The Effect Of Film Mulching On Vapor And Heat Fluxes,morpho-physiological Parameters And Yield Of Cucumber In Greenhouse

It is important to know the heat fluxes partitioning characteristics,and to quantify the response of morpho-physiological indicators,yield and irrigation water use efficiency（IWUE）and the evapotranspiration（ET_c）of greenhouse crops under film mulching drip irrigation for reducing water consumption,improving irrigation water use efficiency（IWUE）,promoting sustainable agricultural development and managing scientific irrigation of greenhouse crops.In this study,greenhouse cucumber was used for the experiments.Based on the observated micro-meteorological data,soil water content（SWC）,soil temperature（T_s）,latent heat flux（LET）,morpho-physiological parameters,crop yield and irrigation water use efficiency（IWUE）of greenhouse cucumber during the whole growing stages in 2019 and 2020,the changes in SWC,T_s,LET,sensible heat flux（H）and soil heat flux（G）were compared under the treatments of drip irrigation with and without film mulching（M1 and M0）.The influences of film mulching on plant morpho-physiological parameters,yield and irrigation water use efficiency（IWUE）of cucumber in a greenhouse in different planting years were analyzed.The greenhouse cucumber plants transpiration（T_r）and soil evaporation（E_g）were estimated based on the revised dual crop coefficient（RDCC）model,and achieved high crop yields and efficient water use of greenhouse cucumber under film mulching.The research results obtained are as follows:（1）The influence of film mulching on heat flux partition of greenhouse cucumber under drip irrigation showed that the SWC and T_s of 5-10 cm soil layer increased by 10%and 3.46℃during the whole growth period under the M1 treatment respectively when compared with M0 treatment.The film mulching adjusted the partitioning characteristics of energy heat,with the ratio of LET and soil heat flux（G）to net radiation（R_n）increased by 12.21-14.15%and 1.98-3.37%,respectively,and the ratio of sensible heat flux（H）to R_n decreased by 15.59-17.45%.（2）The influence of film mulching on greenhouse cucumber morphological parameters under the adequate and deficit treatments in different planting years were analyzed and it was concluded that the cucumber plant height,stem diameter and leaf area index（LAI）under M1 treatment were promoted and the order of cucumber morphological parameters under four treatments was found as T1M1>T1M0 and T2M1>T2M0 in both planting years when compared with M0 treatment.In 2019,as compared to T1M0 and T2M0 treatments,the cucumber plant height increased by 24.72%and 50.04%under T1M1 and T2M1 treatment,respectively,while it increased by 16.71%and 59.94%in 2020,respectively.Corresponding,the cucumber stem diameter increased by 21.33%and 30.91%in 2019 and 32.04%and 24.90%in2020,respectively;the cucumber LAI increased by 45.40%and 96.34%in 2019 and46.15%and 81.22%in 2020,respectively.（3）The effects of film mulching on crop physiological,yield and irrigation water use efficiency（IWUE）of greenhouse cucumber in different planting years were investigated and the results showed that the stomatal conductance,photosynthetic rate and sap flow rate of greenhouse cucumber increased in M1 treatment compared to M0treatment.In 2019,as compared to T1M0 and T2M0 treatments,the daily average photosynthetic rates increased by 38.60%and 129.40%under T1M1 and T2M1treatment,respectively,while it increased by 50.20%and 189.70%in 2020,respectively.Corresponding,the daily average stomatal conductance increased by 14.10%and137.30%in 2019 and 41.90%and 57.90%in 2020,respectively;the sap flow rate of greenhouse cucumber increased by 9.94 g?h^-1and 14.06 g?h^-1,respectively,while in2020,it increased by 24.17 g?h^-1and 12.83 g?h^-1,respectively;the cucumber yield increased by 38.1%and 32.80%in 2019 and 31.90%and 22.10%in 2020,respectively;the IWUE also improved by 38.02%and 44.30%in 2019 and 31.90%and 22.10%in2020.（4）The RDCC model was used to estimate ET_c and T_r of the greenhouse film mulching and non-mulching cucumbers under adequate irrigation and good agreements with the measured values were obtained.In 2019,the mean values of estimated ET_c by RDCC model were 2.88 mm?d^-1 and 1.62 mm?d^-1 for T1M1 and T1M0 treatments,respectively,and the corresponding mean values of measured ET_c were 2.92 mm?d^-1and 1.74 mm?d^-1.The estimated ET_c under both treatments in 2020 were 2.35 mm?d^-1 and 1.50 mm?d^-1 corresponding to the measured ET_c were 2.69 mm?d^-1 and 1.70mm?d^-1.The estimated T_r/ET_c for different planting years under M1 and M0 treatments had mean values of 90.94%and 84.07%in 2019 and 92.75%and 82.42%in 2020,respectively.Compared to the M0 treatment,the M1 treatment promoted transpiration and reduced evaporation and the ratio of T_r to evapotranspiration（ET_c）under M1treatment increasing by 8.71-29.5%.The ET_c increased by 97.99 mm in 2019 and 70.35mm in 2020 during the whole growth stage of the M1 treatment compared to M0treatment in different planting years.