Study On Effect Of Ventilation And Water Control On Soil Humidity And Heat Environment And Tomato Root System In Greenhouse

It is of great significance for the quantification of ventilation and water control management measure in greenhouse and the realization of greenhouse tomato yield increase target to master the influence of ventilation and water regulation on surface soil temperature under greenhouse,soil water content and root system.In this thesis,drip irrigation tomatoes in solar greenhouse were selected as the research object.The experiment was conducted in Xinxiang Comprehensive Test Base of Chinese Academy of Agricultural Sciences from March to July2020 and 2021.Two irrigation treatments were set with the cumulative evaporation（E_p）of 20cm standard pan as reference:K_0.9（0.9 E_p）and K_0.5（0.5 E_p）,and three ventilation treatments were set according to different positions of the vents:T_R（open only the top vents）,T_RS（open the top and south vents）and T_S（open only the south vents）.Six test treatments were conducted in total.The air speed,air temperature and relative humidity on the underlying surface of the greenhouse under ventilation treatments were analyzed,and the soil humidity and heat environment and root distribution under the water under different ventilation and water control conditions were analyzed.On this basis,the normalized root length density（NRLD）model was established,and the HYDRUS-1D model was used to simulate the soil temperature and humidity and root water absorption.And then the accuracy of the model was evaluated by comparing the measured and simulated values.The main results were as follows:（1）Ventilation had an important effect on the air environment of the underlying surface of the greenhouse.Air speed of the underlying surface of the greenhouse was in the order of T_RS>T_S>T_R,and there was a very significant difference between T_RS,T_Rand T_Streatments（P<0.01）.The air temperature of the underlying surface of the greenhouse increased gradually with the passage of transplanting days,and the difference was obvious when vents was open（8:00-18:00）.The relative humidity of the underlying surface of the greenhouse showed an opposite trend to the air temperature,which was as follows,T_R>T_S>T_RS.Water vapor in the air increased after vents closed,and relative humidity in greenhouse gradually decreased after vents opened,and the relative humidity dropped to the lowest point between14:00-15:30 during the day.（2）Soil water content was different under different weather conditions,of which the order was:sunny<cloudy<overcast<light rain.During the whole growth period,soil water content was mainly affected by irrigation and presented multimodal variation.Ventilation could affect soil water content,which increased the water vapor exchange inside and outside the greenhouse.The soil watre content of T_Rtreatment during the whole growth period were much higher than those of T_RStreatment.The upper soil was more affected by weather conditions because it was in direct contact with the air environment.The soil temperature increased first and then decreased during the period from 8:00 to 18:00.The temperature of the upper soil（0-20 cm）varied greatly during the whole growth period,and gradually slowed down with the increase of soil depth.（3）In 2020 and 2021,plant height and leaf area under each treatment showed an"S"shaped curve with the passage of transplanting days.In the whole growth period,plant height and leaf area showed a rule:K_0.9>K_0.5.Under the three ventilation treatments,T_RStreatment had the smallest plant height and the largest leaf area,which indicated ventilation could effectively affect plant growth.The root length density of tomato plants decreased gradually with the increase of soil depth,and the roots mainly concentrated in the 0-20 cm soil layer.Under the same ventilation treatment,the water absorption of the roots of high-level water treatment(K_0.9treatment)was higher than that of low water treatment(K_0.5treatment).Under the same irrigation treatment,the water absorption of the roots of T_RStreatment was the largest.Thus it could be seen,T_RSK_0.9treatment was more conducive to the root system to absorb soil water.（4）The model of tomato NRLD was established based on greenhouse ventilation and irrigation.The results showed that R²and RMSE were above 0.98 and 0.20,0.23 and 0.27,respectively,under K_0.9and K_0.5irrigation treatments,and the model had a good fitting effect.（5）The simulation results and verification of the HYDRUS-1D model showed that the R²of soil water content was greater than 0.65,the consistency index was greater than 0.77,the R²of 0-10 cm soil temperature was greater than 0.66,and the R²and d of root water absorption and stem flow value were both greater than 0.9,indicating high simulation accuracy.Compared with low-level water treatment(K_0.5),high-level water treatment(K_0.9)had higher soil water content,lower soil temperature and greater root water absorption.