Abstract:

Using the measured temperature and humidity data inside and outside small plastic shed within a sunlight greenhouse at Qinghe county of Hebei province from January to February in 2013 and the corresponding data from a nearby weather station, temperature and humidity characteristics and their effects in small plastic shed under different weather conditions were analyzed by a mathematical statistics method. The results indicate that the maximum daily temperature in the small plastic shed could reach above 30.0 ℃ and 25.0 ℃ in a clear day and a partly cloudy to cloudy day respectively which are about 1.3-6.6 ℃ and 1.0-4.5 ℃ higher than those of outside shed. The daily minimum temperature in the small plastic shed is 4.0-11.0 ℃ and 6.0-14.0 ℃ corresponding to the above two weather conditions, and they are about 0.0-1.5 ℃ higher than those of outside shed. The minimum daily relative humidity inside the small plastic shed is about 50% and about 2%-11% higher than that outside the small plastic shed, while the maximum relative humidity inside the small plastic shed is either equal to or slightly higher than that of outside the small plastic shed. Inside the small plastic shed, daily variation ranges of temperature and relative humidity on the height of 0.0 m are less than those on the height of 0.5 m. In persistent sunless days, temperature inside the small plastic shed changes from 5.0 ℃ to 15.0 ℃ and relative humidity reaches above 85% in a whole day. Change ranges of temperature and relative humidity inside the small plastic shed are not significant and both values are similar or higher than those outside the small plastic shed. In general, adding small plastic shed within the sunlight greenhouse has evident effects on increasing inner temperature and keeping moisture in sunny or slight cloud to cloudy days, but no distinct effect on maintaining its inner temperature in sunless days. Large temperature and relative humidity differences between inside and outside the small plastic shed could be observed in daytime, especially at noon, but small or no difference in nighttime. In the actual production, thermal burn at noon in sunny days, the frostbite and diseases caused by low temperature and high?relative humidty in sunless days inside the small plastic shed should be prevented.

Key words: Greenhouse, Small plastic shed, Temperature effect, Humidity effect