Abstract
Abstract. The stability of soil aggregates against shearing and compressive forces as well as water-caused dispersion is an integral marker of soil quality. High stability results in less compaction and erosion and has been linked to enhanced water retention, dynamic water transport and aeration regimes, increased rooting depth, and protection of soil organic matter (SOM) against microbial degradation. In turn, particulate organic matter is supposed to support soil aggregate stabilization. For decades the importance of biofilm extracellular polymeric substances (EPSs) regarding particulate organic matter (POM) occlusion and aggregate stability has been canonical because of its distribution, geometric structure and ability to link primary particles. However, experimental proof is still missing. This lack is mainly due to methodological reasons. Thus, the objective of this work is to develop a method of enzymatic biofilm detachment for studying the effects of EPSs on POM occlusion. The method combines an enzymatic pre-treatment with different activities of α-glucosidase, β-galactosidase, DNAse and lipase with a subsequent sequential ultrasonic treatment for disaggregation and density fractionation of soils. POM releases of treated samples were compared to an enzyme-free control. To test the efficacy of biofilm detachment the ratio of bacterial DNA from suspended cells and the remaining biofilm after enzymatic treatment were measured by quantitative real-time PCR. Although the enzyme treatment was not sufficient for total biofilm removal, our results indicate that EPSs may attach POM within soil aggregates. The tendency to additional POM release with increased application of enzymes was attributed to a slight loss in aggregate stability. This suggests that an effect of agricultural practices on soil microbial populations could influence POM occlusion/aggregate stability and thereby carbon cycle/soil quality.
Highlights
Soil organic matter (SOM) comprises 50 % ( ∼ 1700 Gt, including peat) of the near-surface terrestrial carbon budget, compared to ∼ 813 Gt bound in the atmosphere (Lal, 2008)
The proportionate C of each captured fraction is defined as Cfrac C−1, in which Cfrac is the release of LF-soil organic carbon (SOC) per energy level or – in the case of the sediment – the organic carbon remaining in the soil matrix
The E2 scenario shows any tendency of increased occluded light fraction SOC (oLF-SOC) release at 100 J mL−1 compared to the other treatments (p = 0.07 compared to E3)
Summary
Soil organic matter (SOM) comprises 50 % ( ∼ 1700 Gt, including peat) of the near-surface terrestrial carbon budget, compared to ∼ 813 Gt bound in the atmosphere (Lal, 2008). Beside carbon storage and its influence on the atmospheric CO2 balance, manifold ecological soil functions are mediated by different SOM types like dissolved organic matter (DOM), particulate organic matter (POM), molecular organic matter of organo-mineral associations, colloidal organic matter and coprecipitated molecular organic matter (Kalbitz et al, 2000; Weng et al, 2002; Pokrovsky et al, 2005; Eusterhues et al, 2008). POM is a structural component of soil aggregates, and a nutrient source, and it provides surfaces for microbial growth (Chenu and Stotzky, 2002; Bronick and Lal, 2005). Physical isolation protects POM against microbial degradation (Six et al, 2002; Lützow et al, 2006) and maintains its ecological functions, while on the other hand this POM is thought to promote soil aggregation (Bronick and Lal, 2005). Many benefits of soil POM are linked to soil aggregate stability
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
