Using high-resolution monitoring to determine the preferential transport of enteric bacteria and antibiotic resistance genes from liquid pig manure applied to tile-drained arable fields

The degree of preferential transport through soil is crucial to its ability to serve as a barrier to prevent fecal pollutants from reaching surface water and groundwater when liquid manure is applied to arable tile-drained fields. Over a seven-month period, drainage was analyzed for enteric bacteria (CFU), genes [16S, tet(W), and Intl1], turbidity, and two anions (nitrate and chloride) following application of liquid pig manure to two tile-drained arable clayey till fields. Combined with high-resolution monitoring of the temperature and specific conductivity of drainage, the study established that (i) drainage was impacted directly by precipitation bypassing the soil via macropores, (ii) the majority of leached nitrate, chloride, enteric bacteria, and genes was preferentially transported through clayey tills, (iii) enteric bacteria, tet(W), and Intl1 were detected in drainage for five months following application of the liquid manure, and (iv) soils with high potential for preferential transport may not serve as a barrier to prevent pollutants in liquid manure from reaching the aquatic environment.