(Cairns... Far North Queensland)
INDUSTRIAL HEMP INDUSTRY
Hemp - A Versatile Plant
Essentially there are two
fractions to the plant, Seed or Grain and Fibre. Some products made from the
fibre include: all grades of paper, textiles, geo-textiles, structural
reinforcement building materials, fibreglass replacement products, lightweight
sandwich boards, composite boards, absorbency products such as kitty litter,
potting mix, nappies and fem-care products and fuel.
These are but a few of the
potential areas where hemp is already being used but present demand is having
some difficulty in finding supply. Further, hemp fibre has been found to be a
lighter, stronger alternative to fibreglass so it is for technical reasons as
well as environmental reasons hemp is in demand.
HEMP CULTIVATION - GROWERS GUIDE
Hemp (Cannabis sativa L.) is
an annual, herbaceous plant with a slender stem, ranging in height from 4 to 15
feet and a diameter from ¼" to ¾". The innermost layer is the pith,
surrounded by woody material known as hurds. Outside of this layer is the
growing tissue, which develops into hurds on the inside and into the bast fibres
on the outside. The stem is more or less branched, depending on the crop
density. When sown thickly the stems do not branch. The leaves are of a palmate
type and each leaf has 7 to 11 leaflets, with serrated edges. The strong taproot
penetrates deep into the soil. However, if the soil conditions are unfavorable,
the main root remains short, while lateral roots become more developed.
Industrial hemp can be grown
on a wide variety of soil types. Hemp prefers a sufficiently deep, well-aerated
soil with a pH of 6 or greater, along with good moisture and nutrient holding
capacity. Poorly drained soils, however, are not recommended as excess surface
water after heavy rains can result in damage to the hemp crop. Hemp is extremely
sensitive to flooding and soil compaction.
A fine, firm seedbed is
required for fast, uniform germination of hemp seed. Conventional seedbed
preparation and drilling are probably ideal. The seedlings will not emerge
uniformly if the seed is placed at a depth greater than 2 inches. "No-till
systems" can also be used with good results, but may be more vulnerable to
erratic emergence depending on the growing season.
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 80
to 100 lbs/ac (90 to 112 kg/ha) nitrogen, 35 to 50 lbs/ac (39 to 56 kg/ha)
phosphate and 52 to 70 lbs/ac (60 to 80 kg/ha) potash.
Hemp prefers a mild climate,
humid atmosphere, and a rainfall of at least 25-30 inches per year. Good soil
moisture is required for seed germination and until the young plants are well
Industrial hemp is an
extremely efficient weed suppressor. No chemicals are needed for growing this
crop. Industrial hemp is a low maintenance crop. There are no registered
chemicals for weed control in hemp. A normal stand of 200 to 300 plants per
square meter shades out the weeds, leaving the fields weed-free at harvest.
Time of Seeding:
The best time to seed hemp
should be dictated by the weather and soil conditions, rather than the date on
the calendar. Hemp can be seeded as early as two weeks prior to corn provided
that soil conditions are optimum. However, seeding should not begin until soil
temperatures have reached a minimum of 42 - 46 °F (6 - 8°C).
Hemp seed germinates within
24 to 48 hours, and emerges in 5 to 7 days with good moisture and warm
temperature. Hemp grown for fibre should be seeded as early as possible while
hemp for grain should be seeded later to minimize the height of the stalk.
High yields of high quality
fibre can be achieved with proper plant density. Seeding rates of 250 to 400
viable seeds per square meter (50 - 60 lbs/acre) are probably ideal, depending
on soil type, soil fertility and cultivars. The seed or grain production will
require lower seeding rates in the 35-to-45 lbs/acre ranges. Crops grown with 15
to 20 lbs/acre of seed may be at risk with regards to weed infestation.
Generally, hemp is a
dioecious plant. However, there are three classifications of varieties:
Cultivar Types: There are
two types of industrial hemp based on their use:
Both types have low THC
content, of less than 0.3%.
Hemp can be grown on the
same land for several years in succession but rotation with other crops is
desirable. Hemp responds well to most preceding crops. It is also possible that
introduction of hemp in a crop rotation might improve the soil health. Our
observation in 1996 showed that hemp might significantly reduce the population
of soybean cyst nematodes. We need at least 3 years of evaluations for this data
to be conclusive.
Harvesting of hemp for high
quality fibre occurs as soon as the last pollen is shed. Harvesting for seed
occurs 4 to 6 weeks later, when 60% of the seed has ripened. Fibre hemp is
normally ready to harvest in 70 to 90 days after seeding. The end use of the
product may have a significantly impact on the harvesting method. Kenex Ltd
(USA) is developing a harvesting system that will be compatible with the new
processing technology. For fibre production the crop will be cut, dew retted in
the field, baled and stored, or processed.
The best fibres are obtained
by retting - a microbial decay of pectin, the substance that glues the fibre to
the woody core of hemp stem together. Retting is carried out in the field and
depending on the weather it takes 14 to 21 days to be completed. During retting,
the stems need to be turned one or two times in order to allow for even retting,
since the stems close to the ground will remain green while the top ones are
retted and turn brown. Retting is complete when the fibres turn golden or
greyish colour and separate easily from wood in finer fibres.
Based on yield data from
1995, 1996 and 1997 yield expectations are between 3 to 4 tons of baled hemp
stalks per acre on well-drained loamy soils.
For storage, the moisture
content of hemp stalks should not exceed 15%. The bales can be stored for a long
time in dry places, which could include storage sheds, barns or any other
The information provided above is based on 1995, 1996 and 1997 research data that was collected from test plots at Ridgetown College and the Kenex Ltd pre-commercial field trials in Pain Court (USA).
Written and Authorised by Selwyn Johnston, Cairns FNQ 4870 Australia