1. Nitrogen deficiency: the leaves turn yellow, and the leaves turn light green evenly, accompanied by nitrogen transfer in the leaves to maintain new growth. The new shoots of citrus stopped growing due to phosphorus deficiency, with dense leaflets and necrotic spots on the leaves.
Fertilization measures: Appropriate application of high-nitrogen water-soluble fertilizer from sea silkworm nests.
2. Phosphorus deficiency: the growth of new shoots stops, the leaflets are dense, there are necrotic spots on the leaves, the old leaves are bronzed, the branches and petioles are purple, the fruits are thick and loose, and they become soft when they are immature.
Fertilization measures: Appropriate application of high phosphorus water-soluble fertilizer in sea silkworm nests.
3, potassium deficiency: inhibit the growth of the tree, the whole plant grows weak. Leaves become smaller and wrinkles turn yellow. The fruit has poor development, poor quality, chromatic aberration and low yield.
Fertilization measures: Appropriate application of high-potassium water-soluble fertilizer from sea silkworm nests.
4. Calcium deficiency: The leaves turn yellow at the top in spring, and then spread to the edge of the leaves. The diseased leaves are long and narrow, the yellowing diseased leaves fall off early, and deciduous branches often appear in the upper part of the crown. Physiological fruit drop and cracking are serious, and the fruit setting rate is low.
Fertilization measures: Appropriate application of calcium chelated fertilizer from marine products will not easily antagonize other elements and reduce fruit cracking.
5. Magnesium deficiency: The part of the diseased leaf that is balanced with the midvein first yellows, and the yellowed part is mostly prismatic. Leaf tops and leaf bases often remain green for a long time, showing an inverted triangle.