this is where nutrients need to be monitored and replaced annually. A common set of seasonal practices would be:
- Plowing 6 to 8 inches deep on both sides of the row in early spring (or late fall) to roll away the depleted topsoil into the aisle way. This has to be done very early; before the shallow fibrous hop feeder root mat begins its growth for the season. A sharp disc or plow / coulter combination is commonly used to cleanly cut any rhizomes free from the crown at the same time. The unwanted rhizomes are then removed from the hop yard. A shallow trench has been created on each side of the row.
- If the rows were hilled, the remaining hill covering the crowns is next shaved off when the first bull shoots emerge. These shoots and the dirt and debris from the old hill is knocked into the side trenches where it will later be buried when fresh nutrient-charged soil is rolled back against the row.
- The depleted rolled back row soil (now in located the aisle) is then amended with all the necessary replacement nutrients, compost, manure, etc. to rebuild it. Next, this freshly-charged soil is rolled back against the hop row. This creates a nice aerated rooting bed full of new nutrients for the hop feeder roots to form in for the coming growing season.
- The hops are usually strung and trained at this point. Another soil cultivation operation is done after bine training to reduce any new compaction caused by training activities.
- As the season progresses, the aisle ways between the hop rows are periodically tilled when seedling weeds reach 2 to 4 inches in height. (Always till before any weeds mature enough to set seed.) Each time a hop yard cultivation occurs, more aisle soil is rolled against the hop rows to bury new emerging weeds and start rebuilding the hop row hill for the season. A granular fertilizer containing urea is often banded alongside the rows prior too each tillage. This continues adding fresh nutrients and fresh loose aerated soil to the rooting bed as hop growth accelerates into the growing season.
- Some growers then over-seed the rows with nutrient scavenging cover crops for the rest of the season to help smother late-emerging weeds. These cover crops are plowed in annually to release the nutrients they have collected and increase the organic matter content lost each growing season.
Rhizome Management (Back To Top)
Weed Management (Back To Top)
- Allowing weeds to mature and set seed. Weeds are prolific producers of seed; often producing thousands of seeds per plant. Many weed seeds continue to ripen and become viable even after the weed plant is cut or pulled. Growers that allow weeds to set seed face up to a thousand fold increase in weeds the next season. Always control weeds before they set seed. Good weed control programs use a combination of the following:
- Mechanical tillage on a timely basis
- Pre-emergents to eliminate weed seedlings as they germinate and sprout.
- Post-emergent contact sprays such as pelargonic acids. Example: Scythe /Axxe
- Using specialized systemic herbicides to control perennial weeds and grasses. Examples: Glyphosate (Roundup) and Volunteer
- Proper use of annual cover crops used to smother sprouting weed seeds.
- Allowing perennial grasses with rhizomes to become established and spread through tillage operations. Grasses can quickly infest a hopyard and compete heavily for nutrients unless controlled early. Use multiple applications of grass- specific herbicides until control is restored. Example: Volunteer herbicide
- Not mowing tall grasses around the hopyard. Tall perimeter grasses are a harbor for hop borers and army worms.
- Using a permanent weed barrier fabric in the hop rows. A horrible idea in a long term hopyard management plan for multiple reasons.
- Rhizome removal becomes impossible, unless the weed barrier is removed annually.
- Rebuilding the depleted soil with organic matter and fresh nutrients in the hop row is impossible.
- Adding corrective incorporated amendments like phosphates and lime are limited.
- Application of soil drenches for nematodes and fungal pathogens is limited.
- Black weed barrier literally cooks the shallow hop feeder root system during hot mid-summer conditions. Soil temperatures above 95 degrees shut down feeder root functions. Tomatoes may like it; hops do not. The fabric barrier tends to make hops grow a very shallow feeder root system that is exposed.
- Weed barrier fosters wet, warm, and humid soil conditions under the fabric that results in significantly higher levels of water molds, mildews, and root rots in hops.
- Plastic weed / mulch films can limit soil oxygen exchange; reducing biological activity deeper in the soil. This reduces deep soil nutrient availability.
- Misapplication of glyphosate and other herbicides. Hops are very sensitive to glyphosate. Glyphosate can be used in a hopyards only under very specific conditions. Hops take months to grow out of a glyphosate injury. Be very careful – this is the most common herbicide injury encountered in new hopyards.
- Use generic glyphosate without any enhancers or additives. Use at label rates only.
- Only apply as an overall hopyard spray application in early spring or late fall if hops are fully dormant and crown buds are fully covered with at least an inch of soil.
- Do not apply it alongside actively growing hops once the shallow feeder roots have formed; they will absorb it. The plants may not die completely, but the hop crop is shot for the year.
- Do not spray emerged sprouts from rhizomes. They will translocate the glyphosate back to the parent crown and damage or kill it.
- If applying glyphosate as spot sprays use a spray shield to prevent any drift. Do not apply to the soil as a heavy coarse spray or drench. The shallow hop roots will absorb it.
- Apply pre-emergents such as Chateau to freshly tilled soil as evenly as possible. Do not drench in heavily or hop feeder roots will absorb it. Best in-row control applications are done within 5 days of the last soil tilling event. Do not apply pre-emergents to a hop row and then bury it later with tillage or hilling operations. Read the labels carefully and fully.
- Do not apply contact /desiccant herbicides such as pelargonic acid or Aim to hops until all trained bines have matured the bottom 3 feet into brown woody stems or severe damage will occur.
Tillage Techniques (Back To Top)
- Complete all deep cultivation of soil adjacent to the hop rows before hops reach 1 foot tall. The new feeder roots are not formed yet, so soil cultivation can go deep and close to the crowns. Most growers maintain about an 18 inch row width. Rhizomes are removed in this operation, also. The soil is rolled away from the hop row, exposing the rhizomes.
- Raise the depth of cultivation with each successive tillage as the season progresses. By June, most shallow feeder roots are fully in place and the soil immediately adjacent the hop plants should be only tilled an inch or two deep to avoid damaging these new roots. Many growers prefer to shift over another layer of soil from the aisle, slowly building a hill over the feeder roots, instead of risking damage to them. Growers that have damaged the feeder roots find the hops will stall upward growth and shock; turning yellow from the bottom up. Hop recovery is slow and some cultivars may not recover quickly enough to cone properly.
- Damage caused by rotary tillers. (Weed badgers , Buffalo tillers) These types of tillage equipment will spin up rhizomes and yank them from the crowns. This often splits and damages the crowns, allowing easy access for crown rots, decay, and other pathogens. Side cut hop rows first with a sharp disc blade to cleanly cut rhizomes loose from the crown structure before using this type of tiller equipment.
- Don’t work the soil when it is too wet or too dry. Soil structure can be severely damaged and take years to restore. Best to stay out of the yard until soil conditions are right. Soil compaction is one of the major limiting factors in a hop yard. Don’t add to it. If severe compacted soil conditions exist consider seasonal gypsum applications as a corrective measure.
Fungicide / Nutrient Interactions (Back To Top)
- Copper toxicities and nutrient blocking from over application of copper-based fungicides. Excess copper sprays and soil drenches can effect phosphate, zinc, and iron uptake and create deficiencies. Know your soil copper levels before adding more. Zinc levels should always be higher than copper levels. Beware that repeated heavy copper foliar sprays prior to and during burr initiation can create temporary zinc and phosphorus deficiencies and reduce total cone set and yields. A case of petting the puppy to death.
- Using phosphites (also known as phosphorus acids) as replacement for phosphate fertilizers. These products sound like they both supply phosphorus but they are quite different. Phosphites have a biocidal and fungicidal effect and are properly labelled and used as fungicides; not fertilizers. Phosphites compete directly with phosphates and are taken up equally by plants. However, phosphites break down very slowly in a plant and occupy sites in the plant cells that ordinarily use phosphorus. This limits all the important functions that phosphorus plays in plant growth. In short, when using phosphites be certain that adequate phosphate is present to maintain a proper balance between phosphites and phosphorus to avoid a deficiency. Never substitute a “fertilizer” containing phosphites for a true phosphate fertilizer. Having adequate phosphate present also goes for when phosphite (Aliette, Phostrol) drenches are used in the spring for downy mildew control. Adequate phosphorus at this time is crucial for new root development.
- Using phosphites POST-HARVEST in hopyards with existing downy mildew infection seems promising. Downy mildews move into the hop roots, crowns, and buds to over-winter. Phosphites are somewhat unique in that they will translocate downward in plant tissues and roots. Phosphite takes 3 to 4 months to slowly break down completely, and has good downy mildew fungicidal and protective properties; so a post-harvest drench application could potentially provide effective downy mildew protection through the fall, winter, and even into early spring. However, do not over-apply or hops will possibly emerge with toxicity symptoms.
Out of Balance Nutrient Interactions (Back To Top)
- Decomposition of organic matter by biological activity releases organic acids and enzymes that interact with soil colloidal particles to release available nutrients. Levels of organic matter decline annually in cultivated field soils and it is a challenge simply to maintain and replace organic matter levels depleted each season. Without organic matter biological activity grinds to a halt and nutrient availability drops off.
- Compacted soils create low oxygen soil conditions and microbial activity is thus reduced and nutrient uptake is then also restricted. High levels of old fertilizer salts are a major contributor to soil compaction.
- Phosphorus availability is restricted by lower soil pH combined with high level of soil aluminum, iron, and zinc. Excess phosphorus blocks zinc and copper uptake in hops.
- Potassium can be blocked by excess soil calcium, magnesium, and sodium levels. Excess potassium blocks boron, calcium, and manganese.
- Calcium in general will loosen most soils and make nitrogen more available. Excess calcium can block about every other nutrient; especially magnesium, potassium, boron, zinc, and copper.
- High Sodium levels in soils and irrigation water create toxicities in dry arid soils by reducing biological activity and reducing water uptake by roots. High sodium levels combined with high potassium levels blocks manganese availability. Soil compaction levels can become severe.
- Nitrogen availability is limited any time soil microbial activity is reduced. Excess nitrogen can induce zinc, sulfur, and copper deficiencies; burn out organic matter and soil microbes. Nitrogen and sulfur combine to leach out calcium.
- Sulfur aids in microbial decomposition of organic matter. Sulfur combines with and leaches out excess calcium and magnesium. Excess sulfur creates a lowering of soil pH.
- Zinc is an important micronutrient in growing hops. Zinc levels should always be higher than copper levels. (Harder to do than you think if copper-based fungicides are used frequently.)
- Manganese helps set and hold hop cones. Excess manganese blocks iron uptake if iron soil levels are low.
- Iron rapidly becomes unavailable at high soil pH levels. Wet, cold soils often create iron deficiencies. Nutrients bind tightly to deep soil colloids containing high iron. Organic acids (humates) and enzymes produced by biological activity in the topsoil leach down into the deeper soil profile and make these nutrients soluble again. Organic matter in the topsoil is critical for deeper nutrient availability.
- Copper (and boron) are disease fighters. Soil types with organic matter above 5% can have copper deficiencies. Excess copper affects zinc, phosphorus, and iron uptake.
- Boron is necessary for optimal nitrogen conversion. It leaches easily and needs to be replaced in most hopyards annually. Boron can easily be over applied to toxic levels.
Cover Crops in a Hopyard (Back To Top)
- Scavenge nutrients using deep rooted cover crops. Immobile minerals like phosphorus are moved deeper into the soil profile when the cover crop is tilled under and leaves stems and roots decompose. Deep-rooted Daikon radish used as a cover crop is a perfect example of this.
- Increase soil organic matter and biological activity. Just like above, the cover crop has to be tilled under to be effective. This practice aids in replacing depleted organic matter lost each growing season.
- Provide beneficial effects against plant pathogens. Plowed under barley residue has fungicidal effects. Yellow mustard breaks down into a natural nematicide when tilled under.
- To smother competitive weeds. Dense foliage cover crops have to be selected.
- Legume cover crops can be grown to fix nitrogen in depleted soils. Most of this nitrogen is made available to hops only after it is plowed under.
- A cover crop is not a permanent strip of grass between rows. This is called a lawn. It has to be fertilized, mowed and maintained like a lawn. It is separate from growing better hops.
Pests and Pathogens of Hops (Back To Top)
- Many hop fungal pathogens require wet leaves or saturated soils to flourish. Don’t help them develop by creating prolonged wet leaf conditions or overly wet saturated soils. There is an old grower saying: “Don’t send plants to bed wet”. Ideally, leaves and surface soils are not wet during night time hours. Saturated soil does not necessarily mean the whole field. Drip irrigation system operations and schedules that create continuous wet saturation zones around the hop roots is simply asking for trouble.
- Foliar infection and spread of mildews should be thought of as a two-event process. Foliar leaf infection occurs at the first moisture event. The initial spore infection process is invisible to the naked eye. Fungal mycelia threads invade, spread, and grow inside the leaf (still invisible). The second moisture event causes the mature fungal mycelia to break out of the leaf surface and produce spores (now very visible); where upon the hop grower goes into full panic mode. The key is to apply preventative protective controls before the first moisture event. This means watching the weather forecasts closely.
- Downy mildews follow the sugar. Seasonally, downy mildew tends to invade the parts of the hop plants with the highest sugar and carbohydrate content. In the spring it is the new hop shoots; during summer it is hop leaves, at harvest it is cones, in the fall it is crowns, roots, and newly-formed buds. Scout and apply preventative controls to these locations early in anticipation of pathogen infection.
- In general, the strongest systemic chemical controls are applied early in the growing season and controls shift to progressively weaker contact-only controls as cone harvest approaches. Hops are a food crop and almost all chemical controls have cutoff dates for restricted use prior to harvest. Know these cutoff dates for each control used.
- Don’t leave hops naked without protection leading up to harvest. As mentioned above, most controls have cutoff dates. The idea is to apply these protective controls just prior to the last cutoff date so they are effective up to cone harvest. Nothing is worse than watching a good hop crop get ruined by insects or late diseases and not being able to apply a control because it is too close to harvest. Example: Two applications of Quintec (powdery mildew control) applied at burr initiation and mid-burr stage 10 days apart will help protect the hop cones with its residual effect up to harvest time.
- Use broad spectrum horticultural mineral oils early in the season. Cheap and very effective against both spidermites and fungi. Do not apply horticultural oils on parts of a hop plant that have burrs or cones; it will severely damage them. Check out a good manufacturer’s website like JMS Stylet oil for more exact do’s & don’ts of using oils.
- Control Japanese beetles when they first appear. Female beetles emit pheromone scent trails that attract more beetles from downwind. Controlling them early in the yard early means stronger scent trails are established outside the hopyard and beetles will follow those routes instead; leaving the hops alone. Japanese beetles also prefer plants like grapes and rose-of sharon bushes over hops. Consider planting these kinds of plants at ends of hop rows as a trap plant which can be treated with insecticides separately from the whole hopyard. Check these plants first when scouting the hopyard.
- Hop aphids overwinter on cherry trees. If your location is has native wild choke cherry or other prunus species nearby consider removing them or spraying them with dormant horticultural oils to control overwintering adult aphids and eggs. Treating or eliminating the source may mean possibly not having to treat the hops with an insecticide.
- Adult spidermites often arrive in masse from nearby crops like soybeans and hayfields. Watch scouting reports if beans are grown in the area and when hay is being cut nearby. Use a good contact control to keep them in check before they lay the next generation of eggs and nymphs. Once mites establish an egg-laying cycle they multiply quickly and multiple treatments are required to control them. A new generation of mite can occur in as little as every 5 to 7 days.
- Systemic controls that contain Imidacloprid can cause late season spidermite population flares. This systemic control is often applied early in the growing season as a good wide spectrum insect control for aphids, beetles, and caterpillars. However, it apparently does damage to natural predators of spidermites, too. Studies show that plants treated with imidacloprid not only develop more mites, but the mite’s reproductive cycle is accelerated, too. This is not a good problem to have going into harvest season when most effective mite controls are not available to use. Look for alternate control products.
- Don’t overlook pests like soil nematodes and weevils. These pests can do substantial hidden long-term damage in a hopyard and are very common in many regions. There are a couple of new controls out there too, that are much safer than the old treatments. Inspect hop root systems several times during the growing season. Most nematode species go through two cycles per season and can be hard to diagnose during off-cycle times of the year. Highest populations of nematodes occur in July and August. If the long-snouted adult weevils are seen feeding on the leaves, it is safe to assume that the immature grub stage is feeding like Buggs Bunny on the hop roots.
Over Wintering Hops in a Commercial Hopyard (Back To Top)
- It is a good practice to apply some potassium fertilizer post-harvest. It will improve disease resistance and help provide protection from freeze damage during the winter.
- Do not cover dormant hop crowns with heavy wet mulches or manures. This will cause crown rot to set in and very high losses of plants can occur.
Hopyard Site Selection (Back To Top)
- If a hopyard is planned for a site that had exposure to Atrazine herbicide (think old cornfields) a deep subsoil test should be done prior to proceeding any further. There is no cure for residual atrazine and its half-life is 25 years or more. Hops have deep permanent roots that can take up atrazine found locked in deep soil profiles and hardpans. (Don’t confuse the annual shallow feeder root mat with deep permanent mineral roots. Hops have both.)
- Fields with seasonal water tables higher than 18 inches below the surface are poor hopyard sites. Hops have deep root systems. These sites will require field subsoil tiling.
- Old alfalfa fields can carry levels of Verticillium. This pathogen has no controls and kills hops.
- Old orchard land can harbor nematodes, garden symphylans, and Armillaria / Verticillium root rots. Old decaying tree roots harbor these pests and pathogens.
Mulches and Composts (Back To Top)
- Mulches suck up available nitrogen as they decompose. Extra nitrogen has to be applied to compensate. Wood chips in particular remove a lot of nitrogen.
- Composts originating from woody products are more beneficial for acid loving hop varieties. The woody matter encourages the types of beneficial soil fungi species these hops prefer.
- Composts originating form poultry manures are beneficial for building poor sandy mineral soil and hops that prefer more neutral or higher soil pH levels.
- Some compost, like mushroom compost, can have excessively high levels of unwanted salts. These salts can add to soil compaction issues, block other nutrients, and damage sensitive hop feeder roots. Check composts for levels of salts, and age or leach accordingly.
- Wood chips derived from diseased deciduous trees such as oaks and maples can carry infective Verticillium and other hop pathogens. It is advised not to use coarse hardwood chips or bark in a hopyard unless they are fully composted. Pine bark, needles, and wood chips are OK to use because they contain terpene compounds which pathogens cannot survive in.
- Do not place heavy deep layers of mulch or compost over hop crowns. Put it around the plants.
- Heavy application of mulches can slow down soil microbial activity.
- Heavy surface applications of mulch can serve as hiding places for pests. Slugs, symphylans, and weevils in particular.
- Don’t use plastic mulch covers in a commercial hopyard. The reasons why were described earlier in the weed management discussion points.
- Do not apply any harvest bine waste back into the hopyard unless it is fully composted and incorporated into the soil after application. Hop pathogens and pests can reside and overwinter in hop harvest waste. Do not let hopyard waste linger at a hopyard site. Either compost the waste pile or remove it from the site.
Cutting, Mowing, and Carping of Hop Crowns and Bines (Back To Top)
- In the spring, removing the first early emerging hop shoots is often practiced. (Do not confuse this field operation with later mowing hops again to achieve a particular training date). These early “bull “shoots are not the best bines to train and are removed by cutting them just above the crown structure and remaining buds. This practice also removes any mildew infected shoots that may have survived the winter and emerged as spikes. Growers using the hilling practice find that the hop crowns form more upright shoots and rhizome structure. This results in denser, tighter crowns with easier rhizome control and more selectable bines closer to the string for training.
- In hopyards where row hilling practices are not used the rows are simply mowed when the first shoots are about a foot high. This is timed by variety; as some hop varieties emerge much sooner than others. In general, it is noted that early maturity varieties tend to emerge before later-maturing types.
- In hop rows that use soil-hilling practices, as the first bull shoots emerge from the top of last season’s hill; the grower has to dig down and determine how much of the dirt hill and shoots can be removed without scalping the hop crown structure off. If too much of the hop crown is removed, only roots will remain and the hops will not re-sprout unless deeper stray rhizome buds are left. Most growers using the row hilling technique set the carping (cutting) height about 1 inch above the crown bud height. Experienced hop growers often plant new hop acreage with the new hop crowns lower than surrounding field height to ensure the crowns cannot be accidentally scalped off during the spring preparation of the hop rows.
- It takes between four to six weeks for a cut hop to recover and regrow the 12 internode leaf sets needed to accept the long day length signal that initiates burr formation. If another mowing to set a specific bine training date is done later than four weeks prior to the summer solstice, (when day lengths start getting shorter); there is a risk some hop varieties will not form a full potential amount of cones. Some hop varieties initiate burrs early in the season, and others initiate late. In general, the later the maturity date; the later the cutting date can be. Cutting early maturing types too close to the solstice of results in little or no cones being produced. There is no concise information currently available to help determine best mowing and training dates for many hop varieties grown outside the Pacific Northwest region. In the PNW states, large blocks of hops are often trimmed sequentially to stagger harvesting dates. This helps spread out the hop harvest by keeping too many acres of hops from becoming ripe simultaneously and overwhelming the picking and oasting equipment.
- Some hop varieties should not be cut multiple times. Older noble-type hops (Saaz, Hallertauer, Goldings, etc.) are not vigorous enough to recover quickly enough to meet cone initiation dates. These older varieties also tend to be less tolerating of high temperatures during cone set and will shut down during hot weather. Late cutting dates tend to move the cone initiation into later summer with little or no cones being produced. In general; the newer hybrid hops are much more vigorous and recover much more quickly. Cutting dates a week apart on a vigorous hop variety will stagger the harvest maturity dates by an average of 10 days to two weeks.
- At harvest time cut the mature hop bines off at about a two to three foot height. Leave the remaining bine to die back naturally and be killed by frosts. This will allow carbohydrates and sugars to translocate down into the hop crown and strengthen it. Once the bines have died back in late fall they can then be cut shorter or left until spring cleanup. Cutting the older noble-type hops too low, or before the sugars have translocated to the roots will cause following seasonal loss of vigor and gradual decline. Noble hop varieties like Saaz and Star can be killed within 3 or 4 seasons with improper post- harvest care practices.