Swathing
Swathing involves cutting the crop and placing it in rows held together by interlaced straws, supported above the ground by the remaining stubble. It can be considered as an option where:
- The crop is uneven in maturity, or the climate does not allow for rapid drying of the grain naturally.
- There is a risk of crop losses from shedding and lodging.
High yielding crops may gain more from swathing than low yielding crops. Generally, crops expected to yield less than 2 tonne per hectare should not be swathed. Picking up swathed oats is significanly slower than direct heading because of the large volume of material.
If the crop is too thin or the stubble too short to support the swath above the ground, the crop should not be swathed. Heads on the ground may sprout and attempts to pick up heads that are lying close to the soil surface will pick up soil.
Timing
Swathing can begin when grain moisture content is below 35% - when grain is at the medium dough stage, hard but can still be dented with the thumbnail.
- It is better to swath early to prevent losses from shedding and lodging, but not when the ground is wet after rain.
- Avoid swathing too early as the grain is not fully developed and will result in small pinched grain.
- Although it may be easier to swath later, the swaths of a ripe crop may not interlock well enough to withstand disturbance from strong wind.
Cutting
- Cut across the sowing direction, or at 45 degrees for crops with wider row spacing, so the swath sits-up on the stubble. Swathing is not recommended for paddocks where the crop row spacing is over 25cm.
- Avoid placing swaths in the same location each year so nutrients are not concentrated in one place.
- Swather size or width of cut should match header capacity. A double-up attachment to the swather or placing two swaths side by side requires a larger capacity header and concentrates the residue in a narrow band within the paddock.
- Cutting height should be adjusted to keep sufficient straw on the head to hold the swath together (minimum 30cm) and sufficient stubble height to support the wind-row.
- Start the swath height at 10-20cm above the ground (one-third crop height) and adjust to produce an even swath with well-interlaced straws that sit above the ground, this allows good air circulation and rapid drying should rain occur.
Harvesting the swath
Harvesting of the swathed crop must be completed as soon as possible, ideally within 10 days of swathing.
- If left too long and subjected to long periods of wetting (more than 25mm of rain over 4-8 days), grain may sprout and become stained. The swath may also become contaminated with bronze field beetle.
- When the swath is picked up, the reel should be rotating slightly faster than ground speed, but not fast enough to knock the heads off the stems.
- The conveyor canvas should be revolving sufficiently fast to prevent the crop material banking up.
- Rows pick up best when the header follows the direction of the swath (heads first).
One of the major sources of contamination in swathed oats is the stubble being torn out during the swathing operation. This generally occurs when the swather is operated at too high a ground speed or when trying to swath when the straw is tough due to it being cool or damp.