Management Methods and Technical Points for Walnut Seedlings After Grafting

  From grafting in May and June to the grafted seedlings leaving the nursery in October, there are only a few short months. In order to ensure the robust growth of grafted seedlings and cultivate high-grade nursery stock, management needs to be strengthened.

  1. Check survival and fill in grafts. About 1 week after walnut bud grafting, check whether the graft has survived. Fresh and plump grafted buds indicate successful grafting, while blackened grafted buds indicate failure, and timely re-grafting should be carried out. Branch grafting generally takes about 15 days to sprout.

  2. Cut the rootstock. When bud grafting in May, generally at the same time as grafting, keep 1-2 compound leaves on the rootstock shoot above the graft union and cut off the rest to inhibit rootstock growth and favor the survival of the grafted bud. 7-10 days after grafting, cut the rootstock 1.5-2 cm above the grafted bud to promote bud sprouting and growth. However, seedlings grafted after mid-July are not cut at the rootstock; in the current year they are only cultivated into semi-finished seedlings with a grafted bud of one variety, and the rootstock is cut in the spring of the following year, when the grafted bud sprouts and grows into a grafted seedling.

  3. Remove sprouts. About 20 days after bud grafting, a large number of young shoots will sprout from the rootstock and should be removed in time to concentrate nutrients for the growth of the grafted bud. In the subsequent management process, concentrated bud removal should also be carried out 1-2 times. Generally, when the new shoot of the grafted bud grows to more than 30 cm, rootstock buds rarely sprout again.

  4. Remove the binding material. After bud grafting, pay attention to checking the petiole of the scion. If there is rot, the film needs to be pierced to let air in, preventing the entire grafted bud from rotting. After the graft survives, the scion grows rapidly, and the binding material can be removed in time when the new shoot grows to more than 3-6 cm. If untied too early, the graft union will not heal firmly, and the scion is easily blown off by wind or knocked off during field operations. If untied too late, the plastic will inhibit thickening at the bound part, forming a constriction mark, and the future seedling is also easily broken by wind.

  5. Fertilizer and water management. After walnut grafting and before the grafted bud sprouts, do not water or fertilize. When the new shoot grows to more than 10 cm, begin to strengthen fertilizer and water management to promote growth. Topdressing and watering should be carried out simultaneously. In the early stage, apply 10 kg of urea per mu each time; in the middle and late stages, 20 kg (or 10 kg of potassium dihydrogen phosphate). 2-3 days after watering, carry out intertillage and weeding. Soil topdressing and foliar spraying can be combined and alternated, once every half month, each time spraying 0.5% urea plus 0.3% potassium dihydrogen phosphate, with the total concentration not exceeding 1%. After the Start of Autumn, control watering and the application of nitrogen fertilizer, and spray phosphorus and potassium fertilizer on the leaves (0.3% potassium dihydrogen phosphate) to promote shoot maturation.

  6. Set up supports. After the grafted bud sprouts, branches and leaves grow rapidly, while the mechanical support capacity of the graft union is still weak, so it is very easy to be broken by wind or knocked down by people and livestock. A bamboo pole or wooden stick can be inserted beside it, and a thin rope can be used to tie the new shoot and the bamboo pole together to provide fixation. When tying, leave space for the new shoot to grow to prevent injuring the seedling. The support should be inserted deep into the ground and firmly.

  7. Pinching. Nursery fields generally have sufficient fertilizer and water, and branches tend to remain vegetative and grow excessively. Generally in mid-September, pinch the new shoots that have not stopped growing. Pinching can promote lignification of the new shoots and has the effect of enhancing the overwintering ability of grafted seedlings and preventing shoot shriveling.

  8. Pest and disease control. Nursery land has high density, and branches and leaves are tender, making them susceptible to pests and diseases. During management, pay attention to observation, detect in time, and control early.