Detailed Explanation of Key Techniques for Root-Buried Propagation of Black Locust (Robinia pseudoacacia)

1. Site Selection and Land Preparation: The nursery site should be flat terrain, convenient for irrigation and drainage, with deep soil layers, fertile soil, and a groundwater level below 1.5-2m, preferably sandy loam or loam soil. Low-lying areas with excessively high groundwater levels, saline-alkali land, and heavy clay soil are not suitable for nurseries.

2. Selecting Seed Roots: 1-2 year old seedling roots should be selected, including residual root systems after lifting from the nursery or roots trimmed from seedlings. The length of seed roots is preferably 10-20 cm, with the thick end having a diameter of 1.5-4 cm. The collection time for seed roots can be from after leaf fall to before bud break, generally from late February to mid-March. After the seed roots are dug out, they should be promptly cut into root cuttings. The upper end is cut flat, and the lower end is cut at an angle to prevent inverted planting. Alternatively, roots can be collected in autumn for storage and buried the following spring. Storage method: Choose a sheltered, sunny location with good drainage, dig a storage trench 1 m wide and 0.5-0.8 m deep, with the length depending on the quantity of seed roots. Line the bottom of the trench with 5-10 cm of fine sand, place the seed roots upright in the trench with the thick end facing up, fill with a layer of moist sand after each layer is full, then place the second layer, continuing until 20 cm from the ground surface.

3. Timely Root Burial: Late February to mid-March is best. To ensure uniform seedling growth, seed roots should be graded before burial.

Root burial methods: There are three types - vertical burial, slanting burial, and flat burial, among which vertical burial is the best.

4. Seedling Management: After root burial, after about 20 days, germination begins from late March to early April, and seedlings basically emerge completely around mid-May. Management during this period focuses mainly on loosening soil and preserving moisture. When seedlings are about 10 cm tall, timely thin out the weak and keep the strong among the multiple adventitious shoots emerging from the roots, and carry out final spacing. From early May to late June, irrigation should be applied timely according to weather conditions, and soil should be mounded at the base of seedlings to promote root development at the base. From late June to late August, which is the vigorous growth period of root-buried seedlings, apply quick-acting chemical fertilizer every 15-20 days, about 10 kg per mu, or 400-500 kg of human feces and urine, combined with irrigation. After late August, stop watering and fertilizing to prevent excessive late-season growth of seedlings. During the seedling growth process, pest and disease control should be carried out properly, and attention should be paid to drainage and flood prevention.