If you put seedy weeds in the piles you want to get them good and hot, often only a few hours are needed to kill a lot of weed seeds if you heat the pile to 140-160 degrees. I like to use some hot fast piles and some slow cool piles for different things. I was just reading a very interesting article on the loss of nutrients in the composting process, and that makes me think that compost piles do not lose that much in the way of major nutrients. Nitrogen being the main thing lost, and that mostly early on(the first few days), and most of that can be prevented by using the correct carbon to nitrogen ratio of about 30:1. Allowing the piles to sit in the open (under trees) as I do does allow some leaching, but it goes into the soil that may one day also be a garden spot.
Here is the article from Washington State University.
http://whatcom.wsu.edu/ag/comp...
