The approach to day - clip humidness in the semi - closed glasshouse differ much from the conventional greenhouse . But how does the superior air movement affect the plant at Nox ? Godfrey Dol , an expert on culture in semi - unopen glasshouses , grind into it .
In a ceremonious glasshouse , growers will turn on the heat organization when the humidity deficit ( HD ) falls below 1.0 - 2.0 gram per cubic meter , even if there is no heating plant necessary to keep the plant warm . The heat moves and warm up the air creating a modest HD . Moisture is release through the vents . This avail forestall diseases such as Powdery Mildew and Botrytis . In a semi - closed nursery , it is secure to go as low as an HD of 0.2 - 0.5 . This has substantial consequences for heating cost and energy use .
If we think about why conventional nursery growers want to use the heating system to lose weight humidness , it is because the heating moves the air . The fans in a semi - closed glasshouse do a much better problem ( and it is cheaper ) compared to heating plant .
If we think about the real rationality why raiser wrench on the heating system at a humidity of more than 85 % ( HD=1.3 at 18 degree Celsius ) , it is because the measure boxful that measures the humidity , is located near the top of the plant . A humidity of 85 % in a schematic greenhouse means that in the lower region of the glasshouse , where there are Lot of leaves , and piddling air circulation , the humidness must approach 100 % . It is this humidity that causes Botrytis and Powdery Mildew .
In a semi - closed glasshouse , the fans create a more homogeneous climate . A humidity of 85 % near the top means that the humidity is also 85 % near the bottom . It is estimate that 20 - 30 % of fuel usage in a conventional glasshouse is used for dehumidification . A semi - closed in glasshouse will reduce this significantly .
Night - fourth dimension cooling and humidityWhat about cooling at night ? Can we reduce the 24 - hour temperature at dark by using the pad wall for cooling on a warm nighttime ? It seems counterintuitive to impart wet into a greenhouse at night . sure enough this will boost Botrytis and Powdery Mildew . Godfrey wants to show an example .
If the remote temperature is 20 degrees , and the humidness is 60 % , the wet bulb temperature is 15.1 . This means we can blow in air of 15.1 Celsius at 100 % humidity by turning on the pad rampart . If we increase the temperature in the greenhouse to 18 degree , the corresponding humidity is 84 % , which is more than satisfactory for dark - time humidness .
If we opine back to the fear of usher in wet into the glasshouse at night , we can now see that there is no endangerment of condensation if the blow in temperature in the greenhouse is humble than the glasshouse breeze temperature .
As a result , we can cool and humidify the blow in air if we think there is an advantage for the plant , without awe of overdo the chance of disease . This is in particular relevant when the daytime temperature is high , and the greenhouse need to be kept cool at dark to come down the 24 - hour temperature .
It is not strange to see an inside temperate that is more than 10 degree Celsius lower than the outside temperature when the dark humidity is below 35 % . plant opt a higher humidness at night . A relative humidity of less than 75 % at night is not suitable . Figure 1 : Powdery Mildew in Tomatoes
night weatherDuring extended periods of dour weather , plant will shed their roots because , like a muscle , if you do n’t habituate them , you mislay them . Growers in conventional glasshouses hear to foreclose this by put a minimal pipage in the greenhouse and start the vents . This will increase transpiration when there is a lack of sunlight . Root die back will be confine , and the legal action better ready the plant for the next cheery say which will inevitably get along .
In a - rig close greenhouse the fans do the activation and can make a peck more transpiration by go the air more quickly . Even if the greenhouse is in recirculation style and the strain exchange to the exterior is zero , the plant life will still be aerate by the air flow if the humidity is below 100%.Turning up the fan speed and achieve 5 - 6 melodic line exchange per hour is according to Godfrey an first-class agency to forestall ascendant die off and have your industrial plant quick for the first sunny daylight .
Inhis last post , Godfrey displayed a mesa with urge humidity deficits . He made a differentiation between a HD that had a vegetative and procreative effect on the works . Some mass found it unmanageable to empathize why a high humidness has a generative event on a plant . For them , Godfrey recommendsa late postin which this is explained .
In his next mail Godfrey will discuss what pest and disease pressures can be significantly reduced in a semiclosed glasshouse .
This article is part of a series about growing in a semi - unsympathetic greenhouse . record here - go’sfor semi - closed glasshouses , cooling , the remainder between semi - unsympathetic and pad and buff glasshousesandhow to prevent momentum , becoming a crop to vegetativeandhumidity , for examplein tomato .
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Godfrey DolLinkedIn[email protected]+81 80 700 94 006
