Applying Hydropedology To Nutrient Management In The Northeastern US: Lessons Learned From The Mahantango Creek Experimental Watershed.

Understanding the nature and extent of soils prone to nutrient losses in runoff is central to the success of nutrient management in agricultural watersheds. Drawing upon case studies from USDA-ARS’s Mahantango Creek Experimental Watershed in east-central Pennsylvania, this presentation will discuss the application of hydropedology to nutrient management in landscapes where fragipan soil horizons unduly influence runoff generation and nutrient transport. Hydropedology seeks to comprehend the effect of soil morphology on hydrology in the pedosphere, and is an ideal lens through which to examine hydrologic and nutrient transport processes influenced by fragipan soils as well as the implications of those processes for nutrient management. For example, we are monitoring hillslope trenches in two subcatchments of Mahantango Creek to test the hypothesis that fragipan soils contribute disproportionately to surface and subsurface runoff generation and nutrient losses relative to well-drained upland soils. We are also conducting geophysical surveys to explore the premise that discontinuities in fragipans may be focal points for groundwater upwelling, potentially connecting upland recharge zones receiving fertilizers and manures with areas of riparian seepage that drain to streams. Finally, we are applying pedologic models to LiDAR elevation data to predict the distribution and spatial extent of fragipans and other restrictive layers in soils. The resultant restrictive layer maps can be used in short- and long-range nutrient management planning tools to show where nutrient runoff potential is greatest.