Response of microbial communities to long-term fertilization depends on their microhabitat

Abstract

The objective of this study was to characterize the microbial communities attached to clay (< 2 μm), fine silt (2-20 μm), coarse silt (20-63 μm) and sand-sized fractions [> 63 μm; including particulate organic matter (POM)] of an arable soil and analyse their response to more than 100 years of two different fertilization regimes. Mild ultrasonic dispersal, wet-sieving and centrifugation allowed the separation of soil particles with the majority of bacterial cells and DNA still attached. Fertilizations increased soil organic carbon (SOC), total DNA and the abundance of bacterial, archaeal and fungal rRNA genes more strongly in the larger-sized fractions than in fine silt, and no effect was seen with clay, the latter representing above 70% of the total microbial populations. A highly positive correlation was found between microbial rRNA genes and the surface area provided by the particles, while the correlation with SOC was lower, indicating a particle-size-specific heterogeneous effect of SOC. The prokaryotic diversity responded more strongly to fertilization in the larger particles but not with clay. Overall, these results demonstrate that microbial responsiveness to long-term fertilization declined with smaller particle sizes and that especially clay fractions exhibit a high buffering capacity protecting microbial cells against changes even after 100 years under different agricultural management.

Importance of soil organic matter for the diversity of microorganisms involved in the degradation of organic pollutants

“…Apparently, these dominant fractions also caused the overall contrasting effects of soil organic matter seen in the non-fractionated soils: although the negative correlation between SOC and sorbed phenol was due to processes at the clay fraction, the positive correlation of DCP with SOC was Jenkinson and Powlson (1976). ***Achieved using the ultrasonication wet-sieving centrifugation method according to Amelung et al (1998), modified by Neumann et al (2013).…”

“…Soil fractionation was based on the ultrasonication wet-sieving centrifugation protocol described by Amelung et al (1998), with modifications described elsewhere (Neumann et al, 2013). POM was separated by density fractionation and quantified as described before (Neumann et al, 2013).…”

“…POM was separated by density fractionation and quantified as described before (Neumann et al, 2013).…”

“…Similarly, there were no visible PCR products for both targeted domains with DNA Achieved using the ultrasonication wet-sieving centrifugation method according to Amelung et al (1998), modified by Neumann et al (2013). b For more details, see Table 1 and Materials and methods section.…”

“…This heterogeneity of soil organic matter also has a tremendous effect on their sorption potential Huang et al, 2003), and it can thus be expected that partitioning of organic pollutants is strongly affected by soil particle size fractions. Recently, we could demonstrate that these particle size fractions within one soil are also colonized by distinct microbial communities (Neumann et al, 2013).…”