Hemp Factsheet from an Agricultural Standpoint

 

1. 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 1/4" to 3/4". 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 fibers 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 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.

2. Soil and Soil Preparation

Soils

Industrial hemp can be grown on a wide variety of soil types. Hemp prefers a sufficiently deep, well-aerated soil with a pH pf 6 or greater, along with good moisture and nutrient holding capacity. Poorly drained soils, however, are not recommended as excess water after 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 to 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.

3. Nutrition

To achieve an optimum hempyield, 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 vegetative 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./acre (120 to 150 kg./ha) nitrogen, 45 to 70 lbs./acre (50 to 80 kg/ha) phosphate and 52 to 70 lbs./acre (60 to 80 kg/ha) potash.

4. 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.

5. Weed Control

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 for the next crop.
Notice the canopy effect created by the dense planting. When properly planted and cultivated, weed control is a non issue.

6. 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 41 - 46 deg.F. (6 - 8 deg C.). Hemp seed germinates within 24 to 48 hours, and emerges in 5 to 7 days with good moisture and warm temperature.

7. Plant Population

High yields of high quality fiber can be achieved with proper plant density. Seeding rates of 250 to 400 viable seeds per square meter are probably ideal, depending on soil type, soil fertility and cultivars. The seed or grain production will require lower seeding rates.
This stand is ready to harvest. Note the uniformly dense population.

8. Breeding Characteristics

Generally, hemp is a dioecious plant ( a plant having the stamens [male] and the pistils [female] borne by separate plants of the same species ). However, there are three classifications of varieties:

• monoecious varieties - when male and female flowers develop on the same plant;
• dioecious varieties - with distinct male and female plants;
• female predominant varieties, obtained by pollinating dioecious females with monoecious pollen.

9. Cultivar Types

There are two types of industrial hemp based on their use.

• fiber cultivars - with long stalks and little branching; (shown to the left)
• seed cultivars - with shorter stalks, larger seed heads and may have numerous branches (seed contains 30 - 35% oil). (shown to the right)

10. Rotation

Hemp can be grown on the same ground 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. In 1996, Kenex Ltd. of Canada observed that hemp may significantly reduce the population of soybean cyst nematodes.

11. Harvest

Harvesting of hemp for high quality fiber occurs as the last pollen is shed. Harvesting for seed occurs 4 to 6 weeks later, when 60% of the seed has ripened. Fiber hemp is normally ready to harvest in 70 to 90 days after seeding. The end use of the product may significantly impact on the harvesting method.
Kennex Ltd. of Canada, is developing a harvesting system that will be compatible with the new processing technology. For fiber production, the crop will be cut, dew retted in the field, baled and stored or processed.

12. Retting

The bast fibers are obtained by retting - a microbial decay of pectin, the substance that glues the fiber to the woody core of the hemp stem together. Retting is carried out in the field and depending on the weather, takes 12 to 18 days to complete. 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 fibers turn a golden color and separate easily from the mass to finer fibers.

13. Yield

Based on yield data from 1995 and 1996 along with preliminary estimates for 1997, yield expectations are between 3 to 5 tons of baled hemp stalks per acre on well drained loamy soils in South Western Ontario.

14. 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 other covered storage.
The information provided in this fact sheet is based on research sponsored by Kenex Ltd., RR#1, Pain Court, Ontario, Canada, N0P 1Z0. The information reflects research data gathered from the test plots at Ridgetown College and the Kenex pre-commercial field trials at Pain Court. Information is based on research from 1995 thru 1997 at these two facilities.