scholarly journals Two different microbial communities did not cause differences in occlusion of particulate organic matter in a sandy agricultural soil

2016 ◽  
Author(s):  
Frederick Büks ◽  
Philip Rebensburg ◽  
Peter Lentzsch ◽  
Martin Kaupenjohann
Keyword(s):  
Organic Matter ◽  
Microbial Communities ◽  
Particulate Organic Matter ◽  
Agricultural Soil ◽  
Agricultural Soils ◽  
Soil Aggregates ◽  
Soil Extract ◽  
Microbial Life ◽  
Physico Chemical ◽  
Airborne Microbes

Abstract. Apart from physico-chemical interactions between soil components, microbial life is assumed to be an important factor of soil structure forming processes. Bacterial exudates, the entanglement by fungal hypae and bacterial pseudomycelia as well as fungal glomalin are supposed to provide the occlusion of particulate organic matter (POM) through aggregation of soil particles. This work investigates the resilience of POM occlusion in face of different microbial communities under controlled environmental conditions. We hypothesized that the formation of different communities would cause different grades of POM occlusion. For this purpose samples of a sterile sandy agricultural soil were incubated for 76 days in bioreactors. Particles of pyrochar from pine wood were added as POM analogue. One variant was inoculated with a native soil extract, whereas the control was infected by airborne microbes. A second control soil remained non-incubated. During the incubation, soil samples were taken for taxon-specific qPCR to determine the abundance of Eubacteria, Fungi, Archaea, Acidobacteria, Actinobacteria, α-Proteobacteria and β-Proteobacteria. After the incubation soil aggregates (100–2000 μm) were collected by sieving and disaggregated using ultrasound to subject the released POM to an analysis of organic carbon (OC). Our results show, that the eubacterial DNA of both incubated variants reached a similar concentration after 51 days. However, the structural composition of the two communities was completely different. The soil-born variant was dominated by Acidobacteria, Actinobacteria and an additional fungal population, whereas the air-born variant mainly contained β-Proteobacteria. Both variants showed a strong occlusion of POM into aggregates during the incubation. Yet, despite the different population structure, there were only marginal differences in the release of POM along with the successive destruction of soil aggregates by ultrasonication. This leads to the tentative assumption that POM occlusion in agricultural soils could be resilient in face of changing microbial communities.

scholarly journals Casting Activity ofScherotheca gigasin No-Till Mediterranean Soils: Role in Organic Matter Incorporation and Influence of Aridity

2010 ◽  
Vol 2010 ◽  
pp. 1-6 ◽  
Author(s):  
Paloma Bescansa ◽  
Iñigo Virto ◽  
Oihane Fernández-Ugalde ◽  
María José Imaz ◽  
Alberto Enrique
Keyword(s):  
Organic Matter ◽  
Agricultural Soils ◽  
Nw Spain ◽  
Organic C ◽  
No Till ◽  
Physico Chemical ◽  
C Stocks ◽  
Casting Activity ◽  
Total Organic C

The behaviour of earthworms, their role in organic matter incorporation into the soil, and the influence of aridity in such processes in arid and semiarid regions have scarcely been studied. In this study, physico-chemical analyses of the casts and the surrounding no-till agricultural soils of three experimental sites representing an aridity gradient in Navarre (NW Spain) were done. The casts were formed by the activity of the only anecic species,Scherotheca gigas(Dugès, 1828), ubiquitous in no-till soils in this region. We observed a significant depletion of clay and higher concentration of total organic C and labile C in the form of particulate organic matter (POM) in the casts as compared to the surrounding soil, suggesting selective ingestion of soil byS. gigas. This, together with the observation of increased concentration in POM with increasing aridity, suggests a major role of this species in the observed progressive gains of organic C stocks in no-till soils in the region.

Wettability of soil aggregates from cultivated and uncultivated Ustolls and Usterts

Soil Research ◽  
2004 ◽  
Vol 42 (2) ◽  
pp. 163 ◽  
Author(s):  
Anna Eynard ◽  
Thomas E. Schumacher ◽  
Michael J. Lindstrom ◽  
Douglas D. Malo ◽  
Robert A. Kohl
Keyword(s):  
Organic Matter ◽  
Great Plains ◽  
Water Intake ◽  
Agricultural Soils ◽  
Water Drop ◽  
Soil Aggregates ◽  
Management Systems ◽  
Northern Great Plains ◽  
Organic C ◽  
Cultivated Soils

Soil organic matter can modify the interaction of clay minerals with water, limiting the rate of water intake of swelling clays and stabilising soil aggregates. Soil structural stability and organic C content usually decrease with cultivation. Faster wetting increases stresses on aggregates and decreases stability. Aggregate wettabilities of prairie soils under 3 different management systems (grassland, no-till, and conventional-till) were compared in the Northern Great Plains of the USA. Six Ustolls and 2 Usterts were selected as replications along the Missouri River. Wettability was measured as water drop penetration time (WDPT) and as rate of water intake under 30 and 300 mm tension. At low tension, aggregates from both cultivated fields and uncultivated grasslands showed similar wettability. Water intake in grass aggregates was attributed to a greater amount of stable pores relative to cultivated aggregates. In cultivated aggregates, slaking created planes of failure that allowed rapid water entry. Differences of wettability between management systems at 300 mm tension (in Ustolls, grasslands had greater wettability than cultivated soils, 0.24 v. 0.17 g water/h.g dry soil) and between soil orders (Usterts had longer WDPT than Ustolls, 2.9 v. 1.7 s) were explained by both clay and organic C contents. Simple measurements of aggregate wettability may be effectively used for soil quality characterisation. Aggregate wettability is a desirable property for agricultural soils when it is related to stable porosity, as may be found in high organic matter soils (e.g. grasslands). Wettability is excessive when fast aggregate wetting results in aggregate destruction as observed in low organic matter cultivated soils.

scholarly journals Enzymatic biofilm digestion in soil aggregates facilitates the release of particulate organic matter by sonication

SOIL ◽  
2016 ◽  
Vol 2 (4) ◽  
pp. 499-509 ◽  
Author(s):  
Frederick Büks ◽  
Martin Kaupenjohann
Keyword(s):  
Organic Matter ◽  
Soil Quality ◽  
Particulate Organic Matter ◽  
Extracellular Polymeric Substances ◽  
Soil Aggregates ◽  
Aggregate Stability ◽  
Enzyme Treatment ◽  
Rooting Depth ◽  
Experimental Proof ◽  
Biofilm Detachment

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.

scholarly journals Effects of ageing under field conditions on soil organic matter in earthworm casts produced by the anecic earthworm Amynthas adexilis in northern Vietnam

2021 ◽  
Author(s):  
Nicolas Jean Bernard Puche ◽  
Cornelia Rumpel ◽  
Nicolas Bottinelli
Keyword(s):  
Organic Matter ◽  
Particulate Organic Matter ◽  
Soil Aggregates ◽  
Ct Images ◽  
Field Conditions ◽  
Strong Positive Correlation ◽  
Micro Ct ◽  
Earthworm Casts ◽  
Biogeochemical Models ◽  
And Control

<p>Carbon sequestration in soils became a major issue that governments have to face under their sustainable development objectives and the international 4p1000 program. Although, earthworms are recognized to play a key role in the structure and dynamics of organic matter (OM) in soils, their contribution to soil OM cycling is not taken into account in biogeochemical models nor well understood. In particular, the fate of OM protected in earthworm casts is unknown. In this study, we investigated the effects of ageing under field conditions on the OM dynamics contained in casts produced by the anecic earthworm Amynthas adexilis in North Vietnam. To this end we investigated (1) the microscale organisation of particulate organic matter and pores during the exposure of casts and control aggregates during 12 months and (2) compared it to the potential OM mineralisation during a laboratory incubation.</p><p>Our results indicated that fresh casts contained significantly more particulate organic matter (POM) than control soil aggregates and field aged earthworm casts. Conversely, the porosity was higher in soil control aggregates than in casts and the porosity of casts tended to increase with their ageing. The analyses of micro-CT images also revealed that POM and Pores contents between casts samples presented strong variabilities even in the youngest casts category. We found, on average, higher mineralisation rates for casts than for controls and a reduction of the OM mineralisation with the ageing of casts. Our results also highlighted a strong positive correlation (r<sup>2</sup> = 0.89) between POM contents determined by the segmentation of micro CT images and CO<sub>2</sub> emissions from the incubation experiment. We conclude that earthworms impact the microscale organisation of POM and pores in their casts and thereby influence soil OM dynamics.</p>

scholarly journals Particles under stress: Ultrasonication causes size and recovery rate artifacts with soil derived POM, but not with microplastics

2020 ◽  
Author(s):  
Frederick Büks ◽  
Gilles Kayser ◽  
Antonia Zieger ◽  
Friederike Lang ◽  
Martin Kaupenjohann
Keyword(s):  
Particle Size ◽  
Organic Matter ◽  
Particulate Organic Matter ◽  
Recovery Rate ◽  
Soil Aggregates ◽  
Terrestrial Ecosystems ◽  
Physiochemical Properties ◽  
Average Factor ◽  
Carry Over ◽  
Physical Stabilization

Abstract. The breakdown of soil aggregates and the extraction of particulate organic matter (POM) by ultrasonication and density fractionation is a method widely used in soil organic matter (SOM) analyses. It has recently also been used for the extraction of microplastic from soil samples. However, the investigation of some POM physiochemical properties and ecological functions might be biased, if particles are comminuted during the treatment. In this work, different types of POM, which are representative for different terrestrial ecosystems and anthropogenic influences, were tested for their structural stability in face of ultrasonication in a range of 0 to 500 J ml−1. The occluded particulate organic matter (oPOM) of an agricultural and forest soil as well as pyrochar showed a significant reduction of particle size at ≥ 50 J ml−1 by an average factor of 1.37 ± 0.16 and a concurrent reduction of recovery rates by an average of 21.7 ± 10.7 % when being extracted. Our results imply that ultrasonication causes an imitated carry-over of POM to more strongly bound fractions or to the mineral-associated organic matter (MOM) due to enhanced attraction to the mineral phase, which could e.g. lead to a false estimation of physical stabilization. In contrast, neither fresh nor weathered polyethylene (PE), polyethylene terephthalate (PET) and polybutylene adipate terephthalate (PBAT) microplastics showed a reduction of particle size or the recovery rate after application of ultrasound. We conclude that ultrasonication applied to soils has no impact on microplastic size distribution and thus provides a valuable tool for the assessment of microplastics in soils and soil aggregates.

The Impact of Corn Residue Removal on Soil Aggregates and Particulate Organic Matter

2014 ◽  
Vol 7 (2) ◽  
pp. 559-567 ◽  
Author(s):  
Shannon L. Osborne ◽  
Jane M. F. Johnson ◽  
Virginia L. Jin ◽  
Amber L. Hammerbeck ◽  
Gary E. Varvel ◽  
...  
Keyword(s):  
Organic Matter ◽  
Particulate Organic Matter ◽  
Soil Aggregates ◽  
Residue Removal ◽  
Corn Residue ◽  
The Impact
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