What fertilizer is used for onion seedling raising time and base fertilizer?

Onion seeds can germinate at 3-5℃, and the optimum temperature is 15- 18℃. The suitable temperature for seedling growth is 12-20℃, and it grows slowly when it exceeds 25℃. It can withstand the low temperature of 6 17℃. Seedling growth needs moist soil, and the suitable soil pH value is 6.0-6.5, which is not tolerant to salt and alkali. Onion belongs to the green vernalization type, which can be vernalized after a certain period of time (depending on the variety) at a suitable low temperature (generally below 9- 10℃). Therefore, special attention should be paid in the process of sowing and seedling raising in autumn to prevent pulling onions in advance. There is a big gap between north and south in the sowing date of onions. Sowing in winter in South China, sowing in autumn in the Yangtze River basin and sowing in spring in Northeast China. Except in spring, the sowing date should be strictly controlled to avoid excessive growth and even vernalization of seedlings before the arrival of low temperature in winter.

Onions like cold, dry, afraid of high temperature and heat. Onion seeds can germinate at 3-5℃, but the optimum germination temperature is 15- 18℃. The optimum temperature for seedling growth is 12-20℃. When it exceeds 25℃, it grows slowly, but it can tolerate the low temperature of -6-7℃. The growth of seedlings needs moist soil, and the suitable soil pH value is 6.0-6.5, which is not tolerant to salt and alkali. Onions belong to the green vernalization type. When the seedlings grow to a certain size (generally, the diameter of green onions is above 0.8 cm), they can pass vernalization at a proper low temperature (generally below 9- 10℃) for a certain time (depending on the variety). Moreover, onion bulb expansion and bolting need warm and long sunshine conditions, so special attention should be paid to the determination of sowing date and seedling management during autumn sowing to prevent onion bolting in advance.

Too much base fertilizer should not be applied to the seedbed to avoid the seedlings growing too fast. General 100 m2 seedbed is applied with 300 kg of organic fertilizer and 5- 100 kg of calcium superphosphate.