Due to the long-term and excessive application of chemical fertilizers in greenhouses, greenhouses and other protected vegetables, the residual fertilizers form various salts, mainly calcium sulfate, calcium chloride, magnesium chloride, calcium nitrate, potassium nitrate and the like. Anniversary closed management, soil salt can not be washed by rain, strengthen the salt accumulation of topsoil, soil acidification and increase the harm of salt to crops.
The main reason for the high salt content of the soil is the physiological drought, that is, due to the high salt concentration, the soil osmotic pressure is higher than the root cell osmotic pressure, so that the crop loses its ability to absorb water and nutrients, and the lighter inhibits crop growth. With a variety of deficiency symptoms, the entire plant withered and died. For example, the heart of the tomato is curled, and the umbilical rot and stem rot are increased. The surrounding leaves of the old leaves of the strawberry become brown, gradually withering toward the center, and the flower buds become brown and withered. In severe cases, the whole plant dies. Different vegetables have different salt tolerance, and the salt resistance is arranged from strong to weak. The strong resistance is: small oil, cabbage, radish, spinach, cabbage, turnip, celery, etc. : eggplant, onion, carrot, tomato, green pepper, cucumber, etc.; weak resistance: broad beans, onions, kidney beans, lettuce, strawberries, ducks and so on.
The main measures to prevent salt damage are:
The amount of nitrogen applied (N) and the amount of potassium applied (K2O) for scientific fertilizer application is 4-6 kg per mu, generally not more than 8 kg, and it is necessary to combine water and fertilizer, and a small amount of multiple times; The maturity and semi-fermented straw fertilizer is beneficial to absorb and utilize excessive nitrogen fertilizer in the soil and improve soil physical and chemical properties.
The rain wash salt uses the rainy season to change the planting interval, and exposes the rain to wash the salt; if it can be properly deep ploughed, it can also break the surface soil salt layer, improve the soil structure and achieve better results.
Long-term continuous planting of sheds and sheds not only absorbs the nutrients of the crops, but also easily infects pests and diseases, and easily leads to soil salinization and acidification. It is necessary to strengthen the rotation of different crops, or to move the greenhouses once every 3 to 5 years to improve the salinization of the old shed soil. New shed vegetables have a good soil environment.
Emergency measures If salt damage occurs in the crops that have been planted, emergency measures such as watering, water spraying, straw mulching and scraping of the topsoil may be used. If the seedlings are not restored, normal, and other vegetables may be replanted after washing the salt.
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