Study On Soil Water-temperature In Spring Maize Cropland And Water Use Efficiency In Rain-fed Areas

Maize is the largest crop in China,and the increase of maize production in Northeast China contributes more than 78%to the increase of grain yields in the whole country.Uneven rainfall distribution and extreme cold temperature in spring are the main factors which restrict the increase of maize production in rain-fed areas of Northeast China.Therefore,how to use limited rainfall resources to attain high efficient water use in agriculture is of great significance to the stable and high yields of maize in rain-fed areas of Northeast China.On the basis of field experiments,combined with meteorological data,soil data,crop data and field management data,the parameters of HYDRUS-1D water vapor-heat coupling model were sensitively analyzed,calibrated and verificated.Soil water and temperature changes under no-mulching and black film mulching（75000plants/hm²）were simulated;The effects of different mulching treatments（no-mulching and black film mulching）and planting densities（60000 plants/hm²,75000 plants/hm²and 90000 plants/hm²）on maize water use efficiency based on dry matter and economic yield were analyzed;Under 75000 plant/hm²planting density,the relationship between soil moisture,temperature and water use efficiency of maize was further analyzed.The main conclusions are as follows:（1）Sensitivity analysis,calibration and verification were carried out of model parameters.Among soil water parameters,soil moisture is most sensitive to the index of aperture（n）and soil saturated moisture content（θs）,while soil thermal parameters have less influence on soil moisture.Among crop parameters,albedo has the greatest impact on soil moisture,followed by leaf area index（LAI）.Among meteorological parameters,Rainfall has the greatest impact on soil moisture,followed by temperature（T）.The main sensitive parameters affecting soil temperature are soil thermal parameters,followed by meteorological parameters and crop parameters.Soil water parameters have a weak influence on soil temperature.Soil water parameters have a greater impact on soil evaporation,but a smaller impact on plant transpiration.Soil evaporation is sensitive to the changes of soil thermal conductivity coefficient b1,b2,b3,and LAI,Albedo in crop parameters,while plant transpiration is sensitive to the changes of LAI,plant height（CH）and Albedo.Based on the data of soil moisture and temperature measured in no-mulching and black film mulching treatment in 2016 and2017,the model was calibrated and validated.Results showed that,the model can well simulate the changes of soil moisture and temperature.（2）Based on the HYDRUS-1D model,the soil moisture of no-mulching and black film treatment was simulated.Under the condition of continuous no rainfall,the soil moisture of no-mulching decreased gradually with time,and it basically unchanged of black film treatment.At the same soil layer,the water flux of no-mulching to upper soil due to capillary force is more than that of black film treatment;From the point of view of single rainfall,the total increase of water first increases and then decreases,the total infiltration decreases gradually with the increase of soil depth.The fluctuation of evaporation in no-mulching was greater than that in the black film treatment.The average daily transpiration intensity,daily water consumption and average daily water consumption intensity of no-mulching and black-film treatments increased first and then decreased with the growth of maize.The average daily transpiration intensity of black-film treatment was higher than that of no-mulching treatment,but the water consumption of no-mulching treatment was significantly higher than that of black-film treatment,and the variation of evaporation intensity is contrary to transpiration intensity.The change of soil water storage is greater with the increase of precipitation,and the depth of affected soil is deeper.The water uptake rate of maize roots under different treatments increased first and then decreased.The maximum water uptake rate of maize roots occurred at heading stage.Soil water resources in no-mulching and black film treatments at different growth stages of maize showed a state of supply.（3）Based on the HYDRUS-1D model,the soil temperature of no-mulching and black film treatment was simulated.The soil temperature of no-mulching and black film treatments showed a sinusoidal law of diurnal variation.With the increase of soil depth,the diurnal amplitude of soil temperature decreased,and the time of maximum and minimum soil temperatures gradually lagged behind;the diurnal variation of soil temperature of the same soil layer of different treatments decreased with the growth period;At the same soil depth,the effective accumulated temperature of black film soil is greater than that of no-mulching treatment,and the gap is widening with the development of growth process.However,with the increase of soil depth,the difference of effective accumulated temperature between no-mulching and black film soil is decreasing.The proportion of effective accumulated temperature to total accumulated temperature in different growth stages of maize ranges from large to small by:seedling>maturity>jointing>filling>heading.（4）The effects of different mulching and planting density on water use efficiency of maize were analyzed.At heading stage,film mulching has not significant effects on WUE_ET·B,but at other growth stages,the effects of film mulching,planting density and their interaction have significant effects on WUE_ET·B.With the increase of planting density,the water use efficiency of maize based on dry matter increased gradually.Film mulching and planting density have significant effects on water use efficiency based on economic yield(WUE_ET·Y).WUE_ET·Ywas positively correlated with WUE_ET·Bat seedling stage and heading stage.（5）The relationship between soil moisture,temperature and water use efficiency was studied.The bigger ET,E and E/ET is,the smaller WUE_ET·Bof maize is.The bigger ET and E/ET is,the smaller economic yield of maize is.Economic yield was positively correlated with 0-25 cm soil accumulated temperature and 0-30 cm soil average moisture.Grey correlation analysis showed that 0-25 cm soil accumulated temperature and 0-30 cm soil average moisture could promote yield which is mainly due to the increase of grain number per ear and 100-grain weight of maize with suitable tillage temperature and average soil moisture,so as to increase production.0-25 cm soil accumulated temperature was positively correlated with ET,E,WUE_ET·Band WUE_ET·Y.0-60 cm layers average soil water moisture were positively correlated with WUE_ET·Band WUE_ET·Y.