Soluble synthetic fertilizers are the easiest to manage, by far. They allow you complete control over what your plants get, how much they get, and exactly when they get it. Fertilizers in a 3:1:2 or 2:1:2 ratio are good choices. Ratios are different than NPK %s. 24-8-16, 12-4-8, and 9-3-6 are all 3:1:2 ratio fertilizers. If you were to ask for a recommendation, I'd suggest Foliage-Pro 9-3-6, or MSU orchid fertilizer (12-6-13) for pure water, for fruit trees.

Al