Detailed Explanation of New Cultivation Techniques for the Chinese Medicinal Herb Chinese Yam
I. Requirements for Environmental Conditions
Chinese yam is a perennial vine that prefers warmth and cannot tolerate frost. It begins to sprout above 10°C, with the optimum germination temperature being 25°C, the optimum temperature for stem and leaf growth being 25°C-28°C, and the suitable temperature for tuber enlargement and growth being 20°C-24°C; growth stops below 10°C. Chinese yam is shade-tolerant, but tuber formation and nutrient accumulation still require relatively strong sunlight. Chinese yam should not be grown in continuous cropping; it is drought-tolerant but not waterlogging-tolerant, and grows well in deep, neutral, loose, and fertile sandy loam soil.
II. Cultivated Varieties
Chinese yam tubers are long cylindrical, flattened, or cylindrical in shape. The Chinese yam cultivated in China includes two species, common Chinese yam and lesser yam, and the cultivated varieties are all local varieties from various regions. Famous varieties include Huai yam from Bo'ai, Henan and Hua County, Shaanxi; long-haired yam from Jinan, Shandong; flower-seed yam from Pei County, Jiangsu; Gaijiaoban yam from Shanggao, Jiangxi; Jiaoshu yam from Nancheng, Jiangxi; Daban yam from Guangfeng, Jiangxi; and Ruichang yam from Ruichang, Jiangxi.
III. Cultivation Techniques
1. Cultivation season Chinese yam is generally cultivated in open fields, planted in spring and harvested in autumn, with a growth period of more than 180 days. In the Yangtze River Basin, planting is usually carried out in early to mid-April.
2. Land selection and fertilizer application Chinese yam is drought-tolerant and afraid of waterlogging, so sandy loam soil with high, dry terrain, deep soil layers, convenient drainage and irrigation, and rich organic matter should be selected for planting. In winter, dig deep trenches with a spacing of 1 m, a width of 30 cm, and a depth of 1 m. After the Beginning of Spring, apply 5000 kg of decomposed farmyard manure, 100 kg of cake fertilizer, 50 kg of calcium magnesium phosphate fertilizer, and 150 kg of plant ash per mu as base fertilizer, mix thoroughly with the excavated soil, and backfill it into the trenches. Then form ridges with a width of 70 cm and a height of 25 cm, and cover with black plastic mulch while waiting for transplanting.
3. Propagation methods ① Bulbil propagation method. Also called yam bean, it is an aerial tuber formed in the leaf axils of Chinese yam. At harvest time, pick off the bulbils growing on the stems and vines, dry them in the sun, and store them in a low-temperature, dry place. Before sowing, bury the bulbils in moist sand and maintain a temperature of 20°C-30°C; they will sprout after 10-15 days. When 80% of the bulbils have sprouted, plant 2 rows per 1 m wide bed with a plant spacing of 10 cm. In the same year, they grow into small Chinese yam tubers 25-30 cm long, and in the second year the whole tubers are used for planting. ② Tuber cutting propagation method. At harvest time, select large tubers with strong resistance, high yield, pure variety characteristics, and regular shape as seed tubers, air-dry them, and store them in a dry, cool place. Any part of a long tuber tends to produce adventitious buds, so it can be cut into segments at will for propagation. Block-shaped seed tubers often sprout only from the top, so they should be cut vertically when cutting. The seed pieces should be 50-100 g, and the cut surfaces should be coated with plant ash, then kept indoors for 2-3 days before planting. ③ Yam seed piece propagation method. The upper end of the Chinese yam tuber is relatively thin, with latent buds and stem scar marks at the tip, 30-40 cm long and about 100 g in weight; this segment is often cut for use as seed and is called a yam seed piece. Coat the cut surface with plant ash, air-dry it, and store it in a cool, dry place until planting the following year.
Among the above three propagation methods, the yam seed piece propagation method sprouts quickly and produces robust seedlings, but it requires a large workload and is difficult to adopt in large-scale production. The advantage of the tuber cutting propagation method is that it is not prone to degeneration after many years of planting and is beneficial for variety improvement, but it consumes relatively many tubers and is labor- and time-consuming when cutting. The bulbil propagation method can save a large number of tubers and is also relatively labor-saving. In production, bulbil propagation is mainly used, but continuous use of bulbil propagation for many years will lead to germplasm degeneration, so tuber cutting propagation is generally used once every 3-5 years.
4. Planting Plant one row per ridge, dig planting holes at a spacing of 25 cm, and plant the propagation material in the holes, 1 plant per hole. After planting, cover with soil and press firmly, then water thoroughly to settle the roots.
5. Field management ① Trellising and pruning. After Chinese yam emerges, it extends vines, and the vines are slender, brittle, and tender, so supports should be set up in time. A-frame or tripod supports are commonly used, with a height of 1.5-1.8 m. The stems and vines of Chinese yam have strong branching ability, and the vines and leaves cluster together, consuming a lot of nutrients, so pruning should be done appropriately by removing basal side branches or leaving only one main stem to facilitate ventilation and light penetration and increase yield. When using tuber cutting propagation, one cut piece may sprout several buds at the same time; generally retain one robust bud and remove the excess buds. ② Fertilizer and water management. After Chinese yam emerges, apply 5-8 kg of urea per mu diluted in water to promote stem and leaf growth and plant development. When the tubers begin to enlarge, apply 10-15 kg per mu of nitrogen-phosphorus-potassium compound fertilizer as a top dressing. At the same time, starting from tuber enlargement, apply potassium dihydrogen phosphate solution every 10-15 days to prevent premature aging of the plants. In the early stage of Chinese yam growth, generally do not water; during the peak tuber growth period, the soil must be kept moist, and do not water unless there is drought. During the rainy season, be sure to open trenches for drainage to prevent waterlogging. In mid-to-late June, cover the rows with rice straw to lower the temperature. In August, if there is drought, water appropriately. ③ Pest and disease control. The main diseases of Chinese yam are anthracnose, brown spot disease, and nematode disease, and the pests are sawflies and underground pests such as mole crickets and white grubs. For anthracnose, spray 50% carbendazim wettable powder at 300 times dilution or 75% chlorothalonil wettable powder at 500 times dilution in the early stage of disease onset. For brown spot disease, spray 70% mancozeb in the early stage of disease onset, once every 3-7 days, for 2-3 consecutive sprays. For underground pests such as nematodes, mole crickets, and white grubs, use 50% phoxim emulsifiable concentrate at 1500 times dilution to drench the roots or use Miral for soil disinfection. For sawfly control, use 2.5% kung fu emulsifiable concentrate at 3000 times dilution during the peak adult occurrence period and the peak egg hatching period.
6. Harvesting When the leaves wither and the underground tubers stop growing, the Chinese yam can be dug up for market. The general yield per mu is 1200-2000 kg.
7. Introduction of seeds To begin developing Chinese yam production, it is necessary to introduce seeds from the production area and introduce suitable varieties according to consumption habits or uses. First introduce a small amount, observe their adaptability, economic trait performance, and cultivation benefits, and then develop them on a large scale.