How are walnut saplings lifted, graded and stored?
In regions with cold winters, saplings are lifted from the nursery after leaf fall and before the ground freezes. Lifting saplings from the nursery is an important step in raising plants. A plan for leaving the nursery should be made according to needs, and saplings should be lifted in batches according to variety, planting needs and sales situation, to avoid mixing varieties during lifting, storage and transport. In regions where shoots do not shrivel in winter, saplings can be lifted the following spring after the ground thaws and before buds break, and planted immediately after digging; the survival rate is high, the plants establish quickly and the operation is convenient.
Sapling standards
The current standard for grafted walnut saplings is the national standard GB7907 - 87. Saplings sold generally must reach grade 2 or above, and grafted saplings are required to have a well-healed graft union, be fully lignified, and be free of pests, diseases and mechanical damage. Note that sapling height in production generally refers to the height above the graft union. This standard was formulated in 1987, when walnut grafting propagation techniques were not yet up to standard and sapling quality was generally not high. Now, through grafting from late May to early June, higher-quality saplings can be produced, with sapling height reaching more than 1 m, or even taller. Combined with actual production, it is suggested that the standard for grade 1 walnut saplings can be raised to 1.2 m, to facilitate trunk heading after planting.
Lifting, grading and storage
1. Lifting saplings In early winter, after the saplings lose their leaves and before the soil freezes, the saplings must be lifted for planting, transport or centralized storage. Walnut is a deep-rooted tree species, and its roots heal poorly after damage, so the root system should be protected as much as possible when lifting. One week before leaving the nursery, irrigate thoroughly once to increase soil moisture and prevent greater root damage during lifting caused by dry soil; if rain occurs, water less or not at all. When lifting, it is generally enough to dig them out with a spade, taking care to damage the roots as little as possible. Some use mechanical lifting, which is fast and efficient, but note that the lifting depth must reach more than 25-30 cm to prevent cutting too many roots. After the saplings are lifted, prune them appropriately first, mainly cutting off split and broken roots and retaining as many small roots as possible. Prepare mud slurry when lifting, dip the roots in the slurry while lifting, and reduce the time the roots are exposed to air to protect them. The slurry should be thick and sticky; after dipping, a relatively thick layer of slurry should adhere to the roots. Slurry that is too thin is not effective.
2. Grading Saplings for sale must be graded. While lifting, classify them into grade 1, grade 2 and below-standard saplings according to the sapling standard of the national standard GB7907-87, and at the same time remove seedling saplings that were not successfully grafted. Qualified saplings are tied into bundles of 20 or 30, hung with labels, and heeled in, transported or planted as soon as possible. Below-standard saplings can be returned to the nursery for another year of cultivation and lifted the following year. Seedling saplings can also be replanted together and regrafted the following year.
3. Storage Saplings that cannot be planted immediately after lifting must be heeled in. Short-term heeling in is temporary heeling in when saplings cannot be transported promptly after lifting, or when purchased saplings are about to be planted; it generally does not exceed 10 days. In a shady place, open a trench about 3.0 cm deep, bury the sapling roots with moist soil, and sprinkle water to keep them moist; a shade net can also be added to reduce water loss through transpiration. Long-term heeling in refers to heeling in saplings over winter; the time is long, the saplings lose much water, and the requirements are relatively high.
For heeling in, choose a place with higher terrain, shade, little wind and convenient transport, and dig a heeling-in trench. First dig a trench about 50 cm wide, 50-80 cm deep and 3-5 m long. Pile the excavated soil on the south side of the heeling-in trench to form an earth ridge. Open the tied bundles of saplings, tilt them at an angle of 30°-45°, and arrange them in the trench in turn, burying more than 2/3 and leaving the tips exposed. Use soil dug from the second row of trench to fill in the first row of saplings, taking care to fill the gaps between the sapling roots tightly with no empty spaces. When the soil is sticky and heavy, sand can be mixed in; preferably use pure sand, which makes it easier to regulate moisture and handle, and also fills root gaps better. After the second row of trench is dug, place the saplings, and use soil dug from the third row of trench to fill in the second row of saplings, and so on until all saplings are heeled in. At the same time, dig drainage ditches around the heeling-in site to prevent water accumulation. After all saplings are heeled in, spray water once to increase soil moisture and prevent the saplings from drying out, similar to watering before freezing. In cold winter, old straw curtains can be used for covering. After spring temperatures rise, check promptly to prevent the saplings from molding and rot, and plant them as soon as possible. The soil for heeling in should be kept loose and soft, and trampling should be avoided as much as possible to facilitate aeration. In extremely cold regions, all branch tips of the saplings are buried in the soil, because exposed tips tend to dry out.
To store saplings better, where conditions permit, fruit cellars or controlled-atmosphere storage can be used to store the saplings; the temperature in the cellar is low, which can delay sprouting and extend the spring planting time for the saplings. A small number of saplings can also be placed in a vegetable cellar, with the roots covered with moist sand.