composted manure only, this goes for any manures, especially chicken. If it hasn't been actively composted and just was sitting in a pile I'd say a year old. My neighbors have horse stables and brought manure for my veg garden and I'd leave it until the following spring. Now I have my own composter so I don't get the manure delivered any more.
25% compost is a good amount, no more than that. The best thing you can do, in my opinion is to till the soil deep and wide.

Good info from good people HERE