Showing papers in "Geoderma in 1993"

TL;DR: In this paper, the formation of soil structure involves the physical forces of shrinking and swelling created by changes in water status of soils, freezing and thawing, tillage, or by movement of the larger biota in soils.

TL;DR: In this paper, the water drop penetration time (WDPT) of a soil sample and of its sieve fractions, and by microscopic examination of soil components and features in each of these, one can indicate which soil constituents are important to the building up of water repellency.

TL;DR: In this article, experimental clay-polysaccharide associations were taken as models for the soil/biota interface, and their microstructure and physical properties were investigated, where special attention was given to control the water potential and to preserve, as far as possible, the organizations of the original hydrated conditions.

TL;DR: In this paper, the effect of soil type on carbon (C) and nitrogen (N) mineralization rates in grassland soils was investigated along with the physical and biological soil characteristics that may have caused the observed differences in mineralization rate between soil types.

TL;DR: In this article, the authors used densiometric separation to quantify the turnover of organic matter (SOM) in a macroaggregate-derived ELF and found that 18% of the total organic matter turnover in no-till soil was associated with fine-silt size particles having a density of 2.07-2.21 g/cm3 isolated from inside macroaggregates.

TL;DR: In this article, the authors described the preparation and characterisation of silica sand (cristobalite) with well defined iron oxides (e.g., goethite, hematite) on cristobalite as well as quartz surfaces.

TL;DR: A review of existing methods for soil microstructure characterization can be found in this paper, where some of the established methods have been evaluated and suggested for extending their usefulness; and some new approaches where methodologies have not yet been fully developed and their potential for successful application to soils is unknown.

TL;DR: Modifications of the microstructure were recognized with all species, the size depending on the size of organism, and polysaccharide-mediated aggregation was predominant.

TL;DR: In this paper, a quantitative model of the balance between inputs and outputs of nitrogen, phosphorus and potassium in African land use systems (NUTBAL) was developed at two scales: supra-national (38 sub-Saharan African countries) and regional (Kisii District, Kenya).

TL;DR: In this article, the effects of different pretreatment conditions and wet-sieving procedures on water-stable aggregate distributions of sandy and clayey textured soils (Cecil, Pacolet, and Hiwassee Series) from the Piedmont of the southern Appalachian mountains of Georgia, USA.

TL;DR: In this paper, dust-laden Harmattan winds are a recognized phenomenon of the Sahel region of Africa since 1985, and atmospheric dust inputs have been monitored at two sites in Niger, West Africa since July 1985 Dust traps of the open bucket type were placed 25 and 5 m above the soil surface.

TL;DR: In this paper, the structural composition of dissolved organic carbon (DOC) was evaluated by using wet-chemical methods, CPMAS 13C NMR spectroscopy, pyrolysis-field ionization mass spectrometry, and analytical DOC fractionation.

TL;DR: The model quefts (QUantitative Evaluation of the Fertility of Tropical Soils) was calibrated using data from maize fertilizer trials in Kenya as discussed by the authors, and the goodness of fit (r2) between measured and calculated yield was improved from 0.66 in the original version to 0.78 in the modified version of quefts and when including a boundary condition for harvest index.

TL;DR: In this paper, the feasibility of a third approach to parametric survey has been investigated using data from the lower Macquarie Valley, NSW, Australia, where soil characteristics were predicted using generalized linear models with more readily observed environmental variables as predictors.

TL;DR: A comparative study of the soil before ingestion, the gut content and casts of P. corethrurus showed that the soil structure was completely destroyed, which made that organic elements that were protected were recycled and others were protected by the formation of new microaggregates.

TL;DR: The Gaia hypothesis as discussed by the authors states that the earth has evolved over geologic time by feedback processes keeping the earth in a state comfortable for life by the action of living organisms, which can be seen as responsible for the persistence of water on the earth through control of the earth's surface temperature under the influence of greenhouse gases.

TL;DR: In this article, chemical and mineralogical characteristics have been determined for a chronosequence of six soil profiles ranging in age from 80-13,000 years BP developed on river terraces in the western Cairngorms of Scotland.

TL;DR: It is suggested that models should be analysed not only for sensitivity to changes to their parameters but in some circumstances to changes in parameter variance, particularly where the model may not be linear with respect to its parameters.

TL;DR: In this paper, the authors investigated the ecological effects resulting from two different agricultural cultivation systems and found that management practice and type of cultivation had more influence on soil biota than different soil types.

TL;DR: It is shown that quantitative fractal geometry can yield insights into the mechanism whereby spatial organisation influences the interaction between structure and biotic processes in the soil.

TL;DR: In this paper, the authors present the stages of the gravel shattering process by salts in desert Reg soils and discuss factors influencing the rate of development under natural conditions prevailing in the Negev Desert.

TL;DR: Comparison of aggregate size distributions suggested a more porous structure for the inoculated rhizosphere soil than the uninoculated, and an avidin-biotin indirect ELISA procedure, which allows the detection of B. polymyxa in its natural environment, indicated that the population remained at a constant level whatever the treatment or the size of aggregates.

TL;DR: In this article, P sorption in 12 samples of soils of a typical hydrosequence of the Cerrado region (Brazil) was predicted by means of combining data on: (1) the amount and properties of gibbsite, goethite, hematite and kaolinite, and (2) the P-sorption characteristics of these minerals, according to existing data in the literature.

TL;DR: In this paper, the authors present a methodology for a World Soils and Terrain Digital Database (SOTER), which is used in three pilot areas involving five countries (Argentina, Brazil, Uruguay, USA and Canada) using local data and training national staff in operation.

TL;DR: A field trial was started in 1988 to examine the effects of temporary grassland and conventional tillage on aggregate stability and soil microbial processes as mentioned in this paper, and the results indicated that continuous vegetation and the activities of soil organisms are preconditions to maintain high aggregate stability.

TL;DR: In this paper, the effect of humic substances on phosphate adsorption by poorly ordered Fe-oxide aged at pH 4 or 7 for 56 days was investigated at pH 6.2 in a 0.01M CaCl2 matrix.

TL;DR: In this paper, the authors investigated the effects of soil drying and remoistening on microbial biomass and enhanced mineralization of carbon during subsequent moist incubation and concluded that the resistance of soil microorganisms to soil drying is influenced by their metabolic activity (which is determined by their type and physiological state).

TL;DR: Porosity and pore size distribution from thin sections, prepared from undisturbed Ap horizon samples taken from a zero- versus conventional-tillage field experiment, were analyzed by means of a Quantimet 720 image analysing computer.

TL;DR: In this paper, an attempt has been made to integrate and quantify these interrelationships by using the themes of C and N mineralization and porosity using data from soils in western Canada.

TL;DR: The results show that casts of M. anomala are very dense and have an important volume of pores with a diameter of ca.