After years of planting vegetables greenhouses, a layer of purple-red material will appear on the soil surface. When the soil is dry, the soil surface will generate a layer of white material. This is because the soil in the greenhouse has been salinized. Salinization causes physiological drought and metabolic disorders in vegetables caused by water absorption difficulties. It is manifested by slow seedling emergence after seed sowing, low seedling emergence rate, which means that the seedlings will also gradually die; the plants are short, growth is stagnant, root growth is inhibited, and the root tip is new. The roots were brown, and when the roots were severe, the whole roots turned black and rotted and lost their vitality. The leaves curled and lacked green, and the tip was yellow and curled. The stems and leaves died when the damage was severe.
The main causes of salinization in vegetable greenhouses are as follows: 1. Fertilizers in greenhouses have a high level of fertilization. The amount of fertilizer applied exceeds the amount of absorption. Some of them cannot be used as “by-products†and accumulate in the soil. In particular, some farmers are pursuing production. Excessive fertilization has exacerbated the salinization of vegetable greenhouse soil; 2. The greenhouse has a high temperature and large evaporation. When the water evaporates, the salt is left in the soil surface of the shed. 3. The greenhouse is usually in a confined state and the salt is distributed. Rainwater is not washed and rinsed, and therefore it remains in the soil tillage, causing soil salinization in vegetable greenhouses. 4. Raw manure and urine are produced. Due to the high temperature of the greenhouse, human and animal manure is rapidly volatilized and decomposed, and ammonia is abundant. It is volatilized, leaving some sulfides, sulfates, organic salts and inorganic salts left behind in the plough layer of the soil, causing soil compaction and salinization in greenhouses.
The main measures for preventing salinization in greenhouses are as follows: 1. Crop and crop rotation, rotation of greenhouse vegetables and rice wherever possible; 2. Removal of greenhouse roof membrane in summer, especially during rainy season, to allow natural rainwater to be washed and washed; 3 Balanced formula fertilization, avoid excessive fertilization; 4, increase organic fertilizer, chicken manure pigs, straw returned to the field, less fertilizer; 5, as little as possible to apply high-salt organic fertilizers and chlorine-containing fertilizers; 6, Remove 2 cm to 3 cm of soil from the soil surface of the greenhouse, replace it with fertile soil, and remove soil from salt. 7. Improve soil structure and activate soil. This will not only facilitate the extension of lateral roots in greenhouses, but also increase nutrient and moisture absorption in vegetable roots. The ability to increase the organic matter content of the greenhouse soil.
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