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Down on the Farm- Making Silage

“Silage” is what most cows eat during the winter when there is no grass growing in the fields.

How is it made?

It is pickled grass, except instead of farmers adding the vinegar, the grass makes its own acid from the sugars in it! Grass contains between 1% and 2% sugar, depending on how sunny it has been, and how dry the grass is. Sunny dry weather equals high sugars, but we still need to let it dry more to concentrate the sugars to around 3%. This is why we mow the grass and let it dry for 2-3 days. You won’t see a farmer making silage in the rain!

The Fun Bit!

We then chop the grass with the forage harvester (chopping exposes the sugars to encourage acid production) and blows it into the trailers alongside. The trailers take it to our “pit”. A tractor spreads the grass on the pit, and as soon as we have finished filling the clamp (normally 1-2 days), we do the important bit……..

The Important Bit!!

1. Roll the clamp to squash the grass down to get as much air out as possible. A heavy tractor normally does this with their wheels.

2. Cover with a plastic sheet and weight it down with tyres (other solutions are available!). The walls of the clamp will have already been covered with plastic.

If you do the important bit right, the grass produces lactic acid (a ph of 4) and the cows love it. Do it wrong by letting air into the clamp or not having enough sugar in the grass, and it produces butyric acid (a ph of 5) and the silage stinks to high heaven and the cows won’t want to eat it.

A Home Experiment

Mow your lawn.

Put half your clippings straight onto a heap and cover with a plastic sheet with a stone at each corner to weigh it down.

Let the other half dry for a couple of hours, then put into a plastic bin liner, squeeze out all the air and tie the top. Put next to your other heap.

In 2 weeks open both and compare. You should have compost in the first heap and silage in the 2nd!!

Andy Jeffery

Farmer at Farrington's


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