Monthly Change Analysis on Microclimate in Plastic Greenhouse in North China in Spring

[Objective] The purpose was to learn about the microclimate characteristics in plastic greenhouse in north China in the whole spring.[Method] A farm household in the suburb of Kiamusze Municipality was selected as observation location.The air temperature,humidity and light intensity in greenhouse were being observed and measured from Mar.10th to May 30th in 2009.And then the monthly change of microclimate in plastic greenhouse in north China in spring was studied.[Result] The warming effect of plastic greenhouse in north China in spring was significant.In March,compared with the lowest air temperature outside greenhouse,the lowest air temperature in greenhouse was increased for more than 7 ℃ when it was covered in night.In the period from March to May,the humidity in greenhouse was obviously higher than that outside greenhouse.In March,from 17:00 to next 6:00,the relative humidity in greenhouse was maintained at 100% basically.Although the humidity in greenhouse got some deceased in April and May,it was still much higher than that outside greenhouse.From March to May,the average light transmission rate of plastic greenhouse was above 50% and the time when the light intensity in greenhouse was higher than light compensation point of warm season vegetable and light saturation point of cool season vegetable was 6-8 h.[Conclusion] This study supplied reliable basis for northern-Chinese farmers to sensibly arrange their farming activities in plastic greenhouse in spring.