When can I apply slurry, FYM, silage effluent, dirty water?

Slurry and FYM are heavily laden with undesirable  bacteria which can survive on the grass for many months.

Enterobacteria

• compete for sugars required for fermentation
• can produce toxins

Clostridia

• can produce a secondary butyric fermentation
• spores in milk can result in some cheeses blowing

Ideally slurry should not be spread on silage ground at all and certainly not after grass growth has begun, ie within about 10 weeks of 1st cut. Application after the end of January will increase the chances of contamination and if possible it should not be applied between cuts.  FYM should not be applied after Christmas. If you do need to apply slurry late you will need to wilt rapidly to at least 30% DM to minimise the risk of a poor fermentation.

The heavier and less dilute the dressing of slurry/FYM, the more damage to the grass sward and the greater risk of contamination of any subsequent cut.

Silage effluent and dairy washings are potent sources of contaminating bacteria and should not be applied to silage ground.

If you are injecting, rather than spreading, slurry you can apply up to two weeks before harvest.