Evaluation of NCSWAP Model Using Nitrate‐Leaching Data from Soil Core Lysimeters

Abstract

AbstractThe accuracy of the Ṉitrogen and C̱arbon cycling in S̱oil, W̱ater A̱nd P̱lant (NCSWAP) model to simulate (nitrate‐nitrogen) NO3‐N leaching from orchardgrass (Dactylis glomerata L.) pasture was evaluated using data collected from a 3‐yr leaching experiment conducted in central Pennsylvania on Hagerstown silt loam soil (fine, mixed, mesic, Typic Hapludalf). Nitrate leaching losses below the 1‐m depth from N‐fertilized orchardgrass sod were measured with intact soil core lysimeters (0.6‐m diam. by 1‐m long). Five N‐fertilizer treatments consisted of a control, urine application in the spring, urine application in the summer, urine application in the fall, and feces application in the summer were used to test the model. The model was calibrated using the data from 1993 to 1994 and then was validated using 1994 to 1995 and 1995 to 1996 water flow and NO3‐N leaching data. Statistical analysis indicated a good fit between field measured and predicted NO3‐N leaching for most treatments in each year. The model simulations of water flow and NO3‐N leaching losses below the 1‐m depth were compared with the meau of measured field data for these 3 yr. The results of this study showed that the NCSWAP model performed well and accurately simulated water flow and total annual NO3‐N loss through leaching below the 1‐m depth under orchardgrass pasture. However, the model failed to produce accurate simulations for the feces treatment in 1994 to 1995. The simulation error in the feces treatment seemed to be related to N mineralization process in the model. Generally, the results of this study suggest that the NCSWAP model can be used for predicting NO3‐N leached annually from pastured orchardgrass.