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 Enzymatic biofilm detachment causes a loss of aggregate stability in a sandy soil

2016 ◽  
Author(s):  
F. Büks ◽  
M. Kaupenjohann
Keyword(s):  
Organic Matter ◽  
Soil Quality ◽  
Extracellular Polymeric Substances ◽  
Soil Aggregates ◽  
Aggregate Stability ◽  
Agricultural Practices ◽  
Enzyme Treatment ◽  
Rooting Depth ◽  
Experimental Proof ◽  
Biofilm Detachment

Abstract. The stability of soil aggregates against shear and compressive forces as well as water caused dispersion is an integral marker of soil quality. High stability results in less soil compactibility and erodibility, enhanced water retention, a dynamic water transport and aeration regime, increased rooting depth and protection of soil organic matter (SOM) against microbial degradation. For decades the importance of biofilm extracellular polymeric substances (EPS) regarding 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 EPS on soil aggregate stability. The method combines an enzymatic pre-treatment with different activities of α-glucosidase, β-galactosidase, DNAse and lipase, which preserves aggregate structure, with a subsequent sequential ultrasonic treatment for disaggregation and density-fractioning. Soil organic carbon (SOC) releases of treated samples were compared to an enzyme-free control. To test the effectivity of biofilm detachment the ratio of bacterial DNA from sessile and suspended cells after enzymatic treatment was measured by quantitative real-time PCR. Although the enzyme treatment was not sufficient for total biofilm removal, our results confirm, that EPS stabilizes soil aggregates predominantly by a strong intra-aggregate fixation, and enzymatic biofilm digestion caused a shift of occluded particulate organic matter (POM) to more fragile binding patterns. This suggests that an effect of agricultural practices on soil microbial populations could influence aggregate stability and thereby soil quality.

The contribution of biogenic organic matter to aggregation in soil - a review

2021 ◽  
Author(s):  
Tom Guhra ◽  
Katharina Stolze ◽  
Kai Uwe Totsche
Keyword(s):  
Organic Matter ◽  
Extracellular Polymeric Substances ◽  
Soil Aggregates ◽  
Aggregate Stability ◽  
Close Approach ◽  
Small Scale ◽  
Soil Organisms ◽  
Field Scale ◽  
Formation Pathway

<p>Soil organisms (plants, invertebrates, and microorganisms) are involved in soil structuring and are key factors of aggregation through bioturbation, organic matter (OM) decomposition, and secretion of biogenic OM (e.g., root exudates, mucus and extracellular polymeric substances). At the field scale, soil quality, functions, as well as nutrient cycling usually benefit from the activity of soil organisms that frequently cause substantial changes to soil properties by the formation of aggregates. The biogenic formation pathway of soil aggregates reflects a cascade of small-scale sub-processes (e.g., OM supply, OM adsorption, organo-mineral association formation, their transport, immobilization, and involvement into aggregate structure) that are often portrayed solitarily in literature and demand for a comprehensive framework that consistently describes their synergies and dependencies. Particularly, the role of complexly composed biogenic OM as <strong>bridging/aggregation agent</strong> is controversially discussed in literature, as they may promote as well as inhibit aggregation at the same time. This non-uniform behavior is controlled by the complex interplay of milieu parameters (e.g., ionic strength, temperature, pH and redox-potential) and the physicochemical properties of biogenic OM (e.g., protein-to-polysaccharide-ratio, molecular weight of biopolymers, functional groups, and biopolymer structure). Hence, we discuss biogenic OM with respect to the three different roles in aggregation which can be identified from literature: (I) as <strong>bridging agent</strong> which permits the aggregation due to attraction and surface modifications, (II) as <strong>separation agent</strong> which favors the formation, mobility and transport of organo-mineral associations and inhibits their further involvement into aggregates, and (III) as <strong>gluing agent</strong> which mediates aggregate stability, after an external force provokes a close approach of soil particles. In natural systems, OM may take these roles simultaneously and with varying degree across spatiotemporal scales. Considering this for the discussion of the role of biogenic OM in soil aggregate formation, we will achieve a more detailed and interdisciplinary understanding of its pathways into soil aggregates, which can help to draw comprehensive conclusions from lab and field-scale studies, prospectively.</p>

Comparison of aggregate stability within six soil profiles under conventional tillage using various laboratory tests

Biologia ◽  
2009 ◽  
Vol 64 (3) ◽  
Author(s):  
Radka Kodešová ◽  
Marcela Rohošková ◽  
Anna Žigová
Keyword(s):  
Organic Matter ◽  
Soil Aggregates ◽  
Organic Matter Content ◽  
Aggregate Stability ◽  
Clay Content ◽  
Soil Aggregate ◽  
Matter Content ◽  
The Other ◽  
Structure Stability ◽  
Soil Aggregate Stability

AbstractSoil structure stability was studied in every diagnostic horizons of six soil types (Haplic Chernozem, Greyic Phaeozem, two Haplic Luvisols, Haplic Cambisol, Dystric Cambisol) using different techniques investigating various destruction mechanisms of soil aggregates. Soil aggregate stability, assessed by the index of water stable aggregates (WSA), varied depending on the organic matter content, clay content and pHKCl. The presence of clay and organic matter coatings and fillings, and presence of iron oxides in some soils increased stability of soil aggregates. On the other hand periodical tillage apparently decreased aggregate stability in the Ap horizons. Coefficients of aggregate vulnerability resulting from fast wetting (KV 1) and slow wetting (KV 2) tests showed similar trends of the soil aggregate stability as the WSA index, when studied for soils developed on the similar parent material. There was found close correlation between the WSA index and the KV 1 value, which depended also on the organic matter content, clay content and pHKCl. Less significant correlation was obtained between the WSA index and the KV 2 value, which depended on the organic matter content and clay content. Coefficients of vulnerability resulting from the shaking after pre-wetting test (KV 3) showed considerably different trends in comparison to the other tests due to the different factors affecting aggregate stability against the mechanical destruction. The KV 3 value depended mostly on cation exchange capacity, pHKCl and organic matter content.

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 A Mathematical Approach to Evaluating the Influence of Various Factors on the Stability of Aggregates in Vertisols

1969 ◽  
Vol 53 (1) ◽  
pp. 57-60
Author(s):  
M. A. Lugo López ◽  
Raúl Pérez Escolar
Keyword(s):  
Organic Matter ◽  
Soil Aggregates ◽  
Aggregate Stability ◽  
Correlation Coefficients ◽  
Clay Content ◽  
Mathematical Approach ◽  
Single Factor ◽  
Additional Increase ◽  
Independent Variable ◽  
The Stability

A mathematical approach is presented in this paper to evaluate the influence of such factors as clay content, silt content, organic matter, Ca + Mg, and soluble sodium upon the stability of soil aggregates in a group of Vertisols from the Lajas Valley, P.R. The relationships between aggregate stability and silt and clay were not significant. When the percentage of organic matter was considered as the independent variable, a highly significant correlation coefficient of 0.66 was obtained. Therefore, almost 43 percent of the variability in aggregate stability could be explained on the basis of this single factor. Attempts to increase the percentage of the variability which could be explained in terms of the content of Ca + Mg, and also of soluble sodium, yielded correlation coefficients of 0.70 and 0.74, respectively. Thus, only a slight, but significant, additional increase could be explained when these variables were included.

Perbaikan Stabilitas Agregat Tanah Pasir Berlempung Menggunakan Bakteri Pemantap Agregat dan Bahan Organik

2020 ◽  
Vol 42 (2) ◽  
pp. 161
Author(s):  
Diana Utama ◽  
Nuni Gofar ◽  
Adipati Napoleon
Keyword(s):  
Organic Matter ◽  
Incubation Period ◽  
Soil Aggregates ◽  
Aggregate Stability ◽  
Soil Aggregation ◽  
Cattle Manure ◽  
Loamy Sand ◽  
Sand Soil ◽  
Loamy Sand Soil ◽  
Observation Period

<p class="teksabst"><strong>Abstrak.</strong><em> </em>Penelitian ini bertujuan untuk menganalisis stabilitas agregat tanah dengan perlakuan berbagai isolat bakteri pemantap agregat (BPA) dan bahan organik berupa kompos yang terbuat dari campuran 90% rumput <em>Cyperus pilosus</em> Vahl dan 10% kotoran sapi, dengan masa inkubasi yang berbeda. Taraf perlakuan terdiri dari kontrol, kombinasi isolat I, II, dan III masing – masing dikombinasikan dengan komposisi bahan organik 0%, 0.5%, dan 1%. Hasil penelitian ini menunjukkan aplikasi isolat BPA pada tanah pasir berlempung disertai pemberian bahan organik menyebabkan populasi yang lebih tinggi dibandingkan tanpa aplikasi keduanya. <em>Klebsiella </em>sp. LW-13 yang dikombinasi dengan 1% bahan organik dan <em>Bukholderia anthina </em>MYSP113 yang dikombinasi dengan berbagai taraf bahan organik (0 hingga 1%) menyebabkan agregat menjadi sangat mantap sekali pada pengamatan 60 hari setelah aplikasi. Eksopolisakarida yang dihasilkan bakteri akan mengikat partikel tanah dan membentuk agregasi. Penggunaan bakteri <em>Bukholderia anthina </em>MYSP113 dinilai lebih efisien dalam pemanfaatannya untuk memantapkan agregat tanah karena memiliki kemampuan terbaik untuk memantapkan agregat tanah hingga sangat mantap sekali dengan atau tanpa penambahan bahan organik pada periode 60 hari pengamatan.</p><p><em><strong>Abstract</strong></em>. This study aimed to analyze the aggregate stability of soil with sdifferent treatments of aggregate-stabilizing bacteria and organic matter (compost made of mixture of 90% Cyperus pilosus Vahl grass biomass and 10% cattle manure) at different incubation period. Treatments consisted of control, combination of three different isolate with three different composition of organic matter (0%, 0.5%, and 1%). The results showed that the application of aggregate-stabilyzing bacteria to loamy sand soil and organic matter causes a higher bacteria population than without both applications. Klebsiella sp. LW-13 combined with 1% organic matter and Bukholderia anthina MYSP113 which was combined with various levels of organic matter (0 to 1%) showed high aggregation at observation of 60 days after application. The exopolysaccharide produced by bacteria binds soil particles and forms soil aggregation. The use of Bukholderia anthina MYSP113 bacteria is considered to be efficient in its utilization to stabilize soil aggregates because it has the best ability to stabilize soil aggregates to be highly stable with or without the addition of organic matter in the 60-day observation period.</p><p> </p>

scholarly journals Evaluation of the Effects of Organic Matter and Other Soil Characteristics Upon the Aggregate Stability of Some Tropical Soils

1969 ◽  
Vol 43 (4) ◽  
pp. 268-272 ◽  
Author(s):  
M. A. Lugo-López ◽  
J. Juárez, Jr.
Keyword(s):  
Organic Matter ◽  
Soil Aggregates ◽  
Organic Matter Content ◽  
Aggregate Stability ◽  
Tropical Soils ◽  
Development Project ◽  
Matter Content ◽  
Degree Of Stability ◽  
Statistical Studies ◽  
Level Of Significance

This paper reports on statistical studies conducted to evaluate the degree of stability of soil aggregates in terms of the respective organic-matter, clay, and silt contents of selected soils from the Lajas Valley irrigation development project. Simple regression analyses revealed that there was no correlation between aggregate stability and clay or silt content. However, a highly significant correlation was obtained when organic-matter content was considered as the independent variable. In spite of the level of significance only 16 percent of the variability in aggregate stability can be explained on a basis of the soil organic-matter content, thus limiting the possible usefulness of estimates made by using the equation developed.

scholarly journals Trends in Soil Quality Under High Tunnels

HortScience ◽  
2010 ◽  
Vol 45 (10) ◽  
pp. 1534-1538 ◽  
Author(s):  
Sharon J.B. Knewtson ◽  
Rhonda Janke ◽  
M.B. Kirkham ◽  
Kimberly A. Williams ◽  
Edward E. Carey
Keyword(s):  
United States ◽  
Organic Matter ◽  
Soil Quality ◽  
Particulate Organic Matter ◽  
Soil Surface ◽  
The United States ◽  
Total Carbon ◽  
Surface Salinity ◽  
High Tunnel ◽  
High Tunnels

Growers have indicated that changes in soil quality under production in high tunnels is an important problem, but these have not yet been quantified or critically assessed in the central Great Plains of the United States. We conducted surveys of grower perceptions of soil quality in their tunnels (n = 81) and compared selected soil quality indicators (salinity and particulate organic matter carbon) under high tunnels of varying ages with those of adjacent fields at sites in Kansas, Missouri, Nebraska, and Iowa in the United States. Fourteen percent of growers surveyed considered soil quality to be a problem in their high tunnels, and there were significant correlations between grower perceptions of soil quality problems and reported observations of clod formation and surface crusting and to a lesser extent surface mineral deposition. Grower perception of soil quality and grower observation of soil characteristics were not related to high tunnel age. Soil surface salinity was elevated in some high tunnels compared with adjacent fields but was not related to time under the high tunnel. In the soil upper 5 cm, salinity in fields did not exceed 2 dS·m−1 and was less than 2 dS·m−1 under 74% of high tunnels and less than 4 dS·m−1 in 97% of high tunnels. The particulate organic matter carbon fraction was higher in high tunnels than adjacent fields at 73% of locations sampled. Particulate organic matter carbon measured 0.11 to 0.67 g particulate organic matter per g of the total carbon under high tunnels sampled. Particulate organic matter carbon in the soil was also not correlated to age of high tunnel. Soil quality as measured in this study was not negatively impacted by use of high tunnel structures over time.

Soil Quality Indicators in Conventional and Conservation Tillage Systems in the Brazilian Cerrado

2021 ◽  
Author(s):  
Luiz Alberto da Silva Rodrigues Pinto ◽  
Sandra Santana de Lima ◽  
Cristiane Figueira da Silva ◽  
Rafael Gomes da Mota Gonçalves ◽  
Igor de Sousa Morais ◽  
...  
Keyword(s):  
Organic Matter ◽  
Soil Quality ◽  
Conservation Tillage ◽  
Soil Aggregates ◽  
Conventional Tillage ◽  
Soil Aggregation ◽  
Reference Area ◽  
Quality Indices ◽  
Tillage Systems ◽  
No Till

Abstract Conventional and conservation tillage systems can alter soil aggregation and total and labile soil organic matter (SOM) contents. This study aimed to determine the degree of soil aggregation, quantify total carbon (TC), permanganate oxidizable carbon (POXC), light organic matter (LOM), and potentially mineralizable carbon (CO2-C) contents in soils aggregates, and assess soil quality indices at sites under conventional and conservation tillage in the Cerrado region of Minas Gerais State, Brazil. Four experimental areas were analyzed: a area under conventional tillage for 20 years, a area under no-till for 6 years, a area under no-till for 18 years, and a reference area of undisturbed Cerrado vegetation. Soil aggregates retained on 8.0 to 4.0 mm sieves were evaluated for size class distribution and mean weight diameter. TC, POXC, LOM, daily and total CO2-C emissions were also analyzed. These data were used to calculate the C/N ratio and sensitivity, carbon pool, and lability indices. The results of SOM compartments were in agreement with those obtained for the soil aggregation status. Environmental conditions at no-till areas promoted macroaggregate formation and preserved TC and LOM contents, resulting in a high degree of aggregate stability. Soil quality indices were sensitive to identify changes between the reference area and managed areas. Soil aggregates from no-till areas had higher CO2-C emissions and accumulations than those from the conventional tillage area.

Soil and vegetation of ungrazed crested wheatgrass and native rangelands

2000 ◽  
Vol 80 (3) ◽  
pp. 411-417 ◽  
Author(s):  
K. Broersma ◽  
M. Krzic ◽  
D. J. Thompson ◽  
A. A. Bomke
Keyword(s):  
Species Diversity ◽  
Soil Quality ◽  
Soil Aggregates ◽  
Plant Cover ◽  
Size Fraction ◽  
Aggregate Stability ◽  
Penetration Resistance ◽  
Slight Reduction ◽  
Crested Wheatgrass ◽  
Soil C

Seeding of introduced forage grasses, such as crested wheatgrass [Agropyron cristatum (L.) Gaertn. and A. desertorum (Fisch.) Schult.], can lead to the reduction of species diversity and soil quality. This study evaluated the effects of crested wheatgrass on soil and vegetation relative to native rangeland dominated by bluebunch wheatgrass [Pseudoroegneria spicata (Pursh) Scribn. & Smith] under ungrazed conditions. Three sites consisting of adjacent ungrazed stands of crested wheatgrass and native vegetation were sampled in June 1997. Total plant cover was 37% on native and 24% on crested wheatgrass rangeland. Species richness was lower for crested wheatgrass than for native rangeland. Quantities of root biomass and most soil properties were similar for the two rangelands. Native rangeland had a more stable soil structure with 1.7 mm mean weight diameter (MWD) and 38% of soil aggregates in the 2–6 mm size fraction compared to 1.4 mm MWD and 28% of soil aggregate in the 2–6 mm size fraction on crested wheatgrass rangeland. Greater soil penetration resistance was observed at the 6 and 7.5 cm depths for crested wheatgrass rangeland. Crested wheatgrass did not invade adjacent native rangelands and only a slight reduction in soil quality was observed on crested wheatgrass rangelands. Key words: Crested wheatgrass, soil C, soil N, penetration resistance, aggregate stability, species diversity

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