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First, biological characteristics
(1) Growth result habit - root system
1. Walnuts have a well-developed root system and are deep-rooted tree species. On the loess terrace, the main roots of adult trees can be as deep as 6 m, but the main root clusters are distributed in the soil layer of 20-60 cm, accounting for more than 80% of the total root system; the horizontal extension of the lateral roots exceeds 14 m, but the concentration is concentrated in the range of 4 m radius centered on the trunk; the root-to-crown ratio is usually about 2.
2. The initial activity period of walnut root system is the same as the bud germination period, new roots appear on March 31, two growth peaks occur from mid-June to early July, mid-September to mid-October, and growth stops in late November.
Growth outcome habits — branches
There are four types of annual branches of walnuts.
１． 结果枝:由混合芽形成，花序（雌）顶生，营养条件好、顶部仍能形成混合芽、连续结果；早实核桃当年形成的混合芽还可以二次开花结果。
２． Male flower branches: refers to the top bud is a leaf bud, the side bud is a branch of the male flower bud, the growth is thin and weak, the inner chamber or the weak tree is more, and it becomes a bare branch after flowering.
３． Vegetative branches (developing branches): derived from leaf buds or latent buds, moderately robust growth (less than 50 cm) can form flower buds in the same year and produce results in the next year; the inner chamber is mostly formed by the germination of latent buds, which should be controlled and utilized by summer shears.
４． Fruit mother branch (winter state): refers to an annual branch with mixed buds. It is mainly formed by the transformation of nutrient branches and fruiting branches that grow strongly in the same year. 顶端及其下2～3芽为混合芽（早实核桃混合芽数量多），一般长20～25cm，而以直径1cm、长15cm左右的抽生结果枝最好。
Growth result habits - buds
There are 4 types of buds.
1. Mixed buds (female buds): round, fat and plump, covered with 5-7 scales.
2. Male flower buds: naked buds, conical, soft inflorescence, fall off after flowering.
3. Leaf buds: grow at the top and bottom of vegetative branches
4. Latent buds: it is a leaf bud, mostly born at the base of the branch or near the base, generally does not germinate, the life span is up to tens to hundreds of years, and it is buried in the bark with the thickening of the branches.
核桃雄花芽分化始于开花前后（4月下～5月上），至翌年开花前才完成，历时一年多；混合芽分化始于果实硬核期（6月下～7月上），12月上旬基本停止；早实核桃的二次花于4月中旬始分化、5月下旬完成。
Growth fruit habits - flowering
Walnuts are mostly isomeric. 雄花序为柔夷花序，雌花顶生，单生或2～3朵簇生、稀有4～6朵簇生的，雌花无花被、仅总苞合围于子房外，当子房长达5～8mm时、柱头反曲、其表面呈明显羽状突起、分泌物增多、光泽明显时为盛开期，是最佳授粉期、持续时间大约5天左右。
Walnut flowers have the phenomenon of male and female maturation, so the cultivated varieties are also divided into two categories: female precursor varieties and male precursor varieties, and the varieties should be reasonably matched when the garden is established to ensure that the male and female mature period is consistent. Walnut is a wind-borne flower, the pollination distance is related to the terrain and wind direction, the maximum critical distance is 500m, but the pollination effect outside 300m is poor, and the optimal pollination distance is within 100m.
Growth result habit - fruiting
The developmental process can be divided into four stages.
(1) Fruit rapid growth period: before fruit set ~ hard core, last for about 35 days.
(2) Hardcore stage: the fruit stops enlarging, the core shell hardens, and the nucleus changes from translucent paste to milky nucleus. About 35 days.
(3) Seed kernel fullness period: the fruit has slow growth, lasting about 55 days.
(4) Ripening period: the fruit turns yellow.
Naturally, walnuts physiologically fall about 30 to 50%, concentrated within 20 days after the stigma wilting, and basically stop after late June.
Growth fruit habits - fruits
Young fruits
Ripe fruit
(2) Requirements for environmental conditions
Soil Walnuts are deep-rooted tree species with strong adaptability to soil. It can grow in hills, mountains and plains. Walnuts are suitable for the growth of loose and well-drained sandy loams and loams, and clay and compact soil or too thin sandy soils are not conducive to the growth and development of walnuts. The suitable pH of walnuts is 6.2 to 8.2, and the optimal pH range is 6.5 to 7.5. That is, it is best grown on neutral or slightly acidic soils.
Temperature Walnut is a thermophilic tree species, the suitable growth range is the annual average temperature of 9 ~ 16 °C, the extreme minimum temperature of -25 ~ -28 °C, the extreme maximum temperature of 38 °C below, the frost-free period of 150 ~ 240 days in the area. Young walnut trees will suffer frost damage at -20 °C. Spring monthly average temperature of 9 °C began to bud, 14 ~ 16 °C flowering and leaf spreading, at this time if the temperature drops to -4 ~ -2 °C, the new shoots will be frozen. During the flowering or young fruit stage, the yield will decrease when the temperature drops to -2 to -1 °C. In summer, the temperature exceeds 38 to 40 °C, and walnuts are prone to sunburn and nucleolar dysplasia.
Humidity Walnuts are resistant to dry air and are sensitive to soil moisture conditions. Soil that is too dry or too wet is not conducive to walnut growth and fruiting. Generally, when the soil moisture content is 60% to 80% of the maximum water holding capacity in the field, it is more suitable for the growth and development of walnuts. Walnuts are afraid of standing water, flat land should solve the problem of drainage, and the groundwater level should be below 2m.
Illumination Light has an important effect on the growth and development of walnuts, flower bud differentiation and flowering and fruiting. Fruiting walnuts generally require annual sunshine of not less than 2000h, less than 1000h, nut core shell and nucleolar dysplasia. Especially in the female flower flowering period, if the light conditions are good, the fruit set rate will be significantly improved; in the case of rainy and low temperature weather, it is very easy to cause a large number of flowers and fruits to fall.
Altitude From the perspective of the vertical distribution of walnuts in China, the lower the latitude, the higher the vertical distribution. In the northern region, walnuts are mostly distributed below 1000m above sea level, southwest Liaoning is suitable for growing below 500m above sea level, south of Qinling Mountains grows at an altitude of 500~2500m, the highest vertical distribution area is in Tuqinglin Monastery, Lazi County, Tibet, its altitude is 4200m, and the Yunnan-Guizhou Plateau grows at an altitude of 15O0~2500m.
Topography and topography Walnuts are suitable for growing in leeward and sunny plots with deep soil layers and good moisture conditions. Walnuts are suitable for growing in gentle slopes below 10 °, and the slope of 10 ° ~ 25 ° needs to be built with corresponding soil and water conservation projects; walnuts cannot be planted if the slope is above 25 °.
Second, the main types and excellent varieties
There are 7 genera and 60 species of walnut family, of which 2 genera are used for fruit tree cultivation, namely walnut genus and hickory genus.
There are about 500 varieties and types recorded in various parts of China, which are divided into 2 populations, 2 major types and 4 variety groups according to their sources, early and late fruiting, thickness of the core shell and the level of kernel yield.
First of all, the walnut varieties were divided into two major populations, walnut and iron walnut (Yangpu walnut) according to the source;
According to the starting result, it is divided into two major groups: early real type and late real type;
According to the economic shape of the core shell thickness, each taxon is divided into paper-skinned walnuts, thin-shelled walnuts, medium-shelled walnuts, thick-shelled walnuts, and 4 variety groups.
Excellent variety - early fruit walnut
Xiangling: Shandong fruit tree selected breeding, nut oval, medium large, average single fruit weight 10. 6 grams, large fruit weighs 13. 2 g, shell thickness 0. 99 mm. Whole kernels can be taken, and the kernel yield is 57. 6%, light kernel color, fragrant flavor, general adaptability, special and abundant, excellent quality.
Liao core No. 1 nut round, nut weight 9.4g, shell surface is smoother, light color, suture line slightly raised, tightly bonded, shell thickness of 0.9mm, inner fold wall degeneration, can be taken whole kernel, kernel yield 59.6%. The seeds are full, yellowish white, flavorful and slightly astringent. Male precursor varieties, strong growth, thick branches, high fruit branch rate, abundant yield. Strong adaptability, relatively hardy, drought tolerant, strong disease resistance. Nuts are of excellent quality and are suitable for development in walnut cultivation areas in northern China.
Zhonglin No. 1 nut round, fruit base round, fruit top round. Nuts weigh 14g. The shell surface is rough, and there are deep pockmarks on both sides of the suture line; the suture line is wide and convex, with small dots at the top, and the combination is tight, and the shell thickness is 1.0 mm. The kernel yield is 54%. The kernels are full and full, the kernels are yellow and have a good flavor. Female precursor, medium-ripe breed. The tree is strong, the tree posture is more upright, and the yield is strong.
Lu Guang No. 1 nut oblong, fruit base round, fruit top slightly pointed, weight 16.7g. The shell surface is smooth, the suture line is flat, it is not easy to crack, and the shell thickness is about 0.9mm. The inner folds are degenerate, the transverse septum is membranous, and it is easy to take whole kernels. The kernels are full and full, the kernel yield is 59.1%, the kernels are milky yellow, and the taste is fragrant but not astringent. Male type, medium-ripe variety, moderate tree posture, tree posture open.
Vina Is the staple American cultivar, nut conical, flat fruit, tapering top, nut weight 11g, shell thickness 1.4mm, medium shell color, smooth, suture line slightly wide and flat, tightly bonded, easy to take kernels. The kernel color is light, and the kernel yield is 50%. Early fertility is strong. The tree is medium in size, strong in strength, and the tree is relatively upright. Male precursor type. It is not susceptible to late frost, and the walnut lifting moth is less harmful.
Jinlong No. 1 nuts are nearly round, and the nuts weigh 14.85g. The shell surface is smoother, with small pockmarks; the suture line is narrow and flat, the combination is tighter, the shell thickness is about 1.09mm, the inner fold wall is degraded, it is easy to take whole kernels, and the kernel yield is about 61%. The kernels are full and full, and the taste is sweet. Male first type varieties, young trees are more vigorous, and then gradually open after fruit, branching power is medium. Cold, drought and disease resistant. It is suitable for cultivation in North China and Northwest China.
Gift No. 2 The fruit is oblong and the nut weighs 13.5g. The shell surface is smooth, the color is light, the suture line is narrow and flat, the combination is tight, the shell thickness is 0.7mm, the inner fold wall is degraded, it is very easy to take the whole kernel, and the kernel yield is 67.4%. The kernels are full and full, light in color and good in flavor. Female precursor species, the tree posture is moderate, the tree posture is semi-open, and the branching force is strong
Hartley Is the main American cultivar, which resembles a diamond and has a beautiful appearance, and is the most important shelled variety for sale in the US market. The nuts are conical, the fruit is flat, and the top of the fruit is gradually pointed. Nuts weigh 14.5g. The shell surface is smooth and tightly bonded, and the kernel yield is about 46%. 90% are light-colored kernels. The tree is medium to large, semi-open, and grows vigorously on fertile soil, female first. When the soil is thin or the moisture is irregular, it is easy to have deep bark ulcer disease. It is suitable for cultivation in the northern subtropical climate zone.
Third, the main points of cultivation technology
(1) Fertilizer and water management
(i) Fertilizer application:
(1) Late walnut: 1-5 years: N: P: K ratio 5: 1:1; the amount used in 6-10 years is: N: P: K 5: 2 : 2 organic fertilizer 5KG.
(2) Early fruiting walnuts: The amount of fertilizer should be higher than that of late fruiting walnuts. 1-10 years old trees, the annual fertilization amount is: N: P: K ratio 5: 2 : 2, organic fertilizer 5kg. The amount of fertilizer applied to adult trees should be appropriately increased, and the ratio of nitrogen, phosphorus and potassium should be 2:1:1.
(ii) Fertilization period:
Base fertilizer: preferably used in autumn. Topdressing 3 times
(iii) Irrigation:
Irrigation is combined with fertilization. Water should be irrigated before wintering, and attention should be paid to drainage and flood prevention during the rainy season.
(2) Plastic trimming
1. Tree-shaped structure: The common tree shape is mainly the main trunk sparse layer and the natural happy shape, and there are also small crown thin layers.
2. Pruning period: after budding or harvesting to before leaf fall
3. Pruning reaction of walnuts
4. Juvenile and first fruits are shaped and pruned
5. Pruning of fruit trees
(3) Flower and fruit management
1. Artificial assisted pollination
The phenomenon of hermaphroditic ripening, the best time for pollination is when the female flower stigma is cracked and inverted figure-eight.
2. Sparse male inflorescence
The male inflorescence is completed before germination as well
3. Harvesting and processing
The peel changes from green to yellow, and cracks appear on the top of some parts; after harvesting, it is necessary to degreas the green skin and bleach in time
(4) The tall tree is replaced by excellent
1. Anvil and spike selection and treatment
2. Grafting period and method:
The grafting period is suitable from the budding period to the final flowering period of rootstock (about mid-to-late March to early May in northern China). Grafting method Walnut scion disinfection mulch film moisturizing shade grafting technology (patented technology)
Post-pickup management:
After 20-25 days, when the grafted branch grows to 20-30 cm, tie the stick to fix the new shoots and germinate tillers; after two months, unbind.
(5) Prevention and control of major diseases and insect pests
Main pests:
Walnut lifting moth (walnut black), cloud-spotted celestial bull, walnut red spider, thorn moth
Stickworm (ruler moth), walnut fruit weevil
Main diseases:
Walnut anthrax, walnut brown spot disease, walnut black spot disease
Pest: Walnut lifter moth (larvae)
Walnut lifting moth control method
After the fruit is harvested, it is ploughed, expanded and cleared from the middle of May of the following year; the black fruit is picked from June to August and destroyed centrally;
During the feathering period of adult insects from early June to mid-July, 50% of the acacia pine 1000-1500 times liquid or 3000 times of the enemy killed canopies are sprayed in the hard-hit areas.
Cloud-spotted celestial cow
Cloud-spotted cattle control method
1. Artificial killing of adult insects
2. Kill eggs and hatching larvae. Apply 50% borer pine emulsion to the spawning groove to kill the newly hatched larvae.
3. During the drying of larvae, when it is found that there are fecal debris discharged on the trunk, use a knife to peel off the skin to dig out the larvae, or inject 50% of the dichlorvos 100 times liquid from the worm hole, and can also block and seal the worm hole with sludge or soaked cotton balls, and poison and kill the internal pests.
4. From mid-August to late September, zinc phosphide poison swabs were inserted into the intrusion holes of Yunban Tianniu, which had a significant effect on adults and larvae.