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Reasons for dead seedlings:
Salt damage. Chemical fertilizers are mostly composed of various salts, so when they are applied to the soil, they increase the concentration of salt in the soil solution to produce different osmotic pressures. If the osmotic pressure of the soil solution is higher than the osmotic pressure of the cytoplasm due to the large application of chemical fertilizer, the cells can not only absorb water from the soil solution, but reverse the water in the cytoplasm into the soil solution, which causes the cotton to die.
Alkali damage. In the high pH soil, when the local pH value is high due to the application of urea, the nitrification of the soil is inhibited, and the accumulation of high concentration N03- may occur, which may cause certain toxicity to the crop.
The quality of irrigation is not good. At present, the biggest problem in cotton irrigation is that the irrigation is not strictly in accordance with the law of cotton growth and water demand. Instead, flood irrigation and blind irrigation are carried out, and the phenomenon of waterlogging and flooding occurs, which makes the water table rise. In addition, the underground runoff is not smooth, and the degree of mineralization is high. Under strong evaporation conditions, the soil has serious secondary salinization, and a large amount of salt is accumulated in the root concentration area, which is highly toxic and eventually causes cotton to die.
Fertilization is unscientific and unreasonable. After being applied in summer, urea is first decomposed by water into (NH4)2CO3 or NH4HC03 under the action of urinary enzymes. Under the influence of high temperature, especially on high pH soil, it is further rapidly decomposed to produce ammonia gas. Less ions, a large amount of NH3 volatilization and ammonia poisoning, not only the loss of ammonia, but also the death of cotton.
Measures to be taken:
Strengthen the leveling of the land. In saline-alkali soils, soil inequality directly affects the redistribution of soil moisture and salinity. The uneven soil salt content is related to crop seedlings. Therefore, the land leveling work is to ensure the precision irrigation, uniform irrigation, reduce the loss of field water, eliminate salt and alkali spots, and control the foundation of salt and alkali.
Add organic fertilizer and implement straw returning. Take agricultural measures, increase the application of organic fertilizers such as oil slag, implement straw returning, plant alfalfa, oil sunflower green manure, improve the physical and chemical properties of the soil, and consolidate the soil desalination effect.
Filling and arranging, washing salt and alkali. Control the amount of water diversion, dredge the drainage system, discharge the saline-alkaline water, so that the salinization area, especially the heavy salinization area, has irrigation, there is source of irrigation, drainage has a way out, irrigation and drainage combined, lowering the groundwater level, accelerating the soil Desalting and alkali removal.
Soil testing balanced fertilization and improved fertilization methods. Using the soil nutrient content and the water requirement and quantity of cotton to carry out the recommended fertilization, not only save labor and fertilizer, but also improve the utilization rate of fertilizer, and achieve the purpose of saving costs and increasing farmers' income. Can not blindly rely on the amount of fertilizer input to increase cotton yield. In the fertilization method, the combination of full-layer fertilization and topdressing is adopted. The nitrogen fertilizer should be applied as a top dressing or as a base fertilizer, and should not be applied to the surface in a large amount.
Extensively promote high-tech water-saving technology. Change the flood irrigation to fine irrigation or drip irrigation. According to the water demand law and soil moisture condition of cotton, timely and appropriate irrigation can be carried out to improve the uniformity of irrigation, meet the demand for water in different growth stages of cotton, avoid the increase of groundwater fraction, curb the development of secondary salinization of soil, and reduce soil. The salt of the surface layer creates a good environment for the growth and development of cotton roots.
Causes and countermeasures of dead seedlings after cotton water and fertilizer
Water and fertilizer are the two most active factors in cotton production measures. The regulation and control of water and fertilizer plays a very important role in determining cotton yield. However, some cotton farmers are unrealistic. In order to pursue higher cotton yield and higher cotton planting benefits, blindly watering and fertilizing will result in a decrease in cotton yield. Even some cotton fields will die after a large area of ​​water and fertilizer, and the light will reach 10%. 50%, the economic loss is very serious.
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