Can I use horse manure fresh from the barn or should it be treated first. I am planting in earth box's and a plastic tub.I am new at this but I have some beautiful plants going
No cannot be used fresh!! It can burn or even kill your plants, especially when in a small space like a container (hard to get it in small enough concentration).
It needs to be composted. It is a great addition to your compost pile. Otherwise just let it sit somewhere until next year.