Detailed Explanation of Key Techniques for Sowing and Raising Black Locust Seedlings in Mountainous Areas

Black locust (Robinia pseudoacacia) is one of the main tree species for afforestation and greening in mountainous areas. It is not only an important source of timber for mine props, railway sleepers, vehicles and boats, and farm tools, but also a good nectar plant.

1. Nursery site selection and land preparation. The seedling-raising site should be a sandy loam plot with flat terrain, good drainage, and deep, fertile soil, and should have irrigation conditions. After the seedling-raising site is selected, plowing should be carried out in autumn to a depth of 30 cm. In early spring, harrow finely and level while the soil is still frozen, and at the same time pick out grass roots and stones. In conjunction with land preparation, apply 3000-5000 kg of decomposed stable manure per mu. During land preparation, apply poisoned soil made from 50% phoxim emulsifiable concentrate to prevent underground pests.

2. Seed soaking and germination acceleration treatment. It is best to use progressive heating for seed soaking and germination acceleration, and to sow in batches. Put the seeds into a vat, pour in 50-60°C hot water, stirring while pouring until it is no longer hot to the touch. After soaking for 1 day and night, remove the floating shriveled seeds, bad seeds, and impurities, and use a fine-mesh sieve to separate the swollen seeds from the hard grains. Treat the unswollen seeds again with 80-90°C hot water 1-2 times, and most of the seeds will be able to swell. Put the remaining small amount of hard grains into an iron sieve (1.5-2 kg per sieve), soak them in boiling water for 10 seconds, then pour them into warm water and soak for 1 day and night, and the seeds can basically swell. The water-absorbing swollen seeds selected each time should be promptly placed in a clay pot or basket, covered with a wet straw curtain or wet gunny sack, and placed in a warm place to accelerate germination. To prevent the seeds from becoming sticky and deteriorating, wash them with water 2 times daily, then place them in a warm, ventilated place to accelerate germination. After about 4-5 days, when 1/3 of the seeds have split open and exposed white root tips, they can be taken out for sowing. After sowing, all seedlings emerge completely in 3-5 days.

3. Sowing. The sowing period is in late April when the average temperature reaches 16°C. For ridge-cultivated seedling raising, the sowing rate is 3-4 kg. The ridge spacing is 70 cm, using wide-row drilling. First open a furrow on the ridge, with a furrow width of 10-15 cm; when opening the furrow, the bottom should be flat and the depth uniform. Evenly scatter the seeds into the sowing furrow, cover with soil 1-2 cm, then lightly press once with a roller so that the seeds are in close contact with the soil.

4. Seedling-stage tending and management. The first thinning is carried out when the seedlings are 3-4 cm tall, followed by another 1-2 thinnings, with the last thinning carried out when the seedlings are 10-15 cm tall. About 10 seedlings should be retained per meter of sowing furrow, and it is appropriate to retain 10,000 seedlings per mu. Irrigate promptly after transplanting. Watering can be done 4-6 times throughout the year. From early June to mid-July, topdressing can be applied 2 times. Each time, apply 5 kg of urea or 7.5 kg of ammonium sulfate per mu. Irrigate after fertilizing. After mid-August, stop irrigation and topdressing, and frequently hoe and cultivate. Use 0.5-1% equal-amount Bordeaux mixture to control damping-off disease; use 800-fold dilution of 80% wettable trichlorfon to drench the root area to control bean seed flies. When aphids cause damage in June-July, spray 2000-fold dilution of 40% dimethoate emulsifiable concentrate to kill the insects.