Study On Characteristics Of Soil Water Movement And Nitrogen Transportation Under Conditions Of Different Slopes And Fertilizations

In order to reduce agricultural non-point source pollution,to quantitatively understand the nitrogen migration in soil under different conditions is very essential,which will improve the effective utilization rate of nitrogen fertilizer.The Agricultural Valley Experimental Research Base located in the Qujialing Management District,Jingmen City,Hubei Province was selected to conduct bared field experiments.Soil water samples at different periods were collected,and the solute concentrations were analyzed.According to the observed data,the soil hydrodynamic parameters and nitrogen transport and transformation parameters are determined.The HYDRUS-2D model is established to simulate the water movement and nitrogen transport process in soil.Through parameters identification,the model was used to simulate the observed data.Six field experiments were analyzed to study the effects of slope and fertilization types on water flow and nitrogen transport in soil.Based on the analysis of the water flow characteristics in the soil,it is found that from the flat slope of 0°,the gentle slope of 5°to the steep slope of 20°,the start time of collecting soil water decreased with the slope increase.As a whole,with the increase of slope,the soil water flux gradually decreased,and the peak of the soil water flux decreased.The larger the slope,the earlier peak start time of soil water flux.The greater the soil water flux,the lower the nitrogen concentration.After the field experiment end,the soil water flux decreases rapidly,which causes a small increase for the nitrogen concentration.Regardless of whether the fertilization type is urea or animal feces,the power function can be used to simulate the relationship between the cumulative nitrogen flux and cumulative water flux,and R~2can be greater than 0.98,with a minimum value of 0.9894 and a maximum value of 0.9998.This proves that the cumulative nitrogen and the cumulative water flux in soil have a strong positive correlation.On July 30,on August 9,August 19 three rainfall events,through the HYDRUS-2 d model to build water movement and solute transport model,to simulate the soil groove in vertical direction and horizontal direction under three types of slope on the ammonia nitrate nitrogen migration,and the model of moisture migration parameters,such as nitrogen migration parameters to adjust,makes the model run fitting degree is higher,the simulated values and the measured values of statistical parameters are according to the simulation results is better,to demonstrate against the bare land with no vegetation soil conditions,Hydrus-2d can be used to simulate the nitrogen and water transport processes under rainfall conditions in a short period of time.