Characteristics Research Of Fertilizer Concentration On Water And Solute Infiltration In Furrow Irrigation

There are many factors that affect the infiltration of furrow irrigation fertilizer solution.Although it is possible to study the law of soil water and nitrogen transport through experimental methods,it takes time and effort,and the results have certain limitations.With the continuous development of soil water-solute dynamics theory,numerical simulation methods provide a new way for its research.It has the advantage of quickly obtaining data of soil water and nitrogen transport processes under different initial conditions,in order to effectively reveal soil water and nitrogen The coupled migration feature provides the basis.Based on this,this study selected sand loam and tertiary clay loam in the first terrace of Yangling District,Shaanxi Province as the test soil,using indoor 1D vertical fertilizer infiltration and 2D soil box fertilizer infiltration experiments,combined with theory With the method of analysis and numerical simulation,the effect of the change of fertilizer solution(urea)concentration on soil infiltration characteristics was studied,and the following main research conclusions were obtained:(1)Through the one-dimensional vertical fertilizer infiltration test,the influence of fertilizer solution concentration on soil water and nitrogen transport characteristics was analyzed.The results showed that the clay loam and sandy loam increased with the increase of the infiltration fertilizer(urea)concentration,the cumulative infiltration volume and the wet peak migration distance increased,and a function relationship between the fertilizer solution concentration and the wet front migration distance was constructed The average relative error of the estimated value and the measured value are 3.52%and 3.55%respectively,indicating that the estimated formula between the concentration of the built fertilizer solution and the migration distance of the moist front is reliable;the concentration of the fertilizer solution is analyzed Effects of changes on soil moisture content,urea nitrogen,ammonium nitrogen(NH4+-N)and nitrate nitrogen(NO3--N)concentration distribution characteristics,the results show that clay loam and sandy loam are at the same soil depth,and the soil is moist The content of urea nitrogen,NH4+-N and NO3--N in the body increased with the increase of fertilizer concentration.(2)The numerical inversion method was used to estimate the soil hydraulic characteristic parameters of clay loam and sandy loam under different fertilizer(urea)concentrations.The results show that the saturated water content(?s),shape coefficient(n)and saturated hydraulic conductivity(Ks)have an exponential function relationship with the concentration of fertilizer solution under the experimental conditions in this paper,and their determination coefficients are all greater than 0.910;The values of ?s,n,Ks at 0.40 and 0.80 g/L in loam and sandy loam fertilizers were used,and the estimated results were used to simulate the cumulative infiltration volume and profile moisture content during the one-dimensional vertical infiltration process.The mean value of the root mean square error(RMSE)of the simulated and measured values of infiltration is 0.238 cm,the mean value of the Nash efficiency coefficient(ENS)is 0.993,and the mean value of the average absolute error(MAPE)is 2.81%;the simulated and measured values of the soil profile moisture content The mean root mean square error(RMSE)is 0.012 cm3 cm-3,the mean Nash efficiency coefficient(ENS)is 0.983,and the mean absolute error(MAPE)is 3.74%.The estimation formula of hydraulic characteristic parameters is reliable.(3)Using one-dimensional vertical fertilizer infiltration conditions to invert the soil hydraulic characteristic parameters under different fertilizer concentrations,the simulation analysis of two-dimensional furrow irrigation conditions of soil water movement process,and compared with the measured values.The results show that the relative errors between the simulated infiltration volume of the furrow irrigation and the migration distance of the moist front under different fertilizer concentrations and the experimental observations are at least 3.07%and 4.16%,and the largest are 7.26%and 9.52%,respectively.The developed soil hydraulic characteristics parameters can simulate the two-dimensional furrow irrigation soil water movement process;by analyzing the effect of fertilizer(urea)concentration on the infiltration characteristics of furrow irrigation,it further shows that fertilizer(urea)can improve soil infiltration to a certain extent.ability.The estimation model between the concentration of fertilizer solution and the cumulative infiltration volume and the distance of wetting front under the furrow irrigation condition was established and verified.The average relative error between the estimated value and the measured value was less than 10%;The estimation model between the liquid concentration and the cumulative infiltration volume and the migration distance of the moist front is reliable.(4)Based on the measured data at the end of the one-dimensional vertical fertilizer infiltration test and redistribution for one day,the soil solute transport parameters were retrieved and verified,and the absolute value of the relative error between the measured and simulated values of NH4+-N was found.The average values are all within 20%,indicating that the model simulation is consistent and that the inverted solute transport parameters are reliable.The obtained solute transport parameters are used to simulate and analyze different factors(fertilizer concentration,water depth in the ditch and the The width of the ditch bottom)affects the nitrogen transport characteristics.The results show that the distribution range of urea nitrogen,NH4+-N and NO3--N increases with the increase of fertilizer concentration,and the depth of the ditch and the width of the ditch bottom are vertical to urea nitrogen,NH4+-N and NO3--N.The effect of migration depth is not significant,but it has a significant effect on horizontal migration As the water depth in the ditch and the width of the ditch bottom increase,its horizontal distribution range gradually increases.