Drum mower
How can I increase the wilting rate?
Mow after the dew lifts. Overnight dew on a standing crop or pasture can contain up to 2 t/ha of ‘free’ moisture. Mowing should be delayed until most of it has evaporated. If not, the moisture ‘trapped’ under the mown swath will delay drying. Drying will be even slower if the swath is left flat, rather than loose and ‘fluffy’.
Cut at an earlier growth stage. Cutting early, when crops are lighter (lower yielding) and of higher quality, will increase the wilting rates. For heavier crops, DM and quality losses during the wilting process are likely to be higher because they dry more slowly than lighter crops. This can be particularly important early in the season, when drying conditions are less favourable and even light crops do not dry as rapidly.
Given the choice, it may be worthwhile to harvest a greater area of early-cut (lower yielding) forage to ensure rapid wilting. Although, when costed on a $/kg DM basis, the silage produced from the lighter crop is more expensive, on a quality basis ($/kg ME) it may be cheaper.
Before mowing, consider the impact of cutting time and growth stage at harvest on regrowth potential and consequences for feed budgeting.
Condition forage. Using a conditioner at mowing can increase the drying rate by 20-40%.
The increase in wilting rate of conditioned forage is due to increased rate of moisture loss through damaged stems, leaves and other plant parts. In addition, the swath produced tends to be loose or fluffy, allowing more air to pass through, which also helps to promote rapid drying.
Conditioning can have the following disadvantages, but these are outweighed by the benefits:
- In the event of rain, conditioned material will reabsorb more moisture than unconditioned forage.
- Over-conditioning or using the wrong type of conditioner can increase DM loss, mainly leaf.
- In very hot weather, particularly with light crops, the forage can dry too quickly. Cutting later in the day, reducing swath width and lessening the severity of conditioning will minimise the losses.
Mower conditioner
Increase swath width. The rate of moisture loss is greater from a flat swath spread over the total mower width than from a high, narrow swath. A wider swath allows more of the mown forage to be exposed to solar radiation and significantly increases the wilting rate. The rate of moisture loss differs throughout the swath, being highest at the outer surfaces and lowest internally, where a ‘microclimate’ develops and further restricts moisture loss.
In fact, the sun has far more drying power than wind, although the two in combination are most effective. In Irish studies, with heavy ryegrass crops,conditioning the forage and having a wide swath increased wilting rate
At Berry on the NSW south coast, kikuyu grass was either windrowed at mowing or left in a wide swath. The windrowed kikuyu took 54 hours to achieve the same DM content as the kikuyu in the wide swath achieved after 30 hours
Use windrow inverters. Windrow inverters have been developed specifically to invert the windrow, picking it up and gently replacing it back on the ground to the side of its original location. Research has shown that the rate of drying can be increased by about 20-30%. The windrow is ‘fluffed up’, reducing the density and encouraging a greater rate of drying in the centre.
Invert windrows with rakes. If machinery is not available to increase the rate of drying by conditioning or spreading, the last resort for material that has been left in a windrow is to invert the windrows by using a rake. Rakes are not designed to handle very moist material so the ‘turning’ of the windrow is usually not successful.
How effectively the material is inverted depends on the type of rake, DM content of the cut material, speed travelled, set-up of the rake and the experience of the operator. A common problem experienced when using rakes to invert windrows is that the windrows become very ‘ropey’, being twisted and becoming narrower, leading to uneven drying.
They are difficult to rerake and harvest. These windrows are even more difficult to handle if rain falls before the harvest is completed.
