bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spatial and Spectral Relationships of Soil Properties and Microtopography: II. Density and Thickness of B Horizon
Authors: Kachanoski R. G. , De Jong E. , Rolston D. E. 
Published: July 2010

AbstractThe effects of microtopography (<50 m) and an intertill stratigraphic sand‐gravel layer on the spatial variability of B horizon thickness, density, and mass are examined using standard, spatial, and spectral statistical methods. The relationships between A and B horizon thickness, density, and mass are also examined. Elevation and maximum surface gradient were significantly correlated to B horizon density. Microtopography parameters were not correlated to B horizon thickness or mass. The B horizon thickness and mass were significantly correlated to the depth to the intertill sand‐gravel layer. Significant autocorrelation was present in the density of the B horizon but not the A horizon. B horizon thickness and mass cycled significantly but at different frequencies than the A horizon. Spatial variability of the B horizon soil properties was related to the depth of the intertill sand‐gravel layer while the variability of the A horizon was related in large part to microtopography, especially curvature. Coherency and cospectral analysis indicated the B horizon mass had some relationship to surface curvature, but opposite correlation existed over different frequency ranges resulting in a non‐significant overall correlation. Average thickness, density, and mass of the solum did not have similar significant cycling or autocorrelation as was present in the individual horizons.
Temporal Stability of Spatially Measured Soil Water Probability Density Function
Authors: Vachaud G. , Passerat De Silans A. , Balabanis P. , Vauclin M. 
Published: July 2010

AbstractSoil water data collected from three different fields are analyzed by two techniques (temporal analysis of the differences between individual and spatial average values; and Spearman's rank correlation) to search if time‐invariant characteristic statistical properties of the probability density functions can be assigned to individual locations. A grass field was equipped with 17 neutron access tubes and surveyed 24 times during a 2 1/2 yr‐period. In another field planted with olive trees, nine neutron access tubes were installed and quarterly measurements were performed during two consecutive years. The latter field cropped in wheat was gravimetrically sampled on a regular spatial pattern five different times and was routinely surveyed during a 1‐yr period at four selected locations by using a neutron moisture meter. All data show the existence of a very significant time‐stability of particular individual locations characterized by the same parameter in the statistical distribution of the observations taken over the field. It is shown that some locations conserve the property to represent the mean and extreme values of the field water content at any time along the year. This stability seems to be explained to a large extent by relationships between soil texture and water content.
Physical and Mineralogical Data to Determine Soil Hydraulic Properties
Authors: Puckett W. E. , Dane J. H. , Hajek B. F. 
Published: July 2010

AbstractA study was conducted to determine relationships among physical, mineralogical, and soil hydraulic properties of Ultisols developed in unconsolidated sediments of the Lower Coastal Plain. Soil water retention curves, saturated hydraulic conductivity, bulk density, quantitative mineralogy, surface area, and particle size distribution were determined by horizon for seven pedons and relationships among them were analyzed by regression analysis procedures. Fine sand, sand and clay percentages were highly correlated with saturated hydraulic conductivity, surface area and volumetric water contents at specific pressure heads. Correlation coefficients > 0.95 were obtained for regression equations estimating soil water retention curves from particle size data. These relationships can be useful for quick characterization of soil hydraulic properties from particle size distribution data. No significant correlations were found between soil hydraulic and mineralogical properties of the clay fraction.
Chemical Modeling of Anion Competition on Goethite Using the Constant Capacitance Model
Authors: Goldberg Sabine 
Published: July 2010

AbstractThe constant capacitance model was used to describe phosphate, selenite and silicate adsorption on goethite (α‐FeOOH) in single anion systems. The model assumes a ligand exchange mechanism and considers the charge on both adsorbate and adsorbent. It is therefore appropriate for describing the adsorption behavior of these specifically adsorbed anions. The computer program FITEQL, a program that fits equilibrium constants to experimental data using an optimization technique, was used to obtain optimal values for the anion surface complexation constants on goethite. The model represented adsorption of these anions well over the entire pH range studied (3–12). The main advantage of the model is its ability to represent changes in anion adsorption occurring with changes in pH. Extension of the model to describing anion competition in mixed systems using the anion surface complexation constants from single anion systems was qualitatively successful. In mixed anion systems the model predictions reproduced the shape of the adsorption isotherms well over the pH range 3 to 12. However, phosphate adsorption was overestimated while adsorption of the competing anion was underestimated.
The Error Taxadjunct and Its Application in Soil Taxonomic Assignment
Authors: Hewitt A. E. , Van Wambeke A. 
Published: July 2010

AbstractPrecisely defined class limits cause taxonomic “splintering” of similar soils. This study follows up the suggestion in chapter 19 of Soil Taxonomy (USDA Soil Survey Staff, 1975) that knowledge of the confidence limits of measurement can allow “reasonable interpretations” which would prevent unwarranted splintering. A region of error adjacent to established taxa is identified, in which pedons, as representations of polypedons, are assigned to incorrect taxa because of errors in measurement of differentiating characteristics. This region is used to define the “error taxadjunct” which provides a means of softening precision of class limits. The size of the region of error is determined by the minimum acceptable probability of incorrectly assigning a pedon, as the representative of a polypedon, to a new taxon. Application of the error taxadjunct reduces taxonomic splintering. For this purpose the measurement errors of differentiating characteristics must be known, and the means of obtaining such data are reviewed. Examples show how the error taxadjunct can be used.
Application of a Statistical Soil‐Landscape Model to an Order III Wildland Soil Survey
Authors: Shovic H. F. , Montagne C. 
Published: July 2010

AbstractData organization, analysis, and documentation have long been a concern in the soil survey process. Existing computer aided systems are often either not widely available, not “user friendly,” or not very applicable to field mapping situations. These concerns are addressed using a simulation approach. A statistical model of the landscape and soils in the survey area is described. The data base used in the soil ‐landscape model consists of discrete sample points that are randomly distributed (for soil taxa only), mutually exclusive, and independent. The data are representative of other site characteristics. The concepts of statistical estimation, conditional probability, quantified prediction improvement, and selective sorting are applied to use the model in the mapping process. Applications include systematic development of soil‐landscape relationships and legends; documented justification for decisions as to data adequacy, soil interpretations, map unit differentia, variability, and taxonomic descriptions; and increasing accuracy of soil correlation. Programs are standard and widely available.
Significance of Ground Freezing on Soil Bulk Density Under Zero Tillage
Authors: Kay B. D. , Grant C. D. , Groenevelt P. H. 
Published: July 2010

AbstractSoil bulk densities remain persistently higher in Ontario on soils on which zero tillage is practiced, than on soils which are conventionally tilled. This occurs in spite of the fact that the formation of ice lenses over winter on soils which are frost susceptible may introduce porosity, which is sufficiently large to cause displacements of the ground surface of several centimeters. Studies were carried out over two winter seasons on soils of two different textures and on which two different tillage treatments (conventional and zero tillage) were practiced in order to determine the reason for this anomalous behavior. Soils under zero tillage accumulated more snow over winter and did not freeze as deeply as soils that were plowed in the fall. However the amounts of water which accumulated in the frozen zone were similar per unit depth of frost penetration. The greater depth of frost penetration resulted in significantly greater surface displacement on the fall plowed soil. However the soils under both tillage treatments quickly reconsolidated upon thawing and returned to near prefreezing bulk densities prior to spring planting. The formation of ice lenses appears to create pores which are inherently unstable and collapse as the ice melts and the soil drains. The loss of pores created by ice lenses occurs in a manner analogous to the removal of a slice of meat from between two slices of bread. The unstable nature of pores created by ice lenses appears to be in contrast to the characteristics of pores created by tillage, which on account of their formation by the vertical and horizontal displacement of peds, are more stable.
Effect of Erosion and Landscape Position on the Productivity of Piedmont Soils
Authors: Stone J. R. , Gilliam J. W. , Cassel D. K. , Daniels R. B. , Nelson L. A. , Kleiss H. J. 
Published: July 2010

AbstractThe objective of this study was to determine the effect of past accelerated erosion in the North Carolina Piedmont on soil physical and chemical properties and soil productivity, and to determine the relationship between soil productivity, soil erosion, and landscape position. Data from five Piedmont fields were collected over a 2‐yr period. Within each field, plots were located on all erosion classes and landscape positions present. Definite relationships between erosion class and soil physical and chemical properties were observed. Clay content increased approximately 10% for each erosion class change from slight to moderate to severe. Organic matter content tended to be higher on the more eroded sites. Differences in topsoil depth among erosion classes in a given field ranged from 2.4 to 8.7 cm and the severely eroded areas were always significantly shallower. Available water‐holding capacity of the A horizon (g g−1) always was slightly higher on the more eroded sites. Available P decreased sharply with erosion severity but all sites had levels ≥ 17 g P m−3 which is considered adequate. The highest corn grain yields were usually obtained on the moderately eroded sites as compared to the slightly and severely eroded areas. This was particularly true in 1981 which was a dry year. In a more favorable year (1982) with regard to amount and distribution of growing season rainfall, the yield differences among erosion classes were less. The differences in corn grain yield among landscape positions were much more consistent than yield differences among erosion classes. Those landscape positions that received water from higher elevations produced the highest yields. Because landscape position and erosion severity are not mutually exclusive, we believe that much of the published data dealing with the effects of erosion on soil productivity are confounded by the effect of landscape positions on soil erosion.
Crop‐Water Production Function Model for Saline Irrigation Waters
Authors: Letey J. , Dinar Ariel , Knapp Keith C. 
Published: July 2010

AbstractThe relationship between crop yield and seasonal amount of applied water (crop‐water production function) is required to determine optimum irrigation management. A model is developed for the computation of crop‐water production functions with saline irrigation waters. The model combines three relationships: yield and evapotranspiration, yield and average root zone salinity, and average root zone salinity and leaching fraction. The model allows plant growth adjustment, and therefore evapotranspiration adjustment, to root zone salinity. Crop‐water production functions were computed for tall fescue (Festuca elatior arundinacea L.) for various levels of salinity in the irrigation water. A comparison was made between calculated and published experimentally measured values of leaching fractions and yields of tall fescue grown under conditions of various irrigation water salinities, water application quantities and applied water frequencies. Calculated and measured yields were in good agreement considering the usual degree of variability of field data. Agreement between calculated and measured leaching fractions was not as good as for yields.
Depth of Surface Soil‐runoff Interaction as Affected by Rainfall, Soil Slope, and Management
Authors: Sharpley A. N. 
Published: July 2010

AbstractThe effective depth of interaction (EDI) between surface soil and runoff (the thickness of surface soil in which the degree of interaction is equal to that at the soil surface) was determined for five soils of varying physical and chemical properties under simulated rainfall, in order to quantify the effect of rainfall and soil characteristics on EDI. For all soils EDI increased (1.30–37.43 mm) with an increase in rainfall intensity (50–160 mm h−1) and soil slope (2–20%), although the magnitude differed between soils. The effect of rainfall intensity was attributed to increased runoff energy enhancing mixing in the surface soil and was also a function of soil aggregation. The magnitude of the EDI increase with increasing soil slope was independent of soil type being a function of runoff energy alone. An avg 73% reduction in EDI following the incorporation of 100 kg wheat straw (Triticum aestivum L. sp.) ha−1 and 80% reduction with a 0.5‐mm2 mesh screen, simulating crop cover, was obtained compared to the control (3.36 mm). For all soils the logarithm (ln) of soil loss was linearly related to the ln EDI. This is to be expected since factors affecting EDI (rainfall intensity, runoff energy, and soil aggregation) also influence soil loss. Regression slope of the logarithmic relationship was similar (at the 5.0% level) for all soils, and regression intercept was related to soil aggregation. Thus, EDI and the effect of rainfall and soil management can be estimated from soil loss. This relationship will improve the prediction of adsorbed chemical (P and pesticides) transport in solution, since chemical transport models presently use a fixed EDI value.
Shadecard and Shelterwood Modification of the Soil Temperature Environment
Authors: Childs S. W. , Holbo H. R. , Miller E. L. 
Published: July 2010

AbstractA study was conducted on steep, south‐facing slopes in southwest Oregon to assess the effect of two common reforestation practices on the soil thermal environment. Three clearcut sites and three shelterwood sites were instrumented to measure soil temperature at five depths in the vicinity of shaded and unshaded Douglas‐fir seedlings. Since the soils studied were skeletal, heat capacities of both fine and coarse soil fractions were determined for each site. These data were used to estimate soil heat fluxes. Shelterwoods decrease soil temperatures approximately 6 K when compared with clearcuts. This result holds at both 20‐ and 320‐mm depths. Shelterwoods also decrease the depth of diurnal heating and decrease maximum hourly heat loss and gain values by 73 and 80 W/m2, respectively. Shadecards, cardboard rectangles placed to the southwest of seedlings, generally have little effect on the soil temperature regime of skeletal soils but are effective in reducing daily heat flux. The dominant shadecard effect is a decrease in average daytime heat flux by 22 W/m2, but shadecards also decrease average nighttime fluxes. Shelterwoods ameliorate seasonal soil temperature conditions significantly and may be an appropriate technique in situations where cumulative soil heating limits reforestation success. Shadecards should be useful in situations where heat stress events of only a few days are a problem. Over a season, shadecards exert little control, and their influence on stress is limited. Since all soils studied had high heat capacities due to large rock fragment content the conclusions of this study may be limited to soils with large soil heat capacity.
A Core Sampler for Puddled Soils
Authors: Sharma P. K. , De Datta S. K. 
Published: July 2010

AbstractA core sampler was designed to collect undisturbed samples of known volume from the 0‐ to 10‐cm depth in soft‐puddled soils. The instrument is simple, inexpensive to construct, and easy to operate. With practice, the operator can routinely collect a sample from flooded, puddled soils in < 2 min.
Evaluation of the Hot Air Method for Measuring Soil Water Diffusivity
Authors: van Grinsven J. J. M. , Dirksen C. , Bouten W. 
Published: July 2010

AbstractThe Hot Air Method (HAM) is a fairly new and simple method for measuring soil water diffusivity. However, with the introduction of temperatures much higher than originally proposed by Arya et al. (1975), the validity of the underlying assumptions must be questioned. Philip's iterative solution was adapted for desorption out of a semi‐infinite column at constant surface water content to evaluate effects of soil type and boundary water contents on the experimental results. Errors due to deviations from assumed isothermal conditions were evaluated with the Philip and de Vries (1957) theory for the large temperature increases that occur in soil columns during execution of HAM. Evaporation losses and water redistribution during sampling of the soil column were evaluated by simulation. Error analysis indicates that, with the present usage of air temperatures up to 250°C and sampling times of several minutes, HAM does not satisfy the prerequisite assumptions. Reports of favorable results from HAM are probably due to mutual compensation of different errors and to considerable smoothing of experimental results. In spite of its great experimental advantages one should be dissuaded from using HAM unless the experimental errors are minimized and the calculation technique is made objective and reproducible. In this paper some improvements for the experimental procedure are proposed.
Estimating Soil Water Characteristics from Simpler Properties or Limited Data
Authors: Ahuja L. R. , Naney J. W. , Williams R. D. 
Published: July 2010

AbstractBroad‐based regression equations of Rawls and associates were investigated for estimating the spatially variable soil water content‐matric potential relationships in a 1.6‐ha watershed (Udertic Paleustolls) from soil textural and structural properties, with and without one or two known values of the relationships. Also examined were a simple log‐log line based on two known values and estimates obtained from one known value for each relationship and a complete relationship for one case using the similar‐media scaling concept. The results were compared with measurements on 189 soil cores representing different sites and horizons. With the equations based on soil texture, bulk density and organic matter content, the soil water contents calculated at different matric potentials were generally larger than the measured values. The mean relative error ranged from 8 to 29%, with the standard deviation of errors ranging from 17 to 36%. The model which incorporated one measured soil water content (at −1500 kPa potential) as an additional independent variable, did not improve the results much. The model which incorporated two measured soil water contents (at −33 and −1500 kPa potentials) as additional variables reduced the errors in calculated values considerably. A simple log‐log line drawn through the two known points gave nearly the same accuracy. The estimates from the method of scaling were better than those from the model based on textural and structural variables alone; the mean relative error in the calculated water contents ranged from −0.96 to 9.10%, and the standard deviation of errors was also reduced.
Potassium Fixation Characteristics of Five Southern California Soils
Authors: Shaviv A. , Mohsin M. , Pratt P. F. , Mattigod S. V. 
Published: July 2010

AbstractPotassium fixation in five southern California soils, sampled at 15‐cm depth increments down to a depth of 105 cm, is reported. The objective was to develop quantitative relationships between K fixation and other soil and solution properties. The experiments were conducted under wet conditions only and the exchangeable cation removal done by BaCl2. Potassium fixation, Kf, was calculated by the difference between total initial K and total final exchangeable plus soluble K in a given system and compared to ΔCEC, the decreases in the initial cation exchange capacity (CECin). The difference between Kf and ΔCEC appeared small, inferring that under wet field conditions, fixation mainly occurred via the mechanism of K entrapment between clay plates. Linear increases of Kf with EP (the ratio of adsorbed K to adsorbed Ca and Mg) and with PAR = {(K+)/[(Ca2+)+(Mg2+)]1/2} were found for each depth for each soil. Potassium fixation also increased with increasing depth. Relating the fractional fixation FKf = (Kf/CECin) to EP and PAR, a more general representation of K fixation was obtained. Fractional fixation and EP showed a linear relationship as FKf = A2 + B2 × EP. Such a correlation resulted in one or two regression lines representative of fixation through a given soil profile to the 105‐cm depth.
Effect of Tillage on the Distribution of Manganese, Copper, Iron, and Zinc in Soil Fractions
Authors: Shuman L. M. , Hargrove W. L. 
Published: July 2010

AbstractThe availability of micronutrients is affected by soil properties such as pH, organic matter content, and clay mineralogy. Some of these properties can be altered by tillage. Therefore, a study was conducted to determine the influence of tillage on the distribution of Mn, Cu, Fe, and Zn among soil fractions. Soil samples were taken at the 0 to 2 cm depth from a long‐term (8 yr) tillage experiment. The treatments were no‐tillage, minimum tillage (fall tillage only), and conventional tillage (spring and fall tillage). Soil samples were fractionated sequentially to determine Mn, Cu, Fe, and Zn in the following fractions: exchangeable, organic, Mn oxide, amorphous Fe oxide, crystalline Fe oxide, and residual. Double acid‐extractable P and Zn, organic matter content, and cation exchange capacity were higher in no‐tillage treatments than in the other tillage treatments. Tillage had more effect on the distribution of Mn and Fe among fractions than on the distribution of Zn and Cu. No‐tillage lowered the Mn in the exchangeable and amorphous Fe oxide fractions and raised Mn in the organic fraction compared to minimum tillage or conventional tillage. Iron in the exchangeable and organic fractions was higher for no‐tillage, while amorphous oxide Fe and residual Fe were lower for no‐tillage compared to conventional tillage. Both Mn and Fe appeared to be shifted by no‐tillage from the oxide and residual forms into the more plant‐available exchangeable or organic forms.