Bupleurum Seed Treatment Methods and Key Cultivation Techniques

1 Seed Treatment Methods

1.1 Selecting Plants for Seed Production

During the growth stage of Bupleurum, differences in field microclimate and in the disease and pest resistance of individual plants lead to the appearance of some weak seedlings and diseased or pest-infested plants. When selecting plants to retain for seed, choose healthy 2-year-old Bupleurum plants free of pests and diseases. Do not remove the bolting stems or suckers from the selected seed plants, and remove all suckers and bolting stems from the plants not retained for seed. In field management, apply extra phosphorus and potassium fertilizer to the selected seed plants. At the flowering and bud stage, spray the leaves with potassium dihydrogen phosphate at a concentration of 0.2%-0.3%, once every 5d for 2 consecutive times. This promotes fruit development and plump seeds. From September to November, when the fruits turn from green to brown, harvest the upper seed-bearing portion together with the branches and stalks, dry them in a ventilated and shaded place, then thresh and sun-dry, and winnow out plump, mature seeds, which are stored sealed in jars or earthenware pots for later use.

1.2 Seed Treatment Methods

Bupleurum seeds have a relatively short lifespan, so new seeds should be used for sowing; seeds kept from the previous year have an extremely low germination rate. Seed treatments mainly include chemical treatment, hormone treatment, warm water and sand stratification treatment, and radiation treatment. Owing to rural conditions, the first three methods are mostly used, and they can increase the germination rate of Bupleurum seeds by 12.6%-15.4%.

Chemical treatment: Soak the seeds in a 0.8%-1.0% potassium permanganate solution for 10-15min, which can increase the emergence rate by 15.4%.

Hormone treatment: Soak the seeds in 0.5x10 (to the negative 6th power)-1.0x10 (to the negative 6th power) cytokinin (6-8A) for 1d, take out the seeds, rinse them clean with water, and then sow, which can increase the seed emergence rate by 12.6%. Warm water and sand stratification treatment: Soak the seeds in warm water at 35-40°C for 1d, remove the shriveled grains floating on the water surface, then mix 1 part seeds with 3 parts wet sand and place at 20-25°C to promote germination; after about 10-12d, when some seeds have cracked open, sow to ensure a sufficient number of seedlings.

2 High-Yield Field Cultivation Technical Measures

2.1 Site Selection and Land Preparation

For the planting site, it is advisable to choose loam and sandy loam or gently sloping land at an altitude of 1100-1500m with deep, loose and fertile soil and good drainage. Before planting, plow and harrow several times so that the soil particles are fine and the soil is soft and level, apply 30,000 kg/ha of decomposed barnyard manure, turn it into the soil and rake level, and make high beds with a surface width of 120-130cm, a ditch depth of 25cm, and a ditch width of 30cm, ready for sowing.

2.2 Ditching and Sowing

Before sowing, on the prepared bed surface, open furrows 10cm deep in rows at a row spacing of 20cm, then sow at a hill spacing of 15cm or sow in drills. There are two sowing methods: direct sowing and seedling raising (transplanting). Because the Qinba Mountain area is often droughty in spring and transplanted seedlings are not easy to survive, the direct sowing method is mostly preferred. Direct sowing of Bupleurum can be carried out in both spring and autumn. Spring sowing is from early April to early May, and autumn sowing starts after the seeds are harvested, ripened and sun-dried, and continues until early November before the soil freezes.

2.3 Thinning, Final Thinning and Weeding

In directly sown Bupleurum fields, seedlings emerge 12-15d after sowing. After emergence, when the seedlings reach 4-5cm, carry out the first thinning, cultivate and weed, thinning out the overly dense seedlings and the weak, small, diseased seedlings. When the seedlings reach a height of 8-10cm, carry out final thinning, and the number of plants retained should preferably be 675,000-825,000 plants/ha. This density range is the ideal density for obtaining high yields. For final thinning, ensure that in drill sowing 1-2 strong plants are left every 10cm; in hill sowing 2-3 strong seedlings are left per hill. Any missing plants in the field should also be replanted at this time, and the replanted seedlings should be watered promptly. After the plants close their rows, no more cultivation is carried out, and weeds are only pulled by hand so as to avoid damaging the roots and reducing yield. Generally, chemical herbicides are not used for weeding.

2.4 Fertilization

In addition to applying sufficient decomposed farmyard manure as base fertilizer at sowing, Bupleurum needs multiple topdressings during its 2-year growth period. The first seedling fertilizer is applied at the first thinning together with cultivation and weeding, applying 22,500 kg/ha of decomposed dilute human and livestock manure water; the second seedling fertilizer is applied at final thinning together with cultivation and weeding, applying 30,000 kg/ha of decomposed dilute human and livestock manure water; the third topdressing is applied when the seedlings are 30-40cm high, together with cultivation and weeding, applying 750-900 kg/ha of rapeseed cake (other cake fertilizers are also acceptable) and 22,500 kg/ha of dilute human and livestock manure water. In the second year, apply quick-acting fertilizer twice, each time applying 150-225 kg/ha of diammonium phosphate; or use superphosphate solution for foliar topdressing; a 0.2%-0.3% potassium dihydrogen phosphate solution can also be sprayed on the leaves 2-3 times. To supplement potassium fertilizer alone, an organic potassium fertilizer produced by Shaanxi Yangling Juchuan Fuwanjia Company can be sprayed on the leaves, applied at 3 kg/ha each time. The above fertilization schemes can be used alternately and can promote rapid swelling of the roots.

2.5 Drainage

Bupleurum likes to grow in a moist environment, but it is most afraid of waterlogging in the soil. Before the rainy season arrives, the bed ditches should be cleaned in time to ensure smooth drainage in the bed ditches and reduce the occurrence of field diseases.

2.6 Removing Suckers and Bolting Stems

After repeated careful management, the aboveground part of Bupleurum grows vigorously; half of the first-year plants can bolt and flower, and all second-year plants can bolt and flower. The flowering period lasts from early August to early October, as long as 40-50d. Flowering consumes a large amount of nutrients inside the plant, thereby affecting nutrient accumulation in the roots and being unfavorable for high yield. Removing the tillers and newly grown flower bolt buds in a timely manner in several rounds can promote the accumulation and swelling of nutrients in the plant roots.

2.7 Strengthening Pest and Disease Control

In the control of Bupleurum pests and diseases, it is necessary to follow the principle of not applying heavy-metal pesticides or highly toxic, highly residual pesticides, adhere to giving priority to prevention through agricultural measures, and adopt control methods using biological pesticide preparations or highly efficient, low-toxicity pesticides. Its pests and diseases and control methods are as follows: Root-knot nematode disease: a disease caused by root-knot nematodes parasitizing the roots of Bupleurum. Control method: 15d before land preparation and sowing, dilute 80% dichloropropane-dichloropropene emulsifiable concentrate with 100-150 times water for soil disinfection. Root rot: root rot mostly occurs in hot and rainy seasons. The main control methods are: strengthen drainage in the rainy season, reduce water accumulation in the field, reduce waterlogging damage, increase the application of phosphorus and potassium fertilizer to enhance disease resistance, and after pulling out diseased plants, soak the roots in a 1000-fold solution of 50% thiophanate-methyl for 5min, take them out and dry them, and spread quicklime in the diseased holes to prevent spread. Underground pests (cutworms, white grubs): for prevention, use fully decomposed farmyard manure and use light traps to kill adults; during occurrence, drench with a 1000-fold solution of 90% trichlorfon or use trichlorfon mixed with stir-fried fragrant wheat bran or rapeseed cake to trap and kill larvae. When occurrence is small, carry out manual catching.

Aphids, yellow swallowtail butterflies: The first method for controlling aphids is to increase the planting altitude of Bupleurum; generally, aphids occur in large numbers in areas at an altitude of 900-1000m, and aphids rarely occur in areas above 1200m. The second is to use biological pesticide preparations or low-residue pesticides for control in June-August each year when aphids occur in large numbers. To control yellow swallowtail butterflies, manually catch and kill the larvae. When occurrence is large, spraying with a 300-fold solution of the biological pesticide Bacillus thuringiensis can achieve good results.