Harvesting hemp for the fibre is less troublesome than harvesting hemp for the grain or for dual purpose (grain and fibre). Forage harvesting and handling implements, commonly used by the Prairie farmers, perform well without major modifications when dealing with hemp grown for fibre. Specialized equipment for cutting hemp for fibre is available from some European or Australian vendors; however, working width or capacity of the overseas models may not be adequate to meet requirements of Canadian hemp growers who farm much larger acreages than their counterparts in other jurisdictions.
Depending on equipment availability, hemp cutting can be done using a discbine (Figure x), a disc mower (discbine without a conditioner), or even a straight sickle mower (Figure xi). Conversely, swathers (Figure xii) and haybines do not work well, particularly with very tall crop as they have tendency to wrap long stems on the reel. Depending on the make and model of the swather, the opening may not be large enough to allow the hemp to go out. Additionally, tangled stems resulted from swathing require longer retting times (or sometimes do not ret properly) as they dry up quickly; however, swathers have been used successfully for cutting the stubble after combining.
Figure x - Hay Conditioner or Discbine
Figure xi - Sickle Mower
Figure xii - Swather
An additional advantage of using a discbine is that cutting speeds can reach 9 mph compared to 1.5 mph achieved by swathers cutting fibre-type hemp cultivars. A straight sickle mower is the most suitable for harvesting hemp for textile applications. This implement leaves cut stems intact, laid neatly and organized directly on the ground (Figure xiii). Such stems arrangement is conducive to faster and more uniform retting.
Figure xiii - Fibre in field after cutting with sickle mower
Hemp should be harvested 10 cm above the ground to avoid cutting through the hard woody portion of the stem found closer to the soil. Leaving stubble considerably taller than 10 cm results in loss of fibre yield. Keep in mind that the knives in cutting implement of choice have to be sharpened frequently to handle the tough, fibrous stems.
Fibre Harvest Equipment Modifications to Consider Sickles and Mowers
- The conditioning rolls should be opened up enough so that there is enough friction to pull the material through, but not crush it too much. Crushing the stalk increases drying and retting but also increases the loss of the hurd in the field.
- Spread the swath out as much as possible to facilitate drying, reducing the potential for mould and matching the size of the baler.
- The end of each roller may need an additional guard put over the end to keep the fibre moving out from the roller end and prevent wrapping.
- Ensure the conditioner rollers are very smooth so they will not catch fibre and start wrapping. Conditioners with metal rollers may be smoother and wrap less.
- Ensure there is a good divider on the end of the unit. This will make dividing the crop a lot easier and prevent the crop from building up and plugging the end of the machine.
- When using a swather ensure the swath is not too large for the baler to be able to pick up. Pull out and use only a portion of the swather width.
- Make a swath size that will fit into the pickup and capacity of the baler. A swath the full width of the baler makes for a better bale and is easier to pick up as weaving is not required.
- Shield all bearings, rollers, belts and canvases that are exposed to the hemp.
- Protect under the swather so hemp stalks will not stick into the swather frame.
- Use a new knife with sharp guards.
- Put a shield over the first 4 inches of the bottom of the canvas. This closes the hole between the bottom of the canvas and the swather knife and prevents stalks from being stuck under the canvas.
- Stem size has a direct impact on the ease of cutting. The smaller the stems, the harder to cut. This means the knife has to be in excellent shape.
- Pick up reels are preferred.
- Cut on dry, warm, sunny days with low humidity.
- Humidity and dew will also reduce the length of cutting time in the evening.
- A swath roller as used for canola makes for a uniform swath and reduces the number of stalks that will stick up and catch on the bottom of equipment.
- Hard and soft core balers could be used.
- Ensure all guards are in place.
- Inspect the machine for exposed shafts or chains and cover them.
- Protect under the PTO shaft from the tractor to the baler.
- Ensure the bottom of the tractor is smooth from the front to the pickup of the baler so stalks will not catch. Mounting of a tarp or other methods may be necessary to prevent the swath from catching.
- Good baling starts with a well laid swath. The wider the swath, the less weaving will need to be done by the baler.