Cindi's post brings up an interesting question and I'd like to hear a scientific answer. I add soil to my flower beds every year. I buy hundreds of bags of potting soil each year and pour it into the flower beds. Why don't the beds start overflowing after a few years? They just seem to get lower and lower. I can tell because my flower beds have rocks around them. I know the rocks aren't rising, so the soil must be sinking. And it's not a compaction process, because the soil stays friable several feet down.
