I have never fertilized my soil. My contention is to build your soil over the years by regular composting and always applying a vegetative mulch. Al

Next year's bloom will develop quite well all on its own just by leaving the foliage in place to mature and ripen. Like Al, I've grown bulbs for years with never applying fertilizer but mulching annually with compost.

If you need to fertilize, do so in early spring just as you see the bulb foliage beginning to emerge.