Search results for "humus"
showing 10 items of 117 documents
Effect of storage and composting on the properties and degradability of cattle manure
1995
Abstract Stockpiling or thermophilic composting of cattle manure resulted in significant carbon losses of 17% and 26.4% and relative nitrogen gains of 25% and 32.7% for stockpiled and composted manure, respectively. As a consequence, C/N ratios decreased with increasing time of storage or composting. However, neither the pH nor the mineral nitrogen and organic carbon contents of the 0–50 μm fractions were significant indicators of the transformations of these materials. The degradability of the manure was measured by incubation for 2 weeks in a brown calcareous soil, following 1 week of preincubation. The biodegradation index (BI) or the proportion of CO 2 released from the amended soil in …
Effects of soil fauna on leaching of nitrogen and phosphorus from experimental systems simulating coniferous forest floor
1990
Long-term experiments (97–98 weeks) were carried out in macrocosm systems simulating the complexity of coniferous forest soil. The macrocosms were partially sterilized by freezing, thawing and drying, then re-inoculated with microbes alone or microbes + soil fauna. Removable microcosms containing birch litter, spruce litter, or humus were inserted into the substrate humus in the macrocosms. Two experiments used organic matter only, and in the third there was mineral soil below the humus. The macrocosms were incubated in climate chambers that simulated both summer and winter conditions. At 4- to 6-week intervals the substrates were irrigated for analyses of pH, total N, NH 4 + −N, NO 3 − −N,…
Evaluation of the soil fauna impact on decomposition in a simulated coniferous forest soil
1990
Long-term experiments (ca. 2 years) were carried out in laboratory systems that simulated the complexity of a coniferous forest floor. The test materials were partially sterilized by freezing and thawing, and reinoculated with (1) microbes alone or (2) microbes with fauna. Removable microcosms containing birch litter, spruce litter, or humus were inserted into a humus substrate. Two experiments used organic matter only, and another included a layer of mineral soil below the humus. Both were incubated in climate chambers that simulated both summer and winter conditions. The evolution of CO2 was measured at regular intervals. In order to determine the C content of the leachates, the macrocosm…
How Humic Substances Dominate Mercury Geochemistry in Contaminated Floodplain Soils and Sediments
1998
The interaction of mercury (Hg) and humic substances (hs) was studied in floodplain topsoils and surface sediments of the contaminated German river Elbe. An intimate coupling exists between the geochemical cycles of Hg and organic carbon (OC) in this ecosystem. Humic substances exert a dominant influence on several important parallel geochemical pathways of Hg, including binding, transformation, and transport processes. Significant differences exist between the Hg-hs associations in floodplains and sediments. Both humic acids (ha) and fulvic acids (fa) contribute to Hg binding in the sediments. In contrast, ultrafiltration experiments proved that Hg in the floodplain soils is almost exclusi…
Effect of earthworms on decomposition processes in raw humus forest soil: A microcosm study
1990
The earthworms Lumbricus rubellus (Hoffmeister) and Dendrobaena octaedra (Savigny) were studied in the laboratory to determine their effects on decomposition and nutrient cycling in coniferous forest soil. CO2 evolution was monitored, and pH, PO 4 3− −P, NH 4 + −N, NO 3 − −N, total N, and total C in the leaching waters were measured. After three destructive samplings, numbers of animals, mass loss, pH, and KCl-extractable nutrients were analysed. The earthworms clearly enhanced the mass loss of the substrate, especially that of litter. L. rubellus stimulated microbial respiration by 15–18%, whereas D. octaedra stimulated it only slightly. The worms significantly raised the pH of the leachin…
Properties and structure of raised bog peat humic acids
2013
Abstract Humic substances form most of the organic components of soil, peat and natural waters, and their structure and properties differ very much depending on their source. The aims of this study are to characterize humic acids (HAs) from raised bog peat, to evaluate the homogeneity of peat HAs within peat profiles, and to study peat humification impact on properties of HAs. A major impact on the structure of peat HAs have lignin-free raised bog biota (dominantly represented by bryophytes of different origin). On diagenesis scale, peat HAs have an intermediate position between the living organic matter and coal organic matter, and their structure is formed in a process in which more labil…
Effects of Pentachlorophenol and Biotic Interactions on Soil Fauna and Decomposition in Humus Soil
1995
In a laboratory experiment, effects of chemical stress (pentachlorophenol, PCP, at concentrations of 0, 50, and 500 mg/kg) and biotic interactions (nematodes in the presence or absence of collembolas and enchytraeids) on the community structure of soil animals and decomposition processes were studied. PCP was strongly adsorbed to humus that contained 65% organic matter. Numbers of fungal-feeding nematodes decreased significantly at the highest PCP concentration, while no effects were found in bacterial feeders. There were differences in the numbers of nematodes between different animal combinations, but at the highest PCP concentration, collembolas and enchytraeids had no effect on them. Nu…
Leaching of n and c from birch leaf litter and raw humus with special emphasis on the influence of soil fauna
1988
Abstract To examine the role of a community of soil animals in N-mineralization and C fluxes in dead organic matter, we established a microcosm system with substrates composed of: (a) birch leaf litter; (b) raw coniferous humus; and (c) litter on humus. Every 3–4 wks the substrates were irrigated with distilled water, and the amounts of NO5-N, NH4-N, total-N and total-C (as well as humic substances at one recording) in the leachates were analyzed. At the end of the experiment, water-soluble and exchangeable forms of N were measured in the test materials. The differences in the release of N were clear both between the replicates with and without soil animals and between the different forms o…
Humic substances along the profile of two Typic Haploxerert
2002
Abstract In Vertisols, organic matter contributes to soil colour by formation of organo-mineral complexes and affects morphological, physico-chemical, biological and biochemical properties. Turbation may affect the chemical and structural composition of the most stabilised fractions of soil organic matter (SOM), i.e., humic substances (HS). The objectives of this study were to: (1) characterise SOM in two Vertisols (V1 and V2) developed under Mediterranean climate in Italy, using some HS characteristics as indicators of SOM turnover in Vertisols, and (2) explore possible differences related to the pedomorphologic conditions of the area under which two soils have formed. SOM evolution along …
Effect of climate and vegetation on soil organic carbon, humus fractions, allophanes, imogolite, kaolinite, and oxyhydroxides in volcanic soils of Et…
2007
A soil sequence along an elevational gradient ranging from subtropical to subalpine climate zones in the Etna region (Sicily, southern Italy) was investigated with respect to organic C, kaolinite, and crystalline to noncrystalline Al and Fe phases. Special emphasis was given to the stabilization of soil organic carbon (SOC) and its interaction with the inorganic phases. The soils were variations of Vitric Andosols that developed on a trachy-basaltic lava flow with an age of 15,000 years. Two main vegetation systems dominated the sites: at the lower sites, it was mainly maquis vegetation and, at the higher elevated sites, predominantly coniferous forest. The concentration of SOC in the topso…