As a general rule, add one pound of general-purpose fertilizer per year for every one inch diameter of the trunk of bearing trees. Add most of the fertilizer after harvest, and then a lighter application at elongation of the fruiting panicle (much-branched indeterminate flower stalk) and when the fruits are the size of a pea.
For more information, look at the College of Tropical Agriculture Fact Sheet:
"Lychee"
