Slurry application tips

After such a prolonged wet period with few opportunities to apply slurry to fields, slurry pits have generally been far fuller than normal.


So what can be done?

Once the land dries out, the temptation may be to empty pits and put out heavier applications. But take care.

Slurry should ideally be applied at least 10 weeks prior to cutting, so count back from when you intend to cut.

It is not the organic matter that we see with slurry that is the problem, it is the undesirable bacteria within it. The 10 weeks is to allow time for the undesirable bacteria to die off.

Basically, slurry is full of ‘bad’ aerobic bacteria. These can live in the bottom of the sward, where they are protected from drying out, from frosts, and from UV rays from sunlight – all of which would help kill them off.


These ‘bad’ bacteria are also completely opposite to what we require for a good silage fermentation. Where it’s an option, injecting slurry is a good way of putting it out of harm’s way.

Slurry should also be applied in light applications to allow the bacteria to die off, especially where it is being applied onto fields with a good cover of grass that has over-wintered.

But what can we do if we think there is a risk of contamination?

As well as allowing more time for the bacteria to die off, ensure that grass is wilted rapidly to around 30% DM, as drier silages are more ‘forgiving’ where contamination is concerned.

In earlier, leafier cuts, DM levels are often deceptive as the moisture is within the cells rather than externally. Test the grass for DM prior to harvesting (microwave test). Wilting rapidly will also reduce the time the undesirable bacteria have to grow in the mown grass.

Ideally, mow grass as soon as practical in the morning. Spreading it out after about 3 to 4 hours will help it wilt rapidly, as grass can lose up to five times more water in the first six hours than later in the wilting process.

However, care must be given to ensure tedders and rakes are set up to avoid ‘scratching’ the ground and bringing in soil contamination – a common problem on many farms. Step out to the field to make sure the kit is set up properly. It costs nothing but could pay dividend.

Peter Smith can be contacted at Volac on: 07920 721955 or