Fate and transport of nitrogen compounds in a cold region soil using DRAINMOD

Freezing and thawing cycles in soil can have a significant effect on field hydrology, which, in turn, can have a major influence on the fate and transport of agricultural chemicals. This study was conducted to evaluate the hydrological performance and NO3−-N movement of the DRAINMOD 5.1 model with respect to freezing/thawing conditions. Measurements made in the years 1999 and 2000 at an experimental site in Truro, Nova Scotia, Canada on four test plots receiving inorganic fertilizer were used to test the model. Monthly subsurface drainage outflows, simulated using the original and DRAINMOD 5.1, were compared with the observed values. The results showed that the original DRAINMOD overestimated drain outflows during the colder months. The average difference between the monthly drainage outflows, simulated with DRAINMOD 5.1, and the observed values ranged from −0.35 to −1.42 mm. Since the new model predicted the timing and magnitude of drainage events quite well and also did a much better job of simulating the hydrology of a colder region, as compared to the original model, it was used to simulate fate and transport of nitrogen compounds. The model was calibrated with the data from two test plots, and validated with the data from the remaining two plots. The difference between the simulated and observed total NO3−-N losses over a period of 2 years were, respectively, 1.32 and 1.40 kg N/ha for the calibration plots. For validation plots, they were −1.64 and 0.97 kg N/ha, respectively. These results indicate that the DRAINMOD 5.1 model, performed satisfactorily, and may be used to estimate NO3−-N losses through drainage outflow in colder regions.