柑桔缺氮时，叶脉发黄，叶片褐黄色，叶小而薄、易脱落，枝梢短而瘦弱，落花落果严重，产量减低。过量施用氮肥则枝梢旺长，花芽不易形成，开花结实率低，须根生长不良，抗旱、抗寒能力降低，同时果皮变厚、粗糙，果味酸，风味淡。缺磷时枝、叶、根均生长不良，叶暗绿无光泽， Citrus nitrogen deficiency, the yellow veins, yellowish brown leaves, small and thin leaves, easy to fall off, short and thin shoots, falling flowers serious, yield reduced. Overexploration of nitrogen fertilizer is a long shoots, flower buds are not easy to form, flowering and fruiting rate is low, fibrous growth is poor, drought, cold ability to reduce, while peel thickening, rough, fruity acid, light flavor. Lack of phosphorus, branches, leaves, roots are poor growth, dark green leaves dull,