Last fall we added 5 cans containing 30 gallons each of horse manure to the garden. I tilled this spring and the garden went nuts this summer. I'm inclined to add more this year, but am concerned about overfertilizing. I don't want to burn the plants with too much. We also add ground leaves from the trees in our yard(no oak leaves though). So, should I add the same amount again? Would there still be some present from last year or would the nutrients be used/dissipated by now.