LEACHM (Leaching Estimation And Chemistry Model) and a modified LEACHM were used to predict NO{sub}3-N and atrazine transport in two Kansas soils. NO{sub}3-N and atrazine concentration data obtained from two monolith weighing lysimeters containing two different Kansas soils were used to calibrate and validate the nitrogen and pesticide versions of LEACHM. Since LEACHM (ver 3.0) does not include any means to deal with macropore flow, the macropore flow subroutine from RZWQM (Root Zone Water QualityModel) was incorporated into LEACHM. Measured concentrations of NO{sub}3-N and atrazine were compared with those predicted by LEACHM with and without the macropore flow subroutine. In general, concentrations predicted by both models tend to follow thetrend of measured concentrations. Addition of the macropore flow subroutine improved the predictions a little, especially for atrazine transport in silty clay loam soil. However no such improvement was observed in sandy loam soil. Overall, the results ofthis study showed that addition of the macropore flow component had potential for improving prediction capability of LEACHM in silty clay loam soils. The use of more site specific macroporosity data is likely to improve the model predictions.
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