A Detailed Tutorial on the Latest Walnut Seedling Raising Techniques and Methods
Walnut is also known as Persian walnut, Qiang walnut, etc. It is a plant of the genus Juglans in the family Juglandaceae, and together with almond, cashew and hazelnut it is known as one of the world's famous “four great dried fruits”. It has strong drought resistance and disease resistance, adapts to growth in many kinds of soil, prefers fertile and moist sandy loam, and is commonly found on both sides of mountain valleys in places with deep soil layers. It has extremely high cultivation value. Now let us take a look at the seedling raising techniques for walnut seedlings!
Seed Selection
When selecting walnut seeds, choose strong-growing superior individual trees 20 to 40 years old with strong adaptability, high and stable yield, thin shells, plump kernels, easy kernel extraction, and high kernel yield and oil content as the mother trees for seed collection. Generally in September, when the outer pericarp changes from green to yellow-brown, the fruit is ripe. However, walnuts kept for seed should be harvested 10 to 15 days later than walnuts for commercial use, which is beneficial for increasing the germination rate. After collecting them, pile and compost them to remove the green husk. Seed walnuts do not need to be rinsed and can be directly air-dried. When drying the seeds, spread them flat in a ventilated and dry place. They must not be placed on concrete ground, wooden boards or iron sheets for direct sun exposure, so as not to affect seed viability. Walnut seeds have no after-ripening period; seeds sown in autumn can be sown with the green husk still on after collection, while seeds sown in spring are stored for a longer time and generally need to be stored in a ventilated and dry place at about 5°C.
Site Selection and Nursery Preparation
In the process of raising walnut seedlings, whether using field seedling raising or self-sufficient courtyard seedling raising, the selected nursery site is required to have flat terrain, shelter from the wind and face the sun, loose soil, deep and fertile soil, convenient irrigation and good drainage. After selecting the nursery site, carry out deep ploughing or deep cultivation and carefully prepare the land, so that the upper layer is loose and the lower layer is firm, the soil is fine and the ground is level, and the fertilizer and soil are evenly mixed. This is generally done before Frost's Descent. While preparing the land, apply sufficient base fertilizer, including 3000 to 5000 kg of farmyard manure per mu and 50 kg of superphosphate per mu. After land preparation is completed, make seedbeds with a width of one meter and a length that varies according to the terrain and the amount of seedlings to be raised, for later use.
Seed Treatment
Walnut seeds sown in autumn do not need treatment and can be sown directly with the green husk on. For spring sowing, seeds should be treated before sowing to ensure germination. The usual method is the cold soaking and sun drying method. The cold soaking and sun drying method is to soak the seeds for 7 to 10 days, changing the water once a day, so that the seeds absorb water and swell. When a small number of seeds have split open, take them out and dry them on a soil yard or the ground for 2 to 3 hours, and then they can be sown.
Sowing Management
1. Sowing period: Walnuts are divided into autumn sowing and spring sowing. Autumn sowing should be carried out before the soil freezes, and should not be too early or too late, otherwise the germination capacity will be affected. Because seeds sown in autumn are susceptible to damage by rats and rabbits, spring sowing for seedling raising is often used. Spring sowing should be carried out after the soil thaws, generally in late March to early April.
2. Sowing method: Walnuts commonly use the dibbling method. In the prepared seedbed, dibble at a row spacing of 20 to 30 cm and a plant spacing of 15 cm. The seed suture line should be perpendicular to the ground, with the pointed end of the seed facing to one side, so that after emergence the seedling root system spreads out, the seedling stem is upright, and growth is vigorous. The sowing depth is 6 to 8 cm, and after sowing cover with soil 9 to 12 cm. When sowing, follow the principle of deep sowing in autumn and shallow sowing in spring, and deep sowing in drought and shallow sowing in waterlogged conditions.
3. Sowing rate per mu: The sowing rate of walnuts varies with plant and row spacing and with seed size and quality. Generally, 100 to 150 kg of dry walnuts are sown per mu, about 9000 to 12000 seeds, producing 8000 to 10000 seedlings per mu, while 400 to 500 kg of green-husked walnuts are used per mu. In addition, whether in the field or in courtyard seedling raising, it is best to use the spring plastic-film mulching seedling raising method, so that seedlings emerge earlier, emerge uniformly, and have a longer growth cycle.
4. Fertilization and irrigation: After spring sowing, walnuts germinate and emerge in about 20 days and emerge completely in about 40 days. Generally, if it is not too dry, no irrigation is needed before emergence, so as to avoid surface crusting. If the soil moisture is too poor, water in time and carry out shallow ploughing and loosening of the soil. After the seedlings have emerged completely, in order to speed up growth, irrigate in time. May and June are key periods for seedling growth; water 2 to 3 times according to soil moisture, and combine this with topdressing quick-acting nitrogen fertilizer, applying 10 kg of urea per mu each time. In July and August there is more rainfall, so appropriately apply phosphorus and potassium fertilizer as topdressing.
5. Intertillage and weeding: In spring walnut nurseries, weeds grow quickly and reproduce strongly, competing with seedlings for water and nutrients, and some weeds are also vectors and parasitic sites for diseases and pests. Therefore, the nursery land should be intertilled and weeded in time.