It is a component that synthesizes protein, nucleic acids, enzymes, hormones and chlorophyll, which affects cell division and promotes the vegetative growth of roots, stems and leaves. Nitrogen content has a great influence on the growth and development of seedlings. In a certain range, increasing nitrogen application can increase the chlorophyll content of leaves and enhance photosynthesis. Under the condition of nitrogen deficiency, the seedlings grow slowly, the stems are small, the leaves gradually turn yellow from bottom to top, the veins turn green, and finally the whole plant turns yellow or brown, and the leaves die and fall off.

After the symptoms of nitrogen deficiency appear, topdressing nitrogen fertilizer, such as urea and ammonium nitrate, can be used to spray 0. 1% ~ 0.3% urea on the leaves of seedlings.

(2) Phosphorus

It is the main component of nucleic acid, phospholipid and nucleoprotein in vivo, which promotes nutrient accumulation and transformation and plays a key role in energy metabolism. Phosphorus fertilizer can promote the absorption of nitrogen fertilizer. When the content of soluble phosphorus in the soil is high, the seedlings grow healthily, the roots are developed and the cold resistance is strong. In addition, phosphate fertilizer can also promote the early differentiation of flower buds and the quality of flower buds is also high. At seedling stage, due to phosphorus deficiency, the growth is slow, the stems are slender and lignified, the leaves are small, the leaves are dark green and dull, and the back of the leaves is purple. Because phosphorus deficiency can also affect the absorption of nitrogen, seedlings can't grow trees.

After phosphorus deficiency, spraying 0. 1% ~ 0.2% potassium dihydrogen phosphate or soaking 1% calcium superphosphate for one day and night, and spraying the clear liquid on the leaves.

(3) Potassium

It exists in the body in an inorganic state, which is related to physiological functions such as maintaining cell swelling pressure, regulating water absorption, improving enzyme activity and synthesis. It can also increase photosynthesis, strengthen stems, resist lodging and enhance resistance. At the beginning of seedling stage, the symptoms of potassium deficiency are not obvious. At the late stage of seedling stage, due to potassium deficiency, the lower leaf margin and tip turned yellow, the stems and leaves were soft, then the leaf margin was scorched and the leaves turned bronze and yellow-brown. In severe cases, spots appear along the veins, and mesophyll rots, necrosis and leaves fall. The roots turn brown and the roots are stunted.

When potassium is deficient at seedling stage, potassium sulfate can be topdressing, 5g per square meter of seedbed, and then watering. Potassium dihydrogen phosphate can also be sprayed.

(4) Calcium

Maintain the normal structure of cell membrane and cell wall, regulate pH and osmotic pressure in vivo, enhance nitrogen metabolism and promote root development. Calcium deficiency is characterized by weak stems and leaves of seedlings, slow growth of roots, stems, leaves and other organs, and necrosis of the top of stems and the edges of tender leaves.

Calcium deficiency at seedling stage is mainly caused by the difficulty of calcium absorption by seedlings under the conditions of high temperature, drought and excessive nitrogen fertilizer. As long as seedling management is strengthened, high temperature is prevented, soil in seedbed is kept moist, and nitrogen fertilizer application is not excessive, calcium deficiency in seedling stage will generally not occur.

⑤ Magnesium

It is a component of chlorophyll and participates in photosynthesis and metabolism of acid and sugar. When magnesium is deficient, the leaves begin to turn yellow from the bottom and gradually develop upwards, and in severe cases, the leaves die. The leaves are yellow, with purple spots locally, and the veins are still green.

After magnesium deficiency, 0. 1% magnesium sulfate can be sprayed on the leaves.

(6) Zinc

It is beneficial to photosynthesis, respiration and carbohydrate conversion. When zinc is deficient, there are white stripes or necrotic spots between veins, and the terminal buds are not dead, but the newly grown leaflets are yellow with yellow and white spots, and then the leaves are necrotic.

After zinc deficiency, 0.05% ~ 0.2% zinc sulfate can be sprayed on the leaves.

(7) Boron

Promote photosynthesis and carbohydrate transport. The main symptoms of boron deficiency are dark green or yellowish brown leaves, atrophy, petiole cork, top growth point necrosis, short plants and blocked flowering. The roots turn yellow and the root tips die.

Alkaline soil and sandy soil are easy to lack boron. It is found that 0.3% boric acid can be sprayed 2 ~ 3 times every 3 ~ 4 days for boron deficiency. You can also spray 0.025% ~ 0.2% borax solution (first dissolved in 40℃ hot water and then diluted).

(8) ferritin

Promote the formation of chlorophyll and keep it green. The seedlings were deficient in iron, and symptoms began to appear from the heart leaves. The growing point is not necrotic, but the leaves are yellow, but the veins are still green. Later, the whole leaves turned yellow and white, and the seedlings were short without necrosis.

The bed soil is too alkaline (above pH8), which makes it difficult for seedlings to absorb iron, resulting in iron deficiency. Therefore, the pH value of the prepared bed soil should be 6.5 ~ 7. If it is alkaline, it should be mixed with acid fertilizers such as calcium superphosphate. After iron deficiency, 0.2% ~ 1.0% ferrous sulfate solution can be sprayed.

(9) Manganese

Participate in photosynthesis and promote the transformation of nitrogen and the accumulation of sugar. The terminal buds of seedlings do not die because of lack of manganese, the leaves and stems are green, the veins are residual green and some veins are yellow. Later, the yellow leaves were necrotic, the stems were thin and weak, and the number of flower buds was small.

Alkaline soil is generally deficient in manganese, so it is necessary to avoid using alkaline soil as nursery soil. When manganese deficiency is found, 0.05% ~ 0. 1% manganese sulfate solution can be sprayed once every 10 day, 1 ~ 2 times.

(10) molybdenum

Promote the formation and transformation of sugar and promote the role of phosphorus.

Molybdenum deficiency is characterized by slow development and few flower buds. Old leaves began to turn yellow except veins, the yellow part bulged, the leaf margin curled inward and died from the tip and periphery. At this time, 0.02% ~ 0.05% ammonium molybdate solution can be sprayed.

(1 1) copper element

Promote chlorophyll formation and photosynthesis. If copper is lacking, the stems and leaves will be weak, the growth and development will be poor, the tip of the leaf will turn white and the leaf tissue will lose its green color. If the above symptoms are found, 0.02% ~ 0.4% copper sulfate solution can be sprayed.