Walnuts like warmth and fear frost. Sandy loam is fertile and moist, and is commonly found in deep soil on both sides of the valley.
The planting time of walnut is around the tenth day of walnut germination in March, and the survival rate of 1~2-year-old seedlings is high. After planting, water and fertilizer management should be strengthened, soil loosening and weeding should be done frequently, drainage should be paid attention to in rainy season, and pest control should be paid attention to in June and July. Pruning should be carried out in the growing period, and the dry height should be kept above 3 m. Do not prune after defoliation, otherwise it will easily cause bleeding and affect the growth of trees. Planting time is generally suitable for deciduous fruit trees in winter and evergreen fruit trees in spring. When planting, it should be standardized, one line at a time. When planting, the joint should be exposed on the ground, the root system should be elongated, then the soil should be cultivated, used, irrigated, and the hole should be sealed to keep water after water seepage.
Walnut has strong adaptability and is not strict with environmental conditions. Generally, the altitude is 500- 1500m, the annual average temperature is 9- 16℃, and the annual rainfall is 800- 1200mm. Sandy loam or calcareous soil with pH value of 6.5-7.5 can be planted in places with deep soil layer, loose and fertile soil and good drainage. The soil is too sticky and wet, and the soil with poor drainage is not suitable for planting. Walnut is a light-loving fruit tree, which needs sufficient light. It is best to choose the south slope to build a garden in mountainous areas.
Because young walnut trees have large pith, high water content and poor cold resistance, they are prone to freeze injury in cold and arid areas, resulting in dry branches. Therefore, in order to ensure the normal growth of young walnut trees, it is very important to prevent cold in winter. Cultivating a mound within 30 cm of the root of walnut seedlings can effectively increase the thickness of the protective layer of the root soil, just like adding an extra layer of cotton-padded clothes to it, thus achieving the effect of cold protection. Burying the soil for cold protection can bend the whole tree to one side, and attach 30-40 cm thick soil to the 1-2-year-old seedlings that can't safely overwinter outdoors, and also achieve the function of heat preservation and cold protection. White coating can effectively alleviate the temperature difference between the yin and yang sides of the trunk by white coating the trunk of seedlings, and the cold-proof effect is very good. Formula of common white coating agent: salt, quicklime and clear water are prepared according to the ratio of 1: 12: 30, and an appropriate amount of adhesive can be added during preparation to increase the coating effect. As a tradition, the method of wrapping cold is also the most direct. That is, the trunk is wrapped with straw or plastic film to achieve the effect of cold protection. Walnut diseases and insect pests and their control: Walnut branch blight is a fungal disease. It mainly harms the branches and causes them to die. The damage rate of walnut branch blight is about 20%, and it can reach 90% seriously, which mainly affects the growth and yield of trees. The symptom of this disease is that 1~2-year-old branches are damaged and gradually dry from the top to the trunk, and the leaves turn yellow and fall off. Dense black spots are produced on the dead branches, and mucus flows out when the humidity is high, forming black tumor-like protrusions. Bacteria overwinter on diseased branches and invade through wounds, only hurting weak trees. The control method is to remove diseased branches and burn them centrally; The control time and chemicals used are the same as those used to control walnut anthracnose. Sclerotinia sclerotiorum mycorrhizal rot, also known as white silk disease, harms seedlings for more than one year, making their taproot and lateral root cortex rot, causing partial or even total death on the ground. 1. Disease symptoms: Under the condition of high temperature and high humidity, white spun silk mycelium is produced at the base of the root neck of seedlings and the surrounding soil and the surface of fallen leaves, and then the sclerotia grows white first and then turns brown. 2. Pathogenic law: Pathogens overwinter in diseased plant residues and soil, and most of them invade from the neck of young walnut tree sclerotium root rot. When encountering high temperature and high humidity, the disease is serious, usually in late May and June-August. Seedling raising in acidic soil or previous crops such as vegetables and grain is easy to get sick. 3. Prevention and control methods: (1) Choose seedling raising place to avoid continuous cropping of diseased seedlings, choose seedling raising place with good drainage and low groundwater level, and adopt high seedling bed to raise seedlings in rainy areas; (2) Dry soil or replacing soil with guest sand can be changed once a year, which is generally valid for 1~2 times; (3) Seed disinfection and soil treatment: Before sowing, seed was dressed with 50% carbendazim powder and 0.3% carbendazim, and appropriate lime or plant ash was added in acidic soil to neutralize acidity, which could reduce the occurrence of diseases. In addition, the roots of diseased trees were watered with 500- 1000 times solution of copper sulfate or thiophanate-methyl, and then hydrated lime was sprinkled on the base or roots of seedling necks. [4]? Note: Diseases include anthracnose, pests include aphids, and leaf-eating insects such as moths.