Detailed Explanation of Key Points for Standardized Cultivation Techniques of Radish
Radish, a biennial or annual herbaceous plant of the Brassicaceae family, genus Raphanus, with a fleshy taproot that is oblong, spherical or conical, and an outer skin that is green, white or red; the stem is branched, hairless, and slightly covered with a powdery bloom. The root is eaten as a vegetable; the seeds, fresh roots, dried roots and leaves are all used medicinally: the seeds aid digestion and resolve phlegm; the fresh root quenches thirst and aids digestion, the dried root promotes urination and defecation; the leaves treat early-stage dysentery and prevent dysentery; the seeds are pressed for oil for industrial and edible use.
Morphological characteristics of radish
Radish is a biennial or annual herb, 20-100 cm tall; the taproot is fleshy, oblong, spherical or conical, with an outer skin that is green, white or red; the stem is branched, hairless, and slightly covered with a powdery bloom. The basal leaves and lower stem leaves are lyrate-pinnatifid, 8-30 cm long and 3-5 cm wide, with an ovate terminal lobe and 4-6 pairs of oblong lateral lobes with blunt teeth, sparsely covered with coarse hairs; the upper leaves are oblong, serrate or nearly entire. Racemes are terminal and axillary; the flowers are white or pink, 1.5-2 cm in diameter; the pedicels are 5-15 mm long; the sepals are oblong, 5-7 mm long; the petals are obovate, 1-1.5 cm long, with purple veins and a claw 5 mm long at the base. The silique is cylindrical, 3-6 cm long and 10-12 mm wide, constricted between the seeds and forming a spongy septum; the beak at the tip is 1-1.5 cm long; the pedicel is 1-1.5 cm long. There are 1-6 seeds, ovate, slightly flattened, about 3 mm long, reddish-brown, with fine reticulate markings. The flowering period is April-May, and the fruiting period is May-June.
The radish stem is erect, stout, cylindrical, hollow, and branches from the base. The basal leaves and lower stem leaves have long petioles, are usually lyrate-pinnatifid, covered with coarse hairs, with 1-3 pairs of lateral lobes, and the margins are serrate or incised; the middle and upper stem leaves are oblong to lanceolate, gradually becoming smaller upward, unlobed or slightly lobed, and not clasping the stem. The raceme is terminal and axillary. The flowers are pale pink or white. The silique does not dehisce, is nearly conical, straight or slightly curved, constricted between the seeds into a bead-like string, with a long beak at the tip, the beak 2.5-5 cm long, and the fruit wall is spongy. There are 1-6 seeds, reddish-brown or yellow, round, with fine reticulate markings.
Key points for standardized cultivation of radish
Site selection and sowing
When selecting a site for radish, the key points to note are that it must not be around heavily polluted industrial factory areas, and the source of irrigation water must also not be polluted. Apart from this, radish has a relatively wide adaptability to soil, with the overall requirements being deep soil, good water retention and drainage, and rich organic matter content. However, radish has high requirements for land preparation. For fields planted with radish, the field should be cleaned early after the previous crop is harvested, and the soil should be plowed and sunned, with plowing to a depth of 20-25 cm. After fertilizing and harrowing, make small high beds or small high ridges to prevent waterlogging and flooding. After applying fertilizer, remove large clods of bricks, tiles, glass, grass roots and waste plastic film and other debris from the field to prevent the radish from forking or splitting during growth.
Use 250-300 grams of radish seed per mu of field. First mix it with 10-15 kg of fine soil and then broadcast it evenly (for ridge cultivation, hole sowing or furrow drilling can be used). After sowing, cover with soil 1-1.5 cm thick. If conditions permit, cover with a shade net to lower the temperature and protect against heavy rain, avoiding the soil being compacted by heavy rain and affecting emergence. For Manshenhong radish, the row spacing is generally about 30 cm and the hole spacing 20-25 cm; for Chunbulao radish, the row spacing is 33 cm and the hole spacing 27 cm. If the weather is dry after sowing, water frequently in small amounts to keep the ground moist and lower the soil temperature, so as to favor emergence. If heavy rain occurs, drain in time to prevent waterlogging. If the beds or ridges are washed away, replant in time after the rain.
Fertilization techniques
Base fertilizer: radish is generally direct-sown, so base fertilizer is the main factor in achieving high radish yields. For base fertilizer, 2500-3000 kg of decomposed (pay special attention to this) barnyard manure, 10 kg of potassium sulfate, and 25-30 kg of superphosphate can be spread per mu and plowed into the soil. In some places, soil manure and a certain amount of cake fertilizer can be applied as base fertilizer, which can make the fleshy root very plump and not prone to becoming hollow during storage, and is beneficial for the production of pollution-free radish.
Topdressing: the first application is when the seedlings grow to the true-leaf stage, applying 1000 kg of decomposed dilute human and animal urine. After thinning to a stand, apply another round of decomposed dilute human and animal urine. When the fleshy root "breaks belly" (the beginning of the fleshy root expanding and accelerating in growth), apply a third topdressing of 800-1500 kg of decomposed human and animal urine at 50% concentration plus 5 kg of superphosphate and 5 kg of potassium sulfate. Manshenhong radish is generally given only these three applications, while Chunbulao radish can be topdressed 1-2 more times during the peak growth period of the fleshy root. If the aboveground leaves are especially dark green and large and the growth is excessive, then no more fertilizer should be applied, and 20 grams of 15% paclobutrazol should be diluted in 50 kg of water and sprayed to inhibit aboveground growth and promote the expansion of the underground fleshy root.
If too much nitrogen fertilizer is applied, and at the same time the air and soil are dry, and the root is damaged, then the plant's absorption of calcium is hindered, causing symptoms such as leaf margin rot and the formation of deep pores and many long lateral roots on the root surface. Therefore, in the later stage of radish growth, the amount of nitrogen fertilizer should be controlled, and attention should also be paid to the supply of soil boron to prevent hollow heart and black heart in radish.
Field management
Thinning and final thinning: thin the radish seedlings once each at full emergence and at the 2-3 true-leaf stage. When there are 4-5 true leaves, thin to a final stand, leaving one plant per hole.
Fertilizer and water management: radish fears both drought and waterlogging. When there is a lot of rain, drain and reduce waterlogging in time. Radish has a relatively large leaf area and strong transpiration, and its drought resistance is relatively poor, so sufficient water must be supplied in a timely and appropriate amount. Before sowing, water thoroughly to ensure rapid and uniform emergence; during the seedling stage and rosette stage, water less to promote deep penetration of the taproot into the soil and prevent excessive leaf growth, following the principle of "do not water unless the soil is dry; water only when the surface turns white"; during the peak root growth period, supply water fully and evenly to promote expansion of the fleshy root, prevent hollow heart, improve quality, and enhance storage tolerance. For autumn cultivation, watering in the evening is best, which helps lower soil temperature and promote the transport and storage of nutrients to the root.
The fertilization principle for radish is "base fertilizer as the mainstay, topdressing as a supplement." Varieties with sufficient base fertilizer and a short growth period can be topdressed less, while varieties with a long growth period should be topdressed in stages, with emphasis on topdressing fertilizer in the early growth stage of radish and the peak growth period of the fleshy root.
Pest and disease control: the main pests and diseases of radish include aphids, cabbage beetles, cabbage caterpillars, striped flea beetles, beet armyworm, as well as viral diseases and black rot. To achieve pollution-free radish, the following points should be carried out well. First, rational crop rotation, rational close planting, and cleaning the field to improve the field microclimate and reduce the occurrence and damage of diseases; second, using shade net and insect-proof net covering techniques can reduce the occurrence of pests such as cabbage caterpillars and beet armyworm; third, selecting biological pesticides and high-efficiency, low-toxicity pesticides, and adhering to timely and appropriate application. Fourth, strictly observe the pesticide interval, and stop applying pesticides two weeks before harvest.
Harvest at the right time: when the radish fleshy root is fully expanded and the leaf color fades and begins to turn yellow-green, harvest and bring to market in time. Harvest as early as is appropriate, which on the one hand can improve economic returns, and on the other hand can avoid hollow heart caused by factors such as overgrowth or drought.