Sources and local factors influencing the effectiveness of implementing nutrient management practices for pollution...

Best management practice (BMP) implementation strategies have often overlooked the integration of both nutrient source and local environmental factors. This research developed a targeted BMP implementation approach using parcel-level nutrient load contribution alongside land use type, slope, depth to water table, stream order, and distance to watershed outlets. The Upper Kissimmee and Taylor Creek and Nubbin Slough watersheds were selected to represent contrasting land use patterns. Ten incremental scenarios, ranging from 10% to 100% of source cells' cumulative nutrient contribution, were mapped in ArcMap 10.4. Four BMPs, chosen based on technological and economic criteria, were applied to suitable land uses, and nutrient reduction parameters were incorporated into the Watershed Assessment Model to simulate watershed-scale effects. Results showed the greatest TN reduction of 1452 and 1204 tons under the 100% scenario for two watersheds, while the highest cost effectiveness occurred under the 10% scenario, with 1.33 and 1.82 tons of TN removed per million dollars. BMPs implemented in citrus groves and improved pasture contributed most to TN reduction. Marginal nutrient reduction was primarily influenced by the additional nutrient reduction and costs associated with newly added land use types, while changes in existing land use types dominated overall nutrient reduction. To maximize watershed-scale nutrient load reduction, BMPs should be prioritized in source cells with higher baseline nutrient load, greater contribution of nutrient load, and near higher-order streams.