Cropping

Agriculture Victoria offers tips to help farmers achieve successful silage harvest

By Rodney Woods

Ensuring quick wilting this year for your silage will be important due to the likelihood of a wetter than average spring.

Rain on curing silage can lead to a decline in quality and quantity harvested.

The aim is to harvest and store chopped stack silage about 30 to 35 per cent dry matter and baled silage about 40 to 50 per cent dry matter.

If wetter, the silage will undergo a less suitable fermentation and will be of lower quality and will lose dry matter and palatability.

Very low losses in quality (energy and protein) and dry matter occur if the wilted crop is in the pit or bale within 24 to 48 hours after mowing.

Losses increase substantially after this, and an extended wilting period increases the risk of the next shower of rain resulting in even higher impacts on quality.

Ideally, pastures should be cut at or near when they should be grazed.

This encourages quicker regrowth, promotes tillering and maintains pressure on the remaining grazing area.

Mowing with a mower conditioner and/or using a tedder will speed up the rate of wilting substantially and also help to beat any pending rain.

Plant leaves contain thousands of holes (stomata) per square centimetre through which moistures moves in and out during respiration.

These stomata close within one to two hours of mowing.

The warmer the weather, the faster they close.

Once this occurs, the rate of wilting is substantially reduced and although wilting still occurs, it becomes extended.

Mower conditioners have a wide range of conditioning techniques.

The tined and flail types are most suited to pastures, young lucerne, clovers and vegetative cereal crops.

The roller types, on the other hand, are more suited to the more stemmy crops such as cereals cut with a seed head, mature lucerne and summer forages, such as sorghum.

The operator's experience, the speed of the operation, the correct clearance settings and maintenance of the equipment, width of swathe etc. can also markedly affect the rate of wilting.

Using a tedder to spread the forage as thinly as possible straight after mowing, while the stomata are still open, will greatly increase the rate of moisture loss by 50 to 80 per cent.

The tedding action will leave the plants in a fluffed-up state which will allow airflow to remove evaporating moisture and encourage further wilting.

Some bruising of leaves and stems will also occur at the same time, promoting faster wilting.

Be careful when harvesting on wet soils as mud and manure are sources of undesirable bacteria which may be incorporated into the forage in the silage stack or bale.

These bacteria are highly likely to cause a poor fermentation. This will result in relatively high losses of dry matter and nutritive value of the silage, and reduce palatability.

There are several additives which may aid the fermentation process.

For slightly over-wet forage still high in sugars, fermentation stimulating bacterial inoculants are suitable, as are products containing sulphur compounds and amylase.

For forage that has been on the ground for many days and is probably very low in sugars, buffered acid salts are the best option, although expensive due to the high application rate needed.

Additives are not a magical solution and effectiveness will depend on the degree of wilting and how much and how well the additive is incorporated.

● For more information on tips for a successful silage harvest, visit: agriculture.vic.gov.au