Growing Hemp in NZ

Global production of industrial hemp

Many countries around the world currently grow Industrial Hemp, These include those who have continually grown hemp such as China, France, India, Romania, Hungary, North Korea, Ukraine and Russia, while other countries have only recently begun researching a hemp Industry. These include England (1993), Holland, Germany (1995), Canada (1994), Australia (1990), and New Zealand (2002). (The dates shown indicate the years in which these countries began their trials).

Hemp is an ideal rotation crop helping to break up and condition the soil for following crops due to its long root structure penetrating deep into the soil when fully matured, this helps aerate the soil. Significant amounts of heavy metals have been removed from polluted ground by hemp crops in Poland and other Eastern European countries.

Fertilising and nutrients

Whilst it is true that hemp is grown in small plots in so-called under-developed countries with no fertiliser, often in poor soils, the reality is that Hemp (Cannabis Sativa L) is not a nitrogen fixer, and to produce it on the scale necessary to make it an economically viable crop in the modern world, hemp requires finely tilthed soils, that are rich in organic matter.

Industrial Hemp requires nitrogen, phosphorous & potassium to produce maximum economic returns. And although specifically developed genotypes have been produced in Russia and Hungary that require minimal or no fertiliser, the real facts appear to be if you farm hemp, you have to look after both it and the soil.

To achieve an optimum hemp yield, twice as much nutrient must be available to the crop as will finally be removed from the soil at harvest. A hemp field produces a very large bulk of plant material in a short vegetative period. The nitrogen uptake is most intensive the first 6 to 8 weeks, while potassium and in particular phosphorous are needed more during flowering and seed formation.

Industrial hemp requires 105 to 130 lbs/ac (120 to 150 kg/ha) nitrogen, 45 to 70 lbs/ac (50 to 80 kg/ha) phosphate and 52 to 70 lbs/ac (60 to 80 kg/ha) potash.

Courtesy of: Doug Brown , White Buffalo Renewables, Canada 1995

Best hemp growing locations

There is some debate on this, given that the plant is and has been grown throughout the world in all sorts of soil & climatic conditions. A fair assessment would be that Industrial Hemp is global in distribution with regional specific cultivars obviously performing well in their regions of origin. In the New Zealand context as an agricultural crop, Hemp is more suited to temperate climates, with reasonable rainfalls (3-4 inches per month). The further from the equator the better as Hemp is light / daylength sensitive. Read more about hemp growing locations and regional cultivars here.

Soil temperature and water

Hemp should not be planted until soil temperatures reach at least 6- 8°C, in the first month or so. The seedlings require 3-4 inches of rain or irrigation, during this first month of growth, 25-30 inches rainfall per annum. As they grow larger these requirements drop dramatically due to the dense canopy enabling water retention and the deep taproot seeking out the water table. Hemp tolerates temperature extremes, and Industrial Hemp is frost tolerant. In the drier regions of New Zealand suitable for growing Industrial Hemp such as Canterbury, Tasman & Hawkes Bay it is highly likely that irrigation would be necessary. Industrial hemp is also sensitive to soil compaction and waterlogged soil conditions.

Pests and diseases affecting hemp

The International Hemp Association has published a two-part review identifying over 300 insect pests. John McPartland wrote: “Cannabis has a reputation for being pest free. Actually, it is pest tolerant. Most Cannabis pests are insects. Nearly three hundred insect pests have been described on Hemp & Marijuana, but very few cause economic crop losses”. Further on, he states: “The claim that Cannabis has no diseases is not correct. Cannabis suffers over one hundred diseases, but less than a dozen are serious”. In his final analysis, he describes industrial hemp as “hardy, tolerant, versatile”.

Hemp suppresses weeds

For every text on hemp going back thousands of years, see “Marijuana The First Twelve Thousand Years” by Ernest L Abel, which describes in detail the smothering ability of Hemp. There is however one catch, which is that the plant is vulnerable at the seedling stage.

Once it is a week or two old, and provided the strike rate has been high & evenly distributed, nothing else seems to be able to compete. Hemp has been successfully used as a smother crop throughout history. Even when grown as a seed crop at a density of one or two plants per square meter, hemp shows this ability to smother other plant life. The Chinese have a seed variety with seeds produced in abundance the size of small peas & reportedly use NO herbicides in their production.

Hemp has both male & female plants

This is the cannabis plant’s natural state and is called dioecious, which means that the male and female are separate plants. The male plant bears the pollen, while the female plant grows the seeds. The male plant also has superior, finer, stronger fibre, although the fibre quality reduces significantly in both plants once the reproductive process starts.

It is worth noting that only the female cannabis plant is considered useful by marijuana growers, the male plant is pulled and discarded for fear of pollinating the female and thus reducing the female’s THC content. Authorities should note this fact, as, in the NZHIA view, it demonstrates the futility of attempting to produce marijuana in industrial Hemp crops. Click here for more information about the male and female plant specifics and cultivar variations.

Harvesting and processing

Harvesting time is dependent on end usage. Hemp is harvested prior to seeding for the strongest fibres, or when the seeds are mature for a multi purpose crop. The crop is hard on conventional farm machinery & some minor modifications are required due to the long stalk length and its toughness.

Sickle side cutters (forage harvesters?) are used in combination with big square or round bailers. No doubt, as the crop develops worldwide, more of the appropriate Modern machinery will be developed. For now, traditional machinery does the job, if somewhat onerously.

Harvesting for high quality fibre takes place as soon as pollen is shed, 70 – 90 days after sowing, although this varies greatly dependant on cultivars and location. For seed 4- 6 weeks later, (when at least 60% of the seed is ripe).

Click here for information on the retting and processing that must take place after harvest.

Local Bio Regional Development

New Zealand and its rural communities are desperately seeking sustainable alternative land uses. Hemp, because it provides enormous amounts of value added potential offers just such an alternative. (See “After Harvest” for more info on how the processing can benefit local regional development.)

The Idea behind the Bio Regional Development of a hemp crop, involves local industry and the community working with local farmers to provide and manage suitable machinery and infrastructure close to the crop. The size and extent of this processing and the associated returns will depend on the location, local support, and financial commitment available. Suitable locations do exist in New Zealand for this Bio Regional Development to occur.

This value added production, done locally, brings in the export dollars once the primary produce/commodity is sold.


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