Teagasc: key drivers of top-quality silage

Advanced planning is required to provide a sufficient amount of good-quality silage for the winter ahead.

Every farmer should draw up a feed budget at the beginning of the year for the following winter. When you know how much feed is required for a four- or five-month winter, you can decide which fields to earmark for silage, how many cuts to take and so on.

Aim for most of the silage to be conserved from the first cut as it is cheaper than the second cut and usually has a higher DMD percentage.

In taking out fields for reseeding, it is important when formulating a grass mixture to decide what the end use is – grazing or silage.

Sward type is a key driver of good preservation. Perennial rye-grass is four times more likely to give a good preservation than with red fescue.

Air-free conditions are the single most important requirement for good preservation.

Fill silage pits quickly and seal them perfectly. Wrap bales immediately after baling and ensure no damage of any description occurs to the plastic film.

Grass sugar content is likely to be relatively high during cool, dry, sunny weather; and low during warm, overcast and wet weather.

This is the reason most of the year’s silage requirement should be from first cut as grass harvested in autumn is usually much harder to preserve.

The target for sugar content is 2.5 to three per cent.

It is advisable to get a grass ensilability test done before you cut the grass. Stemmier crops are usually easier to preserve as silage than leafy crops for a number of reasons, including their tendency to be drier, higher in sugar and lower in buffering capacity.

High buffering capacity means it’s more difficult to ensile grass and relates to high nitrate levels in the crop.

But if sugar levels are adequate, nitrate levels in the grass have little or no effect on the efficacy of preservation.

Grass silage has a large nutrient demand and adequate N, P and K is essential for maximising grass yield and producing sufficient winter feed.

Grass swards with high levels of perennial rye grass will use Nitrogen more efficiently than older swards.

Chemical fertiliser recommendations for silage ground are based on soil sample analysis and whether slurry is applied or not.

Ensure the recommended rates are applied sufficiently early to achieve the full yield response.

Expect the crop to utilise two units of nitrogen per day. So if spreading 100 units per acre of nitrogen, allow over seven weeks before harvesting.

In good growing conditions with very responsive swards, nitrogen uptake may be greater than two units.

Wilting grass to above 25 per cent dry matter reduces or eliminates effluent production and can facilitate preservation where difficult to ensile.

Crops should be cut for wilting after the dew has dried off, as dew will dry faster from a standing than a mown crop.

Before mowing, check the weather forecast to ensure good sunshine and drying conditions are on the way and, if possible, tend the grass immediately after mowing for a faster rate of wilting.

If crops are lighter in good drying conditions, over-wilting should be avoided.

In summary, factors that contribute to making good quality silage are harvesting in dry sunny weather, mature grass after ear emergence, mowing in the afternoon when sugar levels are built up, wilting and swards consisting of perennial and Italian ryegrass.

Silage quality determines the weight gain that can be expected from animals over the winter period.