Key Technical Points and Methods for Direct Seeding Afforestation of Caragana microphylla

Caragana microphylla, a shrub or small tree of the Fabaceae (Papilionaceae) family, is extremely light-demanding, resistant to severe cold and intense heat, highly tolerant of drought and barren soil, and highly adaptable. It is an excellent tree species for sand fixation and soil conservation in deserts and grasslands. Its tender branches and fresh leaves are good fodder for livestock, especially sheep, and it is also a good firewood plantation species. Seeds can be collected for direct seeding afforestation.

The seeds mature from July to August; harvest when the pods are hard and yellow-brown. The time from fruit maturity to pod dehiscence is very short, so harvest as they ripen. Dry the harvested pods in the sun and remove the pod shells and debris. Good seeds are yellow-green or cream-yellow and glossy. The germination rate of the current year's seeds is about 90%; after 3 years of storage the germination rate drops to about 30%, and after 4 years they lose the ability to germinate. As long as soil moisture is good, sowing can be done in spring, summer or autumn, but the rainy season is best. Before sowing, soak the seeds in 30°C water for 12-24 hours, then remove and treat with 10% zinc phosphide seed dressing. There are the following 5 direct seeding methods, which should be adopted respectively according to different situations.

1. Hole sowing method: suitable for fixed and semi-fixed sandy land and flat abandoned land. At a spacing of 1.3 m x 1.3 m between plants and rows, dig holes 4-5 cm deep and 10-15 cm in both length and width in a quincunx (checkerboard) pattern, 400 holes per mu, sow 20-30 seeds per hole, using 0.5 kg of seeds per mu, cover with 3 cm of soil, and press down lightly. They will germinate and emerge in 6-10 days.

2. Furrow method: suitable for gentle gully slopes, retired farmland and fixed sandy land. Along the contour lines, from bottom to top, plow two consecutive furrows every 1.5 m, and on the half-slope of the furrow dig holes every 1.3 m and sow 20-30 seeds per hole, covering with 3 cm of soil. Sow 350 holes per mu, using 0.5 kg of seeds. To prevent rainwater from washing and silting along the furrow, a soil barrier can be made at regular intervals within the horizontal furrow. This method can reduce seed theft by jerboas, facilitate seedling rooting, benefit soil and water conservation, and allow tree-crop intercropping.

3. Fish-scale pit method: suitable for steep slopes of 30 degrees or more. Along the contour lines, from top to bottom, at a spacing of 1 m between plants and rows, dig pits 20-30 cm deep, 30 cm wide and 50 cm long, then make a small soil ridge along the lower edge of the pit, and sow the seeds on the ridge slope. This can both store water to promote seed germination and prevent seedlings from being buried by silt.

4. Mound-setting method: used on low gentle slopes and places prone to water accumulation. From top to bottom along the contour lines, at a spacing of 1.3 m between plants and rows, dig pits in a quincunx (checkerboard) pattern, 30-50 cm in length, width and depth, build a steamed-bun-shaped mound 10-15 cm high and 20 cm wide in the middle of the pit, dig holes on the mound, sow 20-30 seeds per hole, press down lightly, then cover with soil. 400 holes per mu.

5. Strip close sowing method: used when establishing protective belts at gully heads, field edges, and the lower slopes of terrace ridges. First, along the contour lines, dig a shallow furrow 30 cm long and 20 cm wide and deep every 3 m, loosen the soil, pick out stones and grass roots, then open a sowing furrow 3-4 cm deep and 20-25 cm long for strip sowing, press down lightly, then cover with soil. The distance between belts is 1 m. Use 1.5-2 kg of seeds per mu. After 3 years, a biological protective belt can be formed.