I made some raised beds in my garden this weekend and I've filled them with soil, garden compost and horse manure. I've dug it in so it's all mixed up with the soil and compost. I know that I'm not supposed to plant anything right away as something in the manure 'burns' the baby things. I have some onion bulbs that I need to plant soon! How soon can I plant in there? It's raining very heavily here and is forecast to do so all week - will this be helping the manure to break up?