The lack of crops will have certain symptoms. Different crops perform differently. Nitrogen deficiency: Plants are pale green, base leaves (old leaves) turn yellow, and brown when dry. Stems are short and fine, branches (branches) are few, and premature aging occurs. If nitrogen deficiency occurs in fruit trees, it is characterized by small fruit, few fruit, and hard skin. Phosphorus deficiency: dark green plants, veins often red or purple, dark green when dry. The stems are short and fine, the base leaves turn yellow, the flowering period is delayed, and the seeds are small and stingy. Potassium deficiency: The stems are easily lodged, the edges of the leaves are yellow, scorch, and fragmented, and necrotic spots appear between the veins. The entire leaf is sometimes reeled or shrunken, and the brown roots are more. Grain crops and other sugar-rich crops require large amounts of potassium at later growth stages, such as cereals and potatoes, sweet potatoes, watermelons, and grapes. Magnesium deficiency: Leaves yellowing, variegated (and the difference in nitrogen deficiency). The veins are still green, but the veins turn yellow, sometimes purple, and necrotic spots appear. Iron deficiency: The veins are chlorosis, showing a clear reticular pattern. When severe, the entire leaf (especially the young leaf) is pale yellow and even white. Northern fruit trees such as apples and pears are prone to symptoms. Boron deficiency: first appear at the top, if the top stops growing. Deformity and shrinkage of young leaves. Irregular green leaves. Rapeseed "flowers but not real", cotton "buds without flowers," Apple's fruit disease, radish heart rot, etc., are all caused by the lack of boron. Zinc deficiency: Leaves clustered, spots appear on both sides of the leaf. The plants are short, the internodes are shortened, and the growth period is delayed. If there is lobular disease in the tree, albino seedlings of corn, etc. Copper deficiency: New leaves lose their greenness, their tips are white, their curls are papery, their leaves show necrotic spots, and they wither and die. Cereal crops show clusters of plants and white tops. When they are severe, they do not produce headings and are not robust. The lack of copper in the fruit tree is characterized by the clustering of the top leaves, and the symptoms of leaf and fruit are faded. Manganese deficiency: small necrotic spots appear between veins, and dark green stripes appear as ribs. Such as citrus manganese deficiency.