Analysis Of Winter Temperature And Light Performance Of Energy-saving Solar Greenhouse In High-cold Area And Comparison Of Utilization Modes

As a part of modern agriculture,the development of solar greenhouse industry is playing a more and more important role under COVID-19 pandemic situation.Solar greenhouse production guarantees the annual supply of fresh fruits and vegetables in cold districts.However,due to the drawbacks of high requirements for agricultural facilities,complex technical processes and high production costs,the development of solar greenhouse in the cold districts is seriou sly restricted.In this study,several solar greenhouses in Heilongjiang Province were taken as research object.The temperature and light indexes of those greenhouses in winter were tracked and measured,and a systematic investigation on the current production mode of those solar greenhouses also conducted.Thus the light and temperature characteristics and the main production mode of solar greenhouse in winter in alpine region were clarified,which provided basis and model reference for comprehensive and efficient utilization of solar greenhouse in alpine region.Main results of this study are as follow:(1)The overall change pattern of winter average temperature can be divided into three stages:cooling stage(early December to early January),low temper ature continuous stage(early January to early February),warming stage(early February to late February);The diurnal variation of temperature is single peak,which can be divided into warming stage,higher temperature stage,cooling stage and low temperature maintaining stage.The duration of warming stage and higher temperature stage in sunny day was longer than that in cloudy day,and the duration of low temperature maintaining stage in cloudy day was longer;The temperature in the solar greenhouse was distributed in different horizontal positions with the same vertical height during each stages in the north-south direction,and gradually increased from the south(near the front of the greenhouse)to the north(near the back wall of the greenhouse)in ea ch stage;The east-west distribution near the ground(0.5m)varies between different horizontal positions during each stages.In the eastern part of the cooling stage is the highest,the temperature in the middle part of the low temperature lasting stage is the highest,and the temperature in the western part of the warming stage is the highest.However,there is no significant difference in the temperature during different stages of the higher vertical position(1.2m).(2)Without heating equipment,the indoor ground temperature(0.10 m underground)of solar greenhouse in alpine area can be maintained above 5℃ in winter;Besides,the variation trend of ground temperature in winter is similar to that of air temperature,bu t the difference is obvious between sunny and cloudy days,the time of the highest ground temperature in cloudy days is delayed;In the north-south direction of the solar greenhouse,the ground temperature in the north(near the back wall of the greenhouse)was higher or significantly higher than that in the middle and south(near the front of the greenhouse);In the east-west direction,in the cooling stage,the temperature in the east is the highest,which is significantly higher than that in the west.In the low temperature maintaining stage,the temperature in the middle is the highest but not reach significant level.There is no significant difference in the ground temperature of each position in the warming stage.(3)The key point of the changes of light intensity in solar greenhouse wer e at winter solstice,which showed the trend of decreasing first and then rising;In sunny weather the light intensity of the light stage can meet the requirements of the growth of regular leafy vegetables,and the light intensity can meet the requirements of fruits and vegetables for 5 hours;In cloudy days,the maximum light intensity appeared earlier,and the overall light intensity decreased significantly.Only 3 hours of light intensity reached the requirements of leafy vegetables.The light intensity of different locations is different in the north and south direction,and the southern part(near the front of greenhouse)is significantly higher than that in the north(near the back wall of the greenhouse),and there is no significant difference in the light intensity in the east-west direction.(4)Solar greenhouses in Heilongjiang Province are mainly distributed in Daqing,Qiqihar,Suihua and Harbin with the main type of brick concrete structure;At present,there are many kinds of cultivation modes in solar greenhouse.Through comprehensive comparison,three cultivation modes with high comprehensive benefits and can be popularized in cold districts were selected:M1(strawberry),M5(spring watermelon summer tomato winter leaf vegetable)and M11(autu mn celery winter rape spring cucumber summer tomato).