膜下滴灌减氮棉田土壤水氮迁移过程模拟OA

Through a drip irrigation micro-plot experiment with four nitrogen application rates:normal nitrogen(100％N),10％reduction(90％N),20％reduction(80％N),and 30％reduction(70％N),this study moni-tored soil moisture and NO3--N levels at key locations:below the dripper(irrigation core zone),below the cotton row(root-dense zone),and below the wide row(root-sparse zone).The HYDRUS-2D model was used to analyze the transport processes of water and nitrogen under reduced nitrogen drip irrigation in cotton fields.The results showed that the HYDRUS-2D model effectively simulated soil moisture and NO3--N dynamics,with coefficients of determination R2 of water ranging from 0.31 to 0.98,and R2 of nitrogen ranging from 0.44 to 0.99,relative error of the mean absolute error(REMAE)varying between 6.00％and 20.00％,and relative root mean square error(RERMSE)varying between 6.50％and 23.33％.The simulation revealed significant spatial heterogeneity in soil moisture under drip irrigation:sufficient water replenishment occurred in the dripper zone,soil moisture in the cot-ton row zone was strongly influenced by root water uptake,and the wide row zone experienced persistent water defi-cit.Soil NO3--N was primarily accumulated in the 0-30 cm soil layer,with peak concentrations following the spatial pattern:below the dripper(63.00 mg·kg-1)＜below the wide row(68.42 mg·kg-1)＜below the cotton row(63.4 mg·kg-1).The peak NO3--N values in each zone decreased gradiently as nitrogen reduction increased.Both measured and simulated values of soil NO3--N indicated that the 20％nitrogen reduction treatment achieved the best nitrogen regulation effect,reducing NO3--N by 20.2％-22.7％compared to normal nitrogen application.This effec-tively minimized leaching without negatively affecting cotton growth.