The harvesting operation is crucial in determining the grain yield and quality of barley. For malting barley, unless the grain has a germination percentage above 98% it is not suitable for sale to maltsters. Therefore, how you handle your barley grain at harvest is critical as viability of the grain must be maintained. Factors such as skinning the grain due to over threshing, storing wet due to harvesting high grain moisture without aeration or drying to temperatures above 43°C all contribute to the reduction in the quality of barley for use in the malting and brewing industry and in the feed industry. Because of this, the potential for a premium price and the possibility of head loss or weather damage means malting barley should be harvested as soon as the crop is at a moisture content that is suitable for storage.
The method of harvesting that is chosen will have a large bearing on grain moisture content, likely yield losses and risk of damage from weathering.
Direct heading of dry barley
The simplest and most common harvesting method for barley is to wait until the grain has ripened and dried to a moisture content of less than 12% so that it can be delivered directly to the receival point. Once the crop is ripe, harvest as soon as possible to reduce the potential losses from wind damage or weathering. It is important when direct heading barley to:
- prevent the skinning and cracking of grain by correctly setting up the harvester
- avoid contamination by ensuring the harvesting and grain movement equipment is clean
- reduce grain losses and damage by monitoring the sample throughout the day and adjust thresher speeds and concave to suit conditions as they change
- use correct screens to remove small grain, weed seed and contaminants.
While the direct heading of dry 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.
It is important to note that once the moisture in the grain falls below 10%, the grain becomes susceptible to skinning due to over threshing. Skinned barley takes up moisture faster during the steeping phase of the malting process than grain with its husk intact. This can lead to death of the grain because it cannot regulate water uptake or excessive root and shoot growth. For the brewer this leads to reduced alcohol yield. Skinned grain is very noticeable to grain buyers in the dried malt sample as it during kilning it turns pink. Correct setup of the header is very important to ensure that over threshing of the barley grain does not occur.
High moisture harvest and aeration or grain drying
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.
Malting barley can be harvested once the grain has reached physiological maturity (dough stage) and when the moisture content is no more than 18%. Harvesting at a moisture level above this is limited by the ability of most harvesters to successfully thresh grain from the head.
Considering aeration or drying costs and practicalities, the best moisture content at harvest for malting barley is around 14-15%. If moist grain cannot be effectively handled, harvest at a moisture content of less than 12.5%.
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.
Swathing and harvesting operation
Swathing involves cutting the crop and placing it in rows held together by interlaced straws, supported above the ground by the remaining stubble.
The crop can be swathed in any direction but is usually cut across the sowing direction or at a 45 degree angle for crops with a wider row spacing. This allows the swath to sit up better on the stubble. Swathing is not recommended for paddocks where the crop row spacing is over 25 centimetres (cm).
Avoid placing swaths in the same location each year. Adjust to distribute the residue across the paddock so nutrients etcetera 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.
The cutting height must be adjusted to allow for sufficient straw on the head to keep the swath together (minimum 30cm) and sufficient stubble height to support the wind-row. It is recommended to start the swath height at 10-20cm above the ground (one-third height of crop or beer can height) and then adjust to produce an even swath with well-interlaced straws that sit above the ground, allowing good air circulation and rapid drying should rain occur.
When the swath is picked up, the reel should be rotating slightly faster than ground speed, but not so fast that heads are knocked off the stems. The conveyor canvas should be revolving sufficiently fast so that it does not clog with crop material. Rows pick up best when following the header follows the direction of the swath (heads first).
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.
Harvesting of the swathed crop must be completed as soon as possible, ideally within 10 days of swathing. If swaths are left too long and are subjected to long periods of wetting (more than 25 millimetres (mm) of rain over 4-8 days), grain may sprout and become stained and may become contaminated with bronze field beetle. Following extensive rain, some growers have attempted to turn or fluff the swaths using a rake or hay baler with an open back door. There has been mixed success with this practice, particularly with heavy swaths. Many growers have reported in hindsight that it would have been better to not have touched the swath row and picked up as normal.
One of the major sources of contamination in swath barley is when the stubble is 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.
Acknowledgements
This information comes from the Barley production in Western Australia site, first compiled by Roslyn Jettner and Pam Burgess from contributions by officers of the Department of Primary Industries and Regional Development then updated in 2006 by Richard O'Donnell, Alaina Smith and Blakely Paynter.