Detailed Explanation of Key Techniques for High-Yield Platycodon grandiflorus Cultivation
Platycodon grandiflorus is suitable for growing on sunny slopes. Shangri-La County's mid-mountain areas have large expanses of sloped land where grain cultivation essentially depends on the weather. Planting Platycodon grandiflorus can reduce inputs and also increase economic income. The high-yield cultivation techniques for Platycodon grandiflorus are introduced as follows:
I. Uses and Value
Platycodon grandiflorus is both a valuable medicinal herb and a vegetable. Because it contains platycodin, polygalin, phytosterol, glucoside, amino acids, etc., it is neutral in nature and bitter in taste, and has effects such as opening the lungs and soothing the throat, eliminating phlegm and resolving phlegm, and reducing inflammation and discharging pus. Platycodon grandiflorus is exported to Japan, South Korea, Southeast Asia and other places, is very popular in the market, and commands a good price. Per mu, about 600kg of dried product of the fleshy root can be harvested; calculated at 60 yuan per kilogram, and with more than 5 kg of seed harvested per mu, calculated at 60 yuan per kilogram of Platycodon grandiflorus seed, an income of more than 4000 yuan can be obtained.
II. Growth Habits
Platycodon grandiflorus has the characteristics of liking light, liking moisture, and tolerating cold, with wide adaptability. Artificial cultivation is mostly carried out on sunny, wind-sheltered hilly slopes. It grows well in deep, loose and fertile sandy loam rich in humus. Excessive soil moisture or waterlogging can easily cause root rot. The suitable growth temperature range is 10°C—20°C, the optimum temperature is 20°C, and it can endure a low temperature of minus 20°C. Seeds begin to germinate above 10°C, and the optimum germination temperature is 20—25°C. The germination rate of one-year-old seeds is 50%—60%, while the germination rate of two-year-old seeds can reach about 85%, and they sprout quickly and evenly.
III. Cultivation Techniques
(1) Site selection, land preparation, and application of base fertilizer
After selecting a sandy loam plot with sufficient sunlight, deep soil layer, and good drainage, apply 3000 kg of farmyard manure per mu, plus 20 kg of superphosphate or 15 kg of diammonium phosphate, spread evenly in the field, plow deeply 25-30 cm, level and harrow fine, and make beds 1.2 m—1.5 m wide and 15 cm high, with length depending on the terrain.
(2) Selecting good seed and soaking seed for germination
1. Seed selection: Platycodon grandiflorus seeds should be selected from seeds more than 2 years old and not stale (if seeds are stale for one year, the germination rate will decrease by more than 70%). The seeding rate per mu is 1.5—2 kg.
2. Soaking seed for germination: Soak Platycodon grandiflorus seeds in warm water at about 40°C, stirring continuously so the seeds are evenly heated, and after the temperature drops to about 20°C, rinse with clean water to remove impurities. Then soak for another 12 hours, or soak the seeds in a 0.3% potassium permanganate solution for 12 hours, then mix evenly with an appropriate amount of wet sand, pile for a few days, and then sow, which can significantly increase the germination rate.
(3) Timely sowing
(1) Direct seeding in the field: Plants grown from direct seeding have fewer branches, straighter roots, and higher quality, and the method is simple, saving time and labor. It is widely adopted, and direct seeding is mostly carried out in spring. For direct seeding in the field, drilling is mostly used. Open horizontal furrows on the prepared bed surface, 2—3 cm deep, with row spacing of 20—25 cm. Mix the treated seeds with 10 times their volume of fine sandy soil, spread evenly into the furrows, cover with soil, press lightly, water after sowing, keep the soil moist before emergence, cover with rice straw or pine needles to increase humidity and preserve warmth, and seedlings emerge in May of the following year.
(2) Seedling raising and transplanting: The method of raising seedlings and transplanting can select good seed and strong seedlings, adjust planting width, and help increase yield per unit area. Select seeds that are large, plump, and free from pests and diseases for seedling raising. Seed treatment for seedlings is the same as that for direct seeding in the field. The seedling bed is 1.2-1.5 m wide and 25 cm high. Before making the bed, apply base fertilizer and mix it evenly with the bed soil, level and harrow fine, then open furrows on the prepared bed surface at row spacing of 10 cm, with furrow depth of 1.0—1.5 cm, sow the seeds, cover with soil 1 cm thick and press lightly, cover the top with grass or leaves, water to keep the soil moist. Generally, seedlings emerge in about 15 days; after the seedlings emerge, remove the covering. Transplant at the end of autumn after the aboveground part withers or before emergence in the following spring. Dig up the roots, open horizontal furrows on the transplanting bed at row spacing of 20-25 cm and furrow depth of 10—15 cm, place the plants obliquely in the furrows at plant spacing of 6 cm, cover with fine soil after planting, press lightly, and water.
(4) Field management
1. Thinning and final singling of seedlings: When seedlings are about 5-7 cm tall, thin and final-single them in time. Remove overly dense seedlings and weak seedlings, and final-single at spacing of 6-10 cm.
2. Topdressing combined with intertillage and weeding: Because Platycodon grandiflorus grows slowly in the early stage, weeds should be removed in time. Generally carry out 3 times: the first when seedlings are 7—10 cm tall, the second one month later, and the third one month after that, striving to remove weeds as soon as they appear. During the seedling stage, apply 1-2 topdressings of dilute human manure and urine to promote seedling growth. In the middle stage, increase fertilizer at the flowering stage, mainly phosphorus and potassium fertilizer, to prevent excessive nutrient consumption from flowering and fruiting from affecting growth. After entering winter, apply a heavy overwintering fertilizer, and cultivate soil in combination with fertilization.
3. Timely drainage: Platycodon grandiflorus is afraid of waterlogging, and soil waterlogging can easily cause root rot. In summer during high temperature and rainy periods, drainage ditches should be opened in time to prevent root rot from waterlogging and reduce yield.
4. Flower and fruit thinning: The flowering period of Platycodon grandiflorus is relatively long and consumes a large amount of nutrients, affecting root growth. Except for seed-production fields, flower and fruit thinning can improve root yield and quality. In production, flower buds can be removed manually, such as cutting off flower buds with a sickle, or spraying paclobutrazol at full bloom to prevent flowering. The plant hormone ethephon can also be used at a concentration of 1000 ppm and sprayed toward the flower buds at full bloom, until the flowers are covered with the liquid. Applying 1125-1500 kg of liquid per hectare can achieve the flower-removal effect. This method has high efficiency, low cost, and is safe to use.
5. Pest and disease control: Ring spot and sheath blight mainly damage leaves. In the early stage of disease, spray 1:1:100 Bordeaux mixture or 50% carbendazim 1000-fold solution for control. Bacterial canker is likely to occur under warm and humid conditions, long dew duration, and frequent rain. Leaves turn brown, and the interior of the stem turns brown from top to bottom. For control, use 72% agricultural streptomycin wettable powder 4000-fold solution, applying continuously 3-4 times. For underground pests such as mole crickets, cutworms, and white grubs, poison bait with trichlorfon can be used to trap and kill them.
(5) Harvesting and processing:
1. Seed harvesting: From August to October, when the outer shell of the capsule is light yellow and the top of the fruit begins to split, and after breaking it open the seeds are plump and black, they can be picked in batches. The harvested seeds should not be directly exposed to sunlight. They can be piled indoors in a ventilated place for 3 to 4 days so the seed embryos mature naturally, then dried in the sun. After removing the fruit shells, store them in cloth bags or paper bags in a dry, ventilated place. Seed life is one year, and low-temperature storage is suitable.
2. Root harvesting: Harvest in the same year after transplanting or in the second year after direct seeding. Harvest at the end of autumn from October to November. First cut off the stems and leaves, dig out the roots, wash off the soil with clean water, drain the water, and while fresh scrape off the cork layer with bamboo slices, glass pieces, porcelain pieces, etc., then wash clean, and dry in the sun or dry by heat to finish. It can also be scraped as soon as it is dug to prevent the outer skin from drying and shrinking, making peeling easier.