EVALUATION OF NCSWAP MODEL USING NITRATE-LEACHING DATA FROM SOIL CORELYSIMETERS

The accuracy of the Nitrogen and Carbon cycling in Soil, Water And Pla nt (NCSWAP) model to simulate (nitrate-nitrogen) NO3-N leaching from o rchardgrass (Dactylis glomerata L.) pasture was evaluated using data c ollected from a 3-yr leaching experiment conducted in central Pennsylv ania on Hagerstown silt loam soil (fine, mired, mesic, Typic Hapludalf ). Nitrate leaching losses below the I-m depth from N-fertilized orcha rdgrass sod were measured with intact soil core lysimeters (0.6-m diam . by 1-m long), Five N-fertilizer treatments consisted of a control, u rine application in the spring, urine application in the summer, urine application in the fall, and feces application in the summer were use d 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 wa ter flow and NO3-N leaching data. Statistical analysis indicated a goo d fit between field measured and predicted NO3-N leaching for most tre atments in each year. The model simulations of water flow and NO3-N le aching losses below the l-m depth were compared with the mean of measu red field data for these 3 yr, The results of this study showed that t he NCSWAP model performed well and accurately simulated water flow and total annual NO3-N loss through leaching below the l-m depth under or chardgrass pasture, However, the model failed to produce accurate simu lations for the feces treatment in 1994 to 1995. The simulation error in the feces treatment seemed to be related to N mineralization proces s in the model, Generally, the results of this study suggest that the NCSWAP model can be used for predicting NO3-N leached annually from pa stured orchardgrass.