Analysis and Numerical Simulation of Water and Nitrogen Transport Characteristics of Fertilizer Solution Infiltration in Wide Ridge and Furrow

To study the water and nitrogen transport characteristics during the infiltration process of fertilizer solution(ammonium nitrate) in wide furrows,the HYDRUS-2D model was used in laboratory experiments.The soil hydraulic characteristics parameters and solute transport parameters were derived by the numerical inversion method under different fertilizer concentrations.The water and nitrogen transports under different water contents and fertilizer concentrations were simulated.The results showed that the parameters obtained by the numerical inversion method were very accurate,and the HYDRUS-2D model was able to simulate nitrogen transport in furrow irrigation.Nitrate nitrogen was more likely to move with water,and ammonium nitrogen was more easily adsorbed by soil.The cumulative infiltration and wetting front migration distance under the condition of 600mg·L^-1 fertilizer concentration increased by 7.51% and 3.98%,respectively,compared with 300mg·L^-1 fertilizer concentration; and the cumulative infiltration and wetting front migration distance under the condition of 900mg·L^-1 fertilizer concentration increased by 14.36% and 9.6%,respectively,compared with 300mg·L^-1 fertilizer concentration.The content of nitrate nitrogen and ammonium nitrogen under the condition of 600mg·L^-1 fertilizer concentration increased by 101.6% and 84.62%,respectively,compared with 300mg·L^-1 fertilizer concentration; and the content of nitrate nitrogen and ammonium nitrogen under the condition of 900mg·L^-1 fertilizer concentration increased by 224.7% and 176.71%,respectively,compared with 300mg·L^-1 fertilizer concentration.The nitrate nitrogen and ammonium nitrogen in soil were redistributed after 5 days:the content of nitrate nitrogen and ammonium nitrogen in shallow soil decreased gradually,and the nitrification rate of ammonium nitrogen was lower than the rate of nitrate nitrogen moving to deep soil with water.