Harvesting Hemp With A Combine
Not all hemp harvesting is created equal. The method used is determined by a number of factors. How many acres need to be harvested? is the hemp being harvested for seed, biomass, flower and/or industrial applications? What capital, resources, and labor will be allocated toward hemp harvesting?
A majority of experienced growers prefer standard combining for hemp harvests, though they are quite expensive to acquire and maintain. However, they typically cut down your harvesting time to almost nothing. The mechanical settings, maintenance cost, and operation experience necessary to ensure optimum harvest are some of the factors to consider. If yours is a large application, the extra expense might be worth the investment. Time is money.
After gaining the necessary experience growing hemp at 2 to 4 acres, using a combine will be the most effective way of harvesting your yield. Unless you will be willing to get a team of manual harvesters, a combine is the only way to harvest hemp successfully in a short window of time. In that case, if hemp is going to be cut using a combine, you need to assess the correct conditions for harvesting beforehand.
Straight combining is also used, but is better suited to those harvesting seed than flower or biomass. A combine header is raised to cut the crop right under the seed head. Usually, that is one-third of the hemp plant (top 23-35 inches or 60-90 cm). That minimizes the amount of fiber that moves through the combine, increasing harvest efficiencies, and reduces fiber wrapping. Shorter plants within a canopy often might not have mature seed. Therefore, it might not be worth it to cut low in order to obtain seed head. Growers report that it is hard to harvest crops that are more than eight feet tall.
The newer combine models are better suited for handling hemp than older ones and require very little modifications. These new machines have larger cleaning areas and bigger cylinders. It is easier to operate headers at higher levels allowing for all hemp stands to be accommodated.
Almost all of the new combines in the market come with a rotary design. In some machines, swaths enter at the bottom of their cylinders – in earlier models, swaths would hit the rotor’s middle when exiting the feeder housing. This would cause the rotors to direct the swaths up their sides. This minor hesitation was normally enough for the hemp to go and wrap itself on the rotor’s front bearing. The flow of harvested crops in newer machines is much smoother.
Following is a suggested starting point to set a combine for harvesting of hemp.
- Cylinder Speed - 450 - 600 rpm
- Concave Size - 30 – 50 mm
- Fan Speed - 1070 rpm
- Sieve/Shoe Size - 3mm
- Chaffer Size - 10mm
Specs & Modifications
Conventional Auger Header
These headers provide more clearance than their counterparts, which allows the cut stalks to lay flat on the combine’s canvas. This makes the combine’s feed process smoother and evener. Though it’s worth noting that some hemp cultivators have enjoyed some level of success with more conventional headers as well.
Puckboard & Sheet Metal
Cultivators have discovered that some combine modifications can help prevent or reduce fiber wrapping . Shielding the exposed moving parts of the combine with sheet metal or puck board can help prevent such wrapping.
Deflectors can be added to narrow the feed-house inlet, keeping the crop away from the header reel ends and fibers from wrapping on pulleys and outer shafts.
ABS pipes can be placed over the front driveshaft to hamper wrapping.
Cables and Hydraulic Lines
Hydraulic lines and cables should be tied close to the combine to reduce the build-up of fiber.
Extending Header Hydraulics
For taller varieties, extending header hydraulics by about 30 cm will help lift the headers higher for greater clearance.
Swathing can be performed at 15-18% seed content before the bottom, and more mature seeds shell out. Swathing hemp when seed moisture is below 15% means increased shatter loss. Cut the crop at about 8 to 12 in. (20 to 30 cm) high.
After you have swathed the crop, you can leave it for two to about four days to allow for seed moisture to drop a few percentages. The leaves will dry down. If left in the swath for more than two days, stem fibers will dry down too much and become a rope-like material that’ll easily plug the combine. In the right drying conditions, seed moisture could go down to about 10 to 12% at combining.
Draper headers installed on common swathers are suitable for the industrial swathing of hemp. New guards and knives are recommended as they help keep the cutter bar unclogged. How wide the swather is will be determined by the capacity of the swather and combine. Some growers have built shields using sheet metals or puck boards to help reduce the build-up of fiber on exposed pulleys, belts, and other moving parts.
Consider swathing only when there is no rain in the forecast for days. If opting for this method, swath your hemp and leave it for two to five days to dry down. However, make sure you combine the harvest before it gets too dry. If the stems get too dry, the fibers in the stalks will start to shatter and separate, causing the resulting fine fibers to wrap on hemp harvesting equipment like chains and bearings.
You mustn’t swath your hemp if the surface of the soil surface is still wet or if there are chances of rainfall. If it is still wet, the plant will sprout quite fast in the head, especially at the bottom of the swath.
Make sure your seed doesn’t come into contact with the ground as it could develop mold and get coliform contamination. Plus, it increases the chances of bacterial development. All of these are factors that affect the quality of the harvest and downgrade the seed.
It is worth noting that seeds can also get contaminated by manure, dirt, and small stones amongst other things.
When harvesting during damp conditions, remember that standing hemp dries faster than swathed hemp.