Experience in Rapid Seedling Raising of Green Husk Walnuts by Direct Sowing in the Field

Through several years of experimental research, the goal of sowing green husk walnuts in autumn and producing finished walnut seedlings in the field in 1 year has been achieved.

1 Nursery site selection and preparation

Walnut seedling raising should select a nursery site with flat ground, irrigation capability, convenient drainage, a deep groundwater table, deep soil layers, and convenient transportation, using sandy loam soil. Apply 50kg of compound fertilizer and 2000kg of organic fertilizer per 667 sq m as base fertilizer, then deep plow and rake level, plan and divide into sections, dig drainage ditches and irrigation channels, and set aside roads.

2 Seed selection and treatment

In early September, harvest pest-free, disease-free, fully mature green husk walnuts from vigorous trees. It is best to sow immediately after harvesting; for temporary storage, place them in a ventilated, cool place to prevent rot and mold. If the quantity is too large to sow in time, they can also be dehulled using a dedicated walnut dehulling machine, then stored in a ventilated, cool place; be sure not to expose them to direct sunlight. Before sowing, sort the seeds and grade them by size, removing defective fruits such as pest-damaged, diseased, and rotten fruits. To prevent damage by rodents and birds, mix the seeds with pesticide or spray them once before sowing.

3 Sowing

Sow in early to mid-September, with a plant spacing of 15-20cm and a row spacing of 40-45cm, adjusted flexibly according to fertility conditions. Wide-narrow row sowing can be used: first, it can improve ventilation and light conditions; second, it makes grafting operations easier in the future. After the land is prepared and raked level, sprinkle white lines according to the designed row spacing, open shallow furrows of 5-10cm, and place the green husk walnuts (or dehulled nuts) along the furrows, with the suture line of the seed perpendicular to the ground and the seed tips pointing in the same direction. After placing them, take soil from both sides to cover them, forming a ridge 10-15cm above the ground. If wide-narrow row sowing is used, the 2 narrow rows should be covered under 1 ridge. Water once in a timely manner according to soil moisture to ensure no drought occurs, so as not to affect the normal development of the seeds.

4 Seedling stage management

After sowing, green husk walnuts begin to emerge successively after 30d, and about 80% of the seedlings emerge from the ground after about 50d. Due to poor lignification, the aboveground parts will freeze to death in the winter of that year. Before freezing, all should be covered with plastic film. In late March of the following year, young buds grow successively; at this time, observe carefully at all times, and every morning promptly tear open the plastic film where seedlings emerge to prevent high temperatures from scorching the seedlings. By early April, the seedlings have basically all emerged. In late April and mid-May, spray 1 time each of “920” amino acid foliar fertilizer at 30mL/667 sq m or an appropriate amount of 0.3% urea solution to promote rapid seedling growth, while always paying attention to weeding and watering.

5 Grafting

In mid-to-late June, when seedlings with a ground diameter of 0.7cm or more account for more than 80%, begin grafting, and complete the grafting task before July 15. Select buds from the middle-upper part of 1-year-old vigorous branches on mother trees or buds from the middle-upper part of new shoots on improved variety seedlings; pinch off the growing tips 1 week before grafting to promote plump buds. The grafting method uses square patch budding. Take a square bud piece of 2-3.5cm, and the bud-protecting flesh must be included. Leave a drainage opening on the rootstock, bind tightly with plastic strips from bottom to top, one loop pressing the next, exposing the bud, especially binding tightly around the base of the bud.

6 Post-grafting management

1) Cutting the rootstock. After grafting is completed, cut the rootstock leaving 2-3 compound leaves above the graft union, and remove all leaves below the graft union. At the same time, promptly remove sprouts; about 10d after grafting, the grafted bud has begun to sprout, so perform a second cutting of the rootstock leaving 3cm above the graft union to force the grafted bud to sprout. After the second cutting of the rootstock, continue to remove sprouts and suckers.

2) Unbinding. When the grafted bud has grown to a height of 10cm, use a blade to make a cut from bottom to top on the back side of the grafted bud to remove the binding plastic.

3) Daily management. Carry out timely intertillage and weeding, control pests and diseases, and water in a timely manner in case of drought.

7 Leaving the nursery

In early November, the grafted seedlings can leave the nursery. The average height above the graft union is 35-40cm, with the tallest reaching more than 80cm. When digging seedlings, care should be taken to protect the root system; irrigate thoroughly 1 time 1 week before lifting the seedlings so that the seedlings absorb enough water and are easier to dig. According to transportation requirements and seedling size, bundle grafted seedlings into bundles of 25 or 50 plants. Bundle different varieties separately and attach labels.