Seeding Date
Seeding date can have multiple impacts on hemp production.The pros and cons are dependent on the producer’s situation. Limited research has been done and the following observations have been documented in Western Canada:
- An early seeding date, May 1 to 15, has generally resulted in a higher mortality rate due to cold soils causing seedling pathogens. Producers may want to consider a higher seeding rate to compensate for the higher mortality however this adds to the cost of production. The earlier seeding date also produces taller plants with a thicker stalk. This is due to the longer vegetative growing period and lower plant populations. It is important to note that a thicker stalk produces more hurd fibre and less bast fibre whereas a thinner stalk produces less hurd and more bast.
Thin stalk less hurd, thick stalk increases hurd
Consequently seeding date is an important consideration depending on the processors requirements.
- The yield advantage to earlier seeding is not conclusive. There are many factors (i.e. soil temperature, moisture) that impact yield and an earlier seeded crop can be more vulnerable to these factors. This is an area in which further research is required.
- A mid-seeding date, May 16 to June 10, is more ideal for hemp production. There is less plant mortality due to warmer soils giving rise to faster emergence. The uniform stand results in better weed competition, a more uniform seed maturation and improved ease of harvest. Plant height is somewhat shorter than with the early seeding date. It is important when considering seeding date to know the crop insurance deadlines.
- Harvest date will not be significantly impacted by seeding dates due to the photoperiod effect.
- A late seeding date, June 15 to July 7, is not recommended and producers should only consider this option as a last resort when there are no other cropping options available. It may be a viable option over summer fallow if weather conditions have prolonged seeding intentions. Producers are advised to review the economics since crop insurance is not available. Observations have shown yields to be reduced and plant height to be shorter.
In other geographic regions in Canada with a longer season, optimum planting dates may be earlier. More research is required in other regions in Canada.
Seeding Rate
The end use of your hemp crop will dictate the seeding rate.
A target seeding rate for grain production is suggested to be 100 to 125 seeds per square metre (10 to 12 plants/ft2, 20-25 lbs per acre). Refer to your seed supplier for specific variety seeding rate information.
When growing hemp for fibre only production, it is suggested the seeding rate should be double what is used for grain production (200 to 300 seeds per square metre). The reason for higher seeding rates is to ensure a higher quality fibre crop. Good quality hemp fibre comes from plants that are “pencil thin”. Higher seeding rates will ensure that there will be a high plant population with tall thin plants with longer internodes. Research is limited in Canada to determine proper seeding rates to achieve high yielding and good quality fibre.
Low plant populations will not provide competition for early weed control. Hemp can have a high mortality rate under adverse growing conditions. Research has shown that 10% to 70% seed mortality can occur under varied climatic conditions. Based on observations, reasons for high mortality are generally attributed to:
- poor growing conditions at seeding
- seeding too deep
- cracking of the seed coat
- toxicity from high rates of seed placed fertilizer
- residual herbicides from previous crop
Seeding Considerations
To enhance hemp plant stands:
- Seed into warm soil.
- At least 8 to 10 degrees Celsius in the top 5 cm (2 inches) for at least 2-3 days.
- Usually after mid-May in Western Canada.
- Seed into a firm seedbed with good soil to seed contact.
- Seed shallow, 1.25 cm (0.5 inches) to on 2.5 cm (1 inch) maximum.
- Do not seed deep into moisture in a dry year. In spite of being a moderately large seed, hemp will struggle to emerge from deep seeding.
- Avoid seeding before an abundance of precipitation is anticipated.
- Seed after a heavy rain rather than before.
- Although most seeding equipment will work for hemp it is important to monitor seeder output to:
- Avoid seed cracking
- Use lower air volumes. Cracking occurs in the manifolds when air volume is too high.
- Take into account mortality rate. A common percentage of 30% mortality rate is often used when calculating seeding rates. If spring seeding conditions are ideal this rate can be lowered.
- Avoid compaction
- Wheel tracks or other soil compaction, as with other crops, will show up under certain conditions.
- Avoid excessive trash that can keep soils cool and could cause hair pinning with disc drills.
Depth control wheels on disk drills results in better control of seed placement
Tracks reduce soil compaction
Row crop planters plant seeds more evenly spaced and at a consistent depth
Triple tires reduce compaction
Seed Calculations
To calculate seeding rates, consider using the 1000 total kernel weight (TKW) and seedling mortality rate. Refer to online seeding rate calculators.
1000 TKW are variety dependent as there is a substantial size difference in seed when comparing varieties and can also be affected by environmental conditions year to year. 1000 TKW can vary from 13 grams to 23 grams for the varieties currently being grown. This can have a huge effect on your seeding rate and overall plant stand.
The following chart demonstrates the potential kernel weight difference between varieties so it is important to use a seeding rate calculator to determine seeding rates for each variety.
1000 Kernel Weight
|
Variety
|
Average 1000 Kernel Weight (g)
|
Site Years
|
Minimum 1000 Kernel Weight (g)
|
Maximum 1000 Kernel Weight (g)
|
Seeding Rate* (lbs/acre)
|
|
Alyssa
|
18.1
|
7
|
15.7
|
19.0
|
24.9
|
|
Anka
|
16.2
|
7
|
13.5
|
17.5
|
22.3
|
|
Canda
|
19.5
|
8
|
14.8
|
21.5
|
26.8
|
|
CanMa
|
16.3
|
2
|
15.5
|
17.0
|
22.3
|
|
CFX-1
|
16.9
|
8
|
14.1
|
18.5
|
23.2
|
|
CFX-2
|
15.9
|
8
|
14.6
|
17.0
|
21.8
|
|
CRS-1
|
17.3
|
8
|
15.6
|
19.0
|
23.8
|
|
Debbie
|
18.0
|
3
|
16.4
|
19.5
|
24.6
|
|
Delores
|
18.2
|
7
|
14.5
|
20.0
|
25.0
|
|
Finola
|
13.1
|
8
|
11.0
|
14.6
|
18.0
|
|
Joey
|
18.3
|
5
|
15.3
|
19.6
|
25.1
|
|
Jutta
|
18.4
|
3
|
17.4
|
19.8
|
25.2
|
|
Petera
|
20.0
|
1
|
20.0
|
20.0
|
27.5
|
|
Silesia
|
15.5
|
4
|
14.2
|
17.0
|
21.3
|
|
USO14
|
17.0
|
4
|
15.0
|
18.0
|
23.3
|
|
X59
|
17.2
|
4
|
13.5
|
21.0
|
23.6
|
|
* Seeding rate assumptions:
|
|
|
|
100
|
Target seeds per square metre
|
|
|
95.0%
|
germination
|
|
|
|
30.0%
|
mortality
|
|
|
|
Source: PCDF, CHTA National Hemp Variety Trials