Garden Pests and Diseases: Yellowing leaves on limes etc., 0 by tavira

tavira wrote:
I am having problems with yellow leaves on limes (I think Bearss seedless), but also palms...Cocos plumosa and Washingtonia robusta and filifera.
They are green when I plant them, but a few months later start to turn yellow. The limes are the worst affected.
I live in Portugal, on the Algarve, with a typical Mediterranean climate, but my soil is rock hard clay, and you need a pickaxe to plant things. I presume that it is a deficiency, possibly of nitrogen, anthough I feed the 3 or 4 times a year with N.P.K 12.8.16, plus trace elements.
I have been told that Epsom Salts (MgSo4) will help the plant to take up nitrogen from the soil, if there is any! Many other shrubs and trees grow well in this soil, including olives, cork, loquats and carob trees, and many flowering shrubs.
Any suggestions please.