Secondary salinization of soil is the main soil barrier factor in the development of protected vegetables. Generally, the vegetable protection land with a life span of more than 3 years, the salt content of the soil surface layer is larger than that of the land soil, the salt content of the greenhouse soil is 0.1%-0.38%, and the salt content of the greenhouse soil is 0.15%-0.5%. Vegetables are harmed to varying degrees. After the secondary salinization of the soil, the soil structure is destroyed and the soil is compacted.
The cause secondary salinization of
First, the closed environmental conditions weaken the leaching effect of soil moisture. The salt accumulated in the soil cannot be washed into the groundwater and accumulated in the surface layer of the soil. In addition, due to frequent irrigation, the soil is in a humid state for a long time, the crops grow vigorously, the evaporation of soil moisture and the transpiration of crops are large, which promotes the accumulation of salt to the surface of the soil.
Second, excessive fertilization increases soil salinity. Under the cultivation conditions of the protected vegetable, the amount of fertilizer applied is often more than one time or more than the vegetable requirement, and a large amount of residual fertilizer and its auxiliary components accumulate in the soil, so that the concentration of the soil solution is increased.
Third, the groundwater level is high and the irrigation water quality is poor. The common feature of coastal saline-alkali soil and inland saline-alkali soil is high groundwater level and high salinity. In these areas, although some plots have been improved and fertilized for many years, they have become fertile soil with low salt content. After being used as a vegetable protection site, salting may occur soon.
Prevention of secondary salinization of
1. Avoid the development of vegetable protection land production in saline-alkali soil areas.
2. Implement soil testing (formulation) fertilization to reduce salt accumulation in the soil.
3. Reasonable irrigation reduces sudden water evaporation. Diffuse irrigation and furrow irrigation will accelerate the evaporation of soil moisture, which will easily accumulate soil salinity to the surface of the soil. Drip irrigation and infiltration irrigation are the most economical irrigation methods and ideal irrigation measures to prevent the accumulation of soil salinity to the surface of the soil.
4. Applying straw reduces the soil salt content. In addition to legume crop straws, other grass crops have larger carbon to nitrogen ratios. After being applied to the soil, they can assimilate nitrogen in the soil and effectively reduce the concentration of soluble salts in the soil. Achieve the purpose of improving the soil. In the soil where the soil salinization is not too serious, 300-500 kg of straw is applied per acre, and the salinization can be increased to 1000-1500 kg. The application period is best arranged after the summer pull, the straw is first cut into pieces of straw less than 3 cm in length, and evenly turned into the soil layer, which can be planted after 15 days.
5. Deep turn and rotation. After the vegetables are harvested, the surface layer and the deep soil are thoroughly mixed by deep turning, which can effectively prevent or alleviate the secondary salinization process of the soil. After several years of continuous use of vegetable protection sites, planting a season of open vegetables or planting a grain crop has a significant effect on restoring soil fertility, reducing physiological diseases of vegetables and diseases caused by germs.
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