First, symptoms:
Symptoms of boron deficiency appear in growing tissues, such as apical growth points, young leaves, tubers and roots or fruits. Symptoms vary from crop to crop. To sum up:
(1) The growth points of the apex and heart leaves are blocked, bleached or browned and die, which stimulates the growth of lateral buds (some lateral buds also die immediately) and are clustered or clustered.
(2) The leaves are deformed, thickened, fragile or shriveled, and some crops have symptoms of yellowing between veins.
(3) The petiole or stem becomes thicker, shorter and thicker, with cracks and cork, or gangrene in water.
(4) Tuber or tuber with cork or black heart.
(5) Boron deficiency inhibits the formation of pollen, nectar and pollen tube, affects pollination, and causes serious flower or fruit drop.
(6) The fruit is deformed, the development is slow, the peel or pulp is partially submerged, the peel is thickened, the juice yield is low, and the seeds are stunted.
Second, the easy environmental conditions:
(1) Due to long-term leaching, the content of boron in riverbed, gravel, sandy soil or red soil in rainfall-rich areas is extremely low, and crops are vulnerable to boron.
(2) In calcareous soil with high pH value, boron is easy to be fixed and its effectiveness is low, which leads to boron deficiency in crops.
(3) During drought, the movement of boron in soil and the absorption of crops are blocked, and boron deficiency is more likely to occur.
(4) Partial application of nitrogen fertilizer aggravated boron deficiency.
(5) Planting sensitive crops. Dicotyledonous plants are more sensitive than monocotyledonous plants, and fruits and vegetables generally lack more boron than field crops. Rape, beet, sunflower, sesame and cotton in field crops; Citrus, apples, grapes, Chinese cabbage, Chinese cabbage and celery in fruit and vegetable crops are sensitive to boron. Gramineae crops are generally insensitive to boron except wheat and corn.
Third, the prevention and control methods:
Applying boron fertilizer to soil is a common method. Borax, boric acid and boron mud are used as boron fertilizer, but borax is commonly used. General field crop consumption is 7.5 ~ 15 kg/ha, and sugar beet with high boron demand is 22.5 ~ 30 kg/ha. Mix mud or water, and spray 0. 1% ~ 0.2% borax solution with the dosage of 750 ~ 1500 g/ha. Fruit trees should be applied according to trees, each tree is 50 ~ 100g.
Because the suitable range of boron in general crops is narrow, the suitable amount is close to the limit of excess, and it is easy to be excessive, so the dosage should be strictly controlled; In fact, borax dissolves slowly, so it should be dissolved with warm water first, and then coated with enough water.
In addition, in order to control soil over-alkali, we should pay attention to the choice of acid fertilizer for fertilization.