Swathing
Swathing (also referred to as wind-rowing) is a simple means of speeding up the drying of grain whilst retaining quality. It involves cutting the crop when the grain has reached the physiological mature stage (moisture usually between 20-30%). The crop is then allowed to dry in the swaths until the moisture content is below 12.5% when it is harvested using a special pick-up front attachment on the header. Swathing is one of the options more frequently used by growers in the southern coastal areas where the likelihood of rainfall at harvest is highest.
Swathing has many advantages:
- Swathed barley matures more rapidly and is ready to harvest 5-15 days earlier than if left standing. This effectively reduces the period that the crop is exposed to potentially damaging rains and is a cheaper way of drying down the crop.
- Yield loss from lodging and head drop is minimised while the crop is in the swath.
- It helps even out the maturity of the crop and dry out any green weeds that might contaminate the crop.
- Swathed barley is drier than grain in a standing crop so harvest can start earlier in the day and continue later than for a standing crop.
These advantages must be balanced against a number of disadvantages including:
- additional costs in the purchase or contract costs of a swather and an additional pass compared to direct heading
- less hectares covered per hour when harvesting (approximately 20% slower),
- prolonged wet conditions may increase the drying time of a swath and reduce its quality
- soil, rocks, beetles and other material may collect in and contaminate the sample.
When to swath
Swathing can begin when grain moisture content is below 35% and when the grain is at the medium dough stage and is hard but can still be dented with the thumbnail. It is better to swath early to prevent losses from shedding and lodging, but do not swath when the ground is wet after rain.
Grain filling studies have shown that barley reaches maximum grain weight when all of the green tissue has gone from the flag leaf sheath and the peduncle (stem immediately below the head). Avoid swathing too early as the grain is not fully developed and this will give small pinched grain. Whilst it is often easier to swath later than earlier, the swaths of a ripe crop may not interlock well enough to withstand disturbance from a strong wind.
High yielding crops are likely to gain more from swathing than low yielding crops. Generally, crops that are likely to yield less than two tonnes per hectare (t/ha) should not be swathed.