Industrial Hemp Information and Education

Time needed for Review
90mins.+

Course Syllabus 

  1. Commercial Applications
  2. Assessing Maturity
  3. Seed Sampling for THC
  4. Swathing
  5. Combining and Straight Combining
  6. Grain Storage
  7. Seed Cleaning
  8. Fiber Harvest
  9. Flower Harvest
  10. Bailing and Fibre Storage
  11. Flower Storage
  12. Retting

Commercial Applications

Industrial Hemp Holds thousands of commercial applications. The chart below outlines the supply chain for most Industrial Hemp applications.

Industrial Hemp Holds thousands of uses after the raw material has been processed. Each step in the Supply chain is creating thousands of jobs and new companies every day. 

Food Production 

Hemp Seed Yields for food production are variable with yields ranging up to 1000 to 1300 lbs./ac. but average between 750 to 900 lbs./ac.

Fiber Production

Fiber yields from high yielding varieties can yield 2.4 to 4.8 tons/ac. Hemp provides greater fiber yields than most other fiver crops and is known for its high tensile strength. 

Hemp Seed Grade Requirements- Physical Properties

Variety: OECD, Health Canada

Color and Appearance: Grayish-brown seeds. Mature good quality hemp seeds will have dark markings on them

Flavor and Odor: Slight nutty flavor and odor

Purity- Seed cleaned to 99.9% purity. The maximum admixture without deductions is 0.1% by weight. Weathered, immature or frozen seed have colorless light brown seed coat. All poor quality seed needs to be removed through the cleaning processes. 

Grading- Peroxide levels are one of the main grading factors. Peroxide values are a measure of rancidity that may occur in the sample. Hemp processors prefer grain with a peroxide value under 2meg/kg. Growers can reduce the peroxide levels by minimizing seed injury during harvest, cleaning, and handling. 

Toxins- Must have acceptable levels of coliform and e-coli. Check with processors for more requirements.

Moisture ContentShould not exceed 8%

Assessing Maturity

Crop height can help determine maturity. Grain varieties are typically shorter and rang from 3 to 9 ft. tall. Fiber varieties can grow to be more than 10 ft. tall. 

Crop height is also influenced by photoperiod. flowering and seed set is triggered by light deprivation IE shortening daylight. 

Most industrial hemp varieties are dioecious where male and female plants are separate in a ratio of 50:50. Male plants flower and pollinate the female plants. After pollination, the male plants die off and the females continue to grow and set seed. Some monoecious (Hermaphroditic) varieties and are mainly bred for fiber. 

Sample Morphological Stage Chart

Assessing for Fiber Only

The crop is harvested when maximum volume and quality is reached. This point is reached prior to seed set. In dioecious varieties harvest timing for fiber occurs prior to seed set and the dying off of the male plants. Monoecious varieties have a similar harvest timing aimed at maximizing fiber volume and quality. Typically, harvest occurs when flowers first emerge.  Environmental conditions and daylength will determine the length of time between seeding and harvesting. Additionally, processors may have specific quality needs and require a specific harvest timing to meet requirements. 

Assessing for Grain and Dual Purpose Varieties

Harvest timing for grain is set to maximize seed yield and quality. Seed maturation starts at the bottom of the seed head and moves upwards, resulting in mature seeds lower down and immature green seeds at the top of the seed head. Once mature, the seed bract that holds the seed dries out, and the seed can shatter quite easily resulting in loss if not careful. 

Harvest

The timing for swath and straight combine is a balance between minimizing shatter loss and dealing with high moisture content. Consideration should be given to harvest capacity of both the combine and grain drying equipment. for larger acreage or lower grain drying capacity, start combining at higher seed moisture content so that the harvest can be completed before the crop becomes to mature and shatter loss occurs. To limit shatter loss combine hemp green at higher moisture content than safe for storage. 

General Harvest seed moisture content:

Short Season: 12-16%
Mid Season: 14-18%
Full Season: 18-24%
Longer Season: 20%+

Hemp Moisture Chart

Visual Assessment

When hemp seed is harvested tough, the seed heads (buds) will still be mostly green. the stem fibers will have shed most of the leaf, but not completely matured, making the stem easier to handle with harvest equipment. the seed hull will become brownish and firm. 

Seed Sampling for THC

For American markets growing industrial hemp is controlled by state pilot programs and as such the rules for thc sampling are put forth in your particular state’s charter. For Canadian markets, approved samplers licensed with Health Canada and is also a professional Agrologist must sample hemp crops. For both markets, the legal level for industrial hemp is less than 0.3%.

Swathing

Swathing of hemp is a risk management tool against shattering loss due to high winds. It does carry considerable risk of seed quality loss and increased levels of microbial contamination if hail or rain flattens the swath onto the ground. It should be considered when the forecast is for dry weather during the next two to five days so harvest can be done prior to any rain. 

Pros of Swathing:

  • Reduction of shattering loss due to wind
  • Partial dry down of seed moisture content before combining
  • Potential reduction of aeration and drying requirements

Cons of Swathing:

  • Seed in contact with the ground may be subject to mold and bacterial development and coliform contamination causing quality loss and downgrading of seed
  • Rain may cause quality deterioration and germination in the swath
  • Risk of seed contamination with small stones, dirt, and other foreign material
  • Standing hemp will dry faster in damp conditions than swathed hemp
  • Some combines are less able to handle the drier stem fiber reducing combine capacity

Swathing and Combine Timing

Swathing can be carried out at 15-18% moisture content prior to the bottom mature seeds shelling out. Swathing at seed moisture lower than 15% means increased shatter loss. The crop is cut at 8-12in. high.

After swathing, the crop may be left in the swath for two to four days to allow the seed moisture to drop by a few percentage points. The leaf matter will dry down. Left in the swath much longer than two days and the stem fiber starts to dry down too much, turning into a rope-like material that can plug the combine. Under good environmental drying conditions, seed moisture may be down to 10-12% at combining. 

Combining and Straight Combining

Prior to harvest, ensure all of your equipment, including combines, trucks, augers, grain cleaners and storage bins are dry and free of foreign material. Purity standards are very high at 99.9% and contamination with other crops, especially wheat, weeds and others can result in higher cleanout at the seed cleaner and reduced or rejected loads. For most growers, straight combining is the preferred method of harvesting hemp for seed. The combine header is lifted to cut the crop just below the seed head, which typically is the top 1/3 of the plant. (23-25in.) This minimizes the volume of fiber moving through the combine, and reduces fiber wrapping and increases harvest efficiencies. Often, the shorter plants in the canopy may not have mature seed are not worth cutting low to get to the seedhead. Growers have reported that crops over eight feet high are difficult to harvest. 

Seed moisture content determines straight combine timing. Start harvesting when seed moisture content is 12-15% for shorter varieties and 14-20% for taller varieties. 

Combine Equipment Requirements

Shorter hemp crops can be harvested with most modern combines with little to no modifications. Use draper headers for straight combining as they feed the combine more uniformly. Fiber stems may wrap on auger headers. New knives and guards are important to eliminate plugging. Both batt and pick-up reels have been used. Conventional and single rotary combines are preferred. Most growers use rotary or conventional John Deere or Case IH rotary combines. Larger capacity combines with conventional cylinders greater than 1.25m (50in.) help deal with the large, fibrous volume going through the combine. Dual rotary combines are less desirable as the risk of fiber wrapping and plugging of the opposing rotors is considerable. 

Feeder chains, shafts and exposed moving parts should be regularly checked for wrapping. Disable the straw chopper to drop the straw and prevent wrapping and plugging of the straw chopper. Combine fires are a risk from wrapped fiber on moving parts and fine dust igniting on hot surfaces. Frequently monitor for fiber wrapping and keep hot engine surfaces clean. Some producers keep a water truck handy during harvest.  

Combine speed should be set to provide uniform crop flow through the combine to prevent plugging and wrapping. Carpet knives are handy tools for cutting away wrapped fiber. Clean all equipment out at the end of the day to prevent pockets of seed from heating and mixing with the next day’s harvest. 

Combine Modification

Growers have found that some modifications help to reduce or prevent fiber wrapping

  • Exposed moving parts can be shielded with buckboard or sheet metal to prevent wrapping
  • deflectors can be added to keep the crop away from header reel ends and to narrow the feed-house inlet to help keep fiber from wrapping on outer shafts and pulleys
  • ABS pipe can be placed over front drive shafts to prevent wrapping
  • Cables and hydraulic lines should be tied in close to the machine to help reduce fiber build up
  • Extend header hydraulics by about 1ft. to help raise the header higher for tall varieties 

General Combine Settings

hemp seed is easy to trash. The seed coat can be easily damaged, exposing the seed to oxidation of the oil, decreasing quality and risking possible rejection of the sample. Combines should be initially set to gently thresh the seed and adjusted as required to minimize seed loss out on the back of the combine. 

Cylinder Speed: Initial settings should be similar to canola settings at around 450-500RPM. Higher speeds may damage the seed and increase chaff going to the cleaning system. 

Concave: With a seed size similar to wheat, standard small grain concaves are suitable. Set concaves similar to canola at 2.5-5cm (1 to 2in.) Wider settings are used for drier crops to help reduce seed damage. 

Fan Speed: Depends on crop maturity. More air is required for higher seed moisture to keep sieves clean and to help blow out immature kernels. Less air may be required if chaff is drier. Slightly less air is required than for wheat at 650-800RPM.

Sieve/Shoe: Setting similar to wheat and slightly wider than canola. Try 8mm bottom setting and 9mm chaffer setting.

Rotor Speed: Similar to canola recommendations of around 350-500rpm at 17-25% moisture. Faster speeds for drier crops. Some growers report Massey combines may require slightly faster rotor speeds. Push the pitch of the flow bars to maximum slope to move fiber through the combine as fast as possible. Excess rotor speed may overload the cleaning system with green material. 

Rotor Concaves: Best results with wheat concaves in the front and slotted concaves in the rear of the rotor cage. 

Hemp Seed Handling

Hemp seed can be easily damaged, resulting in decreased seed quality. Damaged seed hulls are more vulnerable to rancidity. When moving hemp seed from combine to dryer to bin to seed cleaner to processor, handle hemp gently:

  • When unloading combines, reduce unloading speed. This means no unloading on the go.
  • Conveyors are recommended.
  • If using grain augers, run at lower speed and ensure augers are full.
  • Use larger diameter augers of 25-35cm (10-13in) rather than smaller 15-18cm (6-7in) diameter augers.

Sampling

Hemp seed processors require a bin grain sample after the grain has dried to their specifications. Hemp seed samples should be collected when moving grain into bin storage. Samples from each truckload should be taken at regular intervals and combined to create an overall representative sample for each bin. Submit the representative sample to your contracted processor according to their requirements.

Grain Storage

Hemp seed must be properly dried, stored and monitored to preserve grain quality. Heated or moldy seed will result in the rejection of the seed for food use. Heating, sweating, evaporation, and condensation may be excessive in parts of the bin leading to local pockets of mold growth. In the early stages of heating seeds stick together and form lumps. This will lead to a rapid increase in free fatty acid content of the oil resulting in deterioration of oil quality. Heating in storage will lead to mold growth and in some cases where the temperature is high scorching of the seed will be obvious. Damage in the forms of heating or bacteria activity may also cause hot spots, fermentation and in some cases loss in weight. 

Processors require specific moisture content for stored seed of 8-9%. Contact your contacted processor for specific seed moisture requirements. Hemp seed may need to be stored for up to one year and even into subsequent years while processors source seed from growers to meet demand. Properly dried and monitored hemp seed will store for one to two years without loss of food quality.

Hemp seed can rapidly heat, within 2-4 hours of combining and must be immediately put under aeration or through a dryer to preserve seed quality. If harvest speed is slow, do not allow hemp seed to sit in the truck at the side of the field for more than a few hours before getting it to aeration or drying facilities. Do not allow damp hemp seed to sit in the combine hopper or truck overnight.

The suitability of aeration or artificial grain drying will depend on the seed moisture content at harvest and ambient air temperature/humidity conditions. It is essential to match grain drying and conditioning capacity to combine harvest speed. It is advisable to have excess grain drying capacity than to be under capacity and risk losing seed quality. 

Storage Type

When selecting storage systems for hemp, priority should be given to cleanliness, handling, conditioning and aeration capabilities. Hopper bins with aeration are the best choice. Flat metal bins with aeration flooring are also a good choice. Mini-bulk bags have been used to store hemp seed as long as the moisture content is 8% or less. Grain bags are not recommended as little information is available on hemp storage in grain bags and growers should consider other options to safely store their high-value hemp crop. 

Grain Temperature and Moisture Migration

More dried grain loses condition because grain temperatures are not controlled than for any other reason. Improper control of the temperature inside the bin causes moisture to move or migrate from one part of the grain mass to another, where the moisture can accumulate and cause grain spoilage problems. In the fall, when the air temperature decreases, the grain along the bin wall cools down faster than grain in the middle of the bin. The difference in the temperature starts air moving down the bin wall and toward the center of the bin. as the air moves through heh grain it becomes warmer and begins to pick up moisture from the grain. When the warm moist air hits the cool upper surface fo the grain, condensation occurs. Moisture will concentrate on the sies of the bin and the cone at the top during the fall and winter. Flattening the cone can help prevent moisture buildup. In the spring moisture migration is reversed. Them warming action of the sun on the outside of the bin causes moisture currents to move up the bin walls and then down the center of the bin. 

Hemp should be rotated when seasons change, fall to winter, and winter to spring, to minimize moisture migration and spoilage. This is done by removing the grain from the bin and rotating it back into the bin. The grain temperature equalizes and moisture fronts are broken up to help stabilize air movements. 

Aeration

Full floor aeration or rocket systems in hopper bins are suitable for aeration to cool and dry hemp seed. Hemp seed is large, similar to wheat, and air moves through it easily. 1-3 weeks of aeration is required to dry grain, depending on ambient conditions, grain moisture, fan and bin capacity. For nearly dry seed under 12% moisture, a tube aeration system with medium fan capacity may be adequate. If ambient conditions are unfavorable, the addition of artificial heat with a propane heater can help dry grain down more quickly. At higher seed moisture, a grain dryer may be required to dry the grain down the mid-teens and then a good aeration system using a full floor screen and high capacity fan, plus turning or moving the grain once or twice may be required to keep the grain cool and conditioned.

For aeration systems, a hopper bottom bin with a large capacity fan of 5-10hmp and a 100,000BTU propane burning to add artificial heat is one of the best systems for drying hemp seed. Caution must be used when applying supplemental heat. Use low heat less than 35C to ensure the seed does not overheat. Do not overfill aeration bins as the hemp seed may heat before the grain is dried and cooled to safe storage conditions. For seed below 20% moisture, fill to less than the 50% capacity level. Fill to no more than 1/3 bin capacity if the seed moisture is above 20%.

The general rule of thumb for fan hp requirements, provided by processors, is that one hp of fan is required for 150 to 200 bushels in good drying conditions for grain 5-6% above dry. For example, a 5hp fan will efficiently dry down 750-1000 bushels of 15% moisture seed in a 2000 bushel bin. Once aeration has commenced, processors have found that turning 17%+ moisture grain within 24-48 hours, and mid-20s moisture grain within 24 hours will help keep grain in condition. Continue aeration and monitoring. 

If any heating or crusting of grain is observed, the seed should be immediately pulled out of the bin and dried. 

Artifical heat drying

In many installations, a continuous drying system will not be able to handle the seed at the same rate at which it is being combined. Temporary holding the wet seed will be necessary and it is very important to make provision for colling in the pre-drying stage. Ventilation with ambient air at the rate of 0.6-0.8m/min/ton should be adequate. At a depth of 1.5m this would require a pressure of 2.5-5cm w.g.

For growers with artificial heat grain dryers, hemp seed can be quickly dried down to safe storage levels. Batch and continuous flow grain dryers are suitable. Batch dryers have an increased risk of developing hot spots during drying. Continuous flow grain dryers are recommended. 

Use moderate heat. Plenum temperatures around 45C and air temperature in grain of about 35C. Overheating the seed can cause the seed to turn yellow and degrade the oil quality. The seed should be cooled down to ambient air temperatures after drying prior to bin storage. 

Monitoring

As a high-value crop, hemp seed should be frequently monitored during the first six weeks in storage to ensure the crop retains its quality. Continue to regularly check until delivery. Hot spots may develop that could mix with the entire bin and result in the complete loss of the bin. The best monitoring system is a well-designed bin system with cables and automated monitoring. A cable system will help ensure hot spots are detected early with minimal effort. One cable can monitor a bin diameter of 6-7m but more cables will provide better coverage. Larger bins require more cables. Alternatively, probing grain bins frequently at multiple points will allow a grower to monitor each bin. Probing, though, usually only accesses the grain near the bin door at the bottom and the top access doors. Hot spots may be missed. If hot spots are detected, the bin should be turned and aerated to cool the grain.

Seed Cleaning

Once the processor calls for delivery, hemp seed must be cleaned prior to delivery. Each processor has preferred seed cleaners, and each seed cleaner must be licensed if in Canada. Truckers must be licensed to haul hemp from farm to cleaner to processor if in Canada. Ensure all grain handling equipment is cleaned, including augers, conveyors, and trucks. Seed cleaning equipment will also need to be thoroughly cleaned to ensure cross-contamination with other grains, especially wheat, does not occur. 

Most seed cleaning equipment, including air and screen, indent and gravity tables, are suitable. Color sorters are becoming more common for ensuring the seed meets the strict quality specifications of 99.9% purity. Purity is a key issue with hemp seed, as some processors try to meet gluten-free standards. Hemp seed is usually shipped directly from the seed cleaner to the processor. Upon arrival at the processing plant, another sample is collected by the processor and assessed for purity and quality. Rejected seed may be returned to the grower. 

Fiber Harvest 

For dual-purpose seed and fiber production, the crop will have either been swathed or straight cut. The target market for fiber will dictate how the leftover fiber and stubble will be handled. For hemp that is swathed and then combined, the fiber will be left in the windrows for baling or retting. The retting process may take all winter, so baling may be left until spring. Straight cut hemp will generally have tall stubble left behind varying from 0.6-2.4m high. The remaining stubble should be cut with a swather or haybine within several days if the windrow is going to be baled.

Fiber only Harvest

When hemp is grown only for fiber, the crop is typically harvested around the early flowering stage when fiber volume is maximized. Hemp fiber crops are generally well over 2.4m (8ft.) tall and can reach up to 3.5m (12ft) high. Equipment used for cutting hemp must be able to accommodate this large volume. Standard swathers generally cannot handle hemp fiber crops. Research by Alberta Innovates Technology Futures and ARD have found that a sickle bar and disc work well for cutting hemp fiber.

Flower Harvest

In America, the hemp flower market is exploding with the de-regulation and potential legalization of industrial hemp. (0.3% THC) This boom has led to many states implementing Hemp pilot programs. These programs vary in statutes but most, if not all, allow for hemp flower to be cultivated. Hemp flower has many similarities in its growth cycle to fiber and seed but deviates exponentially for harvest and storage. 

Hemp Flower Grade Requirements

Variety: USDA Approved Hemp varieties for import into America (Must work with DEA to import Cannabis Seeds into America under a pilot program), Check with your state pilot program for approved seed ( Or Clone) varieties.

Color and appearance: Hemp Flower can come in hundreds of different colors, which is based on species genetics. Flavinoid and Terpene profiles within a specific species strain will determine the color and olfactory traits.  Hemp flower should have an appearance of being free of mites, mold, mildew, disease or virus. High-grade flower will have fully developed colas. Colas will consist of mature pistils, calyx, and the presence of trichomes on each bud or “flowering” part of the plant. Sugar leaves will be mature with visible trichome dust and fan leaves will be mature on the stem. 

Purity: Hemp Flower is required to be lab tested for THC content and meet a strict less than 0.3% federal requirement as outlined in the Farm Act of 2014. Furthermore, All flower should be free of harsh chemicals, Plant growth regulators, Toxins, Pesticides, and Fungicides at the time of harvest. Flower should be sent for testing at a state-approved lab to ensure it meets your states testing requirements. 

Grading: See Sample Lab Test for grading report. Metrics include PytoCannabinoid Profile, Pesticide Results, Microbiological Results, Terpene Results, and Residual Solvent Results.

Testing is performed with either a High-Performance Liquid Chromatography (HPLC) (Prefered) or Gas chromatography (GC) or Thin Layer Chromatography (TLC) along with UV Chromatography. Currently, your State requirements will dictate which methods are approved and what metrics are required in a test. 

Assessing Maturity

With thousands of different genetic makeups within the species, assessing the maturity of your flower will be based on strain-specific maturity guidelines. Providers of hemp flower seed or clones should have the best information for you to assess maturity for harvest. 

Environmental Conditions

Wind, hail, and rain are important considerations when assessing harvest time. If your crops are not within greenhouses, hoop houses, or indoors, crops should be planted with harvest timing in mind. 

Processing

Drying and Curing require a balance between temperature, humidity, light, air and time. Post Harvest drying is achieved by hanging branches and buds or by using racks and placing colas on the racks. Controlling the temperature range (19-23C) along with the humidity (45-55%) will help ensure your flower does not grow mold or develop spores. Drying is always best done in a controlled facility to help ensure no external contamination occurs and you can control UV exposure, temperature, humidity, and air flow.  This process should last anywhere from 6-10 days. 

Once drying is completed processing branches and colas into buds or final product for curing can occur. This stage can be contracted to Trim companies. For internal processing, trimming should be done in sterile environments to prevent contamination. Your final product will be processed to remove sugar leaves, the buds from stems, and further refine the flower with hand trimming or machine trimming methods. Current markets hold a higher pricepoint value for hand trimmed over machine trimmed. Each method provides pros and cons and selection of a method depends on desired end product and destination. 

Bailing and Fiber Storage

Expedient cutting and baling will minimize fiber wrapping and allow better baling efficiencies. If retting is desired a considerable time between cutting and baling may be necessary. Sisal or hemp twine should be used as poly twine can contaminate the fiber. Plastic netting can be used as it is easily removed. Stalk moisture should be less than 15% at the time of bailing and continue to dry to about 10% in the bale. Once moisture is under 15% no more retting will take place. Round bales may be stored outdoors for a number of years in prairie conditions, but square bales absorb more rainfall and must be stored covered. Hemp straw absorbs air moisture readily so ensure bales are protected from ground moisture and air moisture. 

Flower Storage

Storing Cannabis is best suited for containers that block UV, prevent moisture, can be sealed, and hold large quantities for storage and transportation. If the product is going straight to end consumer packaging check with your state or countries laws regarding packing and labeling requirements. 

Retting

Retting is a microbial process that breaks the chemical bonds that hold the stem together and allows separation of bast fibers from the inner white core hurd. Retting is used to more easily separate bast from hurd during decortication at the processing plant. After retting, the straw is typically baled and transported to a processing plant or stored. There are several types of retting, including field, water, chemical, and enzyme. Fiber processors may have different retting requirements and should be contacted to ensure the retting process meets their needs. 

Field Retting

With field (dew) retting, plant stems after harvest are left in the field to rot. although weather conditions affect the quality of fiber, field retting has been used extensively in Europe for hemp because it is inexpensive, mechanized, and does not use water. The length of retting time is normally 21-28 days when industrial hemp is cut for fiber during late summer. Dry weather may require longer retting.

Water Retting

Water retting produces more uniform and high-quality fiber, but the process is very labor and capital heavy. Water retting can be done in tanks where water flows in for 7-14 days. Heating tanks between 30-40C can reduce the time further. Chemical additives may be added to enhance the process. Further drying is also required.

Chemical Retting

Chemical retting is commonly performed using s sodium hydroxide solution with or without a chelating agent EDTA. This method possesses all the advantages of water and field retting. It can be accelerated to a few hours to fully ret. It is very expensive and labor intensive and not widely used.

Enzyme Retting

Enzyme-retting replaces the bacteria and facilitates fermentation in water retting with enzymes.

 

 

Sources:

  • Alberta Agriculture and Rural Development
  • Industrial Hemp Enterprise
  • Alberta Innovates-Technology Futures
  • Hemp Oil Canada, Inc.
  • Manitoba Harvest
  • Health Canada Industrial Hemp
  • Canadian Hemp Trade Alliance
  • Manitoba Agriculture, Food, and Rural Development
  • Saskatchewan Ministry of Agriculture
  • Ontario Ministry of Agriculture
  • European Industrial Hemp Association