Nitrogen stimulates overall growth of a citrus tree. It is very important for flowering and fruit set.
Nitrogen deficiency will cause the entire leaf becomes light green to yellow in color. The leaves drop premature - normally, a citrus leaf is to last 18 to 24 months, and the plants show stunted growth.
Nitrogen excess signs include reduced fruit color break from green to orange/red, an increase in peel thickness and there is an increase in fruit acidity which can be considered negative.