What CCP said; plus, if your soil is essentially devoid of nutrients, it would make much more sense to use a fertilizer that provides nutrients at a ratio as close as possible to that at which the average plant actually uses nutrients. Normally, no one can give meaningful advice re what fertilizer to apply to plants growing in the landscape w/o a soil test to use for guidance; however, in this case where you're starting with a blank slate, a fertilizer with a 3:1:2 ratio would make the most sense because that RATIO comes closest to providing nutrients in a ratio the average plant actually uses. Products at or very close to a 3:1:2 ratio include 18-6-12, 16-4-8, 13-5-8, 21-7-14, 17-5-11, 18-5-12, 16-5-11, and are all available in a slow release (different than controlled release, like Osmocote) product. If you were using a soluble synthetic fertilizer, 24-8-16, 12-4-8, and 9-3-6 are all 3:1:2 ratio products.
Al
