How much manure should I put per a 2x3ft hole? The manure has been in pile for couple yrs and has worms in it so I don't think it would be too hot. Just don't wanna burn up my plants
That's considered compost if it's been sitting that long, so you shouldn't experience burn at all Add 20% compost to your soil mix and you should be good to go!
if it's got worms it's perfect. just like them man above said use a bunch, if your soil is terrible and the manure/compost is good and loamy you can lay it on even heavier.
You don't have to guess if it's hot or not: Stick your hand into the middle of the pile and feel the stuff. You'll know if it's hot because it literally gets hot. It doesn't only burn chemically, it can physically make the soil too hot for the roots. A couple of years old should be alright but I've seen stuff stay hot for 3-4 years.