Cultivation techniques of sweet carambola in plastic greenhouse

Big fruit sweet carambola is tropical and subtropical evergreen fruit trees, fast growth, early results, many times a year flowering, fruit excellent, crisp and juicy, loved by the masses. However, for a long time, carambola cultivation is extensive management, low yield, poor quality, market competitiveness and economic benefits are poor. Therefore, in April 2001, our institute began to cultivate sweet carambola in plastic shed with an area of 0.43 hm 2. The fruit bearing period was 8~10 months, and the quality was improved. It could avoid the disaster of wind and rain and the frost damage in winter, and greatly improve the market competitiveness and economic benefit.

1. Construction of plastic greenhouse orchard

1.1 Garden construction: choose the flat land with deep soil layer, loose soil and convenient drainage. The orchard is built into a multi-span greenhouse with steel pipe supports, each shed is 6m wide, and its height and length are determined according to the terrain. The shed is covered with insect prevention nets around the shed, and the shed top cover is covered with a polyethylene drip-free film, and drainage ditches are opened around the shed. Proper close planting, plant spacing 2.5m×3.5m, digging holes 0.8m long and width, 1m deep, applying 50kg soil manure, 30kg livestock manure, 1kg calcium superphosphate and 0.5kg lime powder to each hole, fully mixing with hole soil as base fertilizer and returning to hole 10cm above ground.

1.2 Variety selection: select Malaysia red carambola and Taiwan large fruit sweet carambola and other high-quality varieties.

1.3 Planting: Planting in spring from March to May. When planting, the soil around the roots should be compacted, and the piers should be raised, the tree tray should be trimmed, the root water should be poured, and the tree tray should be covered with grass.

2 Soil and water management

Sweet carambola with large fruit likes high temperature and humidity, but its root system is not water-resistant, and its root group is shallow and easy to suffer from drought. Therefore, the orchard must be dredged around the drainage ditch, lower the groundwater level. Before the rainy season comes, the whole garden should be tilled and loosened, and it is appropriate to not hurt too many roots in 6~8cm, so as to improve the drainage and ventilation capacity of the soil and not harden after the rain. Irrigation should be carried out in time to keep the soil moist. Before autumn drought, the whole garden should be tilled and loosened again in September and October to reduce the evaporation of garden water and improve the soil temperature. Frost period to more irrigation, to prevent freezing and drought leaves, to maintain tree vigor.

3 nutrient fertilization: large fruit sweet carambola young seedlings after planting survival, monthly thin application of decomposed human and animal waste urine water or retting bran water 1~2 times, concentration and weight can be increased appropriately. After November, the fertilizer was stopped and 0.2% potassium dihydrogen phosphate was sprayed 2~3 times. At the end of December, calcium superphosphate was mixed with decomposed livestock manure and 5~10kg was applied to each plant.

From the second year onwards, fertilization is applied according to the shoot, flowering, small fruit turning pedicle and fruit development period of sweet carambola, generally 4~5 times a year. 1. Fertilizer for promoting flower growth: available nitrogen fertilizer, peanut bran 2.5kg and urea 0.5kg per plant, should be applied in April to May. In June to July, when the fruit is as big as thumb and the pedicel begins to droop, calcium superphosphate, peanut bran and human excrement can be used in a ratio of 1∶2∶100, and each plant is 25kg. Around August, the fruit has been set and grow rapidly, and continue to bloom, according to the amount and type of fertilizer application of fruit fertilizer, and pay attention to the combination with irrigation;4 fruit maturity fertilizer: fruit has been set when the fertilizer, mainly urea, 50g per plant, can promote fruit maturity, improve quality, at this time should be properly controlled moisture;5 winter cold fertilizer: After December, heavy fertilizer was applied, mainly organic fertilizer, livestock manure 30~50kg per plant, and soil cover.

4 pruning

After planting, the seedlings should be pruned at 40~50cm above the ground to promote bud germination on the trunk, and 3~5 strong buds should be selected and cultured into main branches to form crown skeleton. When the first layer branches of the main branch were 50cm long, the terminal buds were removed to promote the germination of the second layer branches, and 2~3 lateral buds were left in the second layer branches, and the rest were all removed. After that, let it branch naturally, guide the growth direction properly, and make the branches distributed evenly at all levels [2]. Generally, trees were pruned once after fruit picking in autumn and winter and before budding in spring, mainly to remove dead branches and leaves from trees and promote budding in spring. Big fruit sweet poplar peach tree general top vigorous, excessive long branches more, so late May to early June to timely short or thin cut, inhibit the upper crown vigor, promote the middle and lower fruit. When pruning, attention should be paid to retaining the old and ripe "horsewhip branches" around the crown, because this is the best fruit branch of sweet carambola. In addition, when cutting off the shady branches inside the crown, leave 1~ 2 cm branches, so that more flowering branches or leafy fruit branches can be taken out and more branches and fruits can be produced.

5 flowers and fruits

5.1 Pollinating tree configuration: malaysian red carambola and taiwan sweet carambola mixed planting, can improve the fruit setting rate.

5.2 Prevention of drought, typhoon, frost flowering in dry, hot weather, to spray water to protect flowers. Typhoon, rainstorm season, can use bamboo pole support around the crown, pull fixed branches, reduce the fruit drop caused by typhoon and storm attack. Cover with film protection before frost arrives, irrigate water in time and apply organic fertilizer.

5.3 Hormone fruit protection: spraying 50mg/L GA3 solution on leaves at full bloom and small fruit stage has obvious fruit protection effect.

5.4 Ring cut or ring tie to promote flower and fruit preservation: young trees with excessive vegetative growth, in the middle and late June, ring cut 1 circle of cortex on the trunk 10~15cm above the ground, the depth should just pass the phloem without damaging the xylem, or ring tie 2 circles with No.10 iron wire until the middle of August when the iron wire is not completely immersed in the cortex [2].

6 Fruit thinning and bagging

Fruit thinning was carried out twice, the first time within 20~30 days after fruit setting, when the fruit pedicles drooped, the diseased fruits, abnormal fruits and over-dense small fruits were removed, and the second time when the fruit transverse diameter reached 4~ 5 cm, the diseased fruits, abnormal fruits and small fruits in the same batch of fruits whose growth speed could not keep up were removed before bagging. In addition, in order to improve fruit quality and obtain good fruit appearance, improve commodity value, advocate single fruit bagging. The method is that after the last fruit thinning and spraying 50% thiophanate-methyl or carbendazim and other fungicides, the next morning after dew drying, single fruit bagging is carried out with wax paper bags, and the bagging date should be marked, so as to distinguish the time before and after each batch, so as to facilitate harvesting.

7 Pest control

Due to the plastic greenhouse plus insect net cultivation, sweet carambola with large fruit has less pests, but attention should also be paid to preventing bird moth, aphid, black spot brown leaf roller and fruit fly. The first is to spray 90% trichlorfon 800 times solution before flowering, the second is to kill brown leaf roller with black light lamp after fruit turning, and spray 90% trichlorfon 800 times solution plus deltamethrin 4000 times solution at peak stage. The main diseases are withered branches, baldness, leaf spot and anthracnose. Cultivation and management should be strengthened to improve the disease resistance of trees. For the disease plants can be sprayed Bordeaux mixture or can be killed and other pesticides control.

8 Temperature, humidity, gas, light regulation

Big fruit sweet carambola likes high temperature and humidity climate, bears shade, avoids hot sun and northwest cold wind, especially in flowering and young fruit stage, fears dry wind and hot sun, grows poorly below 10℃, branches and leaves are damaged near 0℃, young trees are easy to freeze to death. The pollination and fruiting are good when the temperature is above 27℃ at flowering stage. Therefore, temperature, humidity, light and ventilation control is the key to the success of large fruit sweet carambola cultivation in greenhouse.

8.1 Temperature regulation: greenhouse temperature regulation is carried out according to meteorological data, and the main methods for temperature rise are covering air, irrigation and spraying water [3]. When the temperature drops to 10℃ in winter, the plastic shed top cover polyethylene film without dripping, surrounded by film, day and night closed shed door, improve the temperature and ground temperature in the shed. In case of sunny days, when the temperature in the shed reaches more than 30℃, open the shed door to control the temperature, irrigate and spray water. In summer, when the temperature is higher than 30℃, it is necessary to remove the surrounding film, top film and canopy in time, and cover the sunshade net. Cover the film, cooling method is to remove the film, ventilation change.

8.2 Humidity regulation: In the shoot growth period, the relative humidity in the shed is kept at 70%, from flowering to fruit growth period is 50%~ 60%, and the coloring period is 50%. If the humidity is insufficient, irrigation and spraying should be carried out; if the humidity is too large, ventilation, intertillage, etc. should be carried out.

8.3 The regulation of gas: in the greenhouse cultivation of large fruit sweet carambola, because the gas does not flow or less flow, respiration produces CO2, photosynthesis consumes CO2, so the CO2 concentration in the greenhouse changes greatly. The photosynthetic rate of leaves of sweet carambola tended to decrease at noon, forming a "noon break phenomenon", which was caused by low CO 2 concentration in the greenhouse. The main ways to increase CO2 content in the shed are: one is to apply organic fertilizer, which continuously produces CO2 gas in the decomposition process of fertilizer; the other is to ventilate, so that CO2 in the atmosphere can be supplemented into the shed; the third is to apply CO2 gas fertilizer. In addition, due to less circulation of air in the shed, easy to produce harmful gases such as NH3, NO2, SO2, CO, etc., so in cultivation can not be applied too much nitrogen fertilizer, should be watered after application, when the harmful gas concentration is high to ventilation.

8.4 Regulation of light: cultivation of large fruit sweet carambola in the greenhouse, generally easy to cause insufficient light, so to take measures to enhance, the method is to correctly choose the orientation of the greenhouse, scientific design, as far as possible to make the greenhouse by the light is stronger, longer, at the same time should choose better light transmission without dripping film, replace the old film every year. White mulch is laid on the ground to increase reflected light.