摘要:

0.83) than for surface soil moisture (>0.69). We also found that removing the observed cyclic patterns from the original data drastically reduced the spatial variations of soil moisture, as well as temperature observations.

ISSN:0038-075X    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

We investigated the release of K from 10 surface and subsurface soil horizons at different K concentrations, and used four kinetic equations (Elovich, modified Freundlich, parabolic diffusion, and first-order) to describe the desorption rate data. The results demonstrate the successful use of the first-order equation to describe K desorption rates. The choice of the first-order equations among others investigated was based on the goodness of fit (lower standard error of estimate obtained) and on the more realistic theoretical assumptions of the equation.The relationship between first-order equation constants and the selected physical and chemical properties of the studied soils was investigated. Correlation coefficients relating first-order equation constants to most of the selected soil properties were low, but the interaction between organic C and exchangeable K variables was high. Multiple linear regression models relating first-order parameters to soil variables were highly significant. The ratio of organic C to exchangeable K (OC/Ex. K) was a strong contributor in the first-order constants models. The regression models were successful in predicting the first-order equation constants, as well as the K desorbed from soils.

ISSN:0038-075X    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

The spatial variability of saturated hydraulic conductivity was measured in situ in a clayey soil with macropores.Ksatwas determined at 37 equally spaced transect sampling locations using five different-sized, in situ soil columns. Each column, starting with the largest, was constructed within the confines of the previous column. Excavation of a block of soil on four sides, with the block remaining naturally attached at the bottom, defined a volume of soil to be used inKsatdetermination. The volumes used were 2.4 x 105, 1.2 x 105, 0.5 x 105, 6.28 x 103and 884 cm3. Quantitative estimates of macroporosity were obtained from tracings of visible tubular and planar voids at the exposed upper soil surface. Measurement was also made of bulk density and percentage sand, silt, and clay. The mean (μ) and variance (σ2) ofKsatwere found to be a function of the sample volume used, with the two smallest volumes producing estimated moments much larger than observed using the next two largest sizes. The 2.4 x 105-cm3-volume sample size proved to be an operationally cumbersome method and also produced extreme and probably unreliable estimates of μ and σ2. Geostatistical analysis demonstrated spatial structure to exist for the 1.2 x 105and 0.5 x 105-cm3sample volumes, but only random variation was observed for the other three sizes. Cross-correlation betweenKsatand macrovoids andKsatand physical properties was also demonstrated. Implications of these results for future sampling and soil survey studies are addressed.

ISSN:0038-075X    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

Determination of pH in water, 0.01MCaCl2, and 0.1MKCl, at dilution ratios 5:1, 2.5:1, and 2:1 solution: soil, were found to be highly correlated over a wide pH range. The regression equations, obtained on a small group of New South Wales soils under strict laboratory conditions, were similar to those reported in comparative studies from Britain (Davies 1971) and Canada (van Lierop 1981). The relationship between pH in water (pHw) and 0.01MCaCl2(pHca) at 2.5:1 solution: soil was found to bepHca= 1.05 pHw- 0.9The regression equation is valid only for nonsaline, net negatively charged soils.Our study demonstrates that wide dilution ratios result in the release of hydrolyzable acidity that nearly maintains the pH registered at narrower ratios. Between 2:1 and 10:1 dilution ratios, the release of H+cmol(+)/kg soil was linearly related to the dilution ratio. Periods of solution-soil shaking in excess of a few hours are undesirable because the pH meanders with time and a stable pH is not attained.

ISSN:0038-075X    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

Land managers are concerned with maintaining crop, forest, and range production. If erosion losses from moderately deep or shallow soils occur faster than the soil is replenished by weathering from underlying bedrock or consolidated sediments, productivity will decline. Therefore, rates of soil formationf can be considered constraints on tolerable soil losses from relatively shallow soils; their long-term soil-loss tolerances can be equated with their rates of formation from bedrock or consolidated sediments. There are few data for determining rates of soil formation, however. Data from small, nonagricultural watershed studies in which the inputs and outputs of silica and the major cations have been measured can be utilized for this purpose. Rates of soil formation, based on these data from 18 watersheds with noncarbonate lithologies, range from 0.02 to 1.9 Mg/ha yr. The rates are most highly dependent on (1) the volume of run-off water and (2) the soil-to-rock ratio, where this ratio is a mass of soil divided by the mass of bedrock weathered to produce that mass of soil. An equation developed to predict rates of soil formation from these two parameters has a very high coefficient of determination,R2= 0.94.

ISSN:0038-075X    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

The analysis of soil solutions generated by a large, isolated, summer rainstorm in the boreal forest of arctic Alaska has provided direct evidence for threshold-controlled subsurface translocation in soils. Intense leaching apparently initiates progressive weakening and eventual break-down of amorphous particle coatings in the Bs horizon. The result is a highly punctuated pulse of organometallic soil plasma that originates in the Bs and temporarily transports material at over 100 times normal rates. Episodic pulse mechanisms of this type have not been reported before; they may play a critical role in the formation of other young or unstable soil environments. In this case they help explain the unusual morphology of Spodosols in arctic Alaska.

ISSN:0038-075X    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

This paper reports a mechanism for chelation and removal of exchangeable Al from an acid subsoil. We treated soil columns with ethylenediamine tetraacetic acid (EDTA) and lime (CaCO3) to study the effects on subsoil ionic reactions. As water percolated through soils that had received surface applications of both EDTA and lime, significant levels of exchangeable aluminum were removed to a depth of 60 cm, whereas topsoil treatments of lime alone had little effect on subsoil exchangeable Al below 30 cm. Movement of Ca, Mg, and Fe are also presented as functions of EDTA and lime treatments. The data support the hypothesis that organic ligands can have a marked effect on the migration and subsequent ionic reactions of metal ions within the soil exchange matrix.

ISSN:0038-075X    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

We applied a statistical procedure to soil landscapes to show variability in soil bodies and to aid in recognizing transition (boundaries) between them. Trials were made by collecting soil samples at a depth of 30 cm at 50-cm intervals along a 75-m-long transect on a wooded slope dominated by Typic Hapludalfs. Time series andLstatistics were used in the analysis of the silt and clay contents. The results showed that soil bodies could be partitioned into different series by using as few as two soil properties.

ISSN:0038-075X    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

In a greenhouse experiment, we evaluated the effects of scrubber sludge on the aggregation and the porosity in various combinations of dredged sediments and topsoil in the presence of sudangrass roots. As expected, the water-stable aggregates increase with increasing percentage of topsoil. For all combinations, scrubber sludge decreased aggregation. The topsoil had a total porosity similar to the sediments at the completion of the study in the absence of scrubber sludge. The total porosity increased with additional quantities of scrubber sludge for all combinations of topsoil and sediments. Transmission (>50 μm), water storage (50 to 0.5 μm), and residual (

ISSN:0038-075X    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

Concentrations of dissolved (passing through aerobic filtration) iron and organic carbon (DOC) were determined in water samples collected from subarctic fens near Schefferville and boreal bogs near Sept-Iles, northern Quebec. Total iron and DOC concentrations averaged 19.3 and 1.2 mg/L, respectively, for all the samples analyzed and were weakly negatively correlated. The bog waters were higher in DOC and lower in total iron than the fen waters. Subsurface samples from the fens, underlain by iron-rich materials, showed increased iron concentrations, whereas the bogs, underlain by iron-poor materials, did not. Differences in the DOC: iron ratios can be explained by the different pathways of water and sources of DOC and iron in the two types of peatland. Reaction of the peat water samples witho-phenanthroline suggests both organically complexed and fine colloidal and dissolved forms of iron. The continuous variation method showed that peak absorbance occurs at DOC: iron ratios of 6:1 to 8:1, suggesting that all but the subsurface fen samples contained organic matter complexes that were undersaturated with respect to iron.

ISSN:0038-075X    

出版商:OVID    

年代:1988

数据来源: OVID