Detailed Explanation of Key Cultivation Techniques for the Chinese Medicinal Herb Banxia (Pinellia ternata)
Site Selection and Land Preparation:
It is best to choose moist, fertile, sandy loam or loam soil with strong water and fertilizer retention, loose texture, and good drainage and irrigation for planting; a gently sloping hillside with partial shade is also acceptable. Heavy clay soil, saline-alkali land, and waterlogged low-lying land are not suitable for planting. The previous crop should preferably be a legume; intercropping or relay cropping with corn fields, rapeseed fields, wheat fields, or fruit tree orchards is possible.
After the site is selected, between October and November, plow the land deeply to about 20 cm, remove gravel and weeds, and let the soil mature. Banxia has a shallow root system, generally not exceeding 20 cm, and prefers fertile soil; its growing period is short, so base fertilizer plays an important role. In conjunction with land preparation, apply 5000 kg of farmyard manure, 100 kg of cake fertilizer, and 60 kg of superphosphate per mu, plowing them into the soil as base fertilizer. Before sowing, plow and turn the soil once more, then break up clods and rake it level. In southern areas with more rainfall, raised beds 1.2-1.5 m wide and 30 cm high should be made, with furrow ditches 40 cm wide, and the length should not exceed 20 m to facilitate irrigation and drainage. In the north, after shallow plowing, beds can be made at a width of 0.8-1.2 m, with bed ridges 30 cm wide and 15 cm high. The bed ridges should be tamped firm and leveled smooth to facilitate spring sowing, sprout forcing, and plastic film mulching cultivation during the seedling stage.
Propagation Methods:
In production, Banxia propagation mainly uses tuber and bulbil propagation; seed propagation is also possible, but because the seed production cycle is long, it is generally not used.
1. Tuber propagation: Take out the stored seed tubers in the current winter or the following spring and plant them; spring planting is preferable, as autumn and winter planting gives low yields. For spring planting, earlier is better than later; generally, when the 5 cm soil temperature stabilizes at 6-8 degrees C in early spring, seed tubers can be sprouted using a hotbed or heated kang. When the sprouting temperature is maintained at about 20 degrees C, buds can begin to move in about 15 d. From late February to early March, between Yushui and Jingzhe, when the 5 cm soil temperature reaches 8-10 degrees C and the bud sheaths of the sprouted seed tubers turn white, they can be planted (unsprouted ones should also be planted at this time). Timely early sowing allows Banxia petioles to grow horizontally in the soil and produce bulbils; bulbils formed in the soil are large, can quickly take root and sprout, form a new plant, and give high yields. On the finely raked and leveled bed surface, open horizontal furrows for drilling. The row spacing is 12-15 cm, plant spacing 5-10 cm, furrow width 10 cm, and depth about 5 cm. The furrow bottom should be flat, and two rows should be arranged alternately in each furrow, with buds placed upward in the furrow. After planting, apply a layer of mixed fertilizer soil on top (made by evenly mixing decomposed compost and barnyard manure with human and livestock manure, grass-soil ash, etc.). Use about 2000 kg of mixed fertilizer soil per mu. Then draw the furrow soil up to cover, 5-7 cm thick, level it, and press lightly. It can also be planted in autumn in conjunction with harvest, generally from late September to early October, using the same method as spring sowing.
Each mu requires 50-60 kg of seed tubers; appropriately dense planting gives uniform growth and high yields. If too dense, seedlings grow spindly and weeding is difficult; if too sparse, there are few seedlings and many weeds, and yields are low. The soil covering should also be moderate. If too thick, emergence is difficult, and although future bulbils may be large, they often form within the soil and are not easy to harvest; if too thin, seed tubers tend to shrink from drying and cannot sprout. After planting, if drought occurs, water promptly and always keep the soil moist. If using plastic film mulching cultivation, cover immediately with plastic film after planting. The plastic film used can be ordinary agricultural film (0.014 mm thick) or high-density film (0.008 mm). The width of the film depends on the width of the bed. When covering with film, work in groups of 3: first open a ditch about 8 cm deep on each outer side of the two bed ridges, with consistent depth; 1 person spreads the film while 2 people simultaneously pull the film tight on both sides; after leveling, press the film edges into the ditches with soil, applying even force so that the film lies flat and tightly against the bed ridges, then compact it with soil, achieving tightness, flatness, and strictness.
From early to late April, when the air temperature stabilizes at 15-18 degrees C and about 50% of seedlings have emerged, the plastic film should be removed to prevent high temperatures inside the film from scorching young seedlings. Before removing the film, hardening should be carried out first. The method is to uncover the film at both ends of the bed at noon to ventilate and dissipate heat, then seal it again in the evening; after several consecutive days, remove it entirely. Banxia using early spring sprout forcing and seedling-stage plastic film mulching not only emerges 20 d earlier than Banxia not using these cultivation measures, but also maintains the loose state of the soil from land preparation, promotes root growth, and can increase yield by about 83%.
2. Bulbil propagation: Each petiole of Banxia bears at least one bulbil; the quantity is sufficient, and upon contact with soil they can take root and sprout, with an early maturity period, making them the main propagation material. In summer and autumn, when old leaves are about to wither, the bulbils are already mature; then collect the mature bulbils from the petioles for drilling. Sow at row spacing 10 cm, plant spacing 3 cm, and furrow depth 3 cm. After sowing, cover with fine soil and plant ash 2-3 cm thick, and press lightly. They can also be dibbled in holes at row spacing 10 cm × plant spacing 8 cm, with 2-3 seeds per hole. They can also be propagated by covering with soil in place, that is, each time a batch of plants falls over, cover with soil once, to the extent that no bulbils are exposed. At the same time, apply an appropriate amount of mixed fertilizer, which can both promote bulbil sprouting and growth and add fertilizer for the mother tuber, achieving two benefits at once and helping increase yield.
3. Seed propagation: Banxia propagated by seed that is more than two years old can successively flower and bear fruit. When the spathe turns yellow and droops, collect the seeds. Seeds collected in summer can be sown immediately after collection, while seeds collected in late autumn can be stored in sand until sowing in March of the following year. This method has a relatively low emergence rate and is generally not used in production. Open shallow furrows 2 cm deep at row spacing 10 cm, scatter the seeds in, level, cover with about 1 cm of soil, water to moisten, and cover with grass to preserve warmth and moisture; seedlings can emerge in about half a month. When seedlings are 6-10 cm tall, they can be transplanted. In the first year, the first leaf is an ovate-cordate single leaf, and petioles generally have no bulbils; in the second year, there are 3-4 cordate leaves, occasionally compound leaves composed of 3 leaflets, and bulbils can be seen. Seedlings can form tubers 0.3-0.6 cm in diameter in the current year, which can be used as seed tubers for the second year.
Field Management:
1. Cultivation and weeding: After seedlings emerge completely, remove weeds promptly; use a specially made small hoe for shallow hoeing between rows, and the depth must not exceed 3 cm. Weeds between plants should be pulled out by hand.
2. Fertilization: In addition to applying sufficient base fertilizer, during the mid-growth period, especially around Xiaoman, heavy application of bulbil fertilizer should be made, such as decomposed cake fertilizer, human and livestock manure water, etc. If the base fertilizer is insufficient, topdress with ammonium sulfate at 10-15 kg per mu or urea, etc. in the early stage; before hilling at Xiaoshu, one more topdressing can be applied; no topdressing is needed in the late growth period.
3. Hilling: After June, the bulbils on the petioles gradually mature and fall to the ground, and the seeds also mature successively and fall to the ground as the spathes wither. Hill once each in early June and July: take fine soil from the furrow ditches, scatter it on the bed surface about 1.5-2 cm thick to cover the bulbils and seeds, then press lightly with an iron shovel.
4. Irrigation and drainage: Banxia prefers moisture and fears drought. If there is a long period of clear weather and drought, irrigate promptly. If there is excessive rain, pay attention to opening ditches for drainage.