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  • 1
    Language: English
    In: Soil Biology and Biochemistry, December 2014, Vol.79, pp.57-67
    Description: The study of interactions between minerals, organic matter (OM) and microorganisms is essential for the understanding of soil functions such as OM turnover. Here, we present an interdisciplinary approach using artificial soils to study the establishment of the microbial community and the formation of macro-aggregates as a function of the mineral composition by using artificial soils. The defined composition of a model system enables to directly relate the development of microbial communities and soil structure to the presence of specific constituents. Five different artificial soil compositions were produced with two types of clay minerals (illite, montmorillonite), metal oxides (ferrihydrite, boehmite) and charcoal incubated with sterile manure and a microbial community derived from a natural soil. We used the artificial soils to analyse the response of these model soil systems to additional sterile manure supply (after 562 days). The artificial soils were subjected to a prolonged incubation period of more than two years (842 days) in order to take temporally dynamic processes into account. In our model systems with varying mineralogy, we expected a changing microbial community composition and an effect on macro-aggregation after OM addition, as the input of fresh substrate will re-activate the artificial soils. The abundance and structure of 16S rRNA gene and internal transcribed spacer (ITS) fragments amplified from total community DNA were studied by quantitative real-time PCR (qPCR) and denaturing gradient gel electrophoresis (DGGE), respectively. The formation of macro-aggregates (〉2 mm), the total organic carbon (OC) and nitrogen (N) contents, the OC and N contents in particle size fractions and the CO respiration were determined. The second manure input resulted in higher CO respiration rates, 16S rRNA gene and ITS copy numbers, indicating a stronger response of the microbial community in the matured soil-like system. The type of clay minerals was identified as the most important factor determining the composition of the bacterial communities established. The additional OM and longer incubation time led to a re-formation of macro-aggregates which was significantly higher when montmorillonite was present. Thus, the type of clay mineral was decisive for both microbial community composition as well as macro-aggregation, whereas the addition of other components had a minor effect. Even though different bacterial communities were established depending on the artificial soil composition, the amount and quality of the OM did not show significant differences supporting the concept of functional redundancy.
    Keywords: Dgge ; Illite ; Montmorillonite ; Decomposition ; Respiration ; Soil Formation ; 16s Rrna Gene ; Its Fragment ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 2
    Language: English
    In: Soil Biology and Biochemistry, February 2019, Vol.129, pp.17-28
    Description: The profound intensification of agricultural practices by increased application of agro-chemicals, short crop rotations and ploughing resulted in loss of soil fertility, erosion and accumulation of soil-borne plant pathogens. Soil microbial communities are key players in ecosystem processes and are intimately linked to crop productivity and health. Thus a better understanding of how farming practices affect soil microbiota is needed in order to promote sustainable agriculture. The long-term field trial in Bernburg (Germany) established in 1992 provides a unique opportunity to assess the effects of i) the crop (maize rapeseed) preceding the actual winter wheat culture, ii) tillage practice (mouldboard plough cultivator tillage) and iii) standard nitrogen (N)-fertilization intensity with application of growth regulators and fungicides (intensive) compared to reduced N-fertilization without growth regulators and fungicides (extensive). We hypothesized that these different farming practices affect the soil prokaryotic community structures with consequences for their functional potential. Total community-DNA was extracted directly from soils sampled at wheat harvest. Illumina sequencing of 16S rRNA genes amplified from total community-DNA revealed a significant effect of tillage practice and the preceding crop on prokaryotic community structures, whereas the influence of N-fertilization intensity was marginal. A number of differentially abundant prokaryotic genera and their predicted functions between mouldboard plough cultivator tillage as well as between different preceding crops were identified. Compared to extensive N-fertilization, intensive N-fertilization resulted in higher abundances of bacterial but not of archaeal genes, that are involved in ammonia oxidation. Our data suggest that long-term farming strategies differently shape the soil prokaryotic community structure and functions, which should be considered when evaluating agricultural management strategies regarding their sustainability, soil health and crop performance.
    Keywords: Bacterial Community Composition ; Tillage ; Fertilization ; Crop Rotation ; 16s Rrna Gene Amplicon Sequencing ; Soil Microbiome ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
    Library Location Call Number Volume/Issue/Year Availability
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