What are the key field planting management techniques for Angelica dahurica?

1. Thinning and final thinning

Angelica dahurica seedlings grow slowly, and are generally not thinned in the year of sowing. After they turn green in early spring of the second year, when the seedlings are about 5—7 cm tall, the first thinning is carried out, removing the overcrowded and weak seedlings. For drill sowing, leave one plant every about 5 cm; for hole sowing, leave 5—8 plants per hole; for the second thinning, leave one plant every about 10 cm or leave 3—5 plants per hole. Around Qingming, when the seedlings are about 15 cm tall, final thinning is carried out, with a plant spacing of 13—15 cm or leaving 3 plants per hole, staggered in a triangle to facilitate ventilation and light penetration. During final thinning, the large seedlings that are growing too vigorously and have blue-white leaf stalks should be pulled out to prevent early bolting and flowering.

2. Cultivation and weeding

This should be carried out together with thinning and final thinning. When the leaves gradually grow larger and the bed surface is closed by the canopy and shaded, there is no need to weed any more.

3. Topdressing

Angelica dahurica is tolerant of fertilizer, but generally little or no fertilizer is applied before spring to prevent excessive growth during the seedling stage and early bolting and flowering. After spring, vegetative growth begins to flourish, and topdressing can be applied 3—4 times. The 1st and 2nd times are both carried out after thinning and cultivation, and the 3rd and 4th times are carried out after final thinning and before the rows close. Fertilization should preferably be done on sunny days; it is not suitable to fertilize just after rain clears or on the same day after cultivation and weeding. Fertilizer types can include human feces and urine, decomposed cake fertilizer, barnyard manure, urea, and so on. For the first fertilization, the fertilizer should be thin and small in amount, such as applying 10 loads of dilute human and livestock manure per mu, and afterward it can gradually be made stronger and increased, such as 30—40 loads. The application before the rows close can be combined with phosphate and potassium fertilizers, such as 20—25 kg of superphosphate, to promote thick roots. It has been reported that in the topdressing before the rows close, applying 25 kg of calcium magnesium phosphate and 5 kg of potassium chloride, followed immediately by earthing up, can prevent lodging and promote growth. The number of topdressings and the amount applied each time can also be determined according to the growth of the plants. If, when the rows are about to close, the leaf color of the plants is light green and growth is not very vigorous, one more topdressing can be applied; or if at this time the leaf color is dark green and growth is vigorous, no more topdressing is needed.

4. Drainage and irrigation

Angelica dahurica likes water but fears waterlogging. After sowing, if the soil is dry, it should be watered immediately; afterward, if there is no rainy weather, it should be watered once every few days to keep the bed surface moist before the seedlings emerge, as this is beneficial for emergence; during the seedling stage, the soil should also be kept moist to prevent yellow leaves and the production of too many lateral roots; before the seedlings overwinter, they should be watered thoroughly once. Henan has the experience that “wet freezing is best, dry freezing does not easily survive,” and Hebei has the experience that “in winter, Angelica dahurica only dies from drying, not from freezing.” After spring of the following year, timely irrigation can be combined with topdressing, especially during the dog days when sufficient moisture should be maintained. If in the rainy season there is standing water in the field, ditches should be opened promptly for drainage to prevent root rot and disease occurrence from standing water.

5. Pulling out bolting seedlings

In May of the second year after sowing, some plants will bolt and flower. Their roots cannot be used as medicine, and the seeds they produce also cannot be used as seed, because their next generation will bolt early. Therefore, in order to reduce the consumption of nutrients in the field, bolting plants should be pulled out promptly when found.