original Zhang Zhuoyan Greenhouse Horticulture Agricultural Engineering Technology 2022-09-09 17:20 Posted in Beijing
Common greenhouse types and characteristics for berry cultivation
The berries are harvested year-round in northern China and require greenhouse cultivation. However, various problems were found in the actual planting process using various types of facilities such as solar greenhouses, multi-span greenhouses, and film greenhouses.
01 Film Greenhouse
The advantage of growing berries in a film greenhouse is that there are four ventilation openings on both sides and the top of the greenhouse, each with a width of 50-80cm, and the ventilation effect is good. However, because it is inconvenient to add thermal insulation materials such as quilts, the thermal insulation effect is poor. The lowest average temperature at night in northern winter is -9°C, and the average temperature in the film greenhouse is -8°C. Berries cannot be grown in winter.
02 Solar Greenhouse
The advantage of growing berries in a solar greenhouse is that when the minimum average temperature at night in northern winter is -9°C, the average temperature in the solar greenhouse can reach 8°C. However, the soil wall of the solar greenhouse leads to its low rate of land utilization. At the same time, there are two ventilation openings on the south side and the top of the solar greenhouse, each with a width of 50-80cm, and the ventilation effect is not good.
03 Multi-span greenhouse
The advantage of growing berries in a multi-span film greenhouse is that the multi-span greenhouse structure does not occupy additional farmland, and the land utilization rate is high. There are a total of eight ventilation openings on the four sides and the top of the multi-span greenhouse (take a 30m×30m multi-span greenhouse as an example). The ventilation effect is guaranteed. However, when the minimum average temperature at night in northern winter is -9°C, the average temperature in the multi-span film greenhouse is -7°C. In winter, the daily energy consumption to keep the minimum indoor temperature to 15°C for normal berry growth can reach 340 kW•h/667m2.
From 2018 to 2022, the author’s team has tested and compared the application effects of film greenhouses, solar greenhouses and multi-span greenhouses. At the same time, a smart greenhouse suitable for berry cultivation was designed and constructed in a targeted manner.
Comparison of main features of different greenhouse
Film greenhouses, solar greenhouses and multi-span greenhouses
Double-span greenhouse for berries
On the basis of ordinary greenhouses, the author’s team designed and built a double-span greenhouse for berry planting, and carried out trial planting with raspberries as an example. The results showed that the new greenhouse creates a growing environment that is more suitable for berry planting, and optimized the taste and nutritional content of raspberries.
Fruit Nutrient Composition Comparison
The double-span greenhouse is a new type of greenhouse whose ventilation effect, lighting effect and land utilization rate are more suitable for berry cultivation. The structural parameters are shown in the table below.
Double-span greenhouse profile/mm
Double-span greenhouse structure parameters
The planting height of berries is different from the planting height of traditional vegetables. The cultivated raspberry varieties can reach more than 2m. On the lower side of the greenhouse, the berry plants will be too high and break through the film. The growth of berries requires strong light (total solar radiation 400~800 radiation units (104W/m2). It can be seen from the below table that the long light time and high light intensity in summer have little effect on berries, and in winter low light intensity and short light time resulted in a marked decrease in berry yield. There is also a difference in the light intensity on the north and south sides of the solar greenhouse, which leads to the difference in plant growth on the north and south sides. The soil layer of the soil wall construction of the solar greenhouse is greatly damaged, the land utilization rate is only half, and the rainproof measures are damaged with the increase of service life.
effects of light intensity and light duration on raspberry yield in winter and summer
01 Greenhouse ventilation
The new double-span greenhouse has increased the height of the downwind vent at the lowest position to ensure that there is no film in the planting area that can block the growth of plants. Compared with the lower vents with a width of 0.4-0.6m in ordinary solar greenhouses, the vents with a width of 1.2-1.5m in the double-span greenhouse have doubled the ventilation area.
02 Land utilization rate of greenhouse and Warming & Insulation
The double-span greenhouse relies on a span of 16m and a height of 5.5m. Compared with ordinary solar greenhouses, the internal space is 1.5 times larger, and 95% of the actual planting area is obtained without building soil walls, which improves the land utilization rate by more than 40%. Different from the soil wall built for thermal insulation and heat storage in solar greenhouses, the double-span greenhouse adopts an internal thermal insulation system and a floor heating pipe heating system, which does not occupy the planting area. The large span brings the doubled area and amount of light transmittance, which increases the soil heat storage by 0~5°C year-on-year. At the same time, an internal thermal insulation quilt and a set of floor heating pipe heating systems are added to the greenhouse to maintain the inside temperature of greenhouse to above 15°C under the cold wave of -20°C in the northern winter, thus ensuring the normal output of berries in winter.
03 Greenhouse lighting
The growth of berries has high requirements on light, which requires a total solar irradiance of 400-800 radiation units (104W/m2) of light intensity. The factors that affect the greenhouse light include weather conditions, seasons, latitude and building structures. The first three are natural phenomena and are not controlled by humans, while the latter is controlled by humans. The greenhouse illumination is mainly related to the greenhouse orientation (within 10°south or north), the roof angle (20~40°), shading area of the building materials, light transmittance of plastic film and pollution, water droplets, aging degree, these are the main factors affecting greenhouse lighting. Cancel the external thermal insulation and adopt the internal thermal insulation structure, which can reduce the shading surface by 20%. In order to ensure the light transmission performance and effective service life of the film, it is necessary to remove the rainwater and snow on the surface of the film in time. After experiments, it was found that the roof angle of 25~27° is more conducive to the dropping of rain and snow. The large span of the greenhouse and the north-south arrangement can make the illumination uniform to solve the problem of inconsistent plant growth in the same greenhouse.
Special large-span thermal insulation plastic greenhouse for berries
The author’s team researched and built a large-span greenhouse. This greenhouse has great advantages in construction cost-effectiveness, berry yield and thermal insulation performance.
Large-span greenhouse structure parameters
Large-span greenhouse structure
01 Temperature advantage
The large-span greenhouse does not need soil walls, and the land utilization rate of the ordinary solar greenhouse is increased by more than 30%. It has been determined that the large-span external thermal insulation plastic greenhouse can reach 6°C when the outdoor temperature is -15°C, and the temperature difference between indoor and outdoor is 21°C. In terms of thermal insulation, it is similar to the solar greenhouse performance.
Comparison of thermal insulation and heat dissipation performance between large-span greenhouse and solar greenhouse in winter
02 Structural advantages
The facility has a reasonable structure, a solid foundation, a wind resistance of grade 10, a snow load of 0.43kN/m2, strong resistance to natural disasters such as rainstorm and snow accumulation, and a service life of more than 15 years. Compared with ordinary greenhouses, the internal space of the same area is increased by 2~3 times, which is convenient for mechanized operations, and is suitable for the planting of crops with taller plants (2m ±1m).
03 Light and space environment advantages
Large-span greenhouses are very beneficial to personnel management and scheduling in large-scale planting, and can effectively avoid labor waste. The roof design of the large-span greenhouse fully takes into account the sun altitude angle and the incident angle of sunlight on the film surface under different latitude conditions , so that it can form ideal illumination conditions in different seasons and different sunlight incident periods (combined with the angle between the film surface and the ground is 27° for the rain and snow to slide down comprehensively) , so as to reduce the scattering and refraction of light as much as possible, and maximize the use of solar energy. The space of the large-span greenhouse is increased by more than 2 times, and the CO2 relative to the air is increased by more than 2 times, which is conducive to the growth of crops and achieves the purpose of increasing production.
Comparison of different facilities for growing berries
The purpose of building a greenhouse more suitable for berry planting is to obtain an important growth environment and environmental control in berry planting, and the growth of plants intuitively reflects the advantages and disadvantages of their growing environment.
Comparison of the growth of raspberries in different greenhouses
Comparison of the growth of raspberries in different greenhouses
The quantity and quality of raspberry fruit yield also depend on the growing environment and environmental control. Standard compliance rate of first-class fruit is more than 70% and the output of 4t/667m2 means higher profits.
comparison of the yield of different greenhouses and standard compliance rate of first-class fruit
Zhang Zhuoyan.A special facility structure suitable for raspberry cultivation [J]. Agricultural Engineering Technology, 2022,42(22):12-15.
Post time: Sep-30-2022