| The Hetao irrigation District is a typical arid irrigated area in China,with rare precipitation,intense evaporation and soil salinity,which has been restricting regional agricultural development.As a common agronomic measure,plastic film mulching can save water and soil moisture,improve crop water consumption structure,increase yield and water use efficiency.Although the effect of measures has been widely used in the northwest areas,but in view of the Hetao irrigation District,plastic mulching on soil hydrothermal condition,different color film mulching how to affect the internal mechanism is a lack of system research,this study adopts field experiment and model simulation,two kinds of irrigation water was studied under different film mulching on spring maize growth and the influence of farmland evaporation.The field experiment was carried out in Shuguang Experimental Station of Hetao Irrigation District from 2019 to 2020.The split plot design was adopted,and three main plots of black film mulching(M2),transparent film mulching(M1),and nonmulching(M0)were set.Under each main plot,two irrigation amounts were set,including full irrigation(500 mm,I1)and Deficit irrigation(300 mm,I2).The plant growth and root growth of spring maize under different treatments were observed.Soil water content,field evapotranspiration,evapotranspiration and their proportions were measured and calculated by water balance method during the growth period of maize.At the same time,SIMDualkc model was used to simulate soil moisture,crop coefficient and root zone water balance under different plastic film mulching conditions,so as to understand the water consumption structure and water-saving principle of plastic film mulching under different plastic film mulching treatments,and to provide theoretical basis for the selection of film mulching color in The Hetao irrigation District.Through the above research,the following results were obtained:(1)Film-mulching treatment of farmland water storage and soil moisture conservation effect is obvious.The soil moisture content of 0～120 cm was increased by plastic film mulching.The water saving of transparent film mulching and black film mulching was 5.59%and 6.29%,respectively,compared with that of non-mulching.The water retention effect of film mulching is mainly reflected in the early growth stage,and the soil layer of 0～20 cm has a significant effect.The vertical distribution trend of soil water under different plastic film mulching and irrigation measures was the same.The water content of 0-20 cm soil layer was mainly consumed in the early growth stage,and the water content of 20-80 cm soil layer was mainly consumed in the late growth stage.Different mulching and irrigation treatments had significant effects on evapotranspiration,soil evaporation and transpiration of spring maize.Compared with non-mulching,transparent plastic mulching and black plastic mulching reduced evapotranspiration by 5.52% and 7.93%,respectively.The main reason was that plastic mulching significantly reduced soil evaporation,which was 28.94% and33.17% respectively for transparent plastic mulching and black plastic mulching,leading to the decrease of E/ET under different mulching methods.The plastic film mulching treatment can convert more invalid soil evaporation water into transpiration water.(2)Compared with that of non-film mulching,The leaf area index(LAI)of transparent film mulching and black film mulching increased by 15.05% and 3.1%,respectively;I1 was7.45% higher than I2.At the same time,film mulching increased the dry matter of aboveground parts,and there was no difference between film mulching and non-film mulching in the early stage of spring maize,but gradually greater than non-film mulching in the late stage of spring maize.Transparent film mulching increased 1.8% and 14.2%respectively compared with black film mulching and non-film mulching.The root characteristics(root surface area,root volume and root diameter)of Spring Maize in all treatments were consistent,and reached a stable level at the filling stage.Plastic film mulching could significantly improve the heel surface area,root volume and root diameter of maize,but with the end of growth period,the gap gradually became smaller.Compared with non-plastic film mulching,transparent film mulching and black film mulching increased by23.38%,12.33%,17.69%,17.73%,8.43% and 12.93% at grain filling stage,respectively;The results showed that mulching treatment could increase the root length and dry weight of roots in 0～100 cm soil layer,and increase the root length density of crops.The root length density of transparent film mulching and black film mulching increased by 24.75% and18.88% compared with that of non-film mulching,mainly in 0～40 cm soil layer.The dry weight of roots was mainly distributed in 0～20 cm soil layer,accounting for 84.55% of the total in 2 years.The dry weight of roots was significantly increased by film mulching.Compared with non-film mulching,transparent film mulching and black film mulching increased by 18.28% and 15.92% in each growth stage.(3)Plastic film mulching could significantly increase ear length,grain number per ear and 100 grain weight,and then improve crop yield and water use efficiency;In 2019,the yield of transparent film and black film increased by 20.42% and 9.58% compared with non-film mulching;In 2020,transparent plastic film treatment and black plastic film treatment will increase by 17.96% and 12.33% compared with non-plastic film treatment.Compared with black film mulching,transparent film mulching increased by 9.89% and5.01% in 2 years,respectively.The water use efficiency(WUE)of transparent film mulching and black film mulching increased by 26.07% and 20.34% compared with non-film mulching.In 2020,transparent plastic film treatment and black plastic film treatment will increase by 17.96% and 12.33% compared with non-plastic film treatment.Compared with black film mulching,transparent film mulching increased by 9.89% and 5.01% in 2 years,respectively.The water use efficiency(WUE)of transparent film mulching and black film mulching increased by 26.07% and 20.34% compared with that of non film mulching.(4)Simdualkc model can simulate the change of soil moisture under different mulching conditions,and simdualkc model can be used to estimate the crop coefficient under different mulching treatments.The basic crop coefficient of black film treatment is 0.176,1.11 and0.35 in early growth stage,middle growth stage and late growth stage,respectively;Transparent plastic film treatment 0.18,1.116,0.4;non-film mulching treatment 0.15,1.06,0.25,it can be seen that film mulching can improve crop coefficient.Film mulching can effectively adjust the water balance of farmland,improve the water consumption structure,and make more soil water used for crop transpiration.Transparent plastic film can make more use of capillary to increase water in later growth period.In conclusion,The field experiment was combined with model simulation,Under the irrigation amount of 300 mm+ transparent plastic film,the water use efficiency of spring maize was the highest.The results can provide theoretical basis and technical support for the selection of film mulching color and the establishment of irrigation system in Inner Mongolia Hetao Irrigation District. |
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