Onion is a long-lived Liliaceae vegetable crop. In China's Huanghe-Huaihe River Valley, onion cultivation generally uses 9~10 months of nursery, 2~3 months of transplanting, 5~6 months of harvesting onions or shallots; 3~4 months of nursery, transplanting in June, and collecting white shallots in autumn and winter. Planting mode. During this period, the seedling stage, the period of seedling transplanting, the period of leaf growth, and the times of multiple rooting and scallion formation are different stages. In general, the yield of welsh onion is relatively high, and the average yield per mu is between 3,000 and 6,000 kilograms. The ratio of nutrient absorption of nitrogen, phosphorus, and potassium is about 1:0.4:1.3, which shows that green onions have a higher demand for potassium and nitrogen, followed by phosphorus. Therefore, in the proportion of fertilization, we must pay attention to the balanced supply of potassium.
Especially in the conditions of high-yield cultivation and no application of organic fertilizers, more attention should be paid to applying potassium fertilizer. As for the specific amount of potassium applied, the proportion of N and K fertilization depends first on the ability of the soil to supply potassium, and secondly on the target yield of Welsh onion.
Generally speaking, the recommended onion of scallions at a high level is about 20 to 26 kg/ha of pure nitrogen, too much nitrogen fertilizer, and a large amount of water, which not only results in a waste of nitrogen fertilizer, but also increases the cost, and the output of green onions is not tolerant. Storage, quality decline, but also because of the loss of nitrogen, have a negative effect on the environment, so the amount of nitrogen fertilizer should be appropriate. The most common type of nitrogen fertilizer is urea, but the most suitable type of nitrogen fertilizer is ammonium sulfate because it is a sulfur-loving crop.
In the fertilization method also has stress. Full fertilization should be divided into two parts: base fertilizer and top dressing. The best basal fertilizer is musculosity of 4,000 to 5,000 kilograms of mature organic manure, which is applied to the ground during the site preparation and plowed in the soil. Fertilizer base fertilizer should be applied to all phosphate fertilizers, 40% nitrogen fertilizer and 60% potassium sulfate fertilizer, and the varieties can be compound fertilizer or single fertilizer. In the selection of compound fertilizer, sulfur-based general-purpose or special-purpose type can be used, and high-nitrogen type compound fertilizer is not suitable. The base fertilizer must have a depth of 15 cm. The top dressing of green onions can be divided into 2~3 times, and the remaining 60% of nitrogen fertilizer and 40% of potassium of base fertilizer are applied as top dressing in the middle and early stages of the Shengye and Scallion formation periods, respectively. The method of top dressing should have a good effect of water and fertilizer blending. Avoid using large nitrogen and large nitrogen fertilizers will not only cause low fertilizer utilization, but also spread urea on the surface in the summer, and the loss of nitrogen volatilization will cause smoked leaf burning problems.
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