Key Technical Points for Seedling Management During the Walnut Nursery Stage
Walnut seeds begin to sprout about 20 days after spring sowing and emerge completely by around 40 days. During this period, check the emergence of seedlings every day. Once the seedlings emerge from the soil, promptly cut open the plastic film with a small knife to prevent scalding the seedlings, and at the same time cover the cut film firmly with moist soil. Strengthening management during the seedling stage is the key to cultivating strong seedlings.
Pictured: walnut
1. Replanting (resowing) When severe gaps in seedlings are found after the seedlings emerge, timely resowing is needed. Denser small seedlings can also be transplanted over to ensure the number of established seedlings. When raising seedlings on a large scale, some seeds should also be sown in separate plots to serve as replacement seedlings.
2. Fertilizing and watering Generally, no watering is done before the seedlings emerge. Once the seedlings have all emerged, water promptly. In May and June, water 2~3 times, and apply chemical fertilizer twice together with irrigation, mainly quick-acting nitrogen fertilizer, such as urea, ammonium bicarbonate, ammonium sulfate, etc. In the early stage, 10 kg/mu; in the middle stage, 20 kg/mu. Ammonium bicarbonate and ammonium sulfate have low nitrogen content, so apply appropriately more. In July and August, after entering the rainy season, water less or not at all, and apply phosphorus and potassium fertilizer to promote seedling fullness; 20 kg of diammonium phosphate plus 20 kg of potassium chloride can be applied per mu. In addition to soil fertilization, foliar spraying should also be carried out. Every 7~10 days, spray once with 0.3%~0.5% urea or monopotassium phosphate. Foliar fertilizer needs to be sprayed continuously 3~5 times. In places with a lot of rain, attention should be paid to drainage to prevent root rot and excessive seedling growth. Before the soil freezes, water once with winterizing water to prevent shoot dieback during overwintering.
3. Cultivation and weeding Generally, cultivation and weeding are carried out after watering. On one hand, this reduces weeds competing with seedlings for nutrients; at the same time, it can prevent soil compaction, reduce ground evaporation, and provide a good environment for seedling growth.
4. Root pruning Walnut has a well-developed taproot. Without root pruning treatment, lateral roots grow very weakly, which is unfavorable for survival and seedling recovery when establishing an orchard and planting out. Therefore, root pruning is generally carried out in late summer and early autumn to promote lateral root development. The operation method is to insert a root-pruning shovel at a 45° angle toward the seedling at a distance of 20 cm from the seedling between the rows, cutting off the taproot. After root pruning, water once and fertilize at the same time to promote new root development. After root pruning, the seedlings have well-developed lateral roots and a high transplant survival rate.
5. Burying soil in winter for cold protection Low winter temperatures can easily freeze walnut seedlings to death, so in the past seedlings were often dug out for cold protection. Now, after leaf fall in early winter, they can be cut back to the ground and then covered with 10~20 cm of soil, which works very well. In areas where winter is not too cold, soil can be buried only at the root crown for cold protection.
6. Pest and disease control For methods of pest and disease control on walnut seedlings, refer to the control methods for mature trees. Give priority to prevention, and when pests or diseases are found, spray pesticide early for control.