When Is the Best Time to Plant Isatis Root? A Detailed Guide to Planting Season and Timing
I think everyone is very familiar with isatis root (Isatis indigotica, woad). It is one of the most commonly used Chinese herbal medicines in our daily lives, and it has very good effects in preventing and treating colds. That is why isatis root is kept in most households. It is used very widely, and market demand is also very large.
Planting Season and Timing of Isatis Root
Different sowing seasons for isatis root produce different harvests. According to the sowing time of isatis root, it can be divided into 4 stages: autumn sowing, early spring sowing, spring sowing, and summer sowing. Autumn sowing and early spring sowing are mostly aimed at harvesting seeds; the roots of isatis root planted in these two periods cannot be used as medicinal material. Summer sowing is suitable for areas in the south with a long plum rain season. This method can reduce pests and diseases, but the yield is lower. Spring-sown isatis root can produce both leaves and roots, and the yield is relatively high, making it the most commonly used method.
Cultivation Techniques for Isatis Root
1. Land preparation and fertilization: Isatis root is a deep-rooted plant. It is suitable for a warm and humid climate, is drought-tolerant and cold-resistant, and fears waterlogging; after soaking in water, its roots tend to rot. It can be planted in ordinary soil, but it is best to choose loose soil with good drainage. Fertilizer can be applied rationally in combination with deep plowing and land preparation. Per mu, 3000-4000 kg of farmyard manure, 15 kg of diammonium phosphate, and 4 kg of biological potassium fertilizer can be applied, evenly scattered into the field and deeply plowed more than 30 cm, then made into flat beds 1 m wide. This is beneficial to root growth, making the roots straight, smooth, and with few branches.
2. Sowing method: In the north, isatis root is suitable for spring sowing, and sowing should be appropriately delayed. The most suitable time is April 20-30. Before sowing, soak the seeds in warm water at 40-50°C for about 4 hours, then take them out and mix them evenly with plant ash. Open a shallow furrow on the bed surface with a row spacing of 20 cm and a depth of 1.5 cm, evenly scatter the seeds into the furrow, cover with about 1 cm of soil, press lightly, and water appropriately to keep moist. With suitable temperature, seedlings emerge in 7-10 days. The general seed rate is 2-2.5 kg per mu.
3. Thinning and final thinning: After isatis root emerges, when the seedlings are 7-8 cm tall, thin to a plant spacing of 6-10 cm, removing weak plants and keeping strong ones, and fill in gaps where seedlings are missing. When the seedlings are 10-12 cm tall, combine cultivation and weeding, and thin to a plant spacing of 6-9 cm and a row spacing of 10-15 cm.
4. Cultivation and weeding: After the isatis root seedlings emerge, cultivate shallowly; after final thinning, cultivate. When weeds have 3-5 leaves, chemical herbicides such as quizalofop-p-ethyl can be selected to spray and remove grass-family weeds, using 40 ml per mu, diluted with 50 kg of water for spraying.
5. Topdressing and watering: For those mainly harvesting Daqingye (isatis leaves), topdress 3 times each year. The first is after planting, opening shallow furrows between rows and applying 10-15 kg of urea per mu, watering promptly to keep moist. The 2nd-3rd times are topdressing after harvesting Daqingye. To make the plants grow robustly and vigorously, farmyard manure can be used with an appropriate application of phosphorus and potassium fertilizer. For those mainly harvesting isatis root, do not cut Daqingye during the vigorous growth period, and apply less nitrogen fertilizer, with appropriate phosphorus and potassium fertilizer and plant ash, to promote thick and large root growth and increase yield.
6. Harvesting and processing: Spring-sown isatis root can have its leaves harvested 2 times before root harvest. The first can be in mid-June, and the second in mid-to-late August. Leaves should not be harvested in high-temperature weather, to avoid causing death of whole patches. Isatis root should be dug before winter on a sunny day, and when digging it must be dug deeply to avoid breaking the roots. After lifting the soil, remove soil, stems, and leaves, spread out to dry until 70-80% dry, then tie into small bundles and dry until completely dry.
7. Seed-saving technique: Spring-sown isatis root should be dug before winter, and disease-free, robust root strips should be selected and transplanted at a plant-row spacing of 30×40 cm into the seed-saving field. The seed-saving field should choose a plot sheltered from wind, with good drainage and sufficient sunlight. In the following year when the plants grow, strengthen fertilizer and water management, and in June and July when the seeds turn from yellow to black, harvest the whole plant, dry, and thresh. The isatis root after seed harvest has already become lignified and can no longer be used medicinally.
Effects of Isatis Root
1. Anti-pathogenic microorganism effects: Isatis root has inhibitory effects on many kinds of bacteria. The water infusion has varying degrees of inhibitory effects on Bacillus subtilis, Staphylococcus aureus, Sarcina octamer, Escherichia coli, Salmonella typhi, Salmonella paratyphi, dysentery (Shigella and Flexner) bacilli, and enteritis bacilli; the acetone extract also has similar effects, and is effective against hemolytic streptococcus (all using the agar well plate method). Its antibacterial effect on meningococcus type A is similar to that of garlic and honeysuckle. It has a clear inhibitory effect on influenza virus strain PR8 and strain Jingke 68-1. In test tubes, isatis root has the effect of killing Leptospira.
2. Effects on the cardiovascular system: Experiments prove that this product can increase the perfusion flow of isolated rabbit ears and rat hind limbs, improve mesenteric microcirculation in rabbits, lower the blood pressure of anesthetized rabbits, reduce capillary permeability, and decrease myocardial oxygen consumption in mice.
3. Inhibitory effect on platelet aggregation: Isatis root has a significant inhibitory effect on ADP-induced rabbit platelet aggregation. Uridine, hypoxanthine, pyrimidine, salicylic acid, and others isolated from isatis root also show certain inhibitory activity on ATP-induced rabbit platelet aggregation; at a concentration of 0.21 mg/kg, their inhibition rates were 18.2%, 24.2%, 10.8%, and 20%, respectively.
4. Detoxifying effect: Some reports believe that when dogs are given isatis root, coptis powder, and veratrum together (each 2.0 g/kg), it can counteract veratrum poisoning and reduce mortality; if used after veratrum poisoning, it is ineffective; using isatis root powder or coptis powder alone also has poor effects.
Economic Benefits of Growing Isatis Root
Isatis root is a plant of the genus Isatis in the Brassicaceae family. Its root is used as medicine, and it is one of the commonly used bulk medicinal materials. In recent years, due to continuously increasing social demand, the commercial price of isatis root has risen steadily. At present, the medicinal material market has already seen a situation where supply falls short of demand, and it has been recommended by the National Administration of Traditional Chinese Medicine as one of the 63 scarce Chinese medicinal materials for key development. Therefore, the prospects for artificial cultivation of isatis root are very promising, and medicinal farmers can develop production on an appropriate scale according to local conditions. Isatis root is suitable for cultivation in all parts of China, and can be sown in spring, summer, and autumn. From planting to harvest takes only 6-7 months, and it can be continuously cropped 2 times a year. It belongs to a medicinal material variety with low cost and quick results. Taking the cultivation of 1 mu of isatis root as an example:
1. Input: seed use 2 kg, seed cost 200 yuan, fertilizer (50 kg phosphate fertilizer, 20 kg compound fertilizer, 10 kg urea) 100 yuan, pesticides, herbicides, etc. 30 yuan, totaling 330 yuan.
2. Income: Isatis root normally produces 250-350 kg of root tubers per year (high yield can reach more than 400 kg). The current market purchase price is 20-25 yuan/kg. Calculated at the lowest yield and price, the output value is 250 kg × 20 yuan/kg = 5000 yuan.
3. Net profit: 5000 yuan - 330 yuan = 4670 yuan.
From the above analysis, we can see that the cultivation of isatis root still has very good prospects, and its input is not very high, but its returns are still quite considerable. However, growers should not blindly follow the trend and should promptly understand the market conditions for isatis root.