Multipoint High-Frequency Sampling System to Gain Deeper Insights on the Fate of Nitrate in Artificially Drained Fields

Abstract

The application of high-frequency measurements could potentially enhance current understanding of the hydrology and biogeochemistry of artificially drained agricultural lands. In addition to intensive drainage flow measurements (every 15 min), two high-frequency sampling systems were implanted to monitor, on an hourly basis, nitrate-nitrogen concentrations [NO3-N] in the drainage outlet and at multiple points in the shallow groundwater. This paper provides a description of this novel in situ measurement system and reports example data obtained during a rainfall event. High-frequency measurements of [NO3-N] at the field edge could potentially advance understanding of agricultural drainage systems, including increased accuracy of (1) nitrate loading estimates, (2) spatiotemporal dynamics of nitrate export during rainfall events, and (3) nonlinear hydrochemical (C-Q) relationship. Combining high-frequency measurements of [NO3-N] in drainage water at the field edge and shallow groundwater within the field gives the opportunity for the next steps in identifying and quantifying key processes, mechanisms, hot moments, and active zones that control nitrate dynamics in drained agricultural land.