One of my squash hills is on top of an area formerly inhabited by a willow tree. A stump grinder and nearly a full day of pickaxing huge roots out cleared the spot three years ago; the hole was filled in with good dirt from the rest of the plot and all was rototilled in with peat moss, goat poop, and my own compost. last year the same spot grew neon yellow squash plants with butternuts the same bright yellow - except for the color the squash was great if not as prolific as those planted away from that part of the garden. Any ideas on what there is too much of in that area of soil and what I can add now to green up the plants? Or should that roughly 4' square be a dead zone for planting?