29 March 1996

TIPS FOR TOP PITS

ENSURE good fermentation by using the right additive, filling the clamp with care, avoiding excessive rolling and sealing the pit quickly.

This is the advice from Wiltshire-based Genus consultant Neil Adams. He recommends using inoculant silage additives particularly for dairy cows for it increases dry matter intake and milk yields.

"Research has shown that on most normal grass crops inoculants work well," he says. "You dont need to use acids except perhaps on low sugar grass or when there is a high risk of soil or slurry contamination." To make good silage clamp contamination must be avoided.

"Trailer wheels and other equipment entering the clamp should be mud and slurry free. When its muddy keep tractors and trailers out of the pit area."

It is also essential to be able to seal the pit effectively to stop air getting in. Mr Adams prefers to see side sheets on the clamp that can be folded in before the top sheet is put on. Ideally, side sheets should reach the floor especially when the pit has sleeper walls.

The pit must be filled quickly with a minimum of 8-10ha (20-25 acres) of grass a day. When less is put in aerobic and clostridial bacteria dominate and cause poor fermentation.

Silage should be rolled as the pit is filled and for less than half an hour in the evening. Excessive rolling is unnecessary.

"Consolidation is not usually a problem except down the sides where it is difficult to get against the wall," he says.

"Dont roll the pit in the morning for it squashes out carbon dioxide and draws in oxygen which can lead to poor fermentation."

Lactic acid fermentation begins after about 20 minutes when no more air is getting in and pH should drop after seven to eight hours. When it takes longer for pH to drop the risk of unwanted bacteria causing poor fermentation is greater, he adds.n


&#8226 Cut crop when dry.

&#8226 Cut crop 7.5cm (3in) high to leave rubbish.

&#8226 Dont rake in soil and slurry.

&#8226 Wilt to concentrate sugars but for 24 hours max.

&#8226 Fill the pit quickly and evenly.

&#8226 Roll for 30 min max in the evening and cover overnight.

&#8226 Dont roll in the morning.

&#8226 Use the correct additive.

&#8226 Seal the clamp quickly.

Source: Genus

Fill the pit quickly, with a minimum of 8-10ha (20-25 acres) of grass a day.