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

Abstract

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.

Impact of surface‐applied liquid manure on the drainage resistance profile of an agricultural tile‐drained clay till field

“…Stumpp and Maloszewski (2010) revealed in a lysimeter study that evapotranspiration from barley was ∼50% greater and preferential flow 75% less than from maize, which could indicate that crop type influences the risk of ARGs and MGEs leaching to aquatic environments. A study from the Silstrup field in 2015, where maize was planted, revealed more frequent drainage during the summer months (Bech et al., 2021). Reduced preferential flow may be explained by increased plant cover that would prevent precipitation reaching the bare soil surface, where the fraction that reached the soil surface, would infiltrate into a dense root zone where plant uptake would reduce infiltration into the subsurface.…”

“…The 16S gene was amplified with primer pair 1369F and 1492R (Suzuki et al, 2000), and the intI1 gene was amplified by primer pair LC1 and LC5 (Barraud et al, 2010), with an actual detection limit from 21 intI1 ml −1 drainage. For details on qPCR protocols, see Bech et al (2021). Briefly, PCR amplification was performed in 30-μl reactions containing 15 μl Lo-Rox Probe Mix (PCR Biosystems), 1.2 μl of both primers (100 pmol μl −1 ), 0.6 μl probe (Eurofins Genomics), 11 μl water, and 1 μl DNA template.…”

“…The field is characterized by long-term monitoring data series of precipitation, air temperature, evaporation, agricultural management, and location of the groundwater table. Furthermore, drainage is detailed by specific conductivity and temperature in the tile drain system, revealing that preferential flow and transport dominate percolation and leaching through the field (Bech et al, 2014(Bech et al, , 2021Kjaer et al, 2007;Rosenbom et al, 2015). Additional information about the field is provided in Lindhardt et al (2001).…”

“…This infiltration and redistribution within the soil is influenced by, among other things, the liquid manure properties, application methods, crop growth, and soil properties, where fine‐textured clayey soils can reduce bacterial redistribution (Amin et al., 2013, 2014). It is well known that the soil type, with its inherent transport pathways, influences the leaching risk of bacteria to surficial groundwater and surface water (Arnaud et al., 2015; Bech et al., 2014, 2021; Rosenbom et al., 2008, 2009). This risk of leaching is lower through homogeneous sandy soils that are more prone to piston‐like flow and transport conditions throughout the soil media (Aislabie et al., 2011; McLeod et al., 2019).…”

“…Water is an important carrier of antibiotic‐resistant bacteria (ARB) and antibiotic resistance genes (ARGs) from liquid manure–amended fields to human and animal populations and has recently been identified as a primary vector in the spread of antimicrobial resistance diseases in countries lacking access to clean water and sanitation (WEF, 2021). The occurrence of different ARGs in drainage, groundwater, and surface water has been linked to livestock facilities or liquid manure–amended fields (Bech et al., 2021; Chee‐Sanford et al., 2001; Koike et al., 2007; Uyaguari‐Díaz et al., 2018). Therefore, to protect water resources, it is essential to understand the fate of ARB and ARGs in the liquid manure–amended soil environment and the ability of the soil setting to prevent the spread of ARGs to drainage, surface water, and groundwater.…”