Soil type influences the leaching of microbial indicators under natural rainfall following application of dairy shed effluent

Abstract

The ability of soil to function as a barrier between microbial pathogens in wastes and groundwater following application of animal wastes is dependent on soil structure. We irrigated soil lysimeters with dairy shed effluent at intervals of 3–4 months and monitored microbial indicators (somatic coliphage, faecal enterococci, Escherichia coli) in soil core leachates for 1 year. The lysimeters were maintained in a lysimeter facility under natural soil temperature and moisture regimes. Microbial indicators were rapidly transported to depth in well-structured Netherton clay loam soil. Peak concentrations of E. coli and somatic coliphage were detected immediately following dairy shed effluent application to Netherton clay loam soil, and E. coli continued to leach from the soil following rainfall. In contrast, microbial indicators were rarely detected in leachates from fine-structured Manawatu sandy loam soil. Potential for leaching was dependent on soil moisture conditions in Manawatu soil but not Netherton soil, where leaching occurred regardless. Dye studies confirmed that E. coli can be transported to depth by flow through continuous macropores in Netherton soils. However, in the main E. coli was retained in topsoil of Netherton and Manawatu soil.

Bacterial contamination of tile drainage water and shallow groundwater under different application methods of liquid swine manure

“…In contrast, there was immediate rainfall after manure application in 2008, with a cumulative annual rainfall of 1171 mm (Fig. Studies by Aislabie et al (2011) andTallon et al (2007) both show that in clay soils preferential flow can occur regardless of moisture status. The 30-year norm per annum for this area is 923.3 mm of rainfall, indicating that we had extremes of dry and wet years for this experiment.…”

Metrics Proposed To Prevent the Harvest of Leafy Green Crops Exposed to Floodwater Contaminated with Escherichia coli

“…The negative slope of the field likely contributed substantially to the rapid transport of E. coli observed in these experiments. The force of gravity likely promoted the movement of water down the slope, and the main transport mode of bacteria through soil is by water infiltration (19). The effects of field slope, as well as of soil texture and initial soil moisture, on the transit of bacteria through soil in floodwater conditions require further investigation.…”

“…In contrast to these results, the current study found no significant differences between the populations of E. coli recovered from the bulk and rhizosphere soils or between surface and subsurface soils in either season. This lack of effect may have occurred because the relatively high clay content of the soil (ϳ40%) led to the formation of macropores in the soil that promoted the spread of the bacteria beyond the plant roots (5,19).…”

Microbial ecology research in New Zealand

“…Elucidating the role of microorganisms in soil is thus an important research objective and, unsurprisingly, soil microbiology is a dynamic field internationally (East 2013;Fierer et al 2013). New Zealand itself has a productive history regarding the study of soil microbes including, but not limited to, investigations into carbon and nitrogen cycling (Singh et al 2007;Di et al 2009Di et al , 2010Das et al 2012;Hamonts et al 2013;Morales et al 2013Morales et al , 2015, interactions between above-and below-ground communities (Wardle et al 2004, influence of land management practices Simpson et al 2012;Wakelin et al 2012;Adair et al 2013) and carriage of (potentially pathogenic) bacteria through soil (McLeod et al 2008;Aislabie et al 2011).…”