Here’s some info I found from a lychee grower:
https://www.facebook.com/groups/1918599125074126/permalink/2188331551434214/Copied from Facebook post:
“ Fertilizing Lychee explained .
1. avoid using in ground or on ground fertilizers ( especialy graular ) as the release is governed by water amounts not fertilizer amount ( too much will hurt it , too little poor results )
2. Lychee prefer to absorb their fertiliser through leafs rather than roots
3. use liquid fertilizers desighned for leaf absorbsion they love the stuff & you will see results in days . ( also exess rain will reduce amounts of fertilizer not increase so no root burn )
4. mulch is only good to insulate the soil , the results you get are from reduced hydro / temerature shock not nutrients delivered
5. test your water needs to PH neutral ( same as rain water )
6. fertilizing after fruit formation is done to help set fruit , the flip side is if you over water the fruit will split on the tree .
PS .. if you are growing in pots feel your pot during the day if hot wrap in tin foil
use bigger pots , lychee roots grow down across the botton then up the sides before filling middle of pot ( compared to growing out evenly from middle ) it will give you stronger roots .
during flowering do not water over leaves or let rain fall on flowers the nitrogen will burn the flowers resulting poor fruit yeild , up to nature on the big scale , acheivable with pots or tarpolan
NEED TO CONSIDER
fertilizer & weed killer are the SAME product used in different concentrations they kill by over fertilisation ! you can dilute the poisons & use as fertiliser , so too much rain or watering turns your surface / granular fertilizer into poison .
all lychee stock are clones & will only grow only aswell as the parent tree & will have all the sam genetic faults , select stock from local trees & select from healthy fast growing trees . Be warned most growers keep the best stock for themselves & only sell the 2nds
you need male & female tree's for fruit they may be the same sex or all from the same tree ,. if buying from the same place leave 3 months between puchases they have to be re-potted , so gaurenteed different parent plant , or get grower to mark which tree they came from , they will understand why & be happy to do it
the root base will only grow to the size of the shaded area under the tree this is why mulching around small tree's works until canopy develops , if you leave it 2 years before pruning it will produce more fruit on the 3rd year than the 3 years combined & have larger root base
on larger tree's the same results ( more growth / more fruit ) can be acheived without fertiliser & with better long term results by thrashing tree's with 1 inch link chain !
Hope this helps”