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Search Results: 1 - 10 of 15430 matches for " Soil aggregate "
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Size fractionation and microbial community structure of soil aggregates  [PDF]
Jong-Shik Kim, David E. Crowley
Journal of Agricultural Chemistry and Environment (JACEN) , 2013, DOI: 10.4236/jacen.2013.24011
Abstract: The microbial community structure in various microaggregates in a loamy sand soil was investigated. The microaggregates were separated into outer and inner aggregates using a series of soil washes. Further physical fractionation of inner aggregates was achieved by separation into coarse and fine sand as macroaggregate fractions, coarse and fine silt as microaggregate fractions, and clay. Research on microbial communities and soil microaggregates can aid in our understanding of soil microhabitats and microorganisms in soil structures, with applications that may contribute to increasing crop production and maintaining sustainable agriculture. In order to study the microbial community structure of aggregates, polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) was performed using 16S rRNA genes. The PCR-DGGE of the Bacteria Actinomycetes and Archaea showed divergent results between the different aggregate fractions. The results showed that the bacterial community structure was highly similar between bulk soil and clay; the inner aggregate community structure of Actinomycetes was closely related between coarse and fine sand and coarse silt, and the Archaea community structure of outer and inner aggregates was more similar than that of total bacteria or Actinomycetes.
Effects of Aggregate Extraction on Water Storage in the Pepin Creek Watershed, British Columbia, Canada  [PDF]
Yining Wang, Julie E. Wilson, Drew Brayshaw, Les M. Lavkulich
Natural Resources (NR) , 2017, DOI: 10.4236/nr.2017.87030
Abstract: Aggregate extraction in the Lower Fraser Valley of British Columbia, Canada, has affected the soil water storage of the Pepin Creek watershed. Although local government has set regulations for aggregate extraction projects to avoid negative environmental impacts, the gradual loss of soil materials and associated changes in vegetative cover has led to an alteration of the water balance within the watershed, which may affect surface or groundwater levels, and aquatic habitats. The study assessed the effects of aggregate extraction on the water storage of the Pepin Creek watershed and estimated that 25% of the surface area of the Canadian portion of the watershed has been affected by aggregate mining with an estimated loss of water storage of 10%. Evapotranspiration has decreased as a result of the removal of the vegetative cover. Precipitation has remained relatively constant over the study period but the annual discharge measured at Pepin Creek has decreased. Recommendations for enhancing environmental monitoring to better measure and understand ecological functions of the watershed during aggregate extraction are provided.
Evaluation of Quality of Some Rehabilitated Mined Soils within the AngloGold-Ashanti Concession in Ghana  [PDF]
Witmann H. K. Dorgbetor, Gabriel N. N. Dowuona, Seth K. A. Danso, Julius K. Amatekpor, Ayoade O. Ogunkunle, Enoch Boateng
International Journal of Geosciences (IJG) , 2012, DOI: 10.4236/ijg.2012.31007
Abstract: Land degradation caused by surface mining of gold has been extensive in Ghana. In recent years rehabilitation of some degraded lands by re-vegetation has been undertaken. This study provides quantitative data on the quality of some rehabilitated and un-rehabilitated mined soils within the AngloGold-Ashanti gold concession in parts of the semi-deciduous forest zone of Ghana. Soil properties determined included texture, bulk density and aggregate stability, pH, organic carbon, available phosphorus, total nitrogen, cation exchange capacity, exchangeable bases, exchange acidity, Fe, Mn, Ni, Cu, Zn, Cd, and Pb. Aggregate stability as a physical quality indicator revealed that aggregates of the rehabilitated mined soil had become more stable and similar to the control unmined soil due to litter and carbon additions from planted trees. The nutrient levels were very low because of the presence of low activity clays inherent in the native soil. Organic carbon content in the rehabilitated soil had increased above that of the unrehabilitated soil. Variability in soil properties, especially organic carbon and aggregate stability, was minimal in the unmined and rehabilitated soils implying that soils at the two sites were most robust and resistant to crushing and rupture. Quality index of the unmined control soil was 36.5% indicating that the quality of the soil was 63.5% relative to the optimum quality because of inherent poor soil properties. The mined rehabilitated and unrehabilitated soil had index values of 32.5% and 24.4 %, respectively. The marginal difference of 4% in soil quality between the control and rehabilitated soil shows that it is possible to maintain the health of soils with inherent physical and biochemical deficiencies if reclamation regulations are adhered to. In this way, the socio-economic dilemma of exploiting natural resources for the benefit of societies is ameliorated while maintaining an ecosystem balance.
Influence of the microbiological activity on the soil aggregate stability
N. Rampazzo,A. Mentler,D. Tscherko,M. Pfeffer
International Agrophysics , 1995,
Abstract: The influence of the microbiological activity on the soil aggregate stability of a silty Chernozem was investigated by promoting the microbial activity through D-glucose solution. After 2 weeks of incubation the microbial activity reached 300 % of the initial value, whereas the soil aggregate stability was triplicated. The effect of aggregate stabilization by fungal biomass was higher than the one due to bacterial biomass.
Assessment of Variability in the Quality of an Acrisol under Different Land Use Systems in Ghana  [PDF]
Emmanuel Osadu Ghartey, Gabriel N. N. Dowuona, Eric K. Nartey, Thomas A. Adjadeh, Innocent Y. D. Lawson
Open Journal of Soil Science (OJSS) , 2012, DOI: 10.4236/ojss.2012.21006
Abstract: Three land use types (natural fallow, Leucaena leucocephala woodlot and cultivated plots) on a Ferric Acrisol in a semi-arid tropical zone of Ghana were compared to assess their effects on variability in selected soil properties and plant biomass accumulation. Organic carbon accumulation in the representative natural fallow profile was 22.7 g/kg, followed by 16.5 g/kg for the Leucaena woodlot and lastly 11.8 g/kg for the cultivated site. The mean bulk density of the natural fallow, Leucaena woodlot and cultivated sites were from 1.36 Mg/m3, 0.92 Mg/m3 and 1.33 Mg/m3 with corresponding range in mean weight diameter of 0.5 mm - 1.2 mm, 0.6 mm - 1.2 mm and 1.0 mm - 1.2 mm, respectively. The lower bulk density observed for the woodlot corresponds to increased total porosity, aeration, and root proliferation due to the stronger and extensive rooting system. Significant differences (P < 0.05) in bulk density, mean weight diameter (MWD), clay content, organic carbon and total nitrogen existed among the land use types. Variability in pH and bulk density of the surface soils was less than 15%, in the three land use types. Generally, clay content and exchangeable Na recorded the highest variability (>36%). For the surface soils, exchangeable Na was very variable in the natural fallow. Exchangeable Na, Ca and K and total nitrogen were very variable in the Leucaena woodlot and the cultivated sites. Variability in clay content was very high in the cultivated soils only. The order cultivated land > Leucaena woodlot > natural fallow was noted for properties with high variability (CV > 36%). Plant biomass accumulation was 1834 kg/ha (natural fallow) and 830 kg/ha (Leucaena woodlot) indicating that natural fallows do not only maintain soil quality but they also decrease variability in soil properties which is desirable for soil productivity and quality.
Effect of soil acidification on the formation of Fe-, Al-, and Mn-oxides and the stability of soil aggregates
Rampazzo N.,Schwertmann U.,Blum W.E.H.,Mentler A.
International Agrophysics , 1999,
Abstract: The effect of intensive soil acidification on the genesis of Fe-, Al- and Mn-oxides and their relation to the soil aggregate stability were investigated in the Vienna Woods. Analyses were carried out on soil samples of 2 sites at 4 depths (0-5, 5-10, 10-20, and 20-30 cm) taken from the infiltration zone of the stemflow (S) of beech trees, which is strongly influenced by acid atmospheric depositions (soil-pH KCl 2.5 to 3.0), and from non-contaminated reference areas (R) between the trees, where the acid input is much lower (soil-pH KCl 5.5). The extreme soil acidification in the infiltration zone of stemflow led to intensive weathering of primary minerals, to neoformation and accumulation of crystallized, amorphous and organic-bound Fe-oxides, to lower concentrations of Al- and Mn-oxides and to a high increase in soil aggregate stability, reflecting the aggregation effect of Fe-oxides, and the concomitant leaching of Mn and Al at a very low soil pH. Moreover, chemical extractions of the fine earth (water saturation extract and BaCl2-extraction) showed that Fe had accumulated in the strongly acidified soils also as water-soluble and exchangeable cation.
Accumulative Effect of Soil Organic Carbon and Nitrogen in Water-Stable Aggregates and Soil Stability Characteristics of Robinia pseudoacacia Plantation in the Loess Hilly-Gully Region  [PDF]
Jiao Sun, Junfeng Li, Gaihe Yang, Wenfang Hao
Open Journal of Soil Science (OJSS) , 2016, DOI: 10.4236/ojss.2016.612019
Abstract: Soil water-stable aggregates (WSAs) are the basic unit of soil constitution and can contribute to remaining the stable soil constitution. The objective of this study was to clarify the distribution and stability of WSAs and the soil organic carbon (SOC), the total nitrogen (TN), and the total phosphorus (TP) concentrations in 0 - 20 cm and 20 - 40 cm soil layers under the different ages of Robinia pseudoacacia plantations. The 20, 25, 40, and 50 years-old Robinia pseudoacacia plantations were selected. Stepwise regression analysis showed that >5 mm and 1 - 2 mm WSAs, SOC concentration in 2 - 5 mm WSAs, and TN and TP concentrations in < 0.25 mm WSAs were dominant independent variables affecting aggregate stability and that SOC in 0.25 - 0.5 mm WSAs, TN in <0.25 mm and 1 - 2 mm WSAs and TP in 2 - 5 mm WSAs were dominant independent variables affecting SOC, TN, and TP concentrations in bulk soils.
State of Organic Matter and Particularities of Physicochemical Properties of Soils in the Endogenous Hydrogen Seepage Zones  [PDF]
Natalia Ivanovna Sukhanova, Tatiana Aleksandrovna Zubkova
Open Journal of Soil Science (OJSS) , 2018, DOI: 10.4236/ojss.2018.88015
Abstract: In the territory of the Voronezh region of Russia in ordinary middle loam chernozem the elevated concentration of endogenous hydrogen streams up to 0.65% at the depth of 100 - 120 cm was detected. This phenomenon is observed in the center of depressions. The soils differ in morphological, chemical and physical properties. The top humus horizon is markedly bleached comparing to the soil outside the depression: The lightness L readings increase for 16% - 30%. The soil acidity (up to pH 4.5 - 5.0) and organic carbon content are elevated comparing to the sample for reference. The proportion of fulvic acids increases on average thrice as compared with the soils outside the hydrogen fluids influence zone. Despite the high humus content the mechanical strength of aggregates decreases 3 - 4 times. Under conditions of hydrogen fluids, changes occur at the aggregate structural level in the direction of decreasing their mechanical strength. In the center of the depressions strength of aggregates is reduced by 2 - 3 times in comparison with the control. The opposite regularity was observed in the absence of hydrogen flows, where the strength of aggregates was 3 times higher than in comparison with the control.
Seguel S.,Oscar; García de Cortázar G. de C.,Víctor; Casanova P.,Manuel;
Agricultura Técnica , 2003, DOI: 10.4067/S0365-28072003000300008
Abstract: the present study had the objective of evaluating the potential of a biofertilizer and bovine manure as agents to improve soil physical properties. the applied biofertilizer came from residues produced by a batch biodigestor and the manure came from a dairy. a soil amendment was made in plots of 6 x 3 m with four treatments and three replicates. the treatments, in a volumetric ratio, were: control without amendment; soil:biofertilizer mixture on a 3:1 ratio. soil:biofertilizer mixture on a 1:1 ratio; soil:manure mixture on a 1:1 ratio. in the second year, the plots were divided in two, leaving subplots of 6 x 1.5 m, one of which had a second amendment with the same organic material and the same ratio. the effects of the treatments were evaluated at one month, one year and two years after the first application. the soil parameters evaluated were: bulk density, specific weight, water retention, water infiltration rate and aggregate stability. a cactus pear (opuntia ficus - indica (l.) mill.) plantation was established as a test plant. the application of organic material in great volume provoked a decrease on soil bulk density in the short run; consequently, total porosity increased, particularly the coarse pores (reflected in the pf curve). the specific weight and available water were not different between treatments, while the water infiltration rate increased with amendments. there was an increase in the aggregate stability in the short term, but with successive applications the effect disappeared. finally, the biofertilizer applications promoted cactus growth of shoots and production of dm.
Aporte de carbono orgánico de la labranza cero y su impacto en la estructura de un andisol de la Precordillera Andina Chilena
Sandoval-Estrada, Marco;Stolpe-Lau, Neal;Zagal-Venegas, Erick;Mardones-Flores, María;Celis-Hidalgo, José;
Agrociencia , 2008,
Abstract: the intensive use of soils derived from volcanic ash, due to an increase in livestock and agricultural activities, has generated losses from increasing water erosion in the soils, which are reflected in lower production and an increase in the demand for agricultural inputs. therefore, this study was conducted to evaluate, after three years, the structural state of a soil (typic haploxerand) subjected to four techniques for managing crop residues under zero tillage in wheat-oat rotation: 1) burned residues (t); 2) residues in rows (rh); 3) standing residues (rp); and 4) chopped residues (rpc). the evaluated variables were soil organic carbon (soc), aggregates stability measured by mean weight diameter (mwd), distribution of water stable aggregates, saturated water conductivity (ks), bulk density (da), and resistance to penetration (rp). the experimental design was complete random blocks and means were compared with the tukey test (p<0.05). the results showed a low mwd (0.20 to 0.28 mm) and a dominance of water stable fractions smaller than 0.25 mm that was above 66% in all of the treatments. this suggests that the structural system is susceptible to physical degradation; rp and rpc had better structural stability and a higher proportion (p<0.05) of macroaggregates (> 0.25 mm), as well as a significant increase in soc (p<0.05). the treatment rpc had significantly lower values of ks (0.76 cm h-1), da and rp, which is favorable for sustainability of the soil structural system.
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