Isatis Root Planting Methods and Technical Key Points

Isatis root, also known as woad and indigo, is a cruciferous herbaceous plant and a traditional precious Chinese medicinal material. Both the root and leaves are used medicinally; the root is called “isatis root” and the leaves are called “da qing ye” (woad leaves). Annual demand is very large; according to a national market survey, the annual demand for isatis root is about 4 million kg, with broad market prospects. Isatis root is cold-resistant, drought-tolerant, strongly resistant and widely adaptable, and is planted throughout both northern and southern parts of our country. Especially in recent years, its usage has increased, economic benefits have risen substantially, and the planting area has expanded rapidly. 1 Medicinal Value and Economic Benefits 1.1 Medicinal Value Isatis root has effects such as clearing heat, detoxifying and cooling the blood. It has efficacy in treating fever, wind-cold cold, sore swollen throat, mumps and so on. It has a special curative effect especially for preventing and treating “SARS”. 1.2 Economic Benefits Planting isatis root has high economic benefits. Generally, each hectare yields 3750-5200 kg of dried isatis root and 2250-3000 kg of dried da qing ye; the average price of dried isatis root and da qing ye is 4.00 yuan per kg, and the output value per hectare can reach 24,000-33,000 yuan. 2 Key Points of Planting Technology    2.1 Site Selection and Fertilization    2.1.1 Soil Selection Isatis root is a biennial herbaceous plant; in the first year it grows in a clump on the ground, and in the second year it bolts, with a plant height of about 1.2 m; the fruit is purple and flat; the root is slender, cylindrical, 20-50 cm long; it prefers warmth, is cold-tolerant, and avoids waterlogging. When planted in loose soil, the root is long, smooth and has few forks. Plots with deep soil layers and well-drained sandy loam and humus loam should be selected for planting.    2.1.2 Rational Fertilization In combination with deep plowing, apply 3000 kg of farmyard manure per mu. After deep plowing, level the soil, make beds or form ridges, and achieve a deep plow layer. Apply 200 kg of compound fertilizer per mu, broadcast as starter fertilizer at sowing.    2.2 Seed Treatment and Sowing Methods    2.2.1 Seed Collection and Treatment Isatis root does not bloom or bear fruit in the first year. When harvesting the roots that year, select pest-free, thick, robust, non-forked root strips for storage, and in the spring of the second year plant them at a row spacing of 50 cm and plant spacing of 20 cm, watering promptly; the seeds mature in May, are collected and dried in the shade, and kept as seed for the second year.    2.2.2 Sowing Time and Method Before sowing, soak the seeds in 40°C warm water for 4 hours, then remove them and mix evenly with plant ash. In the north, spring sowing is preferable, from April 20-30. For ridge sowing, wide seedling-band sowing is required, with a ridge width of 60 cm and plant spacing of 3-4 cm, leaving double-row staggered seedlings; for bed sowing, the row spacing is 20 cm, the plant spacing is 7-10 cm [Jilin Province Shuangliao City Agricultural Technology Extension Center], and 400,000-500,000 seedlings are kept per mu. When sowing, open a 2 cm deep furrow, scatter the seeds evenly in the furrow, cover with soil, tread once with the foot, or lightly press once with a roller; the soil moisture must reach 65%-70% of the field maximum water-holding capacity, and seedlings emerge 7-10 days after sowing.    2.3 Field Management    2.3.1 Thinning and Final Singling When the seedlings are 4-7 cm tall, in combination with loosening the soil and weeding, thin to a plant spacing of 3-4 cm. After final singling, the early growth stage should be dry rather than wet, to promote downward rooting of the roots; in the late growth stage, keep the soil appropriately moist to promote nutrient absorption. In hot and rainy seasons, pay attention to drainage.    2.3.2 Hoeing, Ridging and Weeding Only when the soil is loose can the roots be deep, with few forks and lush leaves. During the whole growth period, hoeing and ridging should be done 3 times: when the seedlings have 3-4 leaves (late May), carry out the first hoeing and ridging to loosen the soil, to a depth of 15-20 cm; 1 month later (late June), carry out the second hoeing and ridging, to a depth of 20-25 cm; before harvest (late September), carry out the third ridging. If herbicides are used for weeding, “Jing Ke Cao Neng” can be chosen, sprayed when weeds have 3-5 leaves, at 40 mL per mu mixed with 50 kg of water for spraying.    2.3.3 Topdressing and Leaf Cutting Topdress in early June, applying 40-50 kg of ammonium sulfate per mu, plus 7-15 kg of compound fertilizer containing calcium and magnesium, mixed and applied. Under the condition of ensuring sufficient water and fertilizer and good growth, the leaves can be harvested twice in late June and late August, leaving a stubble height of 3-5 cm when cutting. After each leaf cutting, topdressing and irrigation should be carried out promptly; never apply ammonium bicarbonate, to avoid burning the leaves.   2.4 Pest and Disease Control The main diseases of isatis root are downy mildew and powdery mildew; the main pests are cabbage caterpillars and peach aphids, etc., damaging the seedlings.   2.4.1 Downy Mildew Main symptoms: the leaves and petioles are damaged. In the early stage there are yellow-white diseased spots on the leaf surface, and in the middle and late stages there is a gray-white mold-like substance on the leaf back. As the disease develops, the leaf color turns yellow, and finally the plant dries up and dies brown. Control method: pay attention to drainage and ventilation and light transmission, avoid continuous cropping or rotation with cruciferous and other crops susceptible to downy mildew; during the disease period, use 70% mancozeb at 100-150 g per mu mixed with 50-60 kg of water for spray control, spraying once every 7 days, 2 times in succession.    2.4.2 Powdery Mildew Main symptoms: damages the leaves. The disease occurs in June-July; under conditions such as low temperature and high humidity, excessive nitrogen fertilizer, overly dense plants and poor ventilation and light transmission, it is prone to occur. When hot and dry, the disease stops spreading. Control method: the field should not accumulate water, to inhibit the occurrence of the disease; rational close planting, with combined application of nitrogen, phosphorus and potassium fertilizers. In the early stage of the disease, spray with 65% zineb wettable powder at 300-500 times dilution.    2.4.3 Cabbage Caterpillar Damage symptoms: bites and eats the leaves; lightly damaged leaves become holed and notched, and severely damaged ones have all the leaf mesophyll eaten away, leaving only the veins. Control method: before the larvae reach the 3rd instar, spray with 90% trichlorfon at 800-1000 times dilution for control.    2.4.4 Peach Aphid Damage symptoms: adults and nymphs suck the sap of stems and leaves, causing diseased leaves to yellow and wilt. Control method: during the occurrence period, spray with 40% dimethoate at 1000-1500 times dilution or 50% dichlorvos emulsion at 1000 times dilution for control.    3 Harvest, Processing and Storage After the aboveground parts wither in October, dig up the roots; when harvesting, first dig a 60 cm deep furrow beside the bed, then dig forward in sequence, remove all soil, sun-dry until 70%-80% dry, tie into small bundles and sun-dry until completely dry; this is the medicinal “isatis root”, and the best is long, straight, thick, firm roots with sufficient powdery content. In the north, when the seedlings are 18-20 cm tall in June or August, the leaves can be harvested twice, and sun-dried to make the medicinal “da qing ye”.    Isatis root and da qing ye are generally stored in a dry and ventilated place; the suitable temperature is below 28°C, the relative humidity is 65%-75%, and the safe moisture content of the commodity is 11%-13%. Sell promptly to realize economic benefits.