After 12 years in my home, I had a serious drainage problem after a storm where water came down a hill into the house. We hurriedly built a two feet retaining wall and filled in behind it with cheap dirt that did not contain any nutriets. Now I want to enrich that soil so that I can grow plants. Is there a liquid solution I can buy? If so what? Or do I have to buy bags of fertilizer? If so what and what formula should I use?