Study Of Different Irrigation Modes On Greenhouse Microclimate And Yield Of Cucumber By Sand Culture

The growth of plants is inseparable from the participation of environmental factors such as“water,fertilizer,gas,heat and light”.There is great significance to study the changes of environmental factors in greenhouse for plant growth and microclimate regulation in solar greenhouse.In this thesis,cucumber by sand culture as the research objection,the variation trend of environmental factors?air temperature,air humidity,CO₂ concentration,ground temperature and matrix moisture content?in solar greenhouse under subsurface drip irrigation and surface drip irrigation under membrane in different weather,time and space were studied.The growth index,quality and yield of cucumber under two different drip irrigation conditions were analyzed and compared,and the following research results were obtained.?1?The two types of drip irrigation have little influence on the change trend of environmental factors,and they have the same trend.In the middle growth period of cucumber?5 June to 4 July?,the temperature of surface drip irrigation under membrane was greater than the temperature of subsurface drip irrigation in sunny day,overcast and rainy day.The maximum temperature difference between the two types of drip irrigation is 3.66?,3.02?and 1.32?,respectively.It is opposite in cloudy day.The temperature difference between the two types of drip irrigation is 2.41???2?Temperature of the two drip irrigation forms has the same spatial change trend and different distribution.The highest temperature location of surface drip irrigation and subsurface irrigation under membrane is the rear of the greenhouse and the front of the greenhouse,respectively on sunny days.The temperature difference between the two types of drip irrigation is 2.33?in the middle of the greenhouse?along the greenhouse length in east-west orientation?.The highest temperature location of surface drip irrigation and subsurface irrigation under membrane is the rear of the greenhouse on cloudy days,and the temperature difference is 4.22?in middle of the greenhouse?along the greenhouse length in east-west orientation?.The highest temperature location of surface drip irrigation and subsurface irrigation under membrane is the rear of the greenhouse on overcast,and the biggest temperature difference is 1.63?in rear of the greenhouse?along the greenhouse length in east-west orientation?.The temperature difference between different locations of two types of drip irrigation is small,and the temperature distribution in the greenhouse is more uniform during rainy days;The difference of surface drip irrigation under membrane is greater than that of subsurface drip irrigation under membrane?along greenhouse span in north-south orientation?.On sunny days,the biggest temperature difference of surface drip irrigation and subsurface drip irrigation under membrane is 4.9?and 1.5?,respectively in difference location.The biggest temperature difference of two types of drip irrigations is 3.18?in front corner of greenhouse.The biggest temperature location is in front corner of greenhouse.On cloudy days,the biggest temperature difference of surface drip irrigation and subsurface drip irrigation under membrane is 4.38?and 3.77?,respectively in difference location,and the biggest temperature difference of two types of drip irrigations is1.22?in the same location.The temperature difference between drip irrigation in cloudy and rainy days is small,and the temperature in the greenhouse distributes stepwise along the span direction.The temperature in the greenhouse distributes stepwise on sunny days,cloudy days and rainy days along greenhouse height,and the average temperature difference is 1.97?,1.41?and 0.55?,respectively in bottom of the greenhouse.The biggest temperature location is the greenhouse canopy,and the average temperature difference is0.76?in the canopy on overcast for two types of drip irrigation.?3?The change of humidity is more regular in sunny and cloudy periods.The highest humidity stage in the greenhouse is the late growth period.The difference of humidity under the two drip irrigation is small,and the trend of humidity change is"U"type like deep valley.There is bigger humidity difference between the surface drip irrigation and subsurface drip irrigation in middle of the greenhouse?along greenhouse length?on cloudy days.And there is a smaller humidity difference at the other location between the drip irrigation.Along greenhouse span and height,there is no difference between the drip irrigation for humidity,but the humidity difference is obvious inside the greenhouse.There is a big difference between the greenhouse wall and the rest location of the greenhouse.So does the greenhouse bottom.Temperature is the main reason for the difference.?4?The change trend of CO₂ concentration presents“U”type on sunny day.There is no difference inside greenhouse during the day time for CO₂ concentration.But there is a big difference for CO2 concentration inside greenhouse during the night time because of plant respiration.The difference of CO₂ concentration in the same position under both drip irrigation is large,and the difference of CO₂ concentration in different positions under the drip irrigation under the membrane is obvious.The maximum concentration occurs in the post-greenhouse position.The subsurface drip irrigation only has the post-greenhouse position and the other two which difference is obvious,and the maximum concentration occurs in front of the greenhouse.The change of CO₂ concentration in the cloudy period is“V”type,and the difference is similar to that of sunny days.The CO₂ concentration fluctuated greatly during cloudy and rainy days,but the distribution inside the greenhouse was more obvious.The maximum concentration of surface drip irrigation under the membrane was post-greenhouse position.The minimum concentration was in the middle of the greenhouse?along greenhouse length?.The maximum concentration of subsurface drip irrigation under the membrane was in front of the greenhouse.The minimum concentration was post-greenhouse position.After that,the CO₂ difference between the two types of drip irrigation in the post-greenhouse position is large.?5?The ground temperature under the two drip irrigation forms has obvious changes during the growth period of the whole cucumber.The closer to the late growth stage,the greater the ground temperature,but the temperature difference within one day is getting smaller and smaller,and the ground temperature difference between the two drip irrigations is not obvious.The water content of sand of two types of drip irrigation has obvious difference.The difference of water content under different weather conditions is 1.53%,1.56%,3.4%,0.50%,respectively.After irrigation,the water content of the subsurface water drip irrigation under the membrane is more than surface drip irrigation about 2.74%.?6?The growth index,quality and yield of cucumber were analyzed and found that the maximum plant height under subsurface drip irrigation was 38.11cm,which was 30.8%higher than the maximum plant height of surface drip irrigation by 29.13cm,and the maximum stem thickness under subsurface drip irrigation was 6.428mm,which was 12.9%higher than the maximum stem diameter of surface drip irrigation by 5.692mm.There is a significant difference between leaf length and leaf width growth under different drip irrigation forms.There was no significant difference in the dry matter and vitamin C content of cucumber under the two drip irrigation forms,while the shallow water drip irrigation increased the water-soluble sugar content by 28.6%compared with the surface drip irrigation.During the whole growth period,the yield of subsurface drip irrigation was always higher than that of surface drip irrigation.In the early,middle and late stages,the yield of subsurface drip irrigation increased by 27.6%,8.7%and 24.1%,respectively,and the total yield increased by 10.9%.Therefore,for the cultivation of cucumber in the sand,the subsurface drip irrigation is more suitable.