Flax TIPS: Harvesting and Drying Damp Flax

November 15, 2016 0 Comments

According to the most recent Provincial crop reports the flax harvest is 49% complete in Saskatchewan, 64% complete in Alberta, 50% complete in Manitoba. Harvest conditions in October were poor, with above average precipitation and snow reported in many areas of Saskatchewan and Alberta. In between, drying conditions have been elusive with many cloudy, cool days with high relative humidity. As such, any progress made will have much of the flax testing tough (10.1-13.5% seed moisture content) or damp (>13.5% seed moisture content).

The concerns with combining flax in late fall are not issues with shelling out or shattering, as flax bolls stay intact (although overripe fields or those that have severe disease (pasmo) may have boll drop). The major concerns are the headaches associated with stalks wrapping on the header reel and high moisture seed being binned and at risk for heating and molding.

Here are a few scenarios that may be encountered:

1. Seed is dry, but stalks are still damp

Even though the seed is at 10% moisture content and ready to harvest, the flax stalks can still be green or have sufficient moisture content to cause the stalks to wrap on the header reel when being straight cut. Cooler, shorter days in October and November drastically slow stalk/seed drying, so more attention and additional activities may be needed to get the crop off.

If this is the situation, consider swathing the crop to kill the stalk. Swathing the crop will allow it to dry down, barring significant rain events, reducing wrapping problems during combining. Effectively, the plant is removed from the source of moisture, the soil. Swathed flax may be easier to pick-up later this fall. If significant snow does come sooner than you can get the crop off, its weight may result in significant stalk breakage and/or lodging in flax that is still standing.

2. Seed is tough or damp

Anything over 10% seed moisture content is considered tough and over 13.5% is damp or high moisture. For long-term storage, flax seed should be brought down to 8.5% moisture. The risk of spoilage and heating is considerably higher for tough and damp flax compared to cereal crops due to its high oil content. Natural aeration of flax is possible with these TIPs, however cool and wet weather may limit this process and warrant the use of supplemental heat.

According to Joy Agnew (PAMI), here are some things to keep in mind when using Natural Air Drying (NAD) with supplemental heat:

  • Heating the air increases the air’s capacity to hold moisture and thus its capacity to dry grain. For every 10°C increase in temperature, you are cutting the relative humidity (RH) of the air in half.

  • Try to keep the temperature of the air going into the grain between 10 and 20°C. Do not exceed 20°C. Trying to get 15°C going into the grain is a good target.

  • Ensure you have adequate airflow rate through the grain. You need a MINIMUM of 0.75 cfm/bu when using supplemental heat. Anything lower and you may end up with warming grain and not enough energy to actually pull moisture out of the grain. So you may end up with warm and tough grain…not a good combination. The static pressure that flax generates is higher than all other grains (including canola) so it may be difficult to achieve that 0.75 cfm/bu airflow rate with a full bin.

  • Ensure you have adequate ventilation at the top of the bin to allow the moist air to escape. A good rule of thumb is to have 1 ft² of ventilation area for every 1000 cfm of airflow through the grain.

  • To estimate how much temperature increase you will get with a given heater, or to calculate the capacity of a heater for a given bin and fan use:

    • Heater capacity (btu/hr) = Temp increase (°F) x airflow rate (cfm) x 0.8

    • For example, if you have a 100,000 btu/hr heater and a target temperature increase of 10°C (equivalent to 18°F temperature increase), you will be able to handle an airflow rate of approximately 7,000 cfm. So if you have 7,000 bu of grain and a 1 cfm/bu airflow rate, this heater will work well.

  • Keep an eye on the grain when using supplemental heat to prevent over-drying. You will likely have to turn or mix the entire bin to achieve uniform conditions.

  • Make sure you cool the grain after you have reached the desired moisture content and after you have turned or mixed the grain.

  • Homemade or rigged heating systems offer little to no control over the air temperature and can pose serious safety risks.

  • Propane and natural gas fired heating system technically do add some moisture to the heated air (since water vapour is a by-product of the combustion process), but this amount of water is negligible compared to the amount of water in the grain

  • If heated air drying (in a batch or continuous dryer) is an option, that is preferred over using NAD with supplemental heating

3. Combining this fall is not an option, how will swathed vs. standing flax yield by spring?

If combining in late fall/ early winter is not an option, flax can be combined in spring. Although, the longer the crop is exposed to freeze-thaw conditions, seed quality and appearance will be reduced. Flax that is left in swaths overwinter will be more prone to damage from mice and deer, while standing flax will be at risk of lodging and boll drop from snow packs. Producers should also be aware that there could be marketing issues, in addition to quality and yield losses, come springtime.

Visit Flax TIPS: Late Harvest & Storage for detailed information on natural aeration, safe storage and target airflow rates required for different grain storage management practices: https://flaxcouncil.ca/tips_article/flax-management-tips-flax-harvest-storage/

For detailed information and video’s on grain drying and storage, please visit: http://pami.ca/crops/storage/

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