Flax TIPS: Threshing and Storing Flax

September 21, 2016 0 Comments

Whether you decided to swath, use a pre-harvest/desiccant or are waiting for frost, here are some considerations before starting to thresh and store flax.

Threshing Flax

  • Ideally, flax is combined at 10% seed moisture, 10.1-13.5% moisture is considered to be “tough”.
  • Flax is more susceptible to mechanical damage (cracking, chipping) due to a thin seed coat.
  • Adjust cylinder speed, fan speed, sieve opening and concave clearances to prevent cracking.
  • Use the manufacturer’s recommendations to start and adjust setting depending on environmental and crop conditions.

Frost Desiccation

Waiting for frost? Here’s what you need to know:

  • Immature seeds are damaged around -3 to -5 C range.
  • Leaves and stems are damaged around -4 to -7 C range.
  • Mature seeds are not damaged by frost.

Delayed Harvest Concerns

When you are working around weather, the crop can sit in the field exposing it to moisture and temperature swings. This may result in seed weathering (grey, dull, black) which can reduce human consumption marketing opportunities (people like shiny seed). Delayed harvesting can also increase risk of frost exposure.

Frost is most damaging when seeds are immature (green bolls). Impacted seed can turn black, have light test weight and may be lost at harvest. Immature seeds (>30% moisture) are damaged at -3 to -5 C range, mature seeds (<20% moisture) in brown bolls are not damaged by a frost.

Storage of Tough or Damp Flax:

For long-term storage, the recommended seed moisture for flax is below 10%. Flax at 10.1-13.5% moisture is considered “tough” and >13.5% moisture is “damp”. With higher seed moisture, risk increases for heating and spoilage in storage. To reduce seed moisture to a safe range, aeration and natural air can be used to condition flax. It is important to monitor the bin for changes in moisture and temperature by sampling the top, bottom and middle of the bin separately.

Aeration (cooling) will result in a small reduction of seed moisture content. If the seed is very tough or wet, a grain drier may be more effective to bring the moisture content down to a safer storable level.

Achieving sufficient airflow rate is important to maintain consistent air movement. The size and orientation of flax seeds generates resistance, resulting in a lower airflow rate from fans. Partially filling bins to allow less resistance on the air is recommended. Refer to the table below for the target airflow rates required for different grain storage management practices.

Process % above “dry”* Recommended airflow rates (L/s) m3 [cfm/bu] Recommended minimum perforated floor area (%) Transfer for final storage
Aeration 0 1-2 [0.1-0.2] 15 No
Unheated Air Drying 1-6 5-30 [0.5-3] 100 No
Dryeration 2-3 5-10 [0.5-1] 40
In-Storage Cooling 1 5-10 [0.5-1] 40 No

From: Manitoba Agriculture

Quick TIPs for Safe Storage (Ron Palmer, IHARF)

  1. Turn the fan on as soon as the floor of the bin is covered, and run the fan until 9 AM the next morning. Do this whether the flax is tough or dry. Research has shown that the first 24 hours is very important, typically a 1% drop in moisture content occurs as grain is cooled down in the first 24 hours.

  2. If the flax seed is still tough (greater than 10% moisture content), keep fans on from 9 PM to 9 AM the next morning. If it is raining, or high relative humidity do not turn fans on in evening. Follow this rule until the flax is dry, i.e. less than 10% moisture content.

  3. To aid in the drying, a truck load can be removed to draw down the peak of grain in the bin. This reduce risk of spoilage of tough grain in the upper core of the bin.

  4. If the flax seed is dry, then the objective would be to cool seeds. This can be accomplished by turning the fan on if the outside air temperature is less than the flax temperature. This could continue into winter and even into spring, which would keep the flax cold into the spring and summer of the following year.

Additional information is available on the following websites:

Flax harvesting, please refer to the Flax Grower Guide Chapter 10 – Harvesting, which is posted on the Flax Council of Canada website.

Conditioning tips for stored canola (which has many similarities to flax) is at

General information on Drying and Storage of Damp Grain may be found at

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