Mr. Bao of Shaanxi Baoji said that 10 mu kg of diammonium was planted during the summer corn planting, and the urea was topdressed after jointing. But when it was 5 to 6 leaves, the seedling was yellow, and asked how this happened.
Experts: The main reason for yellow seedlings is the excessive application of phosphorus and nitrogen deficiency. Because diammonium is a high-phosphorus, low-nitrogen fertilizer, the exact proportion of nutrients required by crops is the opposite. Adding less phosphorus to wheat in wheat aphids results in the yellowing of corn seedlings due to nitrogen deficiency.
Too much phosphorus will aggravate the supply imbalance of nitrogen and phosphorus nutrients. In addition, the excessive use of phosphate fertilizer will also fix the active magnesium, iron, zinc and other elements in the soil. In the past, when I answered the questions of the farmers' friends, I had raised too many phosphate fertilizers causing the yellow seedlings. The lack of examples and hope that everyone will pay attention.
Ms. Tian from Liaoning’s Donggang District drew a small plot of rice seedlings in the field and only applied 12 kg of diammonium per acre. As a result, the seedlings generally became yellow, and asked what was the reason. What should I do?
Experts: The yellow seedling is likely to be a deficiency fertilizer, especially caused by nitrogen deficiency. Nursery should use fertile soil and increase organic fertilizer. The amount of chemical fertilizer is also much higher than that of transplanting rice. However, the fertilizer used by Ms. Tian is strong enough for phosphorus, nitrogen is insufficient, and potassium is not used. Because there is no organic fertilizer, trace elements may also be lacking. It is recommended to apply 10 kg of urea per acre, or to increase the amount of ammonium sulfate, ammonium bicarbonate, and 5 to 10 kg of potassium sulfate. If there is a shortage of symptoms such as reduced seedling disease, spray zinc sulfate or multielement fertilizer according to the instructions.
Of course, there are other reasons for the yellow seedlings. If this year’s northeast region suffers from long-term ice and snow cold weather, Putian is prone to pests and diseases, so pest and disease control must be strengthened. In addition, unqualified seeds and poor soil preparation also cause yellow seedlings.
Mr. Wu of Heilongjiang Jiansanjiang asked: Before the newly planted soybeans were planted, diammonium was applied. Now that diammonium is not used, how is this going? Is there fertilizer problem?
Experts: It's not that there is a problem with fertilizer, but fertilizer is not properly used. The newly-cultivated land has high soil fertility, and diammonium is enough. However, the soil fertility has been declining for many years, and light application of diammonium will result in shortage of nitrogen and potassium. It is suggested that diammonium can continue to be applied but nitrogen and potassium fertilizers must be added appropriately, and the defertilization should be prevented at the later stage.
Mr. Wu from Laizhou, Shandong, asked: What is the difference in the solubility of different chemical fertilizers?
Experts: Generally speaking, chemical fertilizers are soluble in water, so the fertilizer efficiency is faster. This is the characteristics and advantages of chemical fertilizers. Among them, nitrogen fertilizer is most easily dissolved, followed by potassium fertilizer. Phosphate fertilizer is further divided into water-soluble, weak acid-soluble and insoluble. The solubility of compound fertilizer depends on the composition of nitrogen, phosphorus and potassium fertilizers and the characteristics of processed materials. Generally, the higher the proportion of nitrogen and potassium, the easier it is to dissolve.
Ms. Guo from Wuhu, Anhui Province, asked that when transplanting the greenhouse, the melons were applied with high-tower granulation compound fertilizer. The ratio of N, P and K was 30:5:5. As a result, the lower leaves were all burned. Is this fake fertilizer?
Experts: Not fake chemical fertilizers. Leaf burns are caused by inappropriate fertilizers. High tower granulation compound fertilizer has high urea content, good water solubility and quick effect, but it is easy to burn seedlings. When used, be separated from the seedlings, or fully mixed with the soil, and timely open the shed ventilation, otherwise prone to ammonia poisoning, burn the lower leaves or flowers.
Mr. Lan from Dezhou, Shandong Province, asked, greenhouse cucumbers use general-purpose compound fertilizer as fertilization, fertilizer does not love to dissolve, seedlings can not grow up, this is how is it?
Expert: The fertilizer used is inappropriate. High-nitrogen-potassium compound fertilizers should be used. This fertilizer has good water-solubility, and the nutrient-distribution ratio is suitable for the nutritive characteristics and fertilization characteristics of the cucumber during the fruiting period. After the solubilization, the fertilizer can be applied with water and can be covered with soil.
Mr. Xu of Zhangjiakou, Hebei Province, asked how potassium dihydrogen phosphate should be applied rationally.
Experts: Potassium dihydrogen phosphate is a phosphorus-potassium compound fertilizer, which is more expensive and is best used as a foliar fertilizer. It is applied late in the crop. For example, after heading wheat, spray 0.2~0.3% of potassium dihydrogen phosphate 2~3 times, it can resist hot and dry wind and increase 1000-grain weight of wheat.
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