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Producing Industrial Hemp in Tasmania - Cultural Management Guide

Smokin Moose

Fallen Cannabis Warrior

"Industrial hemp" is the name used to describe low THC hemp varieties of Cannabis sativa which have potential domestic and industrial uses. THC is the acronym for tetrahydrocannibanol, which is the psychoactive component of hemp. In Tasmania, the law requires that THC levels in industrial hemp should not exceed 50 parts per million in seed components, or 0.35% in other plant parts.

Tasmania is an ideal place to grow industrial hemp for either fibre or seed. Hemp has been grown in Tasmania since 1991, with several companies co-ordinating and fostering producers. However, at the time of writing, there are still no regular contracts available for producers, no local value-adding infrastructure and no proven economic data to calculate profitability. Evidence suggests the crop has the potential to be profitable, environmentally friendly and a good rotational crop for organic production cycles.

Hemp plants consist of leaf material, stems, seeds, and roots. The stem has two major components of interest, these being hurd (or inner) fibre and bast (or outer) fibre. The bast fibre is strong and suitable for making clothing, canvas and rope etc. The hurd is suitable for animal bedding, and is liked by specialised animal breeders because of its high absorbency value. Seed can be used for propagation, seed oil extraction and seed cake. Seed components are suitable for animal food, but are not permitted for human consumption in Australia despite several studies indicating that hemp seed products are beneficial to health. Leaf material is claimed to be a source of good quality dye. Root components have no direct use other than to provide organic matter and some fertility when worked back into the soil, which enhances soil sustainability and has the potential to enhance yields of subsequent crops.

Approval to grow industrial hemp
It is necessary to have a licence to legally grow plants of the genus Cannabis in Tasmania. Production is regulated under the 1971 Poisons Act. Licence applications can be obtained from the Department of Health and Human Services offices, Hobart. Applications for a licence should contain the grower's name, location, total area, variety, reason for production, value adding or processing activity intended and end use of material produced. Police clearance is required before licences are approved. Hemp production sites must be out of view of public roadways and more than 5 km from schools and hop producing areas. The crop will undergo routine inspections by field officers of the Poppy Advisory and Control Board several times during the growing season, and random samples will be taken near flowering time and sent to an independent laboratory to establish THC levels. The cost of analyses is to be borne by the producer or licence holder. Crops found to exceed maximum allowable tolerances of THC will be destroyed.

Plant characteristics
Most cultivars of hemp reach a maximum height of around 2.5 metres. Some cultivars have been developed solely for seed production and grow to a maximum height of 500 mm. Male plants produce very obvious flowers several weeks before female flowers initiate. Female flowers are difficult to identify. About 40% of plants are male and progress into senescence once their flowering is completed. Female plants develop noticeably at this stage. Pollination is predominantly by wind.

The plants are fast growing, and for about 7 weeks after emergence can double their height each 7 days. Vigour peaks and maximum height is reached at this stage. Flowering usually commences at this stage and lasts for several weeks. This is the time that harvesting for fibre should commence. Seed takes another 4 — 6 weeks to mature from completion of flowering. From the time the upper most seeds begin to turn brown on the extremities of the stems, the crop must be checked daily to ascertain optimum harvest time. Hemp plants perform poorly in soil that lays wet, and crops can be lost if this issue is ignored.

Obtaining seed
Tasmanian hemp producing companies hold seed stores of several industrial hemp cultivars and information regarding this can be sourced from the Tasmanian Institute of Agricultural Research (TIAR). Seed can also be acquired from a Queensland based company or from countries such as France, Italy, China and Ukraine. Import protocols apply and are available from Australian Customs or quarantine services. While most cultivars are suited to both fibre and seed production, a seed buyer should specify whether seed production or fibre production is the main objective. Some cultivars are best suited for only seed production. Local seed prices vary around $10/kg. Seed counts vary from 40,000 - 60,000/kg, depending on cultivar and seed grading systems.

Site selection
The best soils for hemp production are sandy to light clay loams. Free draining soils with high humus content seem to encourage growth. Adequate sunlight is important and northern slopes are preferred. Strong winds rarely cause lodging of mature plants if the crop is growing well. Some plants along outer edges may lodge if the soil is very light.

Soil preparation
Deep ripping to 400 mm is recommended and soil should be worked to a fine tilth to a depth of about 150 mm. Raised beds are recommended for heavy soils or sites requiring surface drainage. Poorly prepared soils will cause uneven germination and subsequent plant losses. Prior to sowing, soil should have adequate moisture for even germination. Pre-irrigation may be necessary. The preparation of "stale" seed beds is recommended to minimise weed control problems.

Fertiliser applications, either pre-drilled or band placed during sowing, are recommended on most soils. Free draining, fertile, humus-rich soils will produce a sound hemp crop without fertiliser in most cases. Top dressing of hemp with up to 30 kg of nitrogen prior to flowering time may provide a benefit on some soils depending on existing nutrient status. The hemp plant is very resourceful and generally performs well with a minimum of nutritional assistance.

Hemp can be sown any time from September to January. For fibre production, seed can be sown in September, harvested 60 — 70 days later, and sown again in December for a February - March harvest. Seed crops should be sown October/November for a March/April harvest. Early sowings will produce taller plants, while sowings after mid-December will produce shorter crops. Seed should be sown about 25 mm deep and kept moist until emergence. Emergence in ideal conditions can be as soon as 5 days. Experience to date suggests that two crops can be grown on the same site in the same season without any detrimental effects.

Establish the germination rate before sowing. This can be done on the window sill on damp paper or by a professional service provider if germination data is not provided. The germination rate must be considered when determining the seed sowing rate and desired plant density. The desired plant density will be different depending on whether a fibre crop or seed crop is to be grown.

Fibre crops should be sown at a rate of at least 250 viable seeds per square metre and possibly up to 400 seeds/m2 or 50 - 70 kg/ha. Plants emerge after about 5 - 7 days and grow rapidly to their maximum height, at which time they have uniform stems about 15 mm in diameter for almost their full length. This sowing rate is ideal for maximising hemp fibre yield per unit area.

Seed crops can be sown at a far lesser rate, usually from 30 — 70 seeds per square metre, or 5 — 25 kg/ha.
While a range of sowing equipment and methods can be employed, experience suggests that the use of precision type seeders will provide the most effective end result.

High density crops would be sown in rows about 100 - 150 mm apart to achieve 250 - 400 plants/m2. Seed crops would be sown in rows 200 mm apart to achieve 30 - 70 plants/m2.

Hemp can be grown in most environments with a minimum of irrigation if soil conditions are optimum. For more reliable results, strategic irrigation should be applied, particularly in prolonged drought conditions. Strategic irrigations of about 40 mm each would be applied prior to sowing, then 14 — 21 days after 100% emergence, when the plant reaches 400 mm in height and at early flowering time. Significant rainfalls (10mm or more) during any of the above strategic times would avoid the need for irrigation. Excessive irrigation on clay soils will inhibit proper plant development and possibly lead to crop failure.

Weed control
If the crop is sown in rows, weed control can be carried out with inter-row equipment. Hand weeding is an option for small areas. There are no chemical pesticides registered in Australia for hemp at this stage. Broadcast or dropped and harrowed seed will create a difficult weed control environment and only a high plant density will eventually control weeds in this instance. Weed control is a minor problem if soil conditions, seed germination and sowing methods are at an optimum. Weed control is generally only a problem for the first 3 — 5 weeks, as hemp doubles its height every 7 days after emergence, and will out grow most weeds. Where the crop density is low, or where sunlight regularly penetrates, weeds will compete readily and may reduce the capacity of the hemp to reach its yield potential unless weed control measures are undertaken. "Stale seed beds" are strongly recommended in areas of high weed infestation.

Pest control
There have been no pests of economic importance to control since hemp was first grown in Tasmania 12 years ago. Warm season sowings have occasionally experienced cutworm attack on emerging seedlings, and control spraying may be necessary in this instance. Some seasons have experienced minor heliothis grub attack in maturing seed heads. Minor fungal attack on stems has been noted on one occasion.

The most significant economic damage to date has been from birds on seed crops. Some crops have lost up to 90% of harvestable seed yield in the period from first signs of maturity until optimum harvest time. Native animals have been known to browse the edges of hemp crops at early growth stages.

Fibre crops have been harvested using hay mowing equipment, and either conditioned using a silage conditioner before baling, or baled in the long stem when moisture levels are optimum. Field retting of stems for fibre separation has not been carried out to date. Caution must be used if heading seed with a conventional grain harvester, as hemp fibre is extremely strong and may cause damage to equipment if due care is not exercised. Seed harvesting efficiency should be monitored closely, as many have experienced losses due to incorrect fan settings or high seed threshing drum speeds, which cause fractured seed coats.

Large quantities of dry stem and bagged or bulked seed may need to be stored for a time. Stem components can be round or square baled, and storage in any dry place is satisfactory providing baling occurs at 15% or less moisture content (m.c.).

Seed should be dried to about 8% m.c. Cleaning of seed is essential to remove impurities and achieve a purity of greater than 95%. Seed for planting should have a germination rate of 85% or more. Seed can be stored for a season in dark, dry, cool conditions. Small quantities can be stored in a refrigerator or freezer.

Pressed seed oil should always be stored in containers that exclude light and at a temperature of 2oC or less.

Value adding
Stem mulching and dry baling has been conducted commercially in recent years, with the end product being a high value mulch. The mulch has been successfully used for soil erosion control in vulnerable areas, and moisture retention around perennial crops. Recent research in apple orchards showed that, compared to other mulches, trees mulched with hemp showed yield increases of about 10%.

Pilot commercial techniques have been successfully used to separate bast fibre from stems to produce bast fibre slivers for spinning. The yarn has been used to produce knitted and woven cloth. Blends of wool/cotton/hemp yarn have also been manufactured and successfully woven or knitted at the experimental level.

A Victorian engineering company is developing a hemp decorticator which they claim, will be able to enter a field of standing hemp, harvest the crop, and produce bales of bast fibre suitable for carding or combing without any further treatment such as degumming and softening. This fibre would be suitable for manufacture of high value textiles as well as heavy duty canvasses, ropes and belts and would attract premium prices estimated at more than $3,500 per tonne.

Seed has been cold pressed in small batches to produce pure hemp seed oil and seed cake, which is the seed mash residue. The oil is not permitted for human consumption in Australia, but has a wide range of differing applications including as a cosmetic base, skin conditioner, fuel, paint base and lubricant. Hemp oil may be exported to other countries for use in food. Hemp seed oil should be stored at less than 2oC degrees to maintain long term freshness. It may become rancid quite quickly if left in warm conditions and exposed to light.

Reliable data on profitability is currently unavailable. References suggest that bast fibre is recovered at a rate of 30% from stems. Tasmanian research data from the Forthside Research Station showed that up to 15 t/ha of dry stem can be produced from one planting. It is also possible to grow two crops in the same season if an early (September) and a late (December) sowing were carried out on the same site. Harvesting would need to occur at the first sign of male flowering for the September sowing (about 70 days). If total stem yields are conservatively assumed at 10t/ha, then total yield of stem could be as high as 20 t/ha/year, equating to 6 t of bast fibre and 14 t of hurd fibre when decorticated. Fibre production costs are estimated at $800 - $1,500/ha, depending on decortication costs. Bast fibre can command prices of $500 - $3,500/t and hurd fibre about $100/t. Hemp stems, rotary mowed and pulped in the field, have been baled into 20 kg square bales and marketed locally for $5.50 each for use as prime garden mulch.

Preliminary Tasmanian research data suggests that seed production crops can yield as high as 2 t/ha, with averages across many seasons being nearer to 1 t/ha of cleaned seed. Harvester efficiency is important to maximise recovered yields from a good crop. Birds must be kept away from the crop when seeds begin to ripen, as some research sites have lost 90% of seed in a 4 week period. Seed production costs are estimated at around $4/kg. When pressed into oil, seed will yield about 25%, so 1 kg of seed will make approximately 250 ml of oil and 750 g of seed cake. Oil at this stage is estimated as costing about $17 per litre to produce if all systems are efficient. The oil usually needs more cleaning and purifying after initial extraction and costs of this are yet to be established. Retail prices of imported hemp seed oil have been as high as $90 per litre. Hemp seed mash or seed cake also has many uses that have not been given a value to date. These include animal feed, bird feed and fish food. If permitted for human consumption, then seed cake can be ground into flour or used in muesli bars, confectionary bases etc. References indicate hemp seed has many valuable food properties and is often quoted as having the richest source of essential fatty acids in the plant kingdom.

In a world of diminishing forests, increasing demand for fibres of various sorts and increasing concern over the environmental impacts of production systems, hemp may be a valuable addition to agricultural production systems. Hemp fibre could be used as a sustainable substitute for imported wood kraft fibre for papermaking. With its food value yet to be fully realised, it could prove to be an ideal supplement for animals and humans. The oil is reported to have many uses with a favoured one being for use in skin conditioners.

Until the scale of production increases significantly, and efficient machinery is employed in value adding systems, the economics of industrial hemp production and marketing in Tasmania will remain something of an unknown.

Tasmanian Institute of Agricultural Research (TIAR)
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