| The southern areas of the Loess Plateau belongs to the subtropical monsoon climate,because uneven rainfall distribution in the summer maize growth period,water of crop supply and demand is not coordinated,seriously affecting the crop growth and yield formation.The plastic film mulching can regulate the supply and demand of soil moisture and improve the crop growth status,which is of great significance to crop yield and stability.,the dynamic monitoring of farmland soil moisture was carried out using TRIME-TDR and EM50.The soil moisture of summer maize was simulated by HYDRUS-2D model.Finally,the model was used to study the soil water movement,and the law of water retention was revealed.By studying the cultivation method of plastic film mulching in Guanzhong dry land area,it has a positive effect on understanding the soil water changes and improving the yield of summer maize,so as to provide the necessary theoretical basis for perfecting the technology of film and rainwater harvesting.Through the experimental study,the conclusions are as follows:(1)after harvesting in summer maize,the cover treatment can significantly improve the moisture content of shallow soil.The soil moisture content of 0-40 cm is the most intense.In the rotation system,the winter wheat under plastic film mulching consumed deep soil moisture,but after the whole growth period of maize,the deep water content of the soil is replenished,which is beneficial to the ecological sustainability of crop rotation.In the crop water consumption,the plastic film mulching changed the temporal and spatial distribution of crop water consumption.Under the cover conditions,the water consumption of summer maize decreased in the early stage;the water consumption increased in the middle growth and the later water consumption decreased.The average water use efficiency of RW and RE increased by 36.73% and 33.44%,respectively.The effect of the treatment of RW was better than RE.The film effectively improves the efficiency of rainfall utilization and optimizes the production potential of rainfall.Three-year average rainfall efficiency RW and RE increased by 23.91% and 29.06% compared with CK.(2)the model of HYDRUS-2D was calibrated with the measured water content under the field in 2014.The model was used to verify the soil moisture movement.From three evaluation indicators of the RMSE,MAE,MRE,the evaluation index range of 0.011-0.030 cm3.cm-3,0.0001-0.027 cm3.cm-3 and 3.62-10.49%.The model is suitable for the semi-humid zone in the Loess Plateau,which can make up the deficiencies of the field experiment and provide theoretical and data support for the suitable cropland planting method in the Loess Plateau.The difference between the measured value and the simulated value of soil surface water content is mainly due to the change of soil properties.The measured residual soil water content is higher than the inverse value,and the measured saturated water content is lower than the inverse value.The saturated hydraulic conductivity of the soil surface(0-20cm)is different from that of the measured value,which is mainly due to the change of soil physical properties,which makes the simulation data of the field and the indoor test data differ greatly.(3)exploring the change of water quantity and water fluxes in the furrow and ridge can be found in the summer maize growing season with uneven spatial and temporal distribution.The ridge is used as an independent unit.During the rain,the ridge area is stored as a "reservoir".Seasonal drought,the ridge of water will be replenished to the furrow for soil evaporation and root absorption.The furrow ridge ratios(furrow: ridge)for 20: 40,25: 35,30: 30,35: 25 four gradients were set.It can be found that the main difference about different ratios furrow to ridge in soil evaporation and soil water storage.This shows that the film to reduce evaporation is the main reason for water retention and water storage. |
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