What are the advantages of raising Dancong tea seedlings by short-stem cuttings?
Dancong tea has stable quality and is easy to process into high-grade tea; the finished tea is clear, mellow and refreshing with a honey flavor, making it outstanding among oolong teas. This tea has wide adaptability and strong resistance to stress, sprouts early and grows fast, and generally can be harvested 6-7 rounds a year; it has high yield and good economic returns. Short-stem cutting propagation of Dancong tea can maintain the fine characters and characteristics of Dancong tea and helps create and cultivate new tea gardens with relatively pure characters. Moreover, because the material source is wide and the seedling-raising time is short, it can propagate seedlings in large quantities and rapidly, making it an effective "more, faster, better and more economical" way to solve the shortage of tea seedlings, and at the same time it is conducive to the rapid promotion of improved varieties.
1. Plot selection: choose slightly alkaline loam with flat terrain, shelter from the wind and facing the sun, sufficient water sources, loose and fertile soil, and good drainage and irrigation; avoid using vegetable garden land.
2. Land preparation and bed raising: deeply plow the whole field 15-18 cm, apply 1000-1500 kg of decomposed farmyard manure and 25-40 kg of superphosphate per mu as base fertilizer, mix the base fertilizer thoroughly with the soil, then raise beds 1 m wide and 15 cm high, with a ditch width of 36-45 cm, so that the ditch can serve both as a drainage ditch and as a working path.
3. Spreading yellow subsoil: after the bed surface is leveled, spread a layer of about 7 cm of fine, crushed yellow subsoil without grass roots, and press it slightly. For seedbeds that are not to be cut immediately, do not spread or press the yellow subsoil for the time being; spread, press and insert as you go.
4. Selection of cuttings and cutting of stems: select current-year branches sprouting from the base of the tea plant and free of pests and diseases as cuttings. Before cutting the stems, remove the terminal buds of the branches, and cut the stems when the branches turn yellow-green and hard, or when the surface color is brown-red with yellow, reaching semi-lignified or lignified, and the axillary buds begin to swell until the fish-leaf is about to unfold. When cutting stems, proceed from top to bottom, starting from the green, hardened node; each leaf is one node cutting, and each cutting should be about 3 cm long. If one node is not long enough, remove one leaf and cut two nodes into one cutting; the lower cut should be smooth and slightly slanted, not cracked, and the leaf should be complete and free of pests and diseases. Cuttings should be cut and inserted as you go; before insertion they may be quickly dipped in 500 ppm indoleacetic acid or 1000 ppm indolebutyric acid to promote rooting. Cuttings that need short-term storage should be placed in a cool, ventilated place and protected from sunlight. Cuttings must not be left overnight, and must not be soaked in water.
5. Cutting time and method: the suitable time for cutting is May-June, because tea seedlings cut during this period root quickly, have a high survival rate, and can also become seedlings and leave the nursery in the same year. Generally choose cloudy days for cutting; if it is sunny, it is better to do it before 11 a.m. or after 4 p.m. The cutting spacing should be such that the leaves do not overlap; Dancong tea is a medium-leaf variety, generally with a plant-row spacing of 6 cm x 9 cm, inserting 70,000-80,000 cuttings per mu. Before cutting, first press the yellow subsoil slightly and water it thoroughly; when the yellow mud is slightly dry and no longer sticks to the hand, it is ready for cutting. Before insertion, first draw lines on the bed surface according to the specified plant-row spacing, hold both sides of the axillary bud with the thumb and index finger, and insert slightly slantwise into the soil up to the petiole; after insertion, press the soil beside the cutting slightly with two fingers so that the lower end of the cutting adheres to the soil, then water and shade immediately. The leaf direction of the cuttings is best aligned with the prevailing wind direction of the season to facilitate stable growth. Be careful not to bury the axillary bud in the yellow mud.
6. Nursery management
In the early stage of the nursery, water frequently and shade to increase the survival rate; in the later stage, focus on topdressing, weeding, removing flower buds, and controlling pests and diseases.
1. Water: keep the water content of the seedbed at about 60% at all times; it should not be too dry or too wet, and especially must not accumulate water. After insertion, except on rainy days, water once each morning and evening before rooting; after rooting, water once a day or every other day, just enough to moisten the surface soil of the bed. It is best to use a sprinkling can or watering can to prevent washing away the tea seedlings.
2. Shading: shade from after insertion until September-October, then reduce the covering gradually in 2-3 stages until all covering is removed one month before leaving the nursery to harden the seedlings.
3. Topdressing: 1-3 months after cutting is the period of rooting and root growth. Because the roots are shallow and few, they cannot absorb the base fertilizer, so after the new shoots mature, topdressing should be applied in time. The principle is "apply frequently and lightly, in small amounts and many times, first dilute then concentrated, and alternate chemical fertilizer and organic fertilizer." The first application can be 5% human urine or 0.5% ammonium sulfate or 0.25% urea; later, as the root system develops and the tea seedlings grow, the fertilizer concentration can be gradually increased. When the seedlings are 15-18 cm tall, 2-2.5 kg of ammonium sulfate per mu can be applied with water; fertilizing should be done in the evening of a sunny day or on a cloudy day. Never apply ammonium bicarbonate or ammonium chloride; ammonium bicarbonate easily damages tea seedlings, and ammonium chloride contains chloride ions that are toxic to tea seedlings. In the later stage, 1000-1500 kg of decomposed farmyard manure and 100 kg of plant ash per mu can be thoroughly mixed and broadcast, and watering should be done after application.
4. Weeding and bud removal: when pulling weeds, be careful not to damage the tea seedlings, and water promptly after weeding; flower buds and young fruits appearing at the seedling stage should be removed in time to avoid consuming nutrients.
5. Pest and disease control:
① Main insect pest control: for inchworms in the young larval stage, spray with 1500-2000 times dilution of 50% phoxim emulsifiable concentrate; for mites, spray with 1200 times dilution of 50% bromopropylate emulsifiable concentrate; for leafhoppers and black citrus whiteflies, spray with 2500 times dilution of 10% imidacloprid; for leaf-rolling worms, spray with 600-800 times dilution of 80% dichlorvos.
② Main disease control: for tea southern blight, use 70% quintozene powder and broadcast it on the soil surface at 1-2.5 kg per mu; after application, loosen the soil so that the powder is evenly mixed into the soil, and preferably apply again after about 10-15 days; for stem blight, use 0.7% lime half-strength Bordeaux mixture; in addition, quintozene can be broadcast on the soil surface between tea seedling rows at 1-2.5 kg per mu, and after application loosen the soil, then apply again every 10-15 days; for damping-off, use 0.7% lime half-strength Bordeaux mixture or 600 times dilution of 80% zineb wettable powder; for bud blight, use 1000 times dilution of 70% thiophanate-methyl wettable powder or 600 times dilution of 80% zineb wettable powder.
6. Standard for tea seedlings leaving the nursery: when seedlings are 30 cm tall, about 0.4 cm in stem diameter, green in leaf color, free of pests and diseases, branched, and with a well-developed root system, they can leave the nursery. One day before leaving the nursery, water thoroughly; when lifting the seedlings, they must carry an appropriate amount of soil and be slurry-dipped before transport.