Stevia, alias stevia, sugar grass, sweet grass. The whole plant of stevia has a sweet taste and the leaves are the sweetest.
First, the morphological characteristics
Herbs perennial, plant height 1-1.3m. Root tip hypertrophy, 50-60, up to 25cm long. The stem is erect, the base is lignified, the upper part is tender, and the short part is short, and the leaves are similar to moldy white hair. It is the normal secretion of juice, which is more common in rainy days. Leaves opposite or upper part of stems alternate, draped in shape, with shallow serrations on the edges, short hairs on both sides, and veins three. Flower heads small, total saclike, 5--5-loculed, sessately sately sately long; Achenes linear, slightly flat, brown, with crown hair. Flowering period from July to September, fruiting period from September to November.
Second, growth habits
Stevia is grown in a warm and humid environment, can withstand low temperatures of -5 ° C, and is most suitable for stem and leaf growth at temperatures of 20-30 ° C. Stevia is a short-day plant that is sensitive to light and has a critical day length of 12 hours, so it is cultivated earlier in low latitudes. Flowering fertilized ovules take 25-30 days to develop into mature seeds. When the seeds mature, the crown hairs spread around the wind.
Stevia has poor soil requirements, but it is better to use loose and fertile soil with more humus. Stevia is not suitable for continuous cropping, and soils with a soil pH of less than 5.5 or greater than 7.9 are not suitable for planting.
Third, breeding methods
(1) The seed breeding production adopts the method of sowing seedlings and then transplanting and planting. The southern provinces of China usually use flat seeding to raise seedlings, while in the north, they use hotbed seedlings. The sowing period on the south bank of the Yangtze River is suitable from October to November. The seedlings are wintered in the nursery, and can be transplanted to the field for cultivation in the middle and late March of the next year. In the north, the seedlings are usually planted in greenhouses or hot beds in April. In order to spread the seeds evenly, the seeds can be mixed with fine sand before planting to be rubbed, then immersed in warm water for 10-12 hours, and then mixed with a small amount of grass. After the sowing, gently press the seeds with the wooden board to make contact with the soil, and then spray the water to the bed surface with a sprayer once to keep the bed moist and increase the emergence rate. The temperature and humidity are suitable, and it can be germinated and unearthed 7-10 days after sowing.
Seeding rate: 500 grams per 100m2 seedbed, the actual number of seedlings is 20-25 million, enough to plant 12-15 acres of land. Generally, 8,000-9000 plants are planted per acre, and dense planting can reach 10,000-12,000 plants.
(2) Cutting propagation can be cut from late March to late August, and the survival rate of cutting cuttings before cutting is higher. When cutting, select the strong branches and side stems that meet the requirements, cut a small section of 15-20 cm long, and insert 1/3-1/2 of the cuttings into the bed soil. The row spacing is 2 cm × 5 cm. Watering in time, watering the top with straw curtain or plastic film, keeping warm at night, avoiding direct sunlight at noon, properly ventilating and transmitting when growing sprouts, gradually adapting the adaptability of seedlings to the outside world, forming roots developed, stems and leaves Strong, healthy color and strong seedlings.
In addition, although the bead can also be propagated, it is limited to the application in the selection work to preserve the good individual plants, and is not suitable for large-area cultivation.
Fourth, cultivation techniques
Seedbed seedling: The germination potential and germination rate of stevia seeds at 20 °C were the highest. The sowing period is generally carried out at a temperature of 15 ° C in the spring. Seeds should be removed before sowing, and selected by air or water, dried for 1 day. The seedling bed of the nursery should be smashed and shredded. When the soil is prepared, some decomposed manure is applied. When planting, every 5-7 cm, use a stick to gently draw a groove of 2 to 3 mm deep on the seedbed surface, and sow the seeds into the ditch (also directly Spread on the surface of the clams, gently pat the skin to make it tightly bound to the soil, and then use a watering can to cover it with a plastic film. 15 kg per hectare, seedlings can be planted in 20 hectares of field. After sowing, the bed soil was kept moist, and the seedlings were emerged after 4-5 days. After 30 days, the seedlings with 10 true leaves were selected for transplanting.
Sand seedlings: The selected seeds are soaked in hot water at 50 °C for 4 hours, taken out in a dish containing coarse sand, germinated under normal conditions at a temperature of 25 ° C and a humidity of 75%, until 1-2 pieces are grown. True leaves, colonized when the rhizome is 1 cm.
Cutting seedlings: use the roots of stems that have not been lignified before the buds to make cuttings. The seedbed should be sand, and some pond mud can be mixed. The cuttings are cut into 2-3 knots, inserted into small holes made of wooden sticks, and compacted to leave the buds. The density is about 3 x 5 cm. The seedbed should be shaded and rooted in about 7 days.
V. Planting management
1. Preparation before planting: In the first half of the field before the planting of Daejeon, apply some soil fertilizer to the base fertilizer; use 50% phoxim 1000 times solution or 20% speed to kill the butyl oil 40ml to 50kg for ground spray to prevent the ground. The tiger is harmed.
2. Pay attention to when transplanting:
(1) The seedlings will not damage the roots, and the depth of planting is 1/2 of the height of the seedlings.
(2) Do not press the heart, do not hurt the bottom leaves, do not root
(3) Planting should be carried out in the morning and evening, or you can choose to transplant in a light rainy day.
(4) Reasonable close planting, the row spacing of planting plants is 50×15 cm, and about 8000-10000 grasses per acre.
(5) Root water is poured in time after planting, and the field is kept wet for 7 days after planting.
(6) Check the seedlings to fill the gap, and check the seedlings in time within 10 days after transplanting to ensure the whole seedling
(7) Topping and topping, after the seedling height is 10 cm, the topping can be continuously topped to promote multi-branch.
(8) Weeding: After transplanting, the top of the chrysanthemum is not closed, and when the weeds are more, the weeds in the noodles are manually removed; the weeds in the ditch can be manually removed, and the directional spray can be used without traces or paraquat. 2-3 times (sprinkler plus funnel-shaped directional spray cover)
3. Fertilizer management:
(1) Water management: Stevia is resistant to drought and drought. If it is hot and rainy in summer, it should be drought-resistant in time to prevent the leaves from falling off and reduce production. In sunny and hot weather, when the soil surface is slightly white, it should be timely flooded, and take care The method of late irrigation and early discharge keeps the soil moist. During the rainy season, the drainage work should be done properly to reduce the humidity in the field.
(2) Fertilization management:
Stevia has high requirements for fertilizer and water, so it is necessary to provide sufficient nitrogen, phosphorus and potassium fertilizers for cultivation.
Base fertilizer recommendation: Wolff 15-15-15/17-17-17 balanced fertilizer 1-2 bags + 1 bag of bacterial fertilizer;
Top dressing: Wolft nitric oxide + liquid fertilizer (promoting root type) + water soluble fertilizer + foliar fertilizer.
In order to promote the increase of yield of stems and leaves, when the seedling height is 20-25 cm, topping can be carried out. After the topping, each new branch can reach 12-17. This time, fertilizer is needed, and the root should be fertilized (liquid Fertilizer), or spray 0.2% potassium dihydrogen phosphate solution (foliar fertilizer) to the foliage to achieve high quality and high yield. Stevia is a potassium-producing crop, applying potassium fertilizer (water-soluble fertilizer) half a month before cutting leaves to increase leaf sweetness.
Water management should be paid attention to throughout the growing season, especially during the seedling period. During the prosperous period, it can be applied 2-3 times in a timely manner (every week), and combined with cultivating and weeding.
Sixth, harvesting and ringing
The harvest period of the gerbera leaves should be determined according to the climatic conditions and cultivation techniques of the cultivated land. When the plant buds 5%-10%, it is the time when the leaves contain the highest amount of inulin, and it is also the best period for stevia harvest.
When harvesting, cut from the ground 20 cm away, pay attention to the tool must be sharp, so as not to pull the root system during harvesting, naturally winter can leave some leaves to protect the winter.
Plants that need to be planted can be treated with short-light treatment, that is, in the period of fertility of stevia (90 days after emergence), the shading is started, that is, it is covered at 6 pm, and it is uncovered at 8:00 the next morning, and the shading is continued for 20-25 days. Can bloom results. The seeds are very light and can be harvested after being covered with plastic bags.
Seven, harvesting and processing
Usually, the amount of sputum in the bud period is the highest. It can be harvested three times in the south of the Yangtze River, harvested twice in the Yellow River, and harvested once a year in the north. Cut the stems at harvest, pick the leaves, dry or dry. Large-area planting should be done with a dryer. It can produce 150-200kg dry leaves per acre, up to 500kg.
Eight, pest control
(1) Seedling blight is a disease at the seedling stage. Control methods: 1 Optional well-drained, loose soil plots; 2 Before the sowing, use 50% carbendazim 2 kg/mu for soil treatment; 3 Initially use 1000-1500 borrowed carbendazim spray or 500 Double liquid irrigation; 4 timely removal of the diseased plant, and treatment of the diseased hole with 3:1 grass ash and quicklime mixed powder.
(2) Leaf spot disease is prone to this disease from July to October, causing damage to stems and leaves. Control methods: 1 pay attention to drainage to reduce the humidity of the soil from May to June, and apply potassium fertilizer to improve the disease resistance of the plant; 2 spray 50% carbendazim 1000 times liquid spray control at the beginning of the disease; 3 clearing the garden after harvest, dispose of the residue Strain, burned intensively.
(3) White mites have more rainfall in April-May, and the soil moisture is too large, which is prone to occur and damage the roots. Control methods: 1 reasonable close planting, pay attention to ventilation and light in the field; 2 increase phosphorus and potassium fertilizer to avoid seedlings; 3, once the diseased plant is found, immediately remove it, apply lime disinfection around the diseased hole; 4 use 50% more bacteria in the early stage of the disease Ling 1000 times liquid is poured into the ward to control the spread of the disease.
(4) Prevention and treatment method of ruler (scale insect, bridge-building insect): It can protect the natural enemies of the ruler, or be sprayed with 40% omethoate 1000 times dilution, and disabled 20 days before harvest.
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