Walnut is a tree species that is mainly grown in economic forests in many parts of China. It is widely distributed in northern China. In the project of returning farmland to forest, the planting area of pecans has been further expanded. However, the yield of many walnuts is unstable, and varieties are aging. The operating efficiency has a serious impact, so it is necessary to actively improve the walnut varieties and adopt scientific and rational management methods to further increase the income of forest farmers. This article summarizes the selection of thin-shell hickory varieties, grafting techniques including rootstock treatment and scion preparation, grafting and post-grafting management, providing technical support for fruit growers engaged in the production of thin-shell pecans.
Alpine walnut requires a frost-free period of 140 to 280 days; the annual accumulated temperature exceeds 10 ° C, and the most suitable ambient temperature for growing pecans is 15-20 degrees. The northern varieties of thin-shelled pecans can tolerate a minimum temperature of -29 degrees; the southern varieties can withstand a minimum temperature of -18 degrees; but they can withstand extremely high temperatures, with a maximum temperature of 46.5 degrees Celsius.
Thin-shelled pecans, such as sandy loam or loose loams, are rich in humus. The soil environment is well drained, moist and well drained, but not suitable for acidic soils that are too viscous. Thin-shell pecans have strict requirements for soil pH and can grow well in the pH range of 5.8 to 8.
Alpine walnuts do not have high requirements for soil growth and are suitable for growing in loess or sandy soils. It is not suitable for low-lying water environments. Alpine walnut relies on the primary root to absorb nutrients and water. If the growing environment is low and there is water, coupled with high temperatures, the roots are prone to decay. Alpine walnuts are best grown on sand-red soils and small-grained gravel soils.
For some young trees and low-yielding trees in the process of renovation, trees with deep soil layers, good soil quality and high fertility should be selected for substitution. For some site conditions are relatively small, but due to the management process, for some old trees with soil platelets and malnutrition, it is necessary to carry out corresponding soil improvement operations in time, and further change the growth of trees through deep turning, reaming, fertilization and other technologies, and then replace and optimize.
Reasonable choice of alternative technologies. Walnut and low-yield trees that have a history of more than 20 years should be replaced and optimized accordingly, and renovated year by year. For native fruit trees aged 10 to 20, they need to be renewed year by year. If the planting density of walnut orchards is too large, the method of replanting can be used. For seedlings under the age of ten, it needs to be replaced, while for sick trees, it is no longer necessary to replace. Old trees over the age of sixty do not need to be replaced on a large scale. Only some management is required to extend the service life.
Choose well-grown trees in mountainous areas to ensure that they do not show major pests and diseases. For new shoots that sprout after pulling out 5-20 year old walnut stems, it is necessary to select the base of the tissue 10 ~ at 15 cm during the grafting process, grafting 1-2 buds on each tree to ensure that there are 1-2 new shoots without grafting on the branches after cutting, which can make the growth of the tree more stable.
To provide more convenience in the park management and scion process later in life, you can choose from 2 to 3 varieties to operate without too many complicated situations.
In order to rationally select scion, the main choice is some branches that have no diseases and insect pests, have a relatively high degree of lignification and are relatively robust during the growth process. Locally collected scion avoids a large amount of water loss. Once the collection is complete, the leaves need to be quickly removed, their petioles retained, wrapped in wet gauze, and then stored in the cellar. If it is possible to collect scion harvested from the field in November of the previous year, seal the wound with wax after the collection is complete, tie it and place it in a cool place.
Temperature is an important factor affecting the survival rate of walnut grafting. According to long-term observations in localized mountainous areas between 25 and 28 °C, walnut wounds heal tissue relatively quickly. If the temperature is higher than 30 ° C, or below 16 ° C is very unfavorable to the formation of callus, then when the tree enters a vigorous growth process, especially when the formation of new shoots is active, the survival rate can be greatly improved, so in the process of choosing grafting, the time needs to be controlled between late May and mid-June.
According to the actual situation in the mountainous area, the operation by green plant bud grafting method is the best choice, because the tannins in the walnut body will form an isolation layer after contact with the air, which will have a greater impact on the walnut fruit. After the wound tissue heals, so the transplantation process requires the use of some sharp blades, and the operation process needs to be as fast as possible, as long as the survival rate of the graft can be greatly improved, the specific process is as follows.
Two blades are used to cut the upper and lower parts of the bud at once, and to cut a single blade at 1 cm position of the bud cut by the two blades, cutting one knife and bud longitudinally on the left side to the right.
Cutting the rootstock using the same method, using double blades on the smooth part of the rootstock, cutting the knife deep in the xylem, then cutting longitudinally on the left side, deeply cutting inside the xylem, then connecting the two blades, pinching the bottom of the petiole with the index finger by the thumb and tearing it off with a little force. There must be a certain xylem in the inner depression of the bud flakes, also known as growth points. Some yellow-brown bud flakes cannot be used internally.
After the rootstock is cut, the chips are quickly placed into it so that the forming layer is aligned on both sides or on one side to ensure that the cutting surface and cutting surface of the rootstock can be sufficiently tightly joined together, and then wrapped up using plastic film from the bottom of the cutting surface to the top of the scion.
About 10 days after the completion of grafting, it is necessary to observe, observe and treat the germination situation in time. Germination must be wiped every 10 days so as not to affect the growth of the scion. When the growth of new shoots reaches 40-50 cm, the topping operation can be performed to age the new branches and further accumulate nutrients, making the entire woody part more plump. New branches need to be pruned around the end of September to October to ensure that there can be 3 to 4 buds.
Between October and early November of each year, deciduous walnut trees need to pay attention to deep planing in the canopy projection area to ensure that the planing surface reaches about 20 cm, so as to make the soil more loose and increase the permeability of the soil In order to increase the oxygen content in the soil, it can promote the rapid growth of the root system. At the same time, some pests, such as walnut flatleaf beetle, walnut limb moth, scarab beetle.
Under normal circumstances, pests include blight and rot. Soil improvement is needed to increase the content of organic fertilizer and strengthen soil resistance to disease. Before the rainy season, you need to pay attention to spraying with 70% mancozeb solution, spraying every 10 days, and spraying 3 times in a row, in winter, you need to apply white antifreeze to the trees to avoid disease in the trees. Time and range of propagation are effectively controlled. In the process of pest control, pay attention to walnut flatleaf beetles, walnut moths, etc. Adults generally occur from May to June. According to the phototropism possessed by adults, booby traps are carried out by hanging black lights. If some empty ventilation holes are created after the larvae are found between July and August, it is possible to apply dichlorvos, which can greatly eliminate the insect infestation.
The environment in which thin-shelled hickory trees grow requires a large number of trace elements. The absence of trace elements in thin-shelled pecans can be judged and analyzed by testing the soil and detailed observations of the leaf surface. If there is a phenomenon of trace element deletion, the growth environment of thin-shelled pecans can be improved by improving soil conditions. For example, the nutritional needs of pecans can be met by applying chemical fertilizers to the leaf surface or spraying the corresponding chemical fertilizers, and organic or biological fertilizers can also be added to the soil.
The growth process of thin-shelled peas has two key water requirements. The fruit expansion period is usually from April to May of each year. During this period, sufficient water is needed to satisfy the growth of the fruit; the filling period of the fruit is usually in late summer and early autumn, which is the most tolerable 21d dry period during this period. Therefore, it is necessary to irrigate every 15 days, otherwise it will lead to a decline in fruit.
At present, the main walnut varieties grown in mountainous areas are relatively poor, and it is difficult to bring high economic benefits to farmers. Therefore, it is necessary to strengthen the high-quality alternative of mountain walnuts. In addition, we must strengthen fine management to make the walnut industry fast and sustainable. Healthy development.