| Film mulching technology has accelerated the pace of modern agricultural development.The advantages of film mulching technology such as water saving,heat preservation,and increased production have greatly increased global crop production.This technology is suitable for arid and semi-arid regions such as Xinjiang,Inner Mongolia and other regions It can save agricultural water consumption while increasing crop yields.my country has used this technology in agricultural production for nearly 30 years,and its applicable areas have expanded from arid and semi-arid areas in the northwest to high mountains and cold areas in the south,and its application has evolved from cash crops to food crops.However,as the number and area covered by mulching film increase year by year,the residual amount of plastic film in the soil is increasing year by year.The mulch film is mainly synthesized from polyethylene and other polymer materials,with a stable molecular structure and a degradation cycle of up to 200 years,which makes the residual amount of mulch film in the soil accumulate every year.The accumulated residual film is mixed in the soil and destroys the original structure of the soil.The influence of residual film on soil water infiltration and soil water evaporation in the cultivated layer is worth exploring.In this paper,the indoor one-dimensional soil column test is carried out to study the soil water infiltration and water evaporation according to the distribution of residual film amount.The experiment was carried out at the modern water-saving irrigation experimental station of Shihezi University from2016 to 2017.The main conclusions are as follows:(1)The presence of residual film in the soil will reduce the soil moisture infiltration rate,and as the amount of residual film increases,the infiltration rate at each time point gradually decreases.When the amount of residual film exceeds 79.2 kg/hm~2,the barrier effect on soil infiltration rate is more significant than that of soil without residual film,and the stable infiltration rate of soil is significantly lower than that of soil without residual film.(2)In the case of uniform distribution,when the amount of residual film exceeds 79.2kg/hm2,the effect of residual film on the movement of the soil wetting front is more obvious;in the case of decreasing distribution layer by layer,when the amount of residual film exceeds At 39.6 kg/hm~2,the amount of residual film has an obvious blocking effect on the frontal movement of soil wetting.Under the same amount of residual plastic film,layer-by-layer reduction has a greater impact on soil infiltration rate than even distribution.(3)For the Kostiakov model of soil infiltration rate,the soil with residual film is also applicable.As the amount of residual film increases,the relative root mean square error of the fitting parameters of the Kostiakov model becomes larger,and the fitting effect is better than without residual film The soil has deteriorated.The layer-by-layer declining distribution is larger than the relative root mean square error of the fitting parameters of the uniform distribution,which shows that the fitting effect of the layer-by-layer declining distribution on the Kostiakov model of soil infiltration rate is worse than that of the uniform distribution.For the power function model of soil wet front migration,the soil with residual film is also applicable;as the amount of residual film increases,the relative root mean square error of the fitting parameters becomes larger,and the fitting effect is better than that of soil without residual film getting worse.The layer-by-layer decreasing distribution is larger than the relative root mean square error of the fitting parameters of the uniform distribution,indicating that the fitting effect is worse than that of the uniform distribution.(4)As the amount of residual film increases,the soil moisture in the shallow(0-25 cm)soil layer increases significantly.A large amount of soil moisture is distributed in the upper soil body,while the lower soil body has very little water distribution.As the amount of residual film increases,the upper soil moisture content is greater than that of the soil without residual film,and the lower soil The moisture content is also greater than the soil without residual film.In the upper soil(0-10 cm),the water content of the soil with uniform distribution and layer-by-layer distribution is significantly higher than that of the soil without residual film.,In the middle layer of soil(10-20 cm),the evenly distributed and gradually decreasing soil moisture content is successively lower than that of the non-residual film soil,the lower soil(20-30 cm),the evenly distributed and gradually decreasing soil moisture The rate is less than that of soil without residual film.The soil moisture content of the soil that is gradually decreasingly distributed in the upper and middle layers is generally greater than that of the uniform distribution,and the soil moisture content of the soil that is gradually decreasingly distributed in the middle and lower soils is less than the uniform distribution.(5)The average daily evapotranspiration of soil showed a trend of first decreasing,then fluctuating and then slowly decreasing,and when the amount of residual film was less than158.4 kg/hm~2,the change trend of daily evapotranspiration was not significantly different from that of normal soil.When the residual film amount is greater than 158.4 kg/hm~2,the average daily evaporation change trend first decreases and then increases,and slowly decreases after several fluctuations,which is significantly different from the soil without residual film,and will catch up with the soil without residual film in the later stage of evaporation.This indicates that the presence of residual film makes soil evaporation slow and unstable.When the amount of residual film is greater than 158.4 kg/hm~2,the difference is greater than that of normal soil.As the amount of residual film increases,the greater the amount of residual film,the more significant the reduction effect.When the amount of residual film is greater than 79.2 kg/hm2,the cumulative evaporation decreases significantly;the greater the amount of residual film,the more significant the reduction effect.(6)The layer-by-layer declining distribution in the early and late stages of evaporation is more retarded than the average daily evaporation,and the middle stage of the evaporation is less than the uniform distribution.At the same time,compared to the uniform distribution,the layer-by-layer declining distribution has a larger fluctuation,and the residual film is evenly distributed the average daily evapotranspiration change is relatively smoother than the declining distribution layer by layer.In the early stage of evaporation,the layer-by-layer decreasing distribution evaporates faster than the uniform distribution.In the middle and late stages of evaporation,the uniform distribution is faster than the layer-by-layer decreasing distribution.(7)For the Rose model of cumulative evaporation,as the amount of residual film increases,the relative root mean square error and the standard deviation of the fitting parameters gradually increase,which indicates that when residual film exists in the soil,the cumulative evaporation of the soil the effect of fitting Rose model is poor.The relative root mean square error of the layer-by-layer decreasing distribution and the standard deviation of the parameters are larger than the uniform distribution,which shows that the soil cumulative evaporation under the layer-by-layer decreasing distribution is worse than the uniform distribution. |
