One of my young trees is experiencing severe yellowing of the leaves during the past couple of months, and now some leaves are falling. The leaf veins are especially yellow. Approximately 3 weeks ago I applied a general NPK ferilizer but it hasn't appeared to help. I believe the oldest leaves are a good, dark, green.





I tried to match the yellow vein symptom to photos seen on Google search, but didn't find a good match. It's not mottled like Greening disease. Nitrogen deficiency? Some micronutrient? Something eating the roots? Any advice would be appreciated.

Thanks, John

Looks like nitrogen deficiency, BUT normally symptoms of a nitrogen deficiency appears on the older leaves, and not on the younger leaves. - Millet 75.

Just an idea! May be sulfur deficiency? Not sure but as far as I know the classical symptom of sulfur deficiency is yellowing of younger leaves while old leaves remain green. Symptoms of S deficiency occur particularly in plants well supplied with nitrogen but are sometimes confused with that of nitrogen.
You should check if your fertilizer contains enough sulfur.