1. The content of these nutrients in the soil is limited, and insufficient nutrition will inevitably lead to poverty. When the supply of some essential elements in the soil is insufficient, it will affect the tree vigor, yield and fruit quality, resulting in at least thick skin.
2. Improper application of phosphate fertilizer in navel orange orchard leads to plant phosphorus deficiency, resulting in rough fruit texture, thick peel and increased acid content.
3. When there is too much nitrogen, the plants grow in vain, resulting in weakened resistance, thickened pericarp, decreased juice, decreased solid content and citric acid content, and weakened flavor.