We've had our best luck with horse manure. We have very sandy gravely ground and could only grow thistles until I made raised beds of straight horse compost. Every third year we have to add new as weeds become uncontrollable although the first 2 we barely have to weed at all. I can ask my daughter as she's is going to college for horticulture and knows alot. She worked as greenhouse manager in high-school 4 years, currently works at Colonial Nursery in Ladysmith and is about to start her second year of college. Never knew a kid her age know so much about gardening. She's at work atm but I'll ask and get back.
Stacy
A friend and local organic farming guru uses goat puckie (I use horse puckie). He says the best way to get rid of all the weed seeds is to spread it out in the hot sun with black plastic over it. A few good, hot, sunny days, he says, bakes most of the seeds away. Once I get the gardens settled in I'll give that a try on the mounds of manure I'm composting for next year.