SIMULATION OF NITROGEN AND PHOSPHORUS LEACHING IN A STRUCTURED SOIL USING GLEAMS AND A NEW SUBMODEL, PARTLE

The potential negative impact of agricultural chemicals on the quality of surface and ground water resources is a worldwide concern. The com plexity of factors affecting nonpoint source pollution makes experimen tal assessment of the environmental consequences of different manageme nt strategies laborious and expensive. Therefore, one feasible method is to use the existing research database to validate and modify the co mputer models, then use the models to simulate the long-term impact of these systems. In this study the hydrologic and nutrient loss data fr om a subsurface drained, structured clay soil in southwest Sweden was used to examine the applicability of GLEAMS to simulate the drainage d ischarge and N and P concentrations in the discharge water The results indicated that GLEAMS was capable of simulating drainage discharge, n itrate-N and dissolved-P losses reasonably well, but there were no alg orithms to simulate the particulate-P losses via drain tiles. Therefor e, a submodel, ''PARTLE'' was developed and tested. Our results indica te that the PARTLE submodel, in association with the GLEAMS model, pro vided reasonable estimates of particulate-P loss via drainage in this soil. The study concluded that considering the impact of preferential flow and the ratio of annual drainage discharge to annual precipitatio n is necessary for proper predictions of particulate-P in structured s ails.