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September 1998
Appendix D
Agronomic Backgrounder
(by Peter Dragla)
D1. A Grower's Guide to Hemp
PLANT DESCRIPTION: 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 0.25 to 0.75 inches. 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 o n the crop density. When sown
thickly the stems do not branch. The leaves are of
a palmate type and each leaf has seven to eleven leaflets,
with serrated edges. The strong tap-root penetrates
deep into the soil. However, if the soil conditions
are unfavorable, the main root remains short, while
lateral roots become more developed.
SOILS: Hemp can be grown on a wide
variety of soil types. Hemp prefers a sufficiently
deep, well-aerated soil with a pH of six or greater,
along with good moisture and nutrient holding capacity.
Poorly drained soils, however, are not recommended
as excess surface water and heavy rains can result
in damage to the hemp crop. Hemp is extremely sensitive
to flooding and soil compaction.
SOIL PREPARATION: 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 two inches. No-till systems can also
be used with good results, but may be more vulnerable
to erratic emergence depending on the growing season.
NUTRITION: 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 six to
eight weeks, while potassium and in particular phosphorous
are needed more during flowering and seed formation.
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.
GROWING CONDITIONS: 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 established.
WEED CONTROL: Hemp is an extremely
efficient weed suppresser. No chemicals are needed
for growing this crop. A normal stand of 200 to 300
plants per square metre shades out the competition,
leaving the fields weed-free at harvest for the next
crop.
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 ºF (6-8 ºC), Hemp seed
germinates within 24 to 48 hours, and emerges in 5-7
days with good moisture and warm temperature.
PLANT POPULATION: High yields of
high quality fibre can be achieved with proper plant
density. Seeding rates of 250-400 viable seeds per
square metre are probably ideal, depending on soil
type, soil fertility and cultivars. The seed or grain
production will require lower seeding rates.
BREEDING CHARACTERISTICS: Hemp
is a dioecious plant. However, there are three classifications
of varieties. Monoecious varieties have both
male and female flowers developing on the same plant.
Dioecious varieties have distinct male and
female plants. Female predominant varieties
are obtained by pollinating dioecious females with
monoecious pollen.
CULTIVAR TYPES: There are two types
of hemp based on their use. These are fibre cultivars
and seed cultivars which have shorter stalks, larger
seed heads and may have numerous branches (seed contains
30-35% oil). Both types have low-THC content of less
than 0.3%.
ROTATION: Hemp can be grown on
the same land for several years in succession but
rotation with other crops is desirable. Hemp responds
well to soil from 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 may significantly reduce the population
of soybean cyst nematodes.
HARVEST: Harvesting of hemp for
high quality fibre occurs as soon as the last pollen
is shed. Harvesting for seed occurs 4-6 weeks later,
when 60% of the seed has ripened. Fibre hemp is normally
ready to harvest in 70-90 days after seeding. The
end use of the product may have a significant impact
on the harvesting method. Kenex Ltd. 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.
RETTING: The bast fibres are obtained
by retting a microbial decay of pectin, the substance
that glues the fibres to the woody core of hemp stem
together. Retting is carried out in the field and
depending on the weather it takes 12-18 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 colour
and separate easily from wood in finer fibres.
YIELD: Based on yield data from
1995 and 1996 along with preliminary estimates for
1997 field expectations are between three to five
tons of baled hemp stalks per acre on well-drained
loamy soils in Southwestern Ontario.
STORAGE: 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
covered storage.
| Source: |
Peter Dragla as found in the document, Commercial Hemp-Spring 1998 Edition. |
D2. Other Sources of Information We know hemp can
be grown in various regions of Canada. It is not clear
yet, however, what yields and economics can be expected
under various commercial-scale growing conditions.
To quote one contact, "It is the oldest grown
crop we know nothing about - a substantial part of
the literature cannot be substantiated".
The hemp-marijuana lobby effort has generated volumes
of information. Much of it can be found on the Internet.
The reader must, however, be aware that like any information
source, care must be taken to understand who posts
such information and what are there motives in doing
so. You will literally spend days searching the Internet
given the amount of literature and news groups available.
The following reports were found to be useful and
have been sourced for this study. They contain information
from agronomics to economics. For your convenience,
we have also listed their Internet websites. Please
note some of these reports require the software application,
Adobe Acrobat Reader, as they are archived
in PDF format:
- Government of Canada: Report on Hemp by Gordon Reichert Bi-weekly Bulletin December 16, 1994 Vol. 7 No. 23:
www.psibear.mb.ca/reichert.htm
- Health Canada Commercial Production of Hemp: Fact Sheet (March 1998): www.hc-sc.gc.ca/main/drugs/drhtmeng/hemp.html
- Manitoba Agriculture Hemp Factsheet: www.gov.mb.ca/agriculture/facts/hemp/bko01s01.html
- Ontario Ministry of Agriculture, Food and Rural Affairs Hemp Factsheet
(OMAFRA):www.gov.on.ca:80/OMAFRA/english/crops/facts/hempprod.htm
- Commercial Hemp Cultivation in Canada-An Economic Justification by David Marcus (as found within the homepage for the
North American Hemp Council): www.naihc.org/
- Hemp Factsheet by A. Oliver and H. Joynt of the British Columbia Ministry of Agri-Food:
www.agf.gov.bc.ca/croplive/plant/horticult/hemp/hmpinf.html
- The Economic Impact of Hemp In Kentucky, July 1988, Thompson, Berger and Allen, University of Kentucky:
www.hempgrowers.com/frames.html
- Industrial Hemp: Global Operations-Local Implications, July 1998, Valerie Vantreese, Department of Agricultural Economics,
University of Kentucky: e-mail address: vvantree@ca.uky.edu
- An Evaluation of Opportunities in the Atlantic Agri-Products Sector for Hemp, March 31, 1997, Scovil Associates and Dr. Jim
White of InfoResults Ltd., www.novasight.com/AAPC/
List of research reports available.
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