Good quality, high yield, reducing nitrogen and increasing potassium is the key.

In recent years, the majority of vegetable farmers blindly increase the use of chemical fertilizers, especially nitrogen fertilizers, in order to increase the yield of green onions. According to the investigation, the average application of pure nitrogen and pentoxane phosphorus per mu of green onions is as high as 40,50kg and 1015kg respectively, while little or no potash fertilizer is applied, resulting in a decrease in the yield of green onions and the aggravation of root rot. Excessive application of nitrogen fertilizer and little application of potassium fertilizer can easily lead to nitrogen and potassium malnutrition of green onions. Since 2011, the Agricultural Technology Center of Sheqi County has organized scientific and technological personnel to arrange experiments on fertilization of green onions in Daiying Welsh Onion Base and Xialaozhuang Welsh Onion Base. According to the test results and the principle of nutrient balance of soil testing and formula fertilization, the technical theory of "good quality and high yield of green onions is put forward in the fertilization of green onions". The popularization of this fertilization technology increases the average yield of local green onions by more than 20% per mu. Obvious results have been obtained, and the specific fertilization methods are introduced as follows: 1. Welsh onion is a vegetable crop of Liliaceae with long growth period. In the Huang-Huai River Basin of China, two planting modes are generally adopted for the cultivation of green onions: raising seedlings from September to October, transplanting from February to March, harvesting scallion or shallot from May to June, raising seedlings from March to April, transplanting in June, and harvesting green onions in autumn and winter. During this period, we have to go through different growth stages, such as seedling stage, slow seedling stage, leaf stage, multiple root sealing and green onion formation stage. The yield of green onions per mu is 3000kg to 6000kg, and the proportion of nitrogen, phosphorus and potassium uptake by high-yielding green onions is about 1 ∶ 0.4 ∶ 1.3.It can be seen that green onions have more demand for potassium and nitrogen, followed by phosphorus. Therefore, in the proportion of fertilization, attention should be paid to the balanced supply of potash fertilizer. Especially under the condition of high-yield cultivation and no application of organic fertilizer, more attention should be paid to the supplementary application of potash fertilizer. As for the specific amount of potassium application, the proportion of nitrogen and potassium fertilizer mainly depends on the following three aspects: first, the potassium supply capacity of the soil itself, such as the low potassium supply capacity of sandy soil, it is necessary to appropriately increase the use of potassium fertilizer; second, it depends on the target yield of green onions, if the yield per mu exceeds 10,000 jin per mu, the output of green onions will take away more potassium from the soil every season, so potash fertilizer should be increased accordingly. Third, the amount of other fertilizers, such as the amount of straw returned to the field and the amount of nitrogen fertilizer, can be applied less if a large amount of organic fertilizer is put in, especially the amount of chemical nitrogen fertilizer should be appropriate, and it should be applied in balance with the corresponding potassium fertilizer. in order to have a good effect of increasing production. Otherwise, blind investment is not only not beneficial to the high yield of green onions, but also leads to the decline of the quality of green onions, such as small proportion of green onions, many leaves, not strong onion flavor, even bitter taste and so on. two。 In general, the recommended amount of nitrogen for planting green onions is about 20 kg ~ 26 kg per mu of pure nitrogen. Too much nitrogen fertilizer is applied, coupled with a large amount of water, which not only wastes nitrogen fertilizer and increases the cost, but also produces green onions that are not tolerant to storage and decline in quality. it will also have a negative effect on the environment because of nitrogen loss. Therefore, the amount of nitrogen fertilizer should be appropriate, in the selection of nitrogen fertilizer varieties, the most common is urea, but the most suitable nitrogen fertilizer variety is ammonium sulfate, because green onions are sulfur-loving crops. 3. It is also fastidious in the fertilization methods of green onions. The whole process of fertilization should be divided into two parts: base fertilizer and topdressing fertilizer. In the base fertilizer, it is best to apply 4000kg to 5000kg mature high-quality organic fertilizer per mu, spread it on the ground during soil preparation, and plough the soil. Chemical fertilizer base fertilizer should be applied to all phosphate fertilizer, 40% nitrogen fertilizer and 60% potassium sulfate fertilizer, variety can choose compound fertilizer or elemental fertilizer. When selecting compound fertilizer, sulfur-based general type or special type can be selected, which is not suitable for high nitrogen compound fertilizer. The fertilization depth of the base fertilizer must be about 15 centimeters. The topdressing of green onion can be carried out in 2 to 3 times, and the remaining 60% nitrogen fertilizer and 40% potassium fertilizer will be applied as topdressing in the full leaf stage and the early and middle stage of onion white formation stage, respectively. The best method of topdressing is the combination of water and fertilizer, do not apply water and nitrogen, it will not only cause low fertilizer use efficiency, but also spread urea on the surface in summer, nitrogen volatilization is easy to cause the problem of smoking leaves and burning seedlings.