To wilt or not to wilt; that is the question

‘It’s dry enough’ is common phase used by farmers post mowing when they are trying to decide on whether or not they should wilt the sward.

However, wilting is one of the most important steps when making silage as it increases the dry matter (DM) percentage of the grass – which has an influence on silage quality – and also reduces the quantity of effluent produced.

Ideally, the target should be to wilt the silage to a DM between 28% and 32%. Drying it more than this will not give any improvement in animal performance.

In addition, wilting makes the sugars more concentrated in the grass, allowing the resulting silage to stabilse at a higher pH; which means a lot less acid or inoculant is required to preserve the crop.

In appropriate conditions, farmers should aim to wilt the grass as quickly as possible post mowing – to limit sugar losses.

This is important because approximately 6% of the sugars present in grass can be lost during a 24 to 36-hour wilting period.

At a silage demonstration day last week, Thursday, May 16, Teagasc Grange’s Eddie O’Riordan discussed the most suitable scenario for the best wilt.


Touching on when the best time to mow is, he said: “Obviously, dry conditions are best and before cutting you would like the sward to be above 20% dry matter.”

There are a different combinations of scenarios when you are cutting and wilting.

Explaining these, he said: “If it is dry when you are cutting and dry when you are wilting; this will be ideal for mowing and picking up the sward on the same day provided it is cut when the dew has lifted off the grass.

“If it is wet when you are cutting and and it drys afterwards you can overcome it; but, if it’s wet when you’re cutting and wet when you are wilting it can be very challenging.”

To overcome this, farmers could opt to wilt the crop for 24 hours and cut the sward in the afternoon when the sugar content is at its highest.

However, the issue with wilting it for greater than 24 hours is that it may become excessively dry and this can have disadvantages too.