Tile Water Bacteria and Modeling Macropore Flow in Silt-Loam Structured Field Soils

The MACRO soil water flow model adequately predicted liquid municipal biosolid (LMB) application and precipitation induced tile discharges. LMB was applied via two different application methods; AerWay SSD (Sub Surface Deposition) and a Kongskilde Vibro-Shank-type injection system. The model was able to satisfactorily simulate wetting-front movement through soil profiles. The model, however, could not reproduce the observed tile discharge values under dry, cracking soil conditions. Modeling results showed that LMB induced flow moved instantaneously through the soil profile to tile drains for the injection method. Tile discharge changes for the AerWay method were not notably detected. Bacteria concentrations in tile water were evaluated for each application approach, and tended to decrease over time presumably due to macropore flushing and dilution effects.