June-July is suitable for planting Chinese cabbage.

Summer in Northeast China is characterized by high temperature and little rain in the early stage and sultry and rainy in the late summer. When planting Chinese cabbage in summer, the high temperature and dry weather in the early stage is very unfavorable to the normal growth of Chinese cabbage, while the hot and humid weather in the late summer is also a challenge to the root growth of Chinese cabbage. At the same time, the sultry weather in late summer is easy to breed all kinds of pests and diseases. Therefore, if Chinese cabbage is planted in summer, it is necessary to overcome the characteristics of summer weather in Northeast China. To overcome all kinds of problems encountered in the growth of Chinese cabbage, we must first choose suitable varieties and pay attention to the problems in the planning and planting process; Secondly, in the process of Chinese cabbage planting, field management should be strengthened to solve the problems encountered in the growth of Chinese cabbage. 1. Variety and sowing 1. Variety selection When planting Chinese cabbage in summer, because of the weather, we must choose varieties that are heat-resistant and can form dense leaves in summer, and at the same time, we must take into account varieties with early maturity, short growth cycle and fast growth rate. At present, the main varieties on the market are Xiayou No.2, Xia Tian 1, Xiabai No.45, Xia Feng, Youxiawang, Kangrewang and Xiabao. 2. The sowing conditions are large in the northeast, and the climatic conditions and farming habits in the three northeastern provinces are slightly different. When determining the sowing date, we should fully combine the local meteorological data and the actual sky conditions, choose the best sowing date, and meet the environmental conditions needed for the growth of Chinese cabbage to the greatest extent, which is also the key to a bumper harvest of Chinese cabbage in summer. In Shenyang, the sowing time of summer Chinese cabbage can be from late May to late July, while in Harbin, the best planting time of summer Chinese cabbage is from mid-June to early August. Secondly, direct seeding can be used to raise Chinese cabbage seedlings in summer, but direct seeding is the most commonly used method to grow Chinese cabbage in the open air in summer. There are two kinds of direct seeding, but from the perspective of efficiency and field management in the later stage, line seeding has more advantages. One acre of seeds 150-200 grams of cabbage is enough. The optimum planting density is 50cn row spacing, 40cm plant spacing and about 3000 plants per mu. In summer, Chinese cabbage should be irradiated with strong light after emergence, and shading measures should be taken when necessary. In summer, Chinese cabbage must be watered before sowing to keep the land moist, which is beneficial to the excavation of Chinese cabbage seedlings. After the seedlings are unearthed, they should be thinned in time. Generally, the seedlings should be thinned about twice according to the germination density and growth state. The first thinning occurs when Chinese cabbage seedlings grow to 1-2 leaves, and the second thinning occurs when Chinese cabbage seedlings grow to 3-4 leaves. Generally, strong seedlings with vigorous growth are selected for seedling in summer. When planting seedlings, avoid the high temperature at noon. It is best to choose before 9 am and after 4 pm, and leave about 3000 seedlings per mu. Remember to check the seedlings in time after 3-4 days. Three. Field management Before planting Chinese cabbage, the selected farmland to be planted with Chinese cabbage should be deeply ploughed with a rotary tiller, and at the same time, sufficient fertilizer should be applied. Generally, 3500-4000 kilograms of farm manure and 60-80 kilograms of ternary compound fertilizer are used per mu. Conditional growers can also apply 20 kilograms of calcium superphosphate per mu in summer cabbage fields. Because the growth period of Chinese cabbage in summer is in summer, the weather is hot and dry, the evaporation of water in Chinese cabbage field is large, and the water demand is also large. Cabbage planted in summer, if the water content can't keep up, will lead to loose leaves, lower yield and lower quality. Therefore, when planting Chinese cabbage in summer, it is necessary to keep the vegetable field moist, and wait until the topsoil turns white before drying, so as to prevent the newly grown Chinese cabbage seedlings from being lost or burned. Because the growth cycle of Chinese cabbage planted in summer is generally short, we generally don't squat Chinese cabbage seedlings in summer, but choose fertilizers to promote the growth to the end. When the weather is dry and there is no rain, you should always water the cabbage in summer to ensure that it is moist. If there is water in rainy days, it should be drained in time to prevent cabbage roots from rotting and getting sick. In summer after planting, apply urea 15 kg per mu of Chinese cabbage, and apply topdressing for the second time when Chinese cabbage is harvested. At this time, 20-25 kilograms of compound fertilizer can be applied per mu. Due to the planting season and climate, the proportion of pests and diseases of Chinese cabbage in summer is still relatively high. At this time, it is necessary to strengthen inspection and early detection and early control. Downy mildew and soft rot are the most common diseases of Chinese cabbage in summer. To prevent downy mildew, 50% metformin manganese zinc wettable powder and 40% triethylaluminum film wettable powder can be sprayed 50-600 times and 200-300 times in the early stage of Chinese cabbage. When controlling soft rot, you can choose to spray agricultural streptomycin 2-3 times during the onset of Chinese cabbage, and spray 72% agricultural streptomycin sulfate soluble powder diluted 3000-4000 times before or at the initial stage of Chinese cabbage. When spraying, we should focus on spraying temperate plants and their surrounding plants, petioles and stem bases near the ground, and pull out diseased plants in time to reduce the spread of bacteria and prevent the spread of diseases. The main pests of Chinese cabbage in summer are aphids and cabbage caterpillars. You can choose 4.5% beta-cypermethrin 1000- 1500 times diluted and sprayed for control. It should be emphasized that aphids should be strictly killed in Chinese cabbage in summer to prevent the occurrence of virus diseases. Four. Harvest Because summer in Northeast China is generally high in temperature and humidity, Chinese cabbage should be harvested in advance before it matures. Generally speaking, leaves need to be harvested when they are ripe in the seventh or eighth year. If the Chinese cabbage is harvested too late in summer, due to the high temperature in summer, it is easy to cause leaf soft rot and lead to the overall decay of Chinese cabbage. However, the specific harvesting time of Chinese cabbage in summer depends on the market demand. Generally, when the price is good, you can get better profits by concentrating on harvesting Chinese cabbage.