Hemp (Cannabis sativa)

How well established is this crop?

Initial trial plantings of these crops may have been done. There is little information on plant suitability to the region and no current information on markets, commercial returns or current research. This is a new crop.

Background

The plant known as industrial hemp, has been grown by various civilisations for centuries. In fact the first recorded use of this plant was in Chinese texts dating back 8500 years. Industrial hemp is essentially the same plant as Marijuana however the drug content, known as THC (tetrahydrocannabinol) is much lower. The industrial hemp plant is thought to have originated in parts of Asia but since that time it has become common all over the world. Early settlers took this plant with them when they settled new lands because if was hardy and almost guaranteed to grow. The final plant could then be use for a range of purposes.

The first of these is the fibre production. Hemp fibres are long and strong and can be used for a range of products. Nandoor Tanzos and MP in parliament is known for wearing hemp suits. A company in Nelson has developed a process where hemp fibres and wool are combined into an Eco-pink batt. Paper and composites for automobiles such as Mercedes are also be made from hemp fibres. One text claims that Hemp fibres can be used for over 25,000 industrial products from cellophane to dynamite.

The other main use of the industrial hemp plant is to use the seed to produce oil. This oil contains high levels of alpha-linolenic and linoleic acid. These products are known to be essential for healthy human growth. Although these oils can also be obtained for fish and flaxseed the oil from industrial hemp is thought to have a better flavour.

In the past few years, the New Zealand government has given trial consents to plantings of industrial hemp crops. These have been spaced all over the country including Southland, Otago and Canterbury. Initial results from these crops were mixed and more research has been recommended.

Climate

Industrial hemp is a hardy plant that grows in almost any climate. In general it does well in any climate that will ripen a crop of corn.

Winter Chilling and Frosts

Industrial hemp is relatively tolerant of frosts during the growing season. However if frosts get much over -8C for any period, then damage to the crop is likely.

Rainfall and Irrigation

Water is essential during the establishment phase of an industrial hemp block. Regular rainfall or irrigation will ensure the crop keeps growing.

Wind

Hemp is grown as an arable crop on a paddock scale. Although the plant is tall, shelter from the wind is hard to provide.

Soil

The key physical requirement of the soil for industrial hemp growing is a free draining root zone. Clay soils are not recommended. Sandy soils are acceptable, if irrigation and fertilisers can also be provided.

Fertility

If growing hemp for fibre, moderate levels of fertility are acceptable. If growing the plant for oil then added side dressing of nitrogen and potassium may be needed during the season. All applications should be done based on soil and foliage tests.

Weed Control

Having a clean bed at planting is advisable as this crop is grown on a broad acre basis. Weed control is very difficult after planting because no chemicals are registered. Watch out for perenniel wedds including thistles, couch, yarrow and docks.

Varieties

There are a large number of breeding programs for hemp all over the world. They are producing varieties of both fibre hemp, and oil seed hemps. A lot of trial work will be required before ideal varieties are identified for New Zealand conditions.

Pests and Diseases

Birds have been the major problem on the trial plantings of hemp in New Zealand to date. They get into the crop before harvest and eat the seeds.

Layout

In general, seeds are planted at a rate of 100m2. However this does change depending on the final use of the crop (fibre or seed) and which variety is used. Advice from breeders and other growers is recommended before deciding on what rate is the best.

General Management

Once planted, watching for water stress and adding extra fertiliser if required are the only general management issues a grower has to watch.

Harvest

For fibre production, the stems are cut just when the pollen is being released and before seeds are set. This is usually 4 months after planting. The plant material is left in the paddock to dry and is turned several times. When moisture contents are down to approximately 15% the crop is baled and stored before further processing.

For seed production the plants are obviously left longer. This usually takes approximately 5 months. After the seeds are set and fill out, they are harvested using a header (the same machinery we use on cereal crops in New Zealand). Shorter varieties are more common for seed production as they are easier to access with common machinery. After harvest, seed is dried and stored before processing.

Equipment

Industrial hemp is grown on a paddock scale and machinery requirements will depend on the final use of the plant.

Returns

It is very difficult to estimate returns for New Zealand grown industrial hemp. It will be a low value product if grown purely for processing. Adding value directly on the farm will mean more profit.

Contacts

More information on the growing of hemp in New Zealand can be found on the Ministry of Health website http://www.moh.govt.nz/moh.nsf