Simulation of nitrogen transport and transformation in dry-crop peanut land profiles in a red soil zone
To investigate the factors influencing the vertical migration of nitrogen and its loss characteristics in peanut plantations in a red soil area,we used HYDRUS-1D model to construct a coupled water-nitrogen model applicable to red soil areas.The model was combined with field monitoring data and indoor leaching experiment results to rate and validate the model parameters.The calibrated model was used to simulate the dynamic migration and transformation process of nitrogen in the soil profile under different environmental conditions in the study area.The results showed that the agreement between the simulated and measured values of the HYDRUS-1D model was high,and the model could be used to simulate soil water and nitrogen transport processes at different depths in peanut fields.Soil ammonium N and nitrate N contents increased rapidly after rainfall fertilizer application,and then decreased.Changes in fertilizer application mainly affected the nitrogen concentration in the 0-40 cm soil layer,while changes in rainfall affected nitrogen transport and transformation in the 0-80 cm soil layer.In addition,the nitrogen content decreased with increasing soil depth.The simulation results showed that when the nitrogen application rate was 225.0 kg·hm-2 the nitrate nitrogen concentration in the 80 cm soil layer increased to at least 1 mg·L-1 during the rainy season when the total rainfall was more than 173 mm and the intensity of rainfall was greater than 11 mm·d-1 and during the dry season when strong rainfall events occurred,during which the total rainfall was more than 135 mm and the intensity of rainfall was greater than 135 mm·d-1.The deep soil nitrogen response to rainfall was affected by the clay texture of the red soil,with some lagging effect.With the increase in fertilizer application,the flux of nitrogen uptake by crop roots increased,but the ratio of nitrogen uptake to nitrogen fertilizer application decreased.The effect of rainfall on nitrogen uptake by the roots was relatively small.During the peanut growing season,the main form of nitrogen loss in the soil was nitrate nitrogen leaching.Simulation analysis showed that both rainfall and fertilizer application affected nitrate N loss.The increase in rainfall significantly increased nitrate N leaching,and the cumulative nitrate N loss ranged from 5.23-42.97 kg·hm-2,which demonstrated that the potential contamination of nitrate in the groundwater in red soil zones where peanuts are grown cannot be ignored.
red soilammonium nitrogennitrate nitrogennitrogen transportHYDRUS-1D
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