last past spring i constructed a 25'x25' x20"deep raised bed garden with 15+ yards of top soil on top of weed screen. I planted various vegetables with less than mediocre results. The soil mix is a regular top soil mix with some organic material and some manure, pre-mixed. what can i do to my soil over the winter to turn my mediocre results into lush green vegy's. I have room to top up the garden with manure or soil.