Many peasants who grow vegetables in greenhouses this year report that some melon vegetable seedlings appear dead. Observed is not a bacterial hazard but a typical ammonia poisoning. The main types of hazards are the following:
Free-Acid Hazards The superphosphate used in production and the superphosphate used in compound fertilizers are generally produced from ores. The production process requires the use of sulfuric acid, and many products are of unstable quality. In particular, some manufacturers use poor quality sulfuric acid, which can easily cause excessive levels of sulfuric acid and other acids in SSP products. Unqualified superphosphate contains harmful substances that can contaminate the soil, disrupt the growth of crops, destroy the polar structure of the cell's cell protoplasm, affect the normal division of cells into diseased tissue, destroy the growing point of the crop, affect the synthesis of chlorophyll, and affect crops. Cause varying degrees of harm. If this superphosphate is mixed with rice, wheat and vegetable seeds, it is very easy to burn the seedlings, and in severe cases it will cause bad seedlings.
The danger of biuret The temperature of urea in the granulation process is too high, and it will undergo a condensation reaction to form biuret (also known as biuret), which is a substance with penetrating properties. It can cause dehydration of seeds cells and inhibit seed germination. Application of urea in paddy fields, due to the dilution of irrigation water, rice can tolerate higher concentrations of biuret. Concentrations above 400 mg/l can cause significant damage. Urea is used in melon and vegetable seedlings, and especially attention should be paid to the hazard of biuret to vegetable seedlings; when applied at drought, if biuret concentration exceeds 15 mg/l, the crop will die. The application of urea in dry land, especially winter crops, is slow because the temperature and humidity are both reduced, and urea and biuret are decomposed and converted into ammonium. If sowing or transplanting seedlings, the concentrated solution will be like pickles. The water in the seed or seedling root is aspirated, and the toxicity of the biuret at a high concentration influences the germination of the seed or causes the shoot to die.
Therefore, pay attention to early application of base fertilizer, must be planted 2 weeks after sowing. If you want to grab a peasant, you must apply urea in the seeding ditch, cover the thin soil on top, and sow on thin soil. After the seed germinates, the urea and biuret have been converted to ammonium state when they are gradually extended to the lower layer. The urea and biuret are absorbed by the soil and gradually supply the young shoots. Transplanting seedlings must be disassembled before transplanting.
Ammonia Poisoning The compound fertilizers produced from ammonium bicarbonate and urea as raw materials are prone to produce ammonia gas, especially for compound fertilizer products produced from ammonium bicarbonate. When the water content exceeds the standard or the temperature is high, ammonium bicarbonate will decompose to ammonia and carbon dioxide on its own. And water. Relatively speaking, compound fertilizers produced with urea are less likely to produce ammonia, but in alkaline soils, compound fertilizers containing urea are also prone to ammonia. Ammonia has a strong irritating odor, is severely corrosive, and can burn seeds, seedlings, and roots. In addition, the use of urea or ammonium bicarbonate in greenhouses or greenhouses with high humidity tends to cause ammonia volatilization, which can cause crops such as vegetables to die due to ammonia poisoning. Because ammonium bicarbonate has strong volatility when the humidity is high and the temperature is high, the produced ammonia gas is irritating and corrosive. The contact of the ammonia gas with the seeds will smoke the seeds and even burn the embryos, affecting germination and emergence. According to the test, 12.5 kg of ammonium per acre was used as the seed fertilizer for wheat and the seedling emergence rate was less than 40%. If the ammonium bicarbonate was sprinkled on the rice seed box surface and then sown, the bad bud rate reached more than 50%.

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