29 March 1996

SPREADING MAKES FOR BEST WILT…

What are the benefits of spreading grass? And once the crop is harvested, whats needed to secure a good fermentation and high quality forage?

Jessica Buss reports

HIGH dry matter grass silage can be made by spreading out grass.

According to Prof Mike Wilkinson of De Montfort University, Lincoln, even when rain is likely grass should be spread.

"Heavy rain falling on spread grass will run through and light rain stays on top then evaporates," he says.

"For successful rapid wilting spread the crop over 100% of the ground area immediately after mowing. Then it is possible to achieve 30% dry matter in a few hours when the crop is light and leafy and within 24 hours for heavier crops."

Even a dense crop can be reduced to 30% dry matter within 24 hours.

He adds that producing high dry matter silage is a trade off between field losses and silo losses. Effluent production peters out at about 30% dry matter, and this is before field losses of nutrients associated with long periods of wilting.

However, avoid overdrying to much over 30%, he warns, for then too much air will be trapped in the clamp because it is difficult to consolidate drier material. It will also respire too much and lose some digestibility.

Higher dry matter silage is also prone to aerobic loss at feeding. So silage clamp management is more important than for wetter silage to avoid waste.

"Formic acid is the best additive for wetter crops because it restricts fermentation. However it fails to stop the yeasts and moulds from growing on drier silage."

Prof Wilkinson cites studies that show losses from aerobic spoilage at the silage face can be from 0 to 50% of the dry matter depending on exposure to air and instability of the silage. Losses of digestible energy may be up to two times the loss of dry matter, he adds.

In order to stabilise dry silage the correct additive needs to be used. This should stop the growth of the lactic acid using yeasts.

"This is spending money to buy time. An extra few days could be critical," he says.

For successful rapid wilting spread the crop over 100% of the ground area immediately after mowing. Spread grass even when rain is likely.