Detailed Explanation of Key Technical Points for Planting Walnut Nursery Stock

  1. Planting period. The planting of walnut trees can be divided into two types: spring planting and autumn planting. Autumn planting refers to planting after the nursery stock drops its leaves in autumn and before the soil freezes. Spring planting is carried out after the soil thaws and before the nursery stock buds in spring. In the past, walnuts were generally spring-planted, but in the hilly and mountainous areas of North China, where spring drought is severe and walnut root growth is slow, spring planting affects the growth increment of that year, so autumn planting should be advocated, that is, after leaf fall and before the soil freezes. The advantage of autumn planting is that after leaf fall in autumn, the ground temperature does not drop very much and the soil moisture is relatively high; after planting, this is conducive to the healing of root wounds in that same year. Through a winter of root nurturing in the soil, growth can begin early the following spring, the seedling-establishment period is short, the survival rate is high, and budding is early. Autumn planting generally requires cold protection; otherwise, newly planted trees are prone to freeze injury, which affects the survival rate. If cold protection is done well, problems such as the concentration of spring planting time, drought with little rain, and slow seedling establishment can be avoided, allowing young trees to sprout earlier and extending the growth period.

  In areas with low winter temperatures, strong winds, and relatively deep frozen soil layers, spring planting can be carried out. It should be done as early as possible after the soil thaws, with emphasis on irrigation at planting to preserve soil moisture and prevent the nursery stock from losing water. Spring planting can effectively prevent shoot dieback and freeze injury of planted nursery stock after autumn planting.

  2. Planting density. Planting density should be determined according to site conditions, cultivated varieties, and management level. Reasonable close planting can increase leaf area, make full use of light energy, and improve land utilization. The overall goal of planting density should be to obtain relatively high yield and economic benefit per unit area. Early-bearing varieties have smaller crowns but bear fruit early and have relatively high yields; late-bearing varieties have large crowns but bear fruit relatively late and have relatively low yields. Therefore, when establishing an orchard with early-bearing varieties, the planting density should be greater than that of late-bearing varieties. Usually, for late-bearing walnuts, the spacing between plants and rows can be 6-8 m x 8-9 m; for early-bearing walnuts, the spacing between plants and rows can be 3-4 m x 4-6 m. As for different topography, soil, and climatic conditions, when establishing an orchard on flat terrain with deep soil layers and relatively high fertility, walnuts grow vigorously, have a large amount of growth, and easily form large crowns, so the spacing between plants and rows should be larger; when establishing an orchard on soil with relatively poor soil and climatic conditions, small crowns are easily formed, so the spacing between plants and rows should be smaller. For planting on field ridges, field edges, embankments, and plots mainly used for grain production, where fruit-grain intercropping is practiced, the spacing between plants and rows can be handled flexibly; the spacing between plants is generally 8-10 m, and the row spacing depends on the width of the plot, generally 20-30 m. When planting walnuts on mountain terraces, mostly one row is planted per terrace surface; when the terrace width is greater than 10 m, 2 rows can be planted, with plant spacing varying from 5-8 m. Plains are generally planted in rectangular arrangements, while mountainous and hilly areas are planted according to contour lines based on the terrace surface.

  3. Planting method. Before planting, trim the root system of the nursery stock, cut off dead roots and damaged roots, and soak in clean water for 1 day. Before planting, the roots should be dipped in mud slurry (mud coating) so that the roots fully absorb water; only in this way can survival and vigorous growth be ensured. A scientific planting method first ensures the survival rate. Planting trees well when establishing an orchard not only improves the survival rate but also benefits early growth and development. Before planting, first according to the selected planting density, use marking poles, measuring ropes, and white lime to mark the planting points, then dig the planting holes. The size of the holes generally requires a length of 1 m, a width of 1 m, and a depth of 1 m. For mountain walnut orchards, the planting holes are round holes with a diameter of 0.8-1 m and a depth of 1 m. When digging holes, pile topsoil and subsoil separately. In areas with relatively good water conditions, holes can be dug in advance so that the lower soil layer fully matures. In areas with drought and little rain and no irrigation conditions, dig and plant at the same time during planting, and preserve soil moisture as much as possible. When digging holes, if gravel, rock layers, or heavy clay soil are encountered, the excavation volume should be increased, and the method of filling the holes with introduced soil should be adopted to improve the soil. Explosives can be used in the form of a "muffled blast" for fixed-point or fixed-line blasting, and after thickening the soil layer, holes are dug for planting.

  At planting time, 30-50 kg of farmyard manure should be applied in the pit, mixed evenly with topsoil, and more than half of it filled back into the bottom of the pit, then trampled firm so that the center forms a raised mound shape. If conditions permit, 0.5-1 kg of phosphate fertilizer (superphosphate) can also be added to each pit and mixed evenly. When planting, place the seedling in the center of the pit with the root system spread out in all directions, then while filling soil and trampling firm, gently lift the seedling so that the root system is fully in close contact with the soil. When filling soil, trample firm in layers, and require that after watering and settling, the planting depth of the nursery stock is exactly the growth depth of the nursery stock in the nursery or slightly higher than the ground surface. Generally, the soil mark on the nursery stock at the time of lifting can serve as the marker for planting depth. Planting too deep or too shallow is not conducive to the survival and growth of walnuts. After planting, irrigate promptly. In arid areas, attention should be paid to preserving soil moisture. A plastic film of 1-1.5 sq m can be used to cover around the tree disk with the nursery stock as the center, and the edges of the plastic film should be compacted with soil to prevent it from being blown up by strong winds.