Origin and distribution of species
There are about 15 kinds of walnuts, but only two kinds are widely cultivated as fruit trees, namely king walnut and small walnut. Walnut is native to southeast Europe and west Asia. It is said that in the Han Dynasty, Zhang Qian sent envoys to the Western Regions and brought them back to China, and then spread to all parts of China. So it is also called walnut, which has a history of more than two thousand years.
Walnuts are mainly distributed in China, Turkey, India, Iran, Japan and North Korea in Asia, the Soviet Union, Britain, France, Germany, Italy, Greece, Bulgaria and Romania in Europe, and the United States and Chile in America. 1988 The total output of walnuts in the world was about 843,000 tons, including about 18 1 10,000 tons in the United States, 0/53,000 tons in China, 0/110,000 tons in Turkey and 85,000 tons in the Soviet Union.
Walnuts are widely distributed in China, with the most concentrated in Bashan Mountain area of Qinling Mountains, Taihang Mountain area of Lvliang and Yanshan Mountain area (mainly walnuts in Yunnan-Guizhou Plateau). The main producing areas are Fenyang in Shanxi, Xiaoyi in Shaanxi, Luonan, Yang Shan in Hebei, Shexian and Lulong in Hebei, Mentougou and Pinggu in Beijing, Hotan and Aksu in Xinjiang, Jiacha in Tibet and Qingzhou in Licheng, Shandong. Dali, Chuxiong, Bijie and Weining in Guizhou are the main producing areas of iron walnut.
Features and characteristics
Walnut varieties are different, but their characteristics are the same.
morphological character
The height of this tree can reach 30 meters. The crown of the head is large, with a wide oval or round shape. With a life span of hundreds of years, there are nearly a thousand-year-old walnut trees in Jiacha County, Tibet. Bark is gray and smooth, darkens with age, and forms longitudinal cracks from shallow to deep. The branches are stout, and the new branches are brownish green with white lenticels. The mixed bud is spherical, the vegetative bud is conical or wide triangle, the male flower bud is lateral naked bud, and the conical bud has scales. The leaves are odd pinnate compound leaves, alternate, 30 ~ 40 cm long, 5 ~ 7 leaflets, the base of the total stalk is thick with glandular points, and the leaves are triangular after shedding; Leaflets are oblong, obovate or broadly elliptic, with short stalks, slightly protruding apex, heart-shaped and round base, green surface, pale green back, clustered axils of veins, and whole or slightly serrated leaves. The male flower inflorescence is 8 ~ 12 cm long, the perianth is 6-lobed, the stamens are 12 ~ 26, the filaments are very short, and the anthers are yellow when mature; The female inflorescence is terminal or has 2-3 clusters of florets, the outside of the ovary is densely villous, the stigma is 2-lobed and pinnately rolled back (Figure 1). The fruit is nuts, round or oval; Exocarp fleshy, smooth or pilose surface, light green to dark green, with white glandular spots; Endocarp bone is called core-shell with grooves or shallow pits on the surface; Nuts are brain-shaped (Figure 2) and covered with yellow-white or light brown seed coat, which is the main edible part.
Figure 1
Fig. 2 Growth habit
Walnut is a deep-rooted fruit tree with developed taproots. Young roots of seedlings grow faster than young stems. With the increase of tree age, the crown and root groups continue to expand. The buds of new shoots of walnut can be divided into terminal buds and axillary buds according to their positions. The terminal buds are full and fat, and the branches are developed in the young tree stage, forming backbone branches to form a crown. In addition to the terminal bud, 3 ~ 5 axillary buds below the terminal bud can also produce new buds, and most of the lower axillary buds do not germinate and become hidden buds. Only the terminal buds of weak branches can germinate, so the branches in the crown are sparse. After entering the fruiting stage, most terminal buds form mixed buds. In the second year, branches and branches bear female flowers and become fruiting branches. Results The axillary buds at the top of branches were replaced by terminal buds, which were called false terminal buds, and the terminal buds of other growing branches were true terminal buds. The true terminal bud is pointed and the false terminal bud is round. True terminal buds are easier to differentiate into mixed buds than false terminal buds. Branches grow at a large angle, most of which are horizontal. The buds at the top of some transverse branches are more vigorous on the lower side or upper side, resulting in drooping branches. In the walnut orchard in intercropping crops, the stems should be set high and the drooping branches should be cut off in time. Hidden buds have a long life and are beneficial to the regeneration of old trees.
Fruiting habit
The flower buds of female flowers are mixed buds, which are inserted at the top or slightly below the fruiting mother branches. The fruiting branches bear fruit in the following spring, and each fruiting branch bears 1 ~ 3 or more fruits. Male flower buds are pure flower buds, which are inserted in several nodes below the top buds of fruit-bearing branches, and some are born in the lower parts of fruit-bearing branches. Walnut trees have different flowers, and most plants have different pistils. Wind-borne, fertilization needs a lot of pollen, and a robust male inflorescence can produce 0.5 g of dry pollen. Some varieties of walnuts have parthenogenetic ability. The age at which fruit begins varies with the type and cultivation conditions. The early fruiting type in Xinjiang and Shaanxi blooms and bears fruit in 2-3 years after sowing (individual years), and the late fruiting type takes 8- 10 years. Walnut trees like light, and the fruiting branches are mostly outside the crown. The fruiting branches can account for 95% of the new shoots, and the fruiting branches in the inner cavity do not exceed 33%. The nature, proportion and fruiting ability of the terminal bud of walnut tree are related to the nutritional status of the tree. When nutrition is deficient, the terminal bud will produce more branches, and even if it blooms, a large number of flowers and fruits will fall. When the nutrition is sufficient, the second and third buds below the terminal bud can also form mixed buds, and the fruit-setting ability is also strong.
Requirements for environmental conditions
Walnut is a positive tree species, which can tolerate side shading slightly but not top shading, and has moderate tolerance to shade. Walnut is also a warm-loving tree species, and the suitable growth temperature is: annual average temperature 8 ~ 16℃, absolute minimum temperature -2 ~-25℃, frost-free period 150 ~ 240 days, tolerance limit -30℃ and absolute maximum temperature 35 ~ 38℃. If the temperature is too high in summer, fruits or branches will burn day by day; In late frost in spring, flowers are frozen at -2 ~- 1℃, and new shoots are frozen at -4 ~-2℃. In the cold winter and dry spring areas of North China, young trees are easy to sprout.
As long as the temperature is suitable, walnut can grow and bear fruit normally in the area with annual average precipitation of 400 ~ 1200mm, but it is suitable for cultivation in the arid area with annual average precipitation less than 1000mm. Walnut has certain drought resistance, but according to relevant data, if it is short of water within 6 weeks after flowering, the fruit will become smaller and the nucleoli will not be full. Rainy autumn often causes exocarp to crack, seed coat to turn black and nucleolus to be moldy. Walnut should not be planted where the groundwater level is less than 2 meters from the surface.
Walnut has strong adaptability to soil, and there are normal trees in loam and gravel soil. The pH value of soil is 6.5 ~ 8.0, the suitable range is 7.0 ~ 7.5, and the thickness of soil layer should be greater than 1 m. In the loess hilly area with deep soil layer, it can grow well even if the fertility and precipitation conditions are poor. In the shallow soil layer, drought and water shortage or too wet, solid and sticky land, plants grow poorly and even form small old trees. When the soil salt content exceeds 0.25%, it grows slowly and bears little or no fruit. Chlorides are more harmful than sulfates.
principal item
Walnut is widely distributed in China, and has been bred by seedling for a long time, with many varieties or strains. According to the thickness of the nucleus, it can be divided into four categories: ① exposed nucleus. The shell is extremely thin, and the surface of the shell is locally thin enough to form small holes and expose the seed kernel, so it is named Lou Ren. Nuts are small or medium, and the kernel rate is extremely high, generally around 60%. It is easy to take the whole kernel, but not easy to preserve it. ② Shellfish. Commonly known as cotton walnut. The shell is thin, there are no holes in the shell surface, and nuts are not exposed. The size of nuts varies from place to place, and the kernel rate is high, generally 45 ~ 55%. The inner pleat wall is underdeveloped, and the diaphragm is thin and soft, so it can be whole. ③ Semi-thin shell. It is usually called bisexual walnut. The shell is slightly thick, the inner pleat wall is developed and hard, and the diaphragm leather is thin, so it is a little difficult to take out the kernel, but the whole kernel can be taken out. The kernel yield is generally around 45%. ④ Thick crustaceans. Commonly known as walnut. The shell is the thickest, the inner pleated wall is developed, the diaphragm is bony, thick and hard, and it is extremely difficult to take out the kernel. After the shell is broken, the whole kernel cannot be taken out. The kernel yield is low, generally below 40%.
The main varieties and strains are: ① Hu County Luren Walnut. Produced in Huxian County, Shaanxi Province. Nuts are large, weighing about 14 g, with extremely thin shells and holes in the shell surface. Nuts are full, easy to take and sweet. The grain yield is 53%, and the oil content of grain is 765438 0.37%. It blooms in early May and matures in mid-September. ② Walnut with smooth skin. Produced in Fenyang, Shanxi. Nuts are large, weighing about 17 ~ 25g, with thin shells and easy access to kernels. The grain yield is 58. 19%, and the oil content of grain is 72.65%. Mature in the middle and late September. ③ Ear walnut. Produced in Lingqiu, Shanxi. Nuts are small, weighing about 6 grams, with more than 30 knots per spike 10 ~ 15, which are clustered, so they are also called clustered walnuts. Four walnuts every other year. Produced in Shaanxi to help the wind. It can blossom and bear fruit 2 ~ 3 years after sowing, so it was also called walnut in that year. Nuts vary in size, weighing about10 ~12g, with thin shells and easy access to kernels. The grain yield is 57.7% and the oil content is 56.6 ~ 65.4%. Mature in mid-September. ⑤ Thin-skinned walnut. Kuqa, Xinjiang, is called paper walnut locally. Nuts are big, their shells are extremely thin, and nuts are easy to get. The grain yield was 36.38% and the oil content was 74.79%. Young trees of 2-3 years old can bear fruit, bloom 3 times a year, and the first and second fruits can be mature. There are also walnuts that bear fruit twice a year in Shaanxi. 6 yuan feng walnut. Shandong institute of pomology was bred from Xinjiang early-bearing walnut seedlings, named after 1979. Nuts are ovoid, the shell thickness is 65438 0.3 mm, and the kernel rate is 46.25%. 10 ~ 12 yield is about 12 kg. ⑦ Liaoning walnut 1. Liaoning Economic Forest Research Institute was bred by crossing thin-skinned walnut from Hebei and high-yield paper-skinned walnut from Xinjiang. Nuts are round or rectangular, weighing about 9. 1 g, with a shell thickness of 0.45 mm, and can be whole. The kernel yield is about 73.5%. 8. Thin-shelled walnut. Xinjiang walnut seedlings were selected by Beijing Forest and Fruit Research Institute. Nuts are round, with shell thickness of 1.04 mm, and can be whole. The kernel yield is about 60%. The average yield of 9-year-old plants is 10 kg.
In addition, the excellent varieties and strains screened from all over the country include Xinzhi Pi and Liaoning Walnut No.2 in Liaoning Province, Shangsong No.6 and Dongwang 1 in Shandong Province, Qin Cheng No.35 in Beijing, Sisiyu 1 and Shimen 1. , and the rare red kernel red walnut.
Key points of cultivation techniques
type
Grafting method is suitable for walnut seedling. Rootstocks can be such rootstocks as walnuts and Juglans mandshurica. But this kind of rhizome is the most commonly used. The method of cultivating rootstock seedlings is: by layering or cold soaking in the sun, sowing after most seeds crack their mouths. In spring, apply decomposed manure to the sowing site, prepare the soil for border, water the soles of feet, and furrow 10 cm for sowing. When sowing, walnuts should be placed in the suture line perpendicular to the horizon, and the seeds should be covered with soil for 3 ~ 5 cm. Emerge seedlings 20 ~ 30 days after sowing, pay attention to timely irrigation and intertillage. There are many methods of walnut grafting, which are divided into two categories: branch grafting and bud grafting. Because walnut trees bleed during dormancy, and the blood contains juglone which inhibits healing, grafting is mostly carried out in the growing season without bleeding. During dormancy, grafting measures such as cutting off water under incision or cutting off roots were taken.
get a first reign title after the founding of a dynasty
Walnut orchard should choose loam flat or sloping land with gentle terrain, deep soil layer and good drainage, do a good job in soil and water conservation engineering and plant it in spring and autumn. The row spacing between trees depends on soil fertility and walnut characteristics. Under the condition of moderate soil fertility, the type of early-bearing short branches can be 4 meters ×5 meters, and thinning can be carried out after the trees are crowded; The distance above 8 m× 8 m can be used for late fruit type.
Plastic trimming
When the terrain is flat, the soil layer is deep, and the central trunk of plants is dominant, it can be made into an upright cylinder or an evacuation layered shape; In sloping fields and shallow soil layers, plants have no central main branch or the central main branch is too weak, which can be shaped into gratifying shapes. Mature trees should not only improve the tree structure in time, but also get rid of dead branches, crowded branches and pests and diseases every year or every other year, and properly retract drooping branches. Pruning time should be after harvest and before defoliation. The experience of Shanxi, Beijing, Hebei and other places shows that after bud germination, removing 2/3 ~ 4/5 of male flower buds can increase yield by more than 20%.
intercropping crops
Intercropping crops such as grain, vegetables, medicinal materials and green manure in the open space between rows during the young tree period, and intertillating and weeding in time during the growing season. Juglandin can be secreted from the root of walnut and leached from the leaves, which has inhibitory effect on tomatoes and other crops.
Fertilize soil or land
Walnut fertilization method can refer to the above table.
Harvest and fruit processing
Walnuts can't be harvested until the fruit is fully ripe. Early harvest, low grain yield and low oil content; The germination rate of sowing is low and the seedling growth is poor. After full maturity, harvesting is more than 10% earlier than harvesting 10 days. The characteristic of complete maturity is that the exocarp turns from green to yellow, and some of them naturally crack.
After the stone fruit is harvested, it needs to be peeled and bleached. Peeling is to pile the fruit in a well-ventilated and cool place and cover it with a wet grass curtain to prevent it from falling too high and the topsoil from drying out. After 3 ~ 5 days, tap with a wooden stick and the green husk will fall off immediately. Peeled nuts should be washed in time and bleached after washing. Bleaching powder 1kg, add 6-8kg warm water to melt, pour into 60-80kg clear water to make bleaching solution, pour nuts into bleaching solution, stir with a wooden stick, take them out when the surface turns yellow-white, and immediately rinse them repeatedly with clear water until there are no white spots on the surface, and the bleached nuts can be dried.
Eliminate pests and diseases
(1) walnut moth. Also known as walnut black. Hurt the fruit. Spraying larvae before hatching; Pick up the early fruit drop and bury it deeply; Before freezing, the trees were covered with soil to prevent the larvae unearthed the following year from being killed. ② Walnut moth. Also known as walnut caterpillar. Larvae eat leaves, which will be eaten up in severe cases. Pesticides are sprayed to kill the larvae, and the trunk sokcho lures and kills the mature larvae under the tree. ③ Grass-foot scale insects. Use nymphs to suck juice from branches and buds. Digging ditches around the trunk to prevent nymphs from being unearthed in early spring; The trunk is bound with coated plastic belts to kill nymphs; Spray nymphs on the trees. (4) inchworm. Larvae eat leaves. Spraying in larval stage; Artificial killing or trapping of adults. ⑤ Colletotrichum gloeosporioides. Mainly harmful to fruits. Spraying bactericide. ⑥ Black Spot of Walnut. Damage to branches, leaves and fruits. Spraying sulfur mixture before germination; Spray Bordeaux solution or bacitracin before onset.
economic value
Walnut kernel contains more than 63-75% fat, about 15% protein and about 10% carbohydrate. In addition, it also contains mineral elements such as phosphorus, calcium, magnesium and chromium, and various vitamins, which have various nutritional and medical values. Walnut kernel can be eaten directly, and can also be processed into canned food, candied fruit, amber walnut kernel and pastry accessories. Walnut kernel has been used for cooking since at least the Yuan Dynasty. There are many dishes and snacks with walnut kernel as the main component in court meals and modern food in Ming and Qing Dynasties, and most of them are eaten as non-staple food. Walnut can be used as walnut porridge, donkey-hide gelatin walnut and other foods with therapeutic and medicinal effects; Used in medical treatment, it has the effects of invigorating qi and nourishing blood, moistening dryness and resolving phlegm, warming lung and moistening intestine. Walnut kernel oil contains about 73% linoleic acid, which can reduce plasma cholesterol and excrete it in the form of bile. Renxuan has a good effect on coronary heart disease and bronchial diseases. Green tangerine peel juice Tu Zhi stubborn tinea is quite effective. Walnut has dense wood grain, which is a good material for furniture, crafts and gun butts. Walnut shell can be used to make activated carbon, which is the best carbon species for recovering precious metal chromium. Green tangerine peel can be used as tanning agent and dye.