EAP Publications | Virtual Library | Magazine Rack | Search | What's new

Join the Ecological  Solutions Roundtable

Hemp

(Cannabis sativa)

reprinted from the Bi-weekly Bulletin, vol. 7, no. 23 (1994),

Prior to the end of World War II, hemp made a significant contribution to the economic and social fabric of society. In competition with cotton, jute and other fibre crops, it was used extensively for ropes, twines, tough thread, textiles, paper, building materials, cellulose plastics and resins as well as food and oil from the seeds. However, since it belongs to the species Cannabis sativa, its production was made illegal in some of the developed countries in the mid-1930s. Growing interest in adaptation and diversification has created new opportunities for hemp. Several European countries have passed legislation allowing its commercial cultivation under license. In Canada, cannabis saliva (hemp) can only be grown for research purposes under the license granted by the Minister of Health. This Issue of the Bi-weekly Bulletin examines the agronomics and economics of hemp production.

History of hemp

World production of vegetable fibre was 10.2 million tonnes in 1992 with hemp accounting for slightly more than one per cent. Production of hemp originated in Central Asia over 8500 years ago. From the 1 6th to the 1 8th century, hemp and flax were the major fibre crops in Russia Europe and North America. During the late 1 9th and early 20th centuries, Increasing labour costs encouraged a shift away from hemp to cotton, jute and tropical fibres which were less labour intensive. Technological advances, such as the cotton gin, encouraged production of competitive crops. This decline has continued, due to the advent of synthetic fibres and because the cultivation of hemp has been made illegal in many countries. In 1937, the United States government imposed a heavy tax on producers under the Marijuana Tax Act. Canada prohibited production in 1938 under the Opium and Narcotics Control Act. During World War II, the Canadian and U.S. governments lifted the restrictions on hemp production to provide materials for the war effort..

World production peaked in 1940 at about 832,000 tonnes of fibre. After the war. the restrictions were reapplied. In the early 1960's, the U.S. deemed it up to tax production and therefore removed the tax but retained the requirement for a grower's permit. In 1961, the Canadian Narcotics Control Act (CNCA) allowed Cannabis to be grown, at the discretion of the Health Minister, for research purposes only. In 1992, world production of hemp fibre was 124,000 tonnes with India, China, Russia, Korea and Romania as the major producers. In 1994, under the COCA, one license was granted to a Canadian company, Hempline Inc., to grow hemp in Canada under the strict supervision of the authorities.

Hemp is distinct from marijuana. Although hemp and marijuana are from the same plant species, they have different uses and physical characteristics. Hemp generally refers to the fibre producing producing strain of Cannabis. Marijuana usually refers to a mixture of leaves and flowers is used for the drug, delta-9 tetrahydrocannabinol (THC). A THC level of 0.3 per cent is specified in some studies as delimiting narcotic and non-narcotic strains of Cannabis, although narcotic strains generally average three to five per cent THC, about 10 to 15 times the delimiting value.

New strains d low THC hemp have been developed by the French. However, many of the traditional cultivars formerly grown in Canada and the U.S. contained very low amounts of THC. Increased world wide demand for products developed from the hemp fibre, hurds and seed has resulted in a renewed cultivation d hemp h Europe and the crop is being considered by other countries.

Bill C-7, the Controlled Drugs and Substances Act, was introduced Feb. 2. 1994 by the Ministers of Health and Justice to bring Canadian law in line with international accords to which the country is party. The Bill is in the committee stags being considered for possible amendments. If passed it would replace the CNCA and parts al and IV of the Food and Drugs Act. The cultivation of hemp would still be illegal without a license issued by the Minister of Health.

Agronomic characteristics Hemp is a herbaceous annual that can reach up to nine metres in height, but under cultivation it averages between two to four metres. In four months it can produce seven to 15 tonnes per hectare (t/ha) of dry stalk. It is dioecious (having male and female flowers borne on separate plants), but monoecious cultivars have been bred. Modem plant breeding in Europe has produced several dozen hemp strains with the emphasis on the creation and perfection of monoecious varieties. Selecting monoecious strains overcomes the problem of different maturation times between male and female plants, and results in consistent height and weight of the stalk for more uniform quality and higher productivity. Hemp is a short-day plant and since production has historically been concentrated in north-temperate areas, fibre selections are generally photoperiodically adapted to mature in early fall.

Hemp stalk

The stalk is harvested for the fibre and hurds. The centre of the stalk is hollow except at the nodes (where the leaves are attached) and in the best fibre producing types the hollow space occupies at least one-half the diameter. Next is the innermost layer or pith surrounded by thick, short woody cells which support the plant during its growth. The adherent woody core, after it is freed by resting, is referred to as hurds. Outside of the hard woody portion is the soft cambium, or growing tissue which develop into the hurds on the inside, or into the best and bark on the outsides. It is in this layer chat the fibre bearing best splits away from the hurds during resting and breaking. Outside of the cam hi urn is the phloem parenchyma, comprised of short, thin-walled cells, filled with chlorophyll giving it a green colour, and long thick walled cells, making the best fibres. Between 15 to 35 fibre bundles are found in this layer. Outside of the primary best fibre is the cortex, which is a continuation of the thin-walled chlorophyll bearing cells free from fibre. The outside of the stalk is covered by a thin epidermis.

There are three types of fibre: primary best fibres which are long and low in lignin, secondary best fibres which are of intermediate length and high in lignin content and librifomm fibres which are short and high in lignin. Fibre length and the contents of cellulose and lignin are important quality parameters for raw materials used in the cordage, textile, paper and fibreboard industries.

Frost tolerant

Hemp grows best in a humid environment when the ambient temperature ranges between 14 °C and 27 °C, although it can endure greater temperature variations. Hemp grows best with plenty of rainfall during the growing season, especially during the first six weeks. Once well rooted, hemp can endure dry conditions although it hastens maturity, dwarfs growth and reduces yields. Depending upon the area and rainfall conditions, hemp is usually planted between early March and late May in the northern latitudes when the ambient temperature is around 10 °C. Seedlings can survive a short frost of -8 to -10 °C while order plants tolerate frosts of -5 to -6 °C. Since hemp is sensitive to photoperiod, the earlier plantings produce better crops.

Seeding

The optimum seeding depth is two to four centimetres (cm). Row spacing is usually six to 15 cm when using a narrow-width seed drill. The proportion of stem biomass and the content of the more valuable best fibres in the stem increases with plant density, therefore dense crops are usually desired. Recommended seeding rates for fibre hemp vary between 40 and 150 kilograms per hectare (kg/ha), corresponding to plant densities shortly after emergence of about 200 to 750 plants per square metre. If the hemp is grown as a seed Source then the seeding density ranges from one to 24 kg/ha (five to 120 plants per square meter). Unless plant densities are very low (10 to 30 plants per square meter) the hemp crop will suppress weeds, and herbicides are not required. When planted on fertile soils, hemp is the best smother Coop for all kinds of weeds. If the hemp makes a short, weak growth, owing to unsuitable soil, drought or other causes, it will have little effect in checking the growth of weeds, but a good dense Coop will leave the ground practically free from weeds at harvest time.

Hemp seed and oil

The seed is light brown to dark gray, some cases mottled, containing between 25 to 35 per cent oil and 25 per cent protein. Hempseed contains eight essential proteins and three essential fang acids. It can be ground up and used in soups, cereals, cakes and other foods. Raw hempseed has commonly been used as feed for domesticated animals. The oil pressed from hempseed contains 55 per cent (flax has 58 per cent) linoleic acid and 25 per cent linolenic acid. Hemp oil is among the lowest in saturated fats at eight per cent of total oil volume; canola contains six per cent. Oil extracted from the seeds can be used in paints, Famishes, cooking, burning and precision lubrication, as well as in cosmetics and medical uses. Seed yields ranging from 400 to 940 kg/ha have been reported.

Is it profitable to grow?

Yield

Market returns from hemp stalk, fibre, hurds or seed depend on the quantity, quality, end use and the amount of value added processing. Ongoing research in Eastern Europe and Asian countries have improved hemp yield characteristics. For example, dry stem yields of 15 t/ha, 2.6 t/ha of total fibre and 0.94 t/ha of seed have been recorded.

Price

C&S Specialty Builder's Supply Inc. in Harrisburg, Oregon will pay Cdn $60 to $75 a tonne landed basis for defoliated chopped stalk. This is on par with she price of wood chips presently used by fibreboard manufacturers. Others in the industry say hemp should command a premium because of its superior characteristics compared to wood fibre. Harvesting chopped stalk is the lowest common denominator, generating a gross revenue of about $750 per hectare, comparable to Ontario Corn. However, revenue for the raw fibre is not captured. Until fibre extraction facilities are available, the raw stalk option remains attractive until the infrastructure required is in place. Under optimum conditions this would allow the raw fibre and the hurds to be sold separately generating danger returns per hectare.

Research and development is ongoing worldwide to develop mobile processors to crush, hammer and sift the hemp for use in the pulp and paper and fibreboard industries. K is estimated that value-added processing would reduce transportation costs by allowing 10 to 20 times more material to be shipped per volume. Lower transportation costs would increase met returns to the producers if end-users were closer to the source. Canada Cordage located in Kitchener, Ontario is the only cordage company in North America that processes natural fibre crops. At $800 per tonne for raw best fibre, hemp would compete with imported jute which is processed into yam, rope and electrical cable-filler.

Prices shown in the table are gross values, therefore production and transportation costs need to be factored in to determine farm gate prices. If hemp is approved for industrial or commercial production the prices would reflect supply and demand. The cast of production would also decline, for example, if certified seed were imported from the Ukraine it would cost at least $2700 a tonne landed basis. If certified seed was propagated domestically the price would decline substantially.

Although foreign varieties of hemp do well in their homeland it remains a question as to how well they would do in Canada. Since hemp production was prohibited. In Canada there has been limited preservation of germplasm in gene banks. Coupled with the extended lapse in North American breeding programs and declining interest in maintaining cultivars, an impoverishment of germplasm resources has resulted. Nevertheless, an enormous reservoir of natural variation is maintained by wild, weedy forms, which may prove invaluable in the future.

Future prospects

Although alternative fibre crops have usually proven to be more competitive in the past, a reawakening to hemp's industrial potential is being observed worldwide. In an age increasingly interested in sustainable agriculture and crop diversification, hemp offers some attractive possibilities.. It is exceptionally disease and herbivore-resistant, can be easily grown in a wide range of agricultural systems and is an excellent rotation crop which eliminates weeds. It is extraordinarily productive of biomass, and has been shown to have excellent potential for textile and cordage, paper, building materials, cellulose plastics and resins as well as using the seed for food and oil.

World production of vegetable fibre, 1992

Comparative nutrient withdrawn by hemp and grain crops

Gross return per hectare

Copyright © 1994. Agriculture and Agri-food Canada.