Hi. Can i mix manure with multipurpose soil on most plants? I know i must not let it touch the main roots.
Yes, but best to use it sparingly and in composted or aged form, not fresh manure. Or apply it in the fall to prepare for spring planting, so to allow it to age a little in the soil.
Using fresh manure, especially chicken, can burn by desiccation of roots and cause root and foliage dieback.
Here's an article that will help with some basics: