The traditional Japanese approach is little cakes of rape seed staked to the surface of the soil; none too sightly and very smelly! I like organic fertilizer and use blood meal and cotton seed meal on my trees as organic fertilizer stays in the soil. I supplement with an occasional fish emulsion fertilizer, say three times a year; first thing in spring, once in early summer and once mid summer. I keep my trees out all summer so I can use the smellier stuff, but it's only there for a day or two and for the results I get I can tolerate that. I finally have a compost tumbler and will be using compost tea once a week next season (maybe a few weeks this season if this batch hurries up). Water soluble nitrogen is less and less part of my regime although during winter months indoors I will occasionally give a very weak solution to mantain vigor (especially at the end of winter when I'm trying to ramp[ the plants back up for spring). But it's not good for the environment and the plants give me better results long term with the organic stuff (they get like junkies on the blue stuff).
Hope this works for you too, although different locales call for different strategies. Check out a local organization in your area; they'll have developed methods for your specific locale. IN the meantime try this out and see if it works for you...
Let me know how it works,