The design of conservation practices such as vegetative filter strips and riparian buffers typically focuses on surface runoff with subsurface nutrient transport usually assumed to be negligible. However, subsurface transport can become significant with preferential leaching and can negate the intended benefits of widely adopted control practices like riparian vegetative filter strips. To limit degradation of ecosystem services and improve resource use efficiency, foundational research is needed on surface/subsurface transport mechanisms and techniques to simulate these pathways. Through both theoretical development and application-based research, a new USDA-NIFA project was launched in 2017 with the following hypotheses: (i) if gravel outcrops and macropores are prevalent in riparian areas, then nutrients will rapidly leach through the surface to subsurface pathways, be rapidly transported to streams, and can limit the effectiveness of vegetative filter strips as conservation practices; and (ii) if mechanistic processes of preferential leaching and subsurface transport are incorporated into decision-support tools, then prediction of the performance of conservation practices such as riparian buffers will be improved. Simultaneous injection experiments using tracers, colloids, nitrate, and phosphorus will be performed in laboratory tests to identify surface and subsurface transport mechanisms through state-of- the-art monitoring techniques. Experimental data will test and refine decision-support tools for riparian buffers through the use of an innovative model (VFSmod) and new theories (source-responsive model) on the effect of macropores and preferential pathways. This research will have wide reaching implications; the effectiveness of conservative practices will be better understood and more appropriately implemented, ensuring that funds utilized to prevent nutrient transport are successful in providing long-term agricultural sustainability.

Influence of preferential flow on agrochemical transport through riparian buffers

254th National Meeting (2017)

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