Flax TIPS: September Tips – Harvest, losses and storing flax under varying conditions

October 2, 2017 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. Cracked seeds have poor germination and are prone to oil degradation during storage.

  • Adjust cylinder speed, fan speed, sieve opening and concave clearances to prevent cracking. When the concave is too close, seeds may crack.

  • Use the manufacturer’s recommendations to start and adjust setting depending on environmental and crop conditions.

Be extra diligent in dry, warm conditions that straw is flowing through and out the combine. Flax straw is prone to wrapping. Check your fire extinguishers. Be safe!

What about harvest losses?

There is growing awareness of harvest losses from various crops. While little research has been done on this issue in flax this is certainly something that should be monitored for all crops, flax included. Here are some facts to consider:

  • To prevent losses, sieves should closed as tight as possible. Screen size and type will depend on the combine and seed size.

  • Fan speeds should be adjusted to avoid loss of light seed.

Based on the Combine Seed Loss Guide prepared by PAMI and the Canola Council of Canada we can calculate approximate yield losses using a harvest pan. N.B. These values assume bushel weight of flax is 56 lbs.

  • Example 1.
    Assuming a 45 ft. combine header and a 5 ft. discharge width:

    • 5 grams seed/ 1 sq. ft. collected = 1.1 bushels/acre yield loss

    • 10 grams seed/ 1 sq. ft. collected = 2.2 bushel/acre yield loss

  • Example 2.
    Assuming a 24 ft. combine header and a 4 ft. discharge width:

    • 5 grams seed/ 1 sq. ft. collected = 1.4 bushels/acre yield loss

    • 10 grams seed/ 1 sq. ft. collected = 3.1 bushel/acre yield loss

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.

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.

Storage of Warm Flax:

Many regions of the Prairies are dealing with drier conditions than the two previous seasons, however producers should still be aware of the condition of flaxseed entering the bin. Spoilage occurs because of moisture and temperature. Warm, dry grain entering the bin should still be conditioned and monitored.

According to the Canada Grains Council, grain binned at high temperatures can retain heat in unaerated bins for many months after being harvested. This can favour spoilage two ways:

1. Temperature and moisture influence enzymatic and biological activities and thus the rate of spoilage. Using an example from canola (Fig.1), one can see that warm grain stored at 25°C and 9% moisture is more likely to spoil than grain that is 15°C and 9% moisture.

Figure 1. Canola storage time chart based on temperature and moisture at binning.


2. Temperature gradients that develop in the bin favor mold development. As warm air rises, it carries moisture upwards through the grain resulting in moisture adsorption near the roof of the bin. This can created pockets of condensation, especially as night temperatures cool.

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 5-30 [0.5-3] 40 No

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.

Combine Seed Loss Guide – PAMI/ Canola Council of Canada: http://pami.ca/wp-content/uploads/2017/09/Canola-Coucil-of-Canada-Combine-Seed-Loss.pdf

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