In Situ Method for Measuring Water Fluxes, Sediment, and Phosphorus at High Drip Infiltrometer Intensities in the Upper Half Meter of a Tilled Clay Soil

The first step in evaluating phosphorus (P) loss risks should be to investigate the topsoil, which is generally considered a source of P transport via macropore flow. A procedure is presented for in situ measurement of hydraulic response times, critical water outflow rates, as well as turbidity (T), sediment (SC), and total phosphorus (Ptot) concentrations in outflowing soil water solution from the upper half meter of a clay soil. The method applies to a range of controlled experimental rainfall intensities from a drip infiltrometer, and a zero-tension collection tray located at 0.5 m depth through which percolating water/sediment solution is sampled. Reasonable positive relationships were observed between T, SC, and Ptot versus steady output flow rates (qs). Dependencies were strong between Ptot and each of qs and T, and weaker between Ptot and SC. The methods require further validation and will be further developed in upcoming studies.