The wife and I are going to have a walled raised bed put in. The walls will be about 14-18 (+/-)inches tall. I am wondering what kinda soil we should fill it with. I am thinking either straight up compost, topsoil or a combo of the two? I will also add a small amount of homemade compost that is supercharged with horse manure, fish remains and seaweed along with your standard home compost ingredients.