Simulation On Soil Water Dynamics Of Rice Field

Soil water is one of the important environment limitation factors,Rice is the first corp of food supplies in our country,water resource is serious shortage in China. Rice production safety will also be limited by serious scarce of water resource. Seasonal soil water deficit in rice field will reduce rice yield so as to endanger food security.Strengthening the study of rice field soil water dynamic changes can be achieved the accurately prediction of soil water content dynamic changes in rice field, make fully use of existing water resource,produce water saving schemes and achieve the scientific management of water resource in rice fields.Through actual experiment some soil hydraulic characteristic parameters was determined first,sampled in each 10 centimeter depth of 0-50 centimeters soil profiles.Soil particle size analysis was made in laboratory to determined soil texture. Soil bulk density,Saturated water content and saturated hydraulic conductivity were also measured.Soil hydraulic characteristic parameters are fitted through RETC software based on soil particle analysis,and important parameter's values in soil water dynamic equations are obtained such as soil water characteristic curve,θ_s,θ_r,K_s,α,m,n,etc.The testing in rice field also proved that the simulation of parameters from RETC software is useful,methods also avoids the complex actual physical parameters testing in fields.Soil is saturated when flooded in rice field,based on Darcy theorey and water balance expression a simulation model in paddy rice field was obtained.The rice field testing proved that the simulation model can use to simulate the dynamic of water layer depth above rice field surface.Based on the theory of soil hydrodynamics,Richards equation and conservation of mass,add some conditions,θexpressed equation and h expressed equation were used to simulate the soil water movement in rice field.With the measured data analysis results of simulation show that the simulation model basing onθexpression forecasts the water content in surface and deep soil profile is better,and forecast the middle soil profiles should be improve,The simulation results basing on h expression are very close to the actual measured values,h expression can accurately simulate the soil water dynamic changes in each depth of soil profile.