(1) scion cultivation

① Establishment of scion nursery It is of great significance to establish scion nursery to cultivate high-quality scion for improving scion quality and promoting walnut planting variety. Grafted seedlings of excellent varieties (or strains) can be directly used when establishing the scion nursery; It can also be made by grafting young walnut orchards and changing their heads. It is best to build the scion nursery nearby. The seedlings used must be strictly selected, the varieties must be pure, and there are no pests and diseases. Fill in the registration form and draw the planting map when planting, and don't mess it up. The plant spacing can be slightly smaller, generally 2 ~ 4m, and the plant spacing is 4 ~ 5m.

Generally, the tree shape of the cutting mother tree is not strict, but because high-quality scions mostly grow in the upper part of the crown, the tree shape is mostly open, round or natural, and the height of the tree is controlled within 1.5 meters. Pruning is mainly to adjust the tree shape, thinning out dense branches, dry and dead branches, drooping branches, diseased branches and injured branches. In spring, when the new shoots grow to 1 ~ 3 cm, the branches that grow too strongly should be cored to increase the number of scions and prevent them from growing too thick to be grafted. In addition, if there are male flowers, they should be erased before the expansion period.

too much cutting will weaken the tree potential because of large injury flow and small leaf area, so it is not possible to cut too much cutting. In addition, a large number of scions are picked every year, resulting in many wounds, which are prone to dry rot, rot, black spot and anthracnose. No matter whether the disease is serious or not, we should give priority to prevention. Generally, spray 5 Baume stone sulfur mixture once before germination in spring; From June to July, spray 2 times the same amount of Bordeaux solution every 1 to 15 days, and spray it three times in a row. The dead branches and leaves in the garden should be cleaned up in time.

generally, tree shape and fruit yield should be considered after 4-5 years of ear picking, and the ear picking garden should be turned into a high-yield garden when appropriate.

② Collection and treatment of scions Walnut grafting methods can be divided into two categories: branch grafting and bud grafting. Due to different grafting methods and different periods, there are also different requirements for the time and quality of scions.

collection of branch scions: the whole dormancy period from defoliation to bud germination can be collected. In the northern areas where the phenomenon of walnut branching is serious and branches are vulnerable to freezing injury in winter or early spring, it is advisable to collect them in late autumn and early winter; In areas with slight chilling injury in winter or when the parent tree is an mature tree, the cuttings can be picked before the buds sprout in spring. During this period, the cuttings can be used as they are picked or stored for a short time, and the grafting survival rate is high. The quality of scion is an important factor related to the survival rate of grafting. The scion used for branch grafting is generally about 1 meter long and 1 ~ 1.5 cm thick. It is required to be full and strong, with small pith and no pests and diseases. When collecting scions, the cutting mouth should be flat, not oblique stubble. After harvest, the scions are graded according to length and thickness, and every 3 or 5 scions are tied into a bundle, and the varieties are marked. When storing for the winter, a ditch with a width of 1.2m and a depth of 8cm can be dug in the shade, and the length depends on the number of scions. Then, bundles of scions are put into the ditch, with wet sand or wet soil about 1cm between the two layers, and finally, the wet sand or wet soil is buried with a thickness of 2cm, and the soil is thickened to 4cm with wet soil before freezing. The optimum storage temperature of walnut scion is ~ 5℃, and the highest temperature cannot exceed 8℃. Scions placed in refrigerator and cold storage should avoid power failure and temperature rise, otherwise, the grafting survival rate will be seriously affected. When the temperature rises in spring, the scions stored in the soil should be moved to places with lower temperature, such as cellars, pits, cold storage, etc. to avoid excessive temperature. Scions used for branch grafting should be cut and waxed before grafting. The length of scion cutting varies with the grafting method. The scion used for indoor grafting is generally about 13 cm long with 1 ~ 2 full buds, and the outdoor branch grafting is generally about 16 cm long with 2 ~ 3 full buds. When cutting, the first bud at the top should be complete, full and free of pests and diseases, and the first bud at the top should be about 1.5 cm away from the cut. The tip of walnut branches is generally not full, so it is best not to use it when cutting; The middle part and the base grow abundantly, which has a high grafting survival rate. The cut branches were dipped in paraffin at a medium speed at 95 ~ 1℃, which had a good effect on keeping the moisture in the scion and improving the survival rate of grafting. Wax sealing is best done about 15 days before grafting, not too early. Sealed scions should be bundled and marked with varieties, and stored in wet and cool environment such as cellar and cold storage for later use.

collection of budding scions: most budding scions are collected in summer or stored temporarily. Generally, the storage time should not exceed 5 days. The longer the storage time, the lower the grafting survival rate. After the scion is picked, the compound leaves should be removed immediately, leaving 1 ~ 2 cm petiole to reduce water evaporation. If storage is needed, it should be placed in a ventilated and cool place, and the scion should be inserted into the wet sand and sprayed with water at any time to prevent drying. If it needs to be transported from a distance, it must be packed with moist moss or sawdust, and the outside can be sealed with a sack or hemp before shipment. After arriving at the destination, open the package in time, put it in a damp and cool place, and sprinkle water at any time for later use.

(2) grafting technology

walnut trees are prone to bleeding after injury, and the tannin content in bleeding and branch buds is high, which will have adverse effects on the formation of wound callus. At the same time, excessive bleeding will also accumulate at the interface, which will hinder the material exchange and physiological activities of both rootstocks and panicles, curb the division of callus cells of both sides, and thus affect the survival rate of grafting. In addition, the branches of walnut are stout, the pith is large, the buds and leaves are large and protruding, and the vascular bundles in the buds are easily torn when taking buds, which brings difficulties to walnut grafting. To this end, a lot of research and discussion have been done in various parts of China, so that the problem of walnut grafting can be better solved. In order to obtain a high grafting survival rate, all localities should choose the appropriate grafting period and grafting technology according to the specific situation.

The grafting period of walnut varies with different climate, so all localities should choose the suitable grafting period according to the phenological characteristics of walnut in this area. Generally, after entering the vigorous growth period, rootstocks have less bleeding, active cambium and vigorous physiological activities, which is beneficial to wound healing. According to this characteristic, branch grafting is mostly carried out at the stage of budding and leaf spreading, and bud grafting is mostly carried out at the peak of new shoot thickening growth. Such as Yunnan, Guizhou, Sichuan and other places, the branches are grafted in February and the buds are grafted in March. In the Yellow River basin, the branches meet from late March to mid-late April, and the buds meet from June to mid-late August. If the hidden buds on the annual branches are used, they can also be budded in spring.

Walnut grafting methods can be divided into two categories: branch grafting and bud grafting. Grafting includes split grafting, one-knife and half-belly grafting, skin grafting and tongue grafting, and bud grafting includes T-shaped bud grafting, square bud grafting, tongue bud grafting and improved bag grafting.

① branch grafting is a grafting method with branches as scions. The specific operation is divided into outdoor branch grafting and indoor branch grafting. The amount of injury flow during grafting is the key to the survival of outdoor branches. Generally, measures such as root cutting (about 7 days before grafting), controlling irrigation (15 days before grafting and 2 days after grafting are forbidden), cutting the rootstock in advance (about 7 days before grafting, and then cutting fresh stubble when grafting), draining water from the rootstock base (cutting 3-4 knives obliquely in different directions below the grafting site to reach the xylem), and delaying the grafting period can be taken. Outdoor grafting has the characteristics of simple operation, high survival rate and strong growth of seedlings, but the suitable grafting time is short and the utilization rate of scions is low. The technical points of each grafting method are as follows.

Splitting: Suitable for rootstocks with older trees and thicker seedlings. Rootstocks of 2-4 years old with a diameter of more than 3 cm can be selected, sawed off at 1 cm above the ground, and cut 5 cm long at 1/2 of the cross section. The scion should be sealed tightly with wax, and both sides should be cut into 4 ~ 5 cm inclined planes (two full buds are reserved). Quickly insert the cut surface of the scion into the split of the rootstock, and make sure that the cambium of the rootstock and the ear is closely attached. If the scion is thinner than the rootstock, the cambium on one side should be aligned, and then tightly bound with plastic strips to ensure the humidity of the interface.

tongue grafting: from the initial stage of sap flow to the initial stage of shoot growth, when the bleeding volume is small and the cortex is easy to peel off. In order to avoid the influence of bleeding, attention should be paid to not watering before grafting, and the rootstock should be sawed off in advance 3 ~ 5 days before grafting to play a role in draining water. When grafting, the rootstock is sawed to remove the air-dried layer and cut out fresh stubble, then the outer skin of the rootstock is cut off into a long tongue shape, and the scion is cut into a 5-6 cm tongue-shaped cut surface, and the cortex and xylem of the tongue-shaped part are separated by hand, and the tongue-shaped xylem of the scion is slowly inserted between the xylem and the cortex of the rootstock, so that the cortex of the scion is closely attached to the cut surface of the rootstock, and the scion is exposed for about 1 cm, and finally the interface is tightly bound with plastic strips.

abdominal grafting: on one side of the scion, cut a horse-ear-shaped inclined plane about 5 cm long, and then cut a small inclined plane of 1-2 cm on the opposite side (not exceeding the pith). Select a rootstock with a thickness of not less than 2-3cm, at an angle of 2-3 with the rootstock at a distance of 2-3cm from the ground, obliquely cut down a cut of 5-6cm (not exceeding the pith), gently pull the upper rootstock to open the cut, gently insert the scion, and make the rootstock and the scion face each other to form a good cambium, let go and clamp it, and cut off the upper rootstock at a position 5cm above the rootstock cut, and tie it tightly.

among many methods of outdoor grafting, tongue grafting and split grafting are more suitable, and sticking method can also be used when it is difficult to peel off the skin. Because the pith of walnut branches is large and the survival rate of abdominal grafting is low, attention should be paid to choosing the appropriate grafting method in practical application.

indoor grafting of walnut is a method of grafting indoors by using seedlings from nursery as rootstocks. This method can effectively avoid the adverse effects of bleeding fluid on grafting survival, artificially create suitable conditions for the healing of rootstocks and scions, and has the advantages of long grafting period, high efficiency and high and stable survival rate. However, the process is complicated, the technical links are difficult to master, and certain equipment conditions are needed, so the seedling raising cost is high. This method can be carried out during the whole dormancy period, but it is suitable for March to April in spring. If the rootstock is in deep dormancy when it is grafted before March, it is necessary to "wake up" the scion and rootstock to relieve dormancy. The method is that the rootstock and scion are buried in wet sawdust at 25 ~ 3℃, and the rootstock lasts for about 1 days and the scion lasts for 3 days. Grafting after March generally does not need to be "awakened". The grafting method is mostly tongue grafting (Figure 36). The suitable temperature for grafting healing is 26 ~ 28℃, the moisture content of sawdust is 5% ~ 55%, and good ventilation conditions should be maintained. Generally, the method of hotbed healing is adopted, and the grafted seedlings can be placed in a wooden box and placed in a greenhouse or a warm room. It is best to set up an electric hotbed in the greenhouse or plastic shed to automatically control the temperature. Firstly, put wet sawdust with a thickness of 5-1 cm on the bottom of the hotbed, and put the seedlings in the hotbed in rows at an angle of 3-45 degrees, with each row separated by wet sawdust, and the top covered with sawdust exceeds the scion by about 1 cm. Sawdust should be fresh and clean, and mixed with 8 ~ 1 times solution of thiophanate methyl or chlorothalonil for wet disinfection. It can be healed in about 15 days, and then transplanted to the nursery.

fig. 36 indoor grafting method (tongue grafting)

1. Cutting rootstock 2. Cutting scion 3. Joining 4. Binding

2. Bud grafting of walnut requires higher scion, and the buds used for bud grafting should be flat, so it is better to have full buds in the middle and lower parts of the robust branches of the year, otherwise it is not easy to closely connect with the rootstock, which will affect the survival rate. Irrigation is not suitable before (1 days) and after (15 days) bud grafting, otherwise bleeding will also occur, which will reduce the survival rate of grafting. There are many bud grafting methods, and the technical points of each method are as follows.

T-shaped bud grafting: it is advisable to choose one or two-year-old branches as rootstocks. Choose full and full buds for bud grafting, and it is not suitable to use buds with too large bulges, so as not to hinder healing. The grafting position should be low, preferably not more than 2 cm, generally about 1 cm from the ground, and other requirements are the same as those of general T-shaped grafting.

Block budding: This method is a good budding method applied in various places at present, with large contact area and high survival rate. The grafting position should not be too high. When grafting, align the grafting position with the bud-taking position of the scion, draw a line mark on the rootstock and the scion at the same time with a knife, and then cut the rootstock, the lower part and the side edge with a knife according to the specified length, and press the bark back to the original position to prevent the incision from drying. Take off the bud slice with the same size from the scion, so that the bud and petiole are in the center of the bud slice, then take off the slice from the rootstock and put the bud slice into the incision of the rootstock, so that the bud slice is closely connected with the incision of the rootstock, and finally tie it tightly with plastic strips, so that the bud and petiole are exposed. In this method, it is best to cut with a special double-edged knife to ensure that the incision of the rootstock is the same size as the bud. When cutting, the bud piece should be 3 ~ 4 cm long and 1.5 ~ 2.5 cm wide. In the case of poor technology, it is better to make the bud piece smaller than the cut of the rootstock than to make the bud piece larger than the cut of the rootstock, otherwise the bud piece will be tilted up and the contact will be poor, which will affect the survival.

tongue-shaped bud grafting: when grafting, a tongue-shaped incision with a length of 4-5 cm is cut on one side of the rootstock with a knife, reaching the xylem, and then the upper half of the cut bark is cut off, and the lower half is reserved for clamping buds. Cut a tongue-shaped bud piece on the scion according to the same length, which should be slightly woody, but not too thick. After cutting the bud, quickly insert it under the bark of the split rootstock to align the cambium of the two, and then tie it tightly and seal it.

(3) Management of grafted seedlings

Walnut shoots and shoots 2 to 3 days after grafting. In order to make grafted seedlings grow healthily, the following management work should be done.

① Except for the sprouting tillers, many sprouting tillers usually grow on rootstocks. In order to ensure the survival rate of grafting and the rapid growth of new shoots and not to consume a lot of nutrients, the sprouting tillers should be removed at any time. When it is confirmed that the grafting has not survived, a good culture place can be reserved for re-grafting, and the rest should be removed at any time.

(2) when the new tip of the upright post is 2 ~ 3cm long, the upright post should be erected to prevent the seedlings from being broken by the wind. Lead the tender branches of the seedlings to the pillars, and tie them again when the height of the seedlings is 6 ~ 7 cm.

③ Generally, the rootstock is not cut immediately after bud grafting. Cutting the rootstock too early will make the grafted buds germinate, and the tender new shoots will be easily killed in the winter. Therefore, before sprouting in spring, the rootstock above the budding should be cut off at 1 ~ 2 cm above the budding. In places where it is not very cold in winter, the rootstocks above the bud grafting can also be cut off in stages or at one time after the bud grafting.

④ Fertilizer and water management and pest control It is forbidden to irrigate and fertilize walnuts within 2 days after grafting. When the new shoots grow to more than 1 cm, they should be watered and topdressed in time, combined with intertillage weeding. In autumn, watering and nitrogen fertilizer should be controlled, and phosphorus and potassium fertilizer should be applied appropriately. Picking the core in mid-August can enhance the degree of lignification. Seedlings are vulnerable to leaf-eating pests in the new shoot growth period, so they should be inspected in time and paid attention to prevention and control.