1, biological characteristics (1) Phenological characteristics The phenological period of Yunnan walnut varies with the latitude, altitude, type and variety of its growing place. In Kunming, when the temperature rises to 9? After 8℃, the dormancy of walnut trees in Yunnan was broken, and the juice began to flow and began to grow and develop for one year. The germination period is from mid-February to late February, the germination period is from early March, the leaf opening period is from mid-March, and the new shoot growth period is from mid-March to early May. The early male flowers are in the middle of March, the full flowering period is in the middle and late March, and the last flowering period is in the late March. Female flowers begin in mid-March, peak in early April and end in mid-April. The rapid growth period of fruit is from mid-April to mid-May, the hard-core period is in late June, and the maturity period is in mid-September. The defoliation period is165438+1early October, and the dormancy period is165438+1mid-October to the next February. From germination to dormancy, the growth period of walnut trees in Yunnan is about 300 days and the dormancy period is about 60 days. (2) The growth and development period of walnut trees in Yunnan is longevity trees. According to the characteristics of each growth and development period in the life cycle of Yunnan walnut tree, the growth and development of this walnut tree can be divided into four periods, namely, young tree growth period, early growth and fruiting period, full fruit period and aging and renewal period. In the cultivation and management of walnut in Yunnan, corresponding cultivation and management technical measures can be taken according to the characteristics of the tree in different periods, so as to fully adjust and give play to the growth and development characteristics of the tree in different periods and produce maximum benefits. ① Young tree growth period (vegetative growth period) The growth of Yunnan walnut from one-year grafted seedlings to flowering and fruiting period is vegetative growth, which is called vegetative growth period, that is, young tree growth period. The length of this period is related to its type and variety. The young tree growth period of late-maturing Yunnan walnut varieties and types is generally 6 ~ 14 years; The growth period of young trees of early-bearing Yunnan walnut varieties is also 3 years ahead of schedule. During this period, young trees grow vigorously, three times a year in spring, summer and autumn, enter the dormancy period early, and the trees are well lignified and not easy to be frozen. During this period, the stems should be fixed and pruned in time, and it is best for walnut trees to form a happy skeleton with 2 ~ 3 main branches to expand the crown. At the same time, the non-backbone branches are controlled, retracted or slowly released to cultivate fruiting branches. In fertilization management, nitrogen fertilizer should be applied mainly, and appropriate phosphorus and potassium fertilizer should be applied to promote walnut trees to enter the flowering and fruiting period. (2) The initial stage of growth and fruiting (also called the initial stage of fruiting) is called the initial stage of growth and fruiting. During this period, the vegetative growth and reproductive growth of walnut trees were carried out at the same time, but the vegetative growth was still the main one. During this period, the tree grew vigorously, a large number of branches germinated, the crown expanded rapidly, and the branch angles of branches kept expanding, indicating that the tree shape of the tree skeleton was basically finalized. The early growth and fruiting period of late-maturing Yunnan walnut trees is about 8-25 years old, and the early-maturing Yunnan walnut trees are about 4-7 years old. Fertilization management in this period is still mainly based on nitrogen fertilizer, and the proportion of phosphorus and potassium fertilizer should be appropriately increased, and the ratio of nitrogen, phosphorus and potassium is about 5︰3︰2, so as to promote the trees to expand and bear fruit year by year. (3) The characteristic of the full fruit period is that the fruit yield of walnut trees increases year by year, reaching a peak and showing a continuous and stable state. This period is called the full fruit period of Yunnan walnut. The length of the full fruit period is mainly related to its variety type and management level. In general, the late-fruiting varieties of walnut trees in Yunnan enter the full fruiting stage in about 30 years, reach the fruiting peak in 50 ~ 100 years, and enter the high and stable yield period in about 80 years. Its full fruit period lasts for a long time. Under the conditions of good site conditions and good cultivation and management, its full fruit period can reach decades or even hundreds of years, and walnut trees are still full of fruits. In Yunnan province, there are hundreds of walnut trees, which have been fruitful for more than a hundred years. At the same time, the vegetative growth and centrifugal growth of walnut trees in full fruit stage are still slow. The early fruiting variety, Juglans yunnanensis, entered the full fruiting stage at the age of 8 ~ 10. Under the condition of cool climate and deep and fertile soil, the early-bearing walnut tree 10 ~ 15 years old with intensive comprehensive cultivation measures entered the rapid fruit growth period, and entered the high and stable yield period after 20 years old, and continued to produce fruit 15 ~ 20 years. ④ During the aging and renewal period, the trunk and bark split deeply longitudinally, the trunk had decayed caves, and some trunk branches died. It can be seen that the regenerated branches came from the base or back of trunk branches, indicating the arrival of the aging and renewal period of walnut trees in Yunnan. The arrival of the aging and regeneration period of walnut trees in Yunnan is related to the site conditions and cultivation management level in the planting area, and also varies with early-bearing and late-bearing varieties. Early-bearing varieties of walnut trees in Yunnan generally enter the aging renewal period when they are 50 ~ 60 years old, and late-bearing varieties of walnut trees in Yunnan begin to enter the aging renewal period when they are around 100 years old. In the early stage of senescence of walnut trees in Yunnan, the top branches and side branches gradually died, the fruit yield gradually decreased and the crown gradually became smaller. There are some regenerated branches at the base, middle and upper part of the trunk in the tree cavity. After many times of death and regeneration, the tree vigor gradually weakened, the fruit yield decreased sharply, and even the significance of economic cultivation was lost. During this period, the main tasks of cultivation management are to strengthen the management of fertilizer and water in the soil of walnut trees, at the same time, to reshape the trees, cut off the dead branches, repair the trunk caves with cement mortar, cultivate and renew the backbone branches in a planned way, form COVID-19 and restore the tree. This can maintain a certain fruit yield of walnut trees and prolong their economic life. (3) Growth and development characteristics ① Root growth characteristics Yunnan walnut is a deep-rooted tree with well-developed root system and wide distribution. Juglans regia (about 80 years old) is a late-bearing variety of Juglans regia in Yunnan. Its main root is 5 ~ 7m deep, its lateral root elongation radius is about 15m, and its root width is 2 ~ 3 times that of the crown. When 1 ~ 2 years old, the main roots of walnut trees grow faster and the lateral roots grow slower. After 3 years old, lateral roots grow faster in the horizontal direction. Its lateral root system is mainly distributed in the soil layer of 20 ~ 60 cm. The root growth performance of different varieties and types of Yunnan walnut seedlings is quite different. Under the same site conditions, the main root length and root width of 2 ~ 3-year-old seedlings showed that the early-bearing varieties were larger than the late-bearing varieties. The root system of early-bearing variety Yunnan walnut is developed, which is beneficial to the tree to absorb water and nutrients. Comprehensive storage is an important basis for early fruiting. Walnut trees in Yunnan have mycorrhiza, which can promote the growth of tree height, trunk diameter, roots and leaves. (2) Growth characteristics of stems and branches. The branches and leaves of walnut tree in Yunnan grow slowly at the early stage of seedling, the radicle grows rapidly, and it accelerates slowly after the embryo is extended. Every time a compound leaf grows, the growth of the stem will stagnate for 4-5 days. The stem grows fastest from July to August. The seedlings of late-bearing varieties of Yunnan walnut began to branch late, generally after 3 years, while the seedlings of early-bearing varieties of Yunnan walnut branched early, with a small number of branches at 1 year. A large number of plants began to branch in 2 years and began to blossom and bear fruit in the third year. The branch growth of Yunnan walnut is related to the age of the tree, the well-managed nutritional status and the planting place. The vigorous walnut trees have new shoots twice a year, that is, spring shoots and summer shoots, and few autumn shoots. Walnut trees that don't grow well usually grow only once in spring. The back branch of walnut tree in Yunnan has strong water absorption and vigorous growth, which is an important feature different from other tree species. Most branches of the outer crown of adult walnut trees in Yunnan have mixed buds. In the following spring, the terminal buds germinate into fruiting branches, and the sprouting branches of lateral buds extend, which is easy to form the phenomenon that there are more fruits in the outer crown and less fruits in the inner cavity. Walnut trees in Yunnan, from defoliation to germination, are prone to bleeding after branches are damaged. Walnut trees grafted on the ground should be drained or grafted without bleeding first. The branches of walnut trees in Yunnan can be divided into the following categories: vegetative branches are also called growth branches. It is a branch with leaf buds and compound leaves, which is divided into two types: developing branch and long branch. Developmental branches are the main branches that form backbone branches, expand the crown, increase the nutritional area and form fruiting mother branches. Long branches germinate from dormant buds (latent buds) on trunk or perennial branches, and grow upright, with long internodes, large growth and poor lignification. According to the actual situation of trees, the vegetative branches are controlled, thinned or cultivated into fruiting branches. Vegetative branches are important branches for rejuvenation of ancient trees. B fruiting mother branches and branches with mixed buds are called fruiting mother branches. Branches that grow from mixed buds are called fruiting branches with female flowers at the top. The fruiting mother branch of late-maturing walnut varieties in Yunnan only has terminal buds, and 2 ~ 3 lateral buds are mixed buds; The mother branches of early-bearing walnut varieties in Yunnan can form mixed buds except the top branches, which has good high yield performance. Only the top bud is a leaf bud and the lateral bud is a male flower bud. Male flowers are mostly weak branches, especially on weak trees or old trees. In order to increase fruit yield, male flower branches should be properly thinned. The buds of walnut trees in Yunnan can be divided into the following categories: buds that only branch and spread leaves after germination. Male flower buds are male inflorescences. Mulberry-shaped, drooping inflorescence when in full bloom. The number of male flower buds is related to the age and strength of the tree. Too many male flower buds will affect the fruit yield, so it should be controlled and the fruit should be thinned properly. C mixed buds are also called female flower buds, and the mixed buds of late-bearing varieties of walnut trees in Yunnan mostly grow at the top of fruiting mother branches, or on nodes 1 ~ 3. The terminal buds and lateral buds of the fruiting mother branches of early fruiting varieties of walnut trees in Yunnan can form mixed buds. The mixed buds are round and the scales are tightly wrapped. After germination, they are drawn into fruiting branches and blossom and bear fruit at the top. D dormant buds, also known as hidden buds or latent buds, are located at the base or middle and lower parts of branches. Generally, it does not germinate, but germinates after the branches are damaged, which is conducive to tree regeneration. There are many kinds of buds of walnut trees in Yunnan, some are single and some are overlapping. Female flower buds or leaf buds are solitary; There are female flower buds and leaf buds overlapping; There are female flower buds and male flower buds overlapping; There are leaf buds and male flower buds overlapping; Leaves and buds overlap; Male flower buds overlap and so on. ③ Characteristics of flowering and fruiting 1. Flowering Yunnan Walnut is a dioecious tree species. Male and female flowering periods are often different, which is called hermaphroditism. The first female flower is called the female type, and the first male flower is called the male type; However, there are few hermaphroditic flowers. Most late-maturing varieties of walnut trees in Yunnan are male, and the male flowers bloom about 15 days earlier than the female flowers, and the male flowers will bloom one after another on the same tree, with a difference of 3 ~ 5 days. In Yangbi area, the male flowering period of walnut trees is in early and middle March; The female flowering period is from late March to early April. The early fruiting varieties of walnut in Yunnan have the characteristics of secondary flowering, but the number is small, and the types of secondary flowers are diverse, including female and male spikes, unisexual inflorescences, hermaphroditic flowers, female flowers in the lower part of the inflorescence, male flowers in the upper part, and few female and male flowers. Pollination and fertilization Yunnan walnut is a wind-borne plant. Its pollen looks like a golden pea under a microscope of 300 times, with a diameter of about 40μm×50μm, and floats to hundreds of meters with the wind. Natural pollination can meet the needs of tree pollination. Pollination trees should be planted in the same area and variety. The germination rate of Yunnan walnut pollen is related to the variety, temperature and humidity during pollen transmission. Under natural conditions, the germination rate of pollen in inflorescence and pollen scattered on branches and leaves after 17 ~ 23 days is 5. 2%~ 1? 3%。 With the passage of time, the germination rate of pollen gradually decreased. Yunnan walnut pollen can be stored at 4℃ for 45 days, and 1? 5% of the pollen germinates. The female flower of Yunnan walnut is a single ovule. When the stigma of the female flower is inverted and there are bright secretions on it, it is the best time for pollination. Only a few pollen tubes can reach the ovule after germination. Too much pollen is easy to cause stigma dehydration, which is not conducive to pollen germination. The fertilized female flower withered and dried up in about 7 days, and the ovary gradually expanded and developed into young fruit. Walnut in Yunnan has certain parthenogenetic ability. It is very common that isolated walnut trees without pollination conditions can bear fruit every year, and nuts can mature and have embryos. Yunnan walnut parthenogenesis rate is 0? 67%~6? 3%; The parthenogenesis rate of northern walnut is 4? 1%~43? 7%。 C After fruit development and pollination, zygote began to divide about 15 days, and quickly differentiated into hypocotyl, radicle, cotyledon and embryo. It takes about 150 days from pollination to nut ripening. The fruit development of Yunnan walnut can be divided into four periods, namely, the fast fruit period-the fast fruit period of late fruit variety Yunnan walnut tree is about 45 days from early April to mid-May. During this period, the volume and weight of the fruit increased rapidly, the embryo sac expanded continuously, the core-shell gradually formed, and the kernel was white and tender. In the hard core stage-from late June to mid-July, about 30 days later, the core-shell gradually became hard from top to bottom, the elasticity and hardness of the septum and pleated wall in the seed nucleus gradually increased, the shell surface was engraved, the hardness increased, and the nucleolus gradually turned white and brittle. The size of the fruit is fixed, the nutrients in it accumulate rapidly, and the oil is transformed rapidly. Oil conversion period-from mid-July to late August, about 50 days. Nutrients of shaped fruit accumulate rapidly, the weight is still increasing, the nucleolus is constantly enriched and full, the moisture of seed kernel is reduced, the oil is constantly rising, and the flavor of nucleolus changes from sweet to fragrant. Fruit maturity-from mid-September to late September, the fruit weight increased slightly. The green skin color of fruit changes from green to yellow, and the sunny skin will appear red. A small number of fruits have cracks in the green peel, nuts are easy to peel off, and fruits show physiological and natural maturity. The fruit growth and development period of early-bearing variety Yunnan walnut tree is 20 ~ 35 days earlier than that of late-bearing variety Yunnan walnut tree, showing the characteristics of early maturity and early market. The age at which walnut trees in Yunnan begin to bear fruit varies with types, varieties and cultivation management level. The fruiting age of late-bearing walnut varieties in Yunnan is generally 8 ~ 10 years, and intensive cultivation and management takes 5 ~ 6 years. Late-bearing varieties of walnut trees in Yunnan first bloom male flowers for 2 ~ 3 years, and then female flowers bear fruit; It takes 2 ~ 3 years for early-bearing varieties of walnut trees in Yunnan to blossom and bear fruit (cross pollination), but it takes 1 ~ 2 years for male flowers. The mature walnut trees in Yunnan are short in fruiting, and the fruit setting rate of mother branches is high. The terminal bud and 1 2 lateral buds of late-maturing walnut varieties in Yunnan bear the best fruit on the same fruiting mother branch. The number of fruit set is closely related to varieties, environmental conditions in planting areas and nutritional status of trees. Late-maturing varieties of walnut trees in Yunnan generally bear 1 ~ 4 fruits per fruit sequence, mostly 2 ~ 3 fruits, accounting for more than 60%, and a few fruit sequences are 5 ~ 6 fruits. The early fruiting varieties of walnut trees in Yunnan bear 1 ~ 3 fruits per fruit sequence, most of which are 2 fruits, accounting for about 50%, and a few of them have 4 ~ 6 fruits or even spikes. More than 80% of the fruiting branches of walnut trees in Yunnan have the habit of continuous pumping and fruiting. With the increase of tree age, the fruit-bearing parts move out rapidly, and the fruit yield is concentrated at the outer edge of the crown, with less fruit in the inner cavity. 2. Ecological characteristics Walnut cultivation in Yunnan has a long history and is widely distributed. It is distributed and cultivated in 16 prefectures and cities and 129 counties and cities in Yunnan Province. The temperature in its distribution area varies greatly, with an average annual temperature of 4? Deqin county 7℃ to 2 1? 65438 0℃ in Mengla County. Moreover, the altitude difference of the distribution area is also huge. Walnuts in Yunnan are naturally distributed from Yunxian 1200m to 3600m in Deqin. It shows that walnut species in Yunnan have strong adaptability to natural conditions. Several main ecological factors affecting the growth and development of walnut in Yunnan are as follows. (1) Requirements for temperature: Walnut in Yunnan is a warm-loving positive tree species, belonging to temperate dried fruit tree species. Different types and varieties of Yunnan walnut have different requirements for temperature. For example, Yangbi salted walnut, Dayao Santai walnut, Huaning large white shell walnut, Shapi walnut and Changning fine fragrant walnut require an annual average temperature of 12? 7~ 16? 9℃, the optimum annual average temperature is about 65438 05℃. Some single plants or strains of Juglans mandshurica and Juglans mandshurica can grow in areas with annual average temperature of 5 ~ 65438 07℃. Too high or too low temperature is not conducive to the growth, flowering and fruiting of walnut trees in Yunnan. When the temperature is around -4℃ in February and March, the buds, flowers and leaves of walnut trees in Yunnan are easily damaged by freezing and wither. In the area where the annual average temperature is about 19℃, the vegetative growth of walnut trees is too strong, the reproductive growth is poor, and there are few or no fruits. Temperature is closely related to latitude and altitude, so the vertical suitable range of walnuts at different latitudes is also different. Some walnut varieties mainly planted in Yunnan Province grow at the altitude of 1600 ~ 2200m, and the suitable altitude is 1800 ~ 2000m. In this vertical zone, Yunnan walnut trees grow well. When the same variety is planted in low latitudes, the altitude of its planting area should be appropriately raised, while when it is planted in high latitudes, the altitude of its planting area should be appropriately lowered to meet the temperature requirements of walnut trees in Yunnan. (2) Requirements for light: Walnut in Yunnan is a light-loving tree species, and the annual sunshine should not be less than 2,000 hours. If it is less than 65,438+0,000 hours, the tree will grow and bear poor fruit, which will affect the development of core-shell and nucleolus and the quality of nuts. Adequate sunshine is beneficial to the germination, leaf spreading, bamboo shoots, flowering and fruiting of walnut trees in Yunnan in that year, and is extremely beneficial to improving their fruit yield and quality. In the walnut orchard with insufficient light and close planting, the growth and fruiting of walnut trees in Yunnan are poor, and the fruit yield is low, only marginal trees bear fruit; The same tree only bears fruit in the outer crown, with few inner cavities. Therefore, when selecting walnut plantation, determining plant spacing and pruning trees in Yunnan, we should consider that walnut trees should have sufficient light conditions. (3) Requirements for moisture Yunnan walnut requires moist conditions. The annual rainfall in the main walnut producing areas in Yunnan Province is 800 ~ 1200mm. In rainy years in winter and spring, walnut trees grow well, with high fruit yield, good quality and few diseases. In areas with little rainfall or years with little rainfall in winter, it is necessary to do a good job in soil and water conservation of walnut plantations in Yunnan, and irrigate them properly in dry season to reduce the flowering, fruit dropping and poor growth of walnut trees caused by drought. Walnut in Yunnan is also a waterlogging-tolerant tree species. Excessive soil moisture and poor ventilation will weaken the physiological function of walnut root system, leading to poor growth and even root rot and death. Therefore, planting Yunnan walnut on waterlogged land requires ditching and drainage. When choosing walnut planting sites in Yunnan, we should try to choose plots that can be irrigated and drained for irrigation and drainage management. (4) Requirements for topography and soil: Walnut trees in Yunnan are suitable for growing under the site conditions of gentle slope, deep and moist soil layer and sunny lee. If planted on the shady and windward slopes with steep slopes, or on plots with high groundwater level and heavy soil, walnut trees tend to grow poorly. Walnut in Yunnan likes loose and fertile soil, and its roots grow vigorously in soil with low groundwater level and good drainage. Walnut in Yunnan is suitable to grow in slightly alkaline and slightly acidic soil, and the pH value of the soil is 6? 3~8? 2, the most suitable is 6? 4~7? 2; Walnut in Yunnan likes fertilizer, so it is necessary to increase the content of organic matter in the soil, apply more farm manure and appropriate chemical fertilizer. (5) Requirements for wind: Walnut in Yunnan is a tree species with weak wind resistance, and wind is also one of the factors affecting the growth and development of its walnut trees. In windy areas in winter and spring, the development, flowering and fruiting of Yunnan walnut trees growing on windward slopes are affected by frequent strong winds. Attention should be paid to land selection and cultivation. Choose plots with less wind as planting areas, or build shelterbelts around the planting areas. However, suitable air volume and wind speed are beneficial to pollination of walnut trees and increase fruit yield.