Key Technical Points and Detailed Methods for Black Locust Seedling Cultivation

(1) Thinning: Black locust seedlings are light-loving and differentiate early. If seedling density is too high, differentiation becomes even more pronounced, so timely thinning is necessary. The first thinning is carried out when seedlings are 3-4 cm tall, removing diseased and weak seedlings. Afterward, based on seedling growth and density, 1-2 more thinnings are carried out. 12-15 seedlings should be retained per meter of row length. Retaining approximately 12,000-15,000 seedlings per 667 sq m is appropriate.

(2) Watering and topdressing: Do not water before black locust seedlings emerge, to avoid surface soil crusting that causes uneven emergence. After emergence, water timely and appropriately, maintaining soil moisture regularly. In the Kuandian area, watering can be done 3-5 times per year. Watering should be moderate; black locust is intolerant of waterlogging, so drainage should be timely during the rainy season to prevent root rot of seedlings.

Apply topdressing once during the seedling stage, in early to mid-July. Apply 15-20 kg of ammonium sulfate per 667 sq m. After fertilizing, water once. Stop topdressing and watering in late July to prevent excessive vegetative growth that affects seedling lignification.

(3) Loosening soil and weeding: The nursery bed should be kept loose and free of weeds. During the first half of seedling growth, carry out loosening and weeding about every half month. During the second half of seedling growth, carry out loosening and weeding every 30 d, generally after watering and after rain.

(4) Pest and disease control: Black locust seedlings are prone to damping-off disease during the seedling stage. After seedlings have fully emerged, spray 0.5%-1% equal-amount Bordeaux mixture or 1%-2% ferrous sulfate solution once every 15 d for control. Aphid damage occurs in June-July and can be controlled by spraying a 0.05% solution of 40% dimethoate.

(5) Tip cutting and leaf stripping: Black locust seedlings grow rapidly with dense branches and leaves, have high requirements for light and aeration, and differentiate severely. Large seedlings that grow and develop quickly suppress the growth of surrounding seedlings. Therefore, the method of tip cutting and leaf stripping is adopted to suppress large seedlings and assist small seedlings, so that they grow and develop in a balanced manner, achieving the goal of high quality and high yield. Tip cutting and leaf stripping is carried out in summer when seedlings grow vigorously with lush branches and leaves, generally starting when seedlings are 60-70 cm tall, then once every 20 d, ending in mid-August. Cut branches and leaves upward from both sides of the ridge; cut more from large seedlings, less from medium seedlings, and none from small seedlings. After cutting, seedling height should not be lower than 50 cm. If seedlings are not too dense and differentiation is not severe, leaf stripping may be omitted.