How to Grow Isatis Root from Seed? A Detailed Guide to the Latest Planting Method
Isatis root, also known as Isatis indigotica and woad, is a plant of the genus Isatis in the Brassicaceae family. It is cultivated throughout the country. Isatis root prefers a warm, sunny environment and is not demanding about soil. It is drought-tolerant, cold-tolerant, and intolerant of waterlogging. Isatis root is propagated by seed and can be sown directly. Let us take a look below at how to grow Isatis root from seed!
Planting Season
Different sowing seasons for Isatis root yield different products. 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 relatively 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.
Preparation Before Sowing
Isatis root is a deep-rooted plant that likes a cool, temperate environment, is relatively cold-tolerant, and fears waterlogged, low-lying land. It is suitable for cultivation in North China and Northwest China. Before sowing Isatis root, some preparatory work must be done, mainly including site selection, land preparation, and fertilization.
1. Site selection: Isatis root is suitable for planting in sandy loam or river alluvial loam with a low groundwater table, good drainage, and loose fertility. Isatis root planted in such land has high yield, good quality, saves labor, requires little investment, and has relatively high economic benefits. What we must pay special attention to here is that when selecting a site, clay soil and low-lying, easily waterlogged plots must not be chosen, as such plots easily cause root rot in Isatis root. In addition, the plot is best chosen in a place sheltered from the wind, facing the sun, and close to a water source, which facilitates light exposure and irrigation during the growth of Isatis root. The previous crop of the selected plot is preferably soybean stubble or corn stubble. If the selected plot is sloped land, the slope generally should not exceed 15°; drainage facilities should be well built on sloped land to prevent the loss of water, soil, and manure, which would affect the growth vigor and yield of Isatis root.
2. Fertilization: Base fertilizer should be applied before land preparation. The best base fertilizer is decomposed pig manure, horse manure, or sheep manure. Never apply raw manure, otherwise the heat generated by fermentation after application will burn the root system of Isatis root. To prevent insect pests, it is best to spray 90% trichlorfon 800-fold solution and mix it evenly during the piling of the manure, so as to kill insect eggs, pupae, and larvae. These fertilizers have a high organic matter content and contain complete nitrogen, phosphorus, potassium, and trace elements. They can not only meet the growth needs of Isatis root, but also loosen the soil and improve soil structure and physical and chemical properties, clearly promoting the growth, development, and yield increase of Isatis root. Apply 2000-3000 kg of base fertilizer per mu; if manure is sufficient, it can be increased to 4000 kg per mu. When manure is insufficient, an additional 50 kg per mu of diammonium phosphate or superphosphate and 15 kg of potassium fertilizer such as potassium chloride or potassium sulfate can be applied.
3. Land preparation: Because Isatis root is a deep-rooted medicinal crop, the root layer of the soil must be loose. Therefore, after fertilization, deep plowing is also needed. To ensure the growth conditions of the Isatis root root system, the plowing depth should be more than 30 cm, which helps the roots extend downward, stay straight and smooth, and remain unbranched. During land preparation, sandy land can be plowed slightly shallower, and heavier clay land can be plowed slightly deeper. Finally, break up the clods and level the plot.?
After the plot is prepared, beds should be made. In the north, in areas with little rainfall, flat beds can be made, with a bed width of 1.5-1.8 m. In the south, high beds should be made to facilitate drainage. The bed height is 20-30 cm; generally, in places with higher terrain, make the beds lower, and in places with lower terrain, make the beds higher. The bed length can be determined according to the terrain: flat plots can have long beds, and undulating plots can have short beds. Leave a 30 cm wide working path between two beds. While making the beds, further break up the clods so that the soil is fine and crumbly, preventing clods and debris from mixing into the beds, which would affect the germination of Isatis root and root growth, and ensuring the quality of land preparation. The standard for a well-prepared planting bed is a level bed surface and fine, crumbly soil. After land preparation is completed, it is time to sow and plant.
Sowing Isatis Root
1. Seed selection: The seeds of Isatis root should be new seeds harvested the previous year with black on the seed coat. Such seeds have good maturity, and the germination rate can be guaranteed to be above 95%. Moreover, such seeds will not bloom in the same year after sowing; if seeds stored for many years are chosen, not only is the germination rate low, but they also easily bloom in the same year, affecting the yield and quality of Isatis root.
2. Seed treatment: After the seeds are selected, in order to improve the germination rate of Isatis root seeds, the seeds should also be treated before sowing. First soak the seeds in clean water for 12-24 hours. This can, first, remove grass debris and blighted seeds mixed in with the Isatis root seeds, and second, soften the seed coat of the Isatis root seeds, which is good for sprouting. After soaking, take them out and dry them, and then they are ready for sowing.
3. Sowing time: In the process of growing Isatis root, there are strict requirements for sowing time and sowing methods. First let us understand the sowing time. For spring-sown Isatis root, northern regions generally sow in early April, while southern regions can sow appropriately earlier, but sowing is only allowed when the local temperature is stable above 12°C, which helps the roots penetrate deeply and extends the growth period.
4. Sowing: One week before sowing, water thoroughly once to ensure the water needed for the Isatis root seeds to germinate and take root. There are many sowing methods for Isatis root, but the commonly used methods are drilling and hole sowing.?Drilling uses a row spacing of 30 cm, with a sowing rate of about 3 kg per mu; hole sowing uses a row and plant spacing of 30×20 cm or 30×30 cm, with a relatively small seed amount, between 1.5-2 kg per mu. The sowing depth is 3 cm. After sowing, cover with a layer of fine soil, with a covering thickness of about 1 cm, and finally cover the bed surface with plastic film to retain moisture. Because spring winds are strong, in order to prevent the wind from lifting the film, after the film is laid over the bed surface, in addition to pressing the edges firmly with soil, soil should also be pressed in the middle of the film. What should be noted here is that because Isatis root seeds have weak seedling emergence and soil-piercing ability, soil should be pressed between the two sowing furrows to avoid affecting seed germination.
Seedling Stage Management
After sowing, Isatis root seeds generally emerge in 7 to 10 days, and all seedlings can emerge in 15 days.
1. Poking holes for ventilation: Once Isatis root seedlings are found to have emerged, the film above the seedlings should be promptly pierced open. This, first, helps the seedlings continue to grow upward, and second, avoids the high temperature under the film burning the seedlings to death. Because the nighttime temperature is still relatively low at this time, the ventilation holes should not be made too large, otherwise the seedlings will stop growing. The best ventilation hole size is slightly larger than the seedling. The work of piercing the film for ventilation must be carried out every day and continued until all seedlings on the bed surface have emerged.
2. Weeding: During this period, because the temperature and humidity under the film are high, some weeds will grow rapidly and pierce through the film. When weeds are found breaking through the film, they should be pulled out promptly. To prevent weeds from continuing to grow from this spot, after pulling out the weeds, a hard clod of soil should also be pressed onto this position.
3. Thinning: As the Isatis root seedlings grow, in order to improve ventilation and light conditions for the seedlings and ensure the normal supply of nutrients, thinning should be carried out once when the seedlings grow to 5 to 6 true leaves. This thinning should follow the principle of removing the small and keeping the large, and removing the weak and keeping the strong, with a seedling spacing maintained at 5 to 8 cm. As the outside temperature rises, the ground temperature also keeps rising. Some people think that the plastic film can be removed at this time, but this is actually a wrong approach, because although the Isatis root seedlings can grow quickly when the ground temperature is high, weeds grow even faster. If the film is removed at this time, weeds will soon cover the entire bed surface, affecting the continued growth of the seedlings. The purpose of not removing the film during this period is to use the high temperature under the film to kill weeds, and it also helps retain soil moisture. When the Isatis root seedlings grow to 10 cm tall, the second thinning should be carried out. This thinning is also the final thinning of the Isatis root seedlings. Before final thinning, first remove the covering film from the bed surface, then carry out one intertillage of the bed surface.
4. Intertillage: Intertillage can, first, change the permeability of the bed surface soil and help retain soil moisture, and second, this intertillage helps the seedling roots penetrate downward. Because the roots of Isatis root seedlings at this time have not yet penetrated deeply, the intertillage depth should be shallow rather than deep, preferably 2 to 3 cm. After intertillage is completed, final thinning should be carried out.
5. Final thinning: The spacing for this final thinning is 20 to 25 cm. While final thinning, weeds among them should also be removed. In addition, if broken rows or missing plants are found during final thinning, seedlings should be replanted promptly. The method of replanting is to dig out overly dense Isatis root seedlings together with their roots, preferably with a soil ball, dig a small hole 5 cm deep where seedlings are missing, and replant the seedlings in the hole. To help the seedlings survive, water promptly after replanting to ease transplant shock. After final thinning is completed, spray once with 50% carbendazim wettable powder 1000-fold solution to prevent the occurrence of sclerotinia disease.
6. Topdressing: 3 days after removing the film, after the seedlings have adapted to the environment, apply one topdressing of organic fertilizer. Isatis root seedlings need nitrogen fertilizer at the seedling stage, so this fertilization should use urea at 3 to 5 kg per mu. Because the Isatis root seedlings are still relatively small at this time and the leaves are tender, chemical fertilizer falling on the leaves can easily burn the leaves to death and affect yield. This requires that after fertilization, gently move the Isatis root seedlings with fine twigs so that the urea falling on the seedlings drops to the ground. After fertilization, water once. Considering that the seedlings are still small at this time, the amount of water for this irrigation should be smaller, preferably just wetting the surface. ?