Cultivation techniques of Walnut

Cultivation value walnut is an important oil fruit tree with high economic value. Walnut kernel is not only rich in fat, but also high in protein, vitamins and a variety of minerals, which is often used as an advanced tonic and has a certain medical effect. Walnut kernels in China are of good quality and high oil content, so they are well received by the international market. Walnuts and walnuts are important traditional export materials. Walnut tree has the advantages of strong sex, strong adaptability, less diseases and insect pests, labor-saving management, convenient fruit storage and transportation and long life. It is a very suitable fruit tree in mountain area development. However, the common walnut cultivation requires dry and cool climate conditions and is not resistant to high temperature and high humidity. after introduction and cultivation in the middle and lower reaches of the Yangtze River, the tree is easy to grow, the flower bud formation is often bad, and the disease is serious, so it is difficult to obtain high yield. The main species and varieties of walnut are walnut plants of the genus walnut, which are mainly cultivated by common walnut and iron walnut. Most of the varieties cultivated in the north and south of China belong to common walnut. Iron walnut, also known as Juglans regia, is mainly distributed in Yunnan, Sichuan and Guizhou. This kind of walnut likes hot and humid but can not bear cold. It is another ecotype different from ordinary walnut. In addition, there are wild Juglans mandshurica and wild walnut, all of which are plants of the same genus. It is worth mentioning that there is also a kind of nut-producing fruit tree called thin-shell pecan, also known as American pecan or long pecan, which was introduced into China at the end of the 19th century. at present, it is sporadically cultivated in Jiangsu, Zhejiang, Fujian, Jiangxi and other provinces. Sex likes warm and humid, big nuts, long oval, thin shell and large kernel, delicious and high quality. It is of great development value in the Yangtze River basin and its southern area. Walnut has always been propagated with seeds, most of which are local types in production, and there are few varieties formed by asexual reproduction. According to the beginning of fruiting and the thickness of the shell, walnut can be divided into two groups: early bearing walnut (2 ~ 4 years after sowing) and late bearing walnut (5 ~ 10 years after sowing). There are two types of thin shell and thick shell. Famous walnut varieties such as * * walnut every other year, Shandong Yuanfeng, Beijing thin shell incense, etc. (the above are early bearing walnut); the famous late bearing walnut varieties are Hebei Shimen walnut, Shanxi Fenyang walnut, Shaanxi cotton walnut, Shandong Jijiaomian walnut and Liaoning Lvda new paper walnut. In recent years, Shandong Fruit Tree Research Institute and other units have successively selected new and improved varieties such as Xiangling, Fenghui and Luguang according to the standards of early fruiting, high yield, high quality and disease resistance, which can be used for trial planting in Huaibei region. Growth and fruiting habit walnut is a tall deciduous tree with deep and broad roots and strong dryness, and the top dominance of branches is particularly obvious. most of the middle and lower lateral buds are dormant or dry off after germination, so the branches in the crown are sparse. According to the type of budding, the annual branches in the dormant period can be divided into growth skills, fruiting mother branches and male flower branches. Every branch is a growing branch with only leaf buds (and occasionally male flower buds). Among them, those who are located in the periphery of the crown and whose growth is substantial are the basis for the expansion of the crown and the formation of fruiting mother branches. Where the top 1-3 nodes of branches (some varieties can be more) bear mixed buds (female flower buds), those who can bear fruit in the second year are the fruiting mother branches. Results in addition to mixed buds, there were leaf buds and male flower buds under the mother branch. Where there are only male flower buds and leaf buds on the branches, only male inflorescences can be produced in the second year and can not bear fruit. This kind of branch is generally short and weak, mostly growing in the old and weak trees and the closed parts of the canopy. The male inflorescence falls behind and is bald below the terminal bud. The lateral buds in the middle and upper part of walnut branches are often compound buds, which are arranged up and down. There are many forms, such as superposition of female flower buds and leaf buds, leaf buds and male flower buds, male and female flower buds, double male flower buds and double leaf buds. The buds at the base of the branches often form hidden buds. Branches can have two growth peaks in a year, forming spring and autumn shoots. The branch has a large branch angle and the crown opens. The weak branches in the lower part of the adult tree are easy to grow horizontally, forming strong back branches and disturbing the tree shape. The initial fruit age of walnut is related to the variety and reproduction mode. Grafted early bearing walnut can bear fruit 2-3 years after planting, while late-bearing walnut can begin to bear fruit in 5-10 years, and grafting can advance the age of fruit. Generally 20-30 years into the full fruit period, the economic life is very long. Walnuts are monoecious. Wind matchmaker. Female flowers inserted on top of fruiting shoots, solitary or 2-or 3-flowered in clusters. Male flowers gather into catkins. The florescence of female and male on the same plant is often different, and there is a phenomenon of female and male heteroplasy, which affects pollination. The living ability of pollen is often low and the effective pollination time is short, which is one of the reasons for low yield. The fruit growth period is longer, the main growth volume is in the early stage, and the shell hardening and kernel filling period is in the middle and later stage. The fruit has a fleshy involucre and dehiscences naturally after maturity. Individual varieties have a certain ability of parthenogenesis. The physiological fruit drop of most varieties was heavy, starting from 10 to 15 days after anthesis, and the shell hardening period basically ended. The fruiting branches produced from the terminal buds of strong fruiting mother branches had a high fruit setting rate and could bear fruit continuously for many years, while those from short weak fruiting mother shoots or lateral mixed buds had lower fruit setting rate. However, at present, varieties with lateral bud fruiting rate of more than 60% have been selected in China. Key points of cultivation techniques 1. Propagation and planting seeds are simple and easy to propagate, but the results are late and prone to variation, affecting the commercialization of fruits. Grafting propagation should be promoted step by step in the future. Grafting propagation is often used on this rootstock or wild walnut. The seeds are sown in autumn or in spring after being stored in sand. The sand storage time is 60-90 days. For example, seeds should be soaked in warm water for 5-7 days before sowing, and the water should be changed once a day to promote seed absorption, fruit shell cracking and seedling emergence rate. The main grafting method is spring grafting (subcutaneous grafting or split grafting). Walnut trees have bleeding phenomenon in the dormant period, and the phenological period of grafting should be delayed than other fruit trees, otherwise it will affect the survival. Usually grasp the rootstock sprouting to leaf expansion period of about 10 days. However, the scion should be cut in advance and stored at a low temperature of 0 ~ 5 degrees. The bud grafting was carried out from July to September, and the square bud grafting method was often used. There are many tannins in the bark of walnut branches, which is easy to form the isolation layer of the interface. Therefore, the grafting operation is rapid and the cutting surface is smooth, which is beneficial to improve the survival rate of grafting. In recent years, indoor grafting is advocated to control the temperature and humidity of wound healing. When the rootstock seedlings fall, the pseudo-planting is dug up, and the scion is also taken for storage when the leaves are nearly falling. 10-15 days before grafting, both sides of the rootstock were placed in a storage box filled with wet sawdust and placed indoors at 25-30 degrees for 2-3 days to promote recovery. After that, the tongue was grafted, bound, waxed and moisturized, and then placed in the storage box to promote wound healing. After the formation of the healing tissue, it was moved to the field and planted in the nursery after the temperature rose. If grafted indoors after the spring is warm, there is no need to "revive". The row spacing of planting plants depends on the characteristics of varieties and the fertility of the soil. The row spacing of fruit-grain intercropping can be expanded to 25 ~ 30 meters when it is planted in a piece of (4 ~ 5) m X (5 ~ 8) m. It is required that the soil layer of the planting land is deep, and the land that is too barren is easy to form "small old trees" and is not suitable for planting. When planting, we should also pay attention to planting pollination trees. Walnut seedlings have few lateral roots and are not resistant to transplantation. the seedlings should be planted quickly and the roots should not be exposed for too long. Pay attention to moisturizing before and after planting. Walnuts can be planted in autumn or spring in Jianghuai area. Attention should be paid to pollination varieties when planting in pieces. 2. Shaping and pruning walnut is a light-loving tree species, especially after entering the fruiting stage, it needs more light. The tree shape can be divided into two types: evacuation hierarchical shape or natural happy shape. The varieties with strong dryness and good site conditions adopt evacuation stratification, and its specific requirements and operation process can be referred to apple. However, walnut has the characteristics of late branching, strong tree body and strong back branch, so it is necessary to grasp the higher fixed stem height (l m ~ 1.5 m) and the late fixed stem period in shaping, and the distance between the layers and the distance between the first secondary branch (that is, the lateral branch) on the main branch and the central trunk should be enlarged appropriately. As well as the requirements that it is not suitable to select the back branch as the auxiliary main branch, the varieties with open crown, weak trunk and poor site conditions can adopt the natural happy tree shape, with 2 or 3 main branches per tree, and 3 or 4 secondary main branches from each main branch to fill the space. Some branches that interfere with the shape of the tree are mainly treated in the pruning of young trees. For example, early bearing walnut is easy to produce a large number of secondary branches and male flower branches, and sometimes it is easy to produce overgrown branches. the secondary branches and overgrown branches that need to be retained should be coring or truncated in time and cultured into fruiting branch group; the rest should be thinned as soon as possible. For the dorsal branches that are easy to rob the host, the dorsal branches located on the first layer of main branches and secondary main branches are all removed from the base; those located on the second and third layers of main branches and secondary main branches shall be left or retained according to their needs and growth strength, and the remaining back branches can be coring or retracted when they are booming, and can be transformed into branch groups. Adult trees should timely remove the outer over-dense branches and drooping branches, and shrink and transform the auxiliary branches that take up more space, so as to improve the light conditions in the crown. When the proportion of short branches and male flower branches in the crown increases, it shows that the tree has gradually weakened and should be renewed and rejuvenated in time. The fruiting branch group can be weak and strong, retract and renew, and make full use of the overgrown branches in the crown, so as to increase the proportion of strong and strong branches. When the scorched tip or large and middle branches die, it shows that the tree has become old. It can retract and renew all levels of backbone branches year by year, and make use of the long life of hidden buds of walnut to form a new crown to restore fruiting ability. Walnut dormant pruning often occurs due to poor cut healing, which seriously affects the tree potential. The suitable pruning period is after fruit harvest in autumn and before the leaves turn yellow. In addition, it can also be pruned after germination. 3. Soil, fertilizer and water management and male walnut mature trees have deep roots and luxuriant leaves, and there is a great demand for fertilizer and water. Turn deeply after defoliation every year, enlarge the tree plate, and apply base fertilizer, and during the growth period, dig and press the weeds deeply after rain. Topdressing was carried out for 2 or 3 times before germination, after falling flowers and during the hard core stage. In the early stage, nitrogen fertilizer was mainly used to promote spring shoot growth and young fruit development, while in the later stage, nitrogen, phosphorus and potassium coordinated with each other to promote flower bud differentiation, nucleolus enrichment and improve nucleolus quality. After each fertilization, it can be combined with irrigation. Walnuts are sensitive to drought and can be covered to preserve soil moisture in areas lacking water sources. In the rainy season, stagnant water in the fields should be removed. Attention should be paid to water control from spring shoot growth to autumn shoot growth in order to control the growth of new shoots in the later stage. In areas where freezing and drought often occur in winter and spring, frozen water should be irrigated once in early winter. The number of male flowers of adult walnut trees is very large, which consumes tree nutrients. When male flower buds begin to expand, male thinning measures should be taken (75%-80% of trees can be removed in full fruit), which is beneficial to increase yield. Main diseases and insect pests and their control 1. the main diseases are walnut black spot, walnut anthracnose and so on. Walnut black spot is not only harmful to fruit, but also to leaves and shoots, causing fruit rot and early fruit drop, reducing kernel yield, which is a bacterial disease. Control method: spray Baume 3 ~ 5 degree stone sulfur mixture before sprouting, spray 200 times lime Bordeaux solution before and after flowering, and then spray continuously for 2 times every 20 days or so. Walnut anthracnose is mainly harmful to fruit, is a fungal disease, and can be transmitted with apple anthracnose. The prevention and control methods can refer to apple anthracnose. 2. The main insect pests are walnut limb moth, walnut gibberellin and wood. Inchworm, Monochamus alternatus, etc. Walnut limb moth, also known as walnut black, occurs seriously in North China, with 1 or 2 generations every year. The larvae eat the green skin, causing the involucre to blacken and rot, the young fruit to fall off, and the nucleolus to shrink, overwintering as mature larvae in the soil. Prevention and control methods: combined with deep planing tree plate, 50% phoxim 300x solution is sprayed on the ground to kill; before adult spawning and fruit decay, 50% fenitrothion 1000 times solution or 20% cypermethrin EC 5000 times solution is sprayed; when the damage is mild, the insect fruit is removed and buried deeply before the larvae take off fruit. The suitable time for harvest and storage of walnut fruit is when the involucre changes from green to yellow and part of the walnut fruit is naturally cracked. If the harvest is too early, the involucre is not easy to peel off, and the kernel yield and oil yield are reduced. If the involucre does not fall off by itself after harvest, it should be retted and peeled. That is, walnuts are piled on the site, with a height of 30 cm ~ 50 cm, covered with wet straw mats, etc., after 3 to 5 days, tap with a stick, and the green skin can fall off. The unpeeled walnut can also be soaked in 40% ethephon 500 / 1000 times solution, then stacked for 24 hours, and then beaten with a stick, the green skin is very easy to fall off, and the core and shell is smooth and clean, free from pollution. After peeling, the wet walnut should be washed with water and bleached immediately. Walnuts for export must be bleached to improve their appearance. First mix the bleach into 80 times the solution, then put the walnuts in, stir continuously, remove the walnuts after 8-10 minutes, rinse with clean water and spread them on the foil to dry. Turn frequently when drying to avoid yellowing of the backlit surface and affect the quality. When the nucleolus becomes brittle, the cross section is white, and the diaphragm is easy to break, it can be stored in a freeze-dried and ventilated place. Check frequently during storage, pay attention to moistureproof and rodent damage. In case of individual mildew and deterioration, it should be taken out to dry.