Harvesting
While the direct heading of grain is the cheapest method of harvesting, the danger is that there may be long periods of high relative humidity in which the harvesting of dry grain is not possible. This may cause considerable delays to the harvesting operation and increase the risk of head loss or grain being discoloured by early summer rains.
To reduce harvesting delays the grain can be direct harvested at a moisture content above 12% and then placed under aeration to maintain quality or passed through a grain dryer to reduce its moisture content to a level that can be safely stored.
- First harvest the varieties that are likely to shed or lodge. Delays can lead to significant lodging and shedding due to crop movement in the wind.
- Care must be taken in harvesting milling varieties to minimise the amount of dehulled grain.
- Consider management of stubble for the succeeding crop (straw length and spreading) and collection of grass seed to reduce weeds in the next year.
- Hull-less oats are susceptible to harvest damage, adjustment to the harvest is therefore critical.
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.
Lodging
Lodging of oats is a problem, particularly in tall varieties. The heavy mat of stems that is formed in a lodged crop can result in delayed ripening due to reduced airflow, increased shading and higher soil moisture.
Lodged crops should be harvested panicles first (one direction only) to ensure maximum pickup. Excessive dehulling needs to be avoided as dehulled oats are more likely to become rancid and delivery specifications limit the number of dehulled oats in a sample. Ensuring correct speed and clearance is important to avoid excessive dehulling.
Storage of oats
Correct storage of oats is particularly important when destined for human consumption. Buyers of milling oats will generally require growers to have a quality management program in place. Before harvest - clean all grain handling equipment - harvester, truck, silos and augers need to have residues removed. Grain stores need to be maintained and kept water tight as water can cause mould and sprouting of grain which is unacceptable if delivered. There are a number of important factors to consider when maintaining oat grain quality in storage.
Grain moisture
Keeping grain dry and free from fungal growth is the most important requirement for safe storage. The maximum moisture content at which oats can be safely stored is 12.5% unless the temperature is reduced below 15°C. Above the safe limit, fungi may develop and cause grain spoilage.
Insect pest control
Stored grain needs to be protected from insect infestation.
- Serious infestation will occur within three months, even in situations where risk is minimised by cleaning harvesting equipment, grain store and the surrounding area.
- With poor hygiene, this interval is reduced to 6-8 weeks, and there is a greater risk of secondary effects such as moisture problems and fungal growth.
Fumigants are eradicants that clean up infested grain. They can also be regarded as a protectant in a sealed silo. The only approved fumigant for oats is phosphine. When applying a phosphine releasing fumigant, the silo must be sealed otherwise the success of the treatment will be limited.
Duration of storage
Storing oats at a temperature below 20°C and a moisture content of less than 12.5% should provide a shelf-life of at least 12 months.
- The initial moisture content should be lower for longer periods of storage.
- Aeration is considered necessary for long term storage of oats to preserve the quality by keeping an even,cool temperature within the storage vessel. It is also a valuable tool for reducing the loss in grain quality caused by moisture, grain insects and mould.
Acknowledgements
This information is based on Farmnotes and Bulletins produced by Kelly Winfield, Blakely Paynter, Raj Malik and Jennifer Garlinge.