The thing with lilies that most people don't realize is that the bulb roots are mostly for anchorage. The roots that form along the stem in the top 4" or so of soil are the ones that bring the nutrients to the plant. So, as Viktoria said, they respond well to mulching, composting, watering, etc.
My Scheherazade had 37 blossoms on an 7' tall plant in its third year. They love, love a compost mulch.