Saskatchewan Flax Development Commission

March 18, 2013 What is Field Retting and How is It Done?

Source: N. Lee Pengilly   |  Category: Fiber

What is Field Retting and How is It Done?
by Lee Pengilly, Saskatchewan Flax Development Commission

In order to extract the fiber from flax straw, the flax needs to decompose or “ret” slightly so that the fiber and shive begin the natural process of separation. Retting requires the straw to come in contact with the soil to allow microbes to get in and begin decomposing the straw.
Early results from demonstrations conducted by the Saskatchewan Flax Development Commission have shown that the earlier in the fall that flax straw is placed in a thin layer touching the ground (i.e. not clumps, and not sitting on the stubble), the faster and more even the straw will ret.
Using a land roller is one method that can be used to put flax straw in an even layer in contact with the ground. It is usually better to leave the straw standing for several days before rolling to allow clumps of seed holders and straw that came out of the combine to fall on the ground before rolling Another method that shows promise is cutting the straw very close to the ground with a disc-bine mower or rotary mower.
SaskFlax research indicates that flax cannot be seeded too deeply or narrowly into furrows, or it will be difficult to break the standing straw at ground level using a land roller. If the straw does not break, it will not remain in contact with the soil and may “pop” back up. More flexible rollers may work best to cope with more deeply-seeded flax or for standing straw grown on uneven terrain.
Producers planning to sell flax straw for high-end fiber uses will need to ret their straw. This may involve spring straw removal if retting is not completed in the fall.

 

How to test when straw is fully retted?

Use this field test to determine to what degree your straw has retted.

  •     Take a small handful of straw from the field.
  •     Hold it in both hands and break the stalks between your hands, using a rotating motion.
  •     You will notice the shives falling off and the long strands of fiber become visible.
  •     Smooth your fingers down the fiber strands (as if “combing”) to clean them of shives.
  •     Check the strength of the fiber by wrapping the strands around each of your pointer fingers and pulling your hands apart. The fiber should be strong enough (and not too brittle) to give some resistance to breaking.