I was going to reply earlier but didn't think it would help as I can't give exact times! We spread muck on our fields and I usually wait until the muck is no longer that obvious on the field, if you look from the gate. The more rain there is, the quicker it goes. We tend to spread cattle muck on the horse fields and vice versa. In an ideal world I would try and leave it a couple of months but in reality they have been back on the field within 3-4 weeks.