bluuebunny/crossref_metadata_2025_split huggingface dataset:
Estimating Soil Parameters and Sample Size by Bootstrapping
Authors: Dane J. H. , Reed R. B. , Hopmans J. W. 
Published: July 2010

AbstractCollecting large numbers of soil samples (observations) to estimate parameters of certain soil properties is not always feasible, especially for undisturbed soil samples. If the number of soil samples is small, however, the usefulness of classical statistics is often limited and an alternative procedure is required to determine statistics of interest. A recently developed, computer‐intensive, statistical procedure; bootstrapping, is discussed for two bulk density applications for which relatively small numbers of observations were obtained. Bulk density was determined at 16 depths along 1.2‐m long soil cores taken at each of 60 locations in a 50‐ by 100‐m cultivated field (Norfolk sandy loam, Typic Paleudults). Initially, 16 locations were sampled. At a later date, the additional 44 locations were sampled at similar soil‐water conditions. For each core, bulk density was determined at 0.20‐, 0.40‐, 0.60‐, 0.80‐, and 1.00‐m depths by a paraffin technique and at 0.14‐, 0.26‐, 0.34‐, 0.46‐, 0.54‐, 0.66‐, 0.74‐, 0.86‐, 0.94‐, 1.06‐, and 1.14‐m depths by a direct method. Semivariograms, determined for each depth, generally showed no evidence of spatial interdependence between locations. Additional statistical tests indicated that the samples for the two dates came from different populations. Bootstrapping was used to determine confidence intervals for the population mean, variance, and range by sampling date without a priori assumptions as to the distribution of bulk density in the population. Bootstrapping was further used to develop a general method for determining the minimum sample size (minimum number of observations) that can be used to estimate the population mean with a selected degree of precision and level of confidence. Application of the bootstrap method indicated not only differences in bulk density on the two sampling dates but also differences in the precision of the bulk density measurement techniques.
A Simple Model to Describe the Dissolution of Phosphate Rock in Soils
Authors: Mackay A. D. , Syers J. K. , Tillman R. W. , Gregg P. E. H. 
Published: July 2010

AbstractDissolution of phosphate rock (PR) in contrasting soils was evaluated by extraction with 0.5 M NaOH following a prewash with 1 M NaCl to remove exchangeable Ca2+. This provides a simple and direct method for measuring the rate and extent of PR dissolution in soils. Dissolution of Sechura phosphate rock (SPR) in six soils was essentially complete at 90 d and the pattern of dissolution could be described by a modified Mitscherlich equation of the form y = A (1 − e‐ex), in which y = amount of SPR dissolved at time x; A = asymptote, and c = curvature coefficient. Whereas A varied markedly across soils, c was independent of soil type. This exponential equation formed the basis of a simple model which describes and predicts the dissolution of SPR in soils. By establishing the relationship between A and a range of properties for 30 contrasting soils it was possible to identify those soil parameters that controlled PR dissolution in soil. Percent Ca‐saturation, P‐sorption capacity, and Ca‐exchange capacity of the soil were the three most important parameters influencing SPR dissolution in soils. When a model incorporating these three parameters was tested on soils not used to construct the model, the variance accounted for ranged from 66 to 76%, depending on the population of soils selected. These parameters determine the concentrations of Ca2+ and H2PO‐4 in the soil solution.
Small Grain Response to Potassium Fertilizers as Related to Soil and Site Characteristics
Authors: Veeh R. H. , Skogley E. O. 
Published: July 2010

AbstractThe major objective of this study was to determine what environmental characteristics best related to increased small grain yield when fertilizer K was included in a balanced soil fertility management program. These results would help explain why contemporary soil test approaches for predicting crop response to applied K fertilizers do not work in this region, and help lead to alternative approaches to resolve this problem. Two hundred twenty‐two small grain experiments established over a 13 yr period on 127 site locations throughout the Great Plains of Montana were selected for this study. Two to five rates of K, ranging from 0 to 135 kg K/ha, had been applied in the field experiments. Both KCl and K2SO4 were included as fertilizer sources in most experiments. Adequate rates of N and P were constant within an experiment, but varied from one experiment to another. Originally a total of 47 independent variables in various combinations were used in 45 multiple linear regression analyses. The dependent variables were (i) maximum, and (ii) average percent grain yield response to applied K. The statistical analysis was confounded considerably because of missing data for certain independent variables at some sites and because of intercorrelations between variables; however, significant relationships (simple r) existed in many of the regression analyses between independent variables and the dependent variables. In the final analyses, 32 sites were examined using 27 independent variables with a universal data base. Variables with the highest correlation to percent yield response (in decreasing order) were: (i) dry consistence of the Bk horizon; (ii) textural family; (iii) average soil temperature in May; (iv) growing season rainfall; and (v) stored spring soil moisture from 0 to 90 cm. Together these five variables produced a significant R2 of 0.34 (P=0.05).
Soil‐landscape Relationships and Soil Variability in North Central Florida
Authors: Ovalles F. A. , Collins M. E. 
Published: July 2010

AbstractMorphological and selected chemical and physical properties of 12 pedons on three landscape positions (summit, shoulder, and backslope) were determined to evaluate how soil properties and landscape positions are related in north central Florida. A multistage nested design was employed to compare the variance of selected soil properties within and between landscape positions. Soil properties in the study area were related to landscape position. Soil‐landscape relationships were enhanced by the nonuniformity of the parent material. The parent material of the soils studied on the backslope was the clayey‐phosphatic Hawthorn Formation. This geologic formation also influenced the genesis of the soils on the shoulder but to a lesser extent. The soils on the summit were developed from sandy marine sediments. Classification problems were encountered for some of the soils on the shoulder and all of the soils studied on the backslope. The principal differences and trends across the landscape were decreases in A horizon thickness, matrix colors with chroma >2, sand percentage, pH, and organic C content below the A horizon downslope. Mottles and matrix colors with chroma ≤2, silt and clay percentages, and total P contents increased downslope. Clay and total P depth distributions were genetically and statistically related and highly significant (0.01 level) when studied for the whole landscape (rs = 0.77) and for the soils (rs = 0.81) on the backslope. Substantial increases in total P and clay contents were associated with the Hawthorn Formation. Several statistical analyses were performed. Kolmogorov D test showed nonnormal distribution of the data. The x2 test indicated a highly significant (0.01 level) dependence between soil properties and landscape position. Several relationships were masked when the Spearman correlation (rs) analysis was performed using data for the whole landscape. When rs was low (<0.50) for the whole landscape, rs values computed according to landscape position increased. The results of the Kruskal‐Wallis test indicated significant differences (0.01 level) for each soil property, except organic C, in at least two of the three landscapes. In a nested design >50% of the variability for pH in KCl, total P, sand, silt, and clay was due to differences between landscapes. For organic C content, >70% of its variability was due to differences between horizons.
Effects of Soil Drying on Ammonia Volatilization from Surface‐applied Urea
Authors: Ferguson R. B. , Kissel D. E. 
Published: July 2010

AbstractTwo laboratory experiments were conducted to evaluate the effects of rapid soil drying on the potential for ammonia (NH3) volatilization from urea. Urea was applied to the surface of a sandy loam soil in acrylic chambers at a rate equivalent to 200 kg N ha−1. Static traps for NH3 and carbon dioxide (CO2) were added to the chambers and left in place for 48 h. Humid or relatively dry air was passed over the soil in the chambers between 48 and 72 h at rates sufficient to not inhibit NH3 volatilization. Concentrations of NH3 in the airstream leaving the chambers was monitored during this period. At 48 and 72 h, soil in selected chambers was sampled in 2‐mm depth increments and analyzed for pH, urea‐N, and ammonium‐nitrate (NH4+‐N). Rapid drying of the soil was found to rapidly decrease the rate of NH3 loss from the soil. Drying also reduced the amount of urea that hydrolyzed during the period from 48 to 72 h to practically zero. In the surface 2 mm, the urea concentration of the chambers receiving the dry air treatment increased substantially during the period of airflow. This increase was due to the mass flow of urea towards the soil surface as water evaporated from the soil. These data indicate that the potential for NH3 volatilization from urea applied to a soil that is initially moist but dries rapidly is low, if the soil water content/potential falls to a level at which urea hydrolysis is inhibited.
The Adsorption of o‐Phosphate on Alumina: A Solid Solution Model
Authors: Miller J. W. , Logan T. J. , Bigham J. M. 
Published: July 2010

AbstractAlumina‐P interactions were examined over a range of PO4 concentrations (0.8 µM‐0.2 mM) and pH's (7–9) conducive to adsorption rather than precipitation. The equilibria established were interpreted using chemical thermodynamic concepts to distinguish adsorption from precipitation and to evaluate the nature of the surface interaction. The chemical speciation model GEOCHEM, supplied with selected thermodynamic values, was used to predict adsorption‐free equilibria for the aqueous PO4/alumina systems. Relative to these predictions, the adsorption of PO4 increased soluble Al levels, apparently as a result of increasing the solid alumina surface activity. The formation of a soluble Al‐PO4 complex did not appear to contribute significantly to total soluble Al. The total soluble Al and PO4 concentration product was pH and total P addition dependent, as expected for equilibria controlled by the presence of a solid solution. An estimate of the ratio of activity coefficients, calculated for differing total PO4, indicated that the activity coefficient of the Al‐OH‐PO4 surface component increased with increasing amount of PO4 added. It was concluded that adsorption of PO4 at the inorganic oxide surface could be viewed as the formation of a surface‐limited solid solution. An attempt to apply a solid solution quasithermodynamic model to soil PO4 adsorption appears warranted, with particular emphasis on Fe, Al, and Ca oxide and carbonate minerals as the primary matrix for adsorption/solid solution formation.
Alfalfa Stand Losses from Irrigation: Influence of Soil Temperature, Texture, and Aeration Status
Authors: Meek B. D. , Donovan T. J. , Graham L. E. 
Published: July 2010

AbstractLosses of alfalfa (Medicago sativa L.) occur under the combination of high summer temperatures and clay soils. This paper examines the relationship between these losses and soil temperature, texture, and aeration. The study consisted of short tests (one irrigation) and long‐term experiments (2.5 yr) in the field, and gas exchange experiments in a greenhouse. The design for the field experiments was a randomized block with four replications for the short‐term experiments and three replications for the long‐term experiment. It was necessary to flood 56 h (silty clay soil under high temperatures) to damage alfalfa in the field. Root damage was only 1% in a clay loam soil compared to 10% in a silty clay soil (56‐h flooding time and high temperature). Sufficient water could not be applied in the long term experiment to the alfalfa to leach salts (84% Epan treatment) without severe losses in stand. Long flooding times (96 h) at medium temperatures (maximum air temperature 32°C) did not result in root damage to the alfalfa. Oxygen deficiency, not ethylene toxicity, seemed to be the problem when alfalfa was flooded. Ethylene levels in the field were low and symptoms of toxicity were not observed. In the greenhouse, no damage to alfalfa occurred until O2 fell to 0.01 L/L at high temperatures. Results of this experiment indicate that there is a high probability of damage to grower fields when O2 stress under high temperature extends over many irrigations.
Physical and Chemical Soil Properties of Three Big Sagebrush Subspecies
Authors: Swanson Sherman R. , Simonson Gerald H. , Buckhouse John C. 
Published: July 2010

AbstractThe three subspecies of Artemisia tridentata Nutt. typically occupy qualitatively different sites. Wyoming big sagebrush, A. t. ssp. wyomingensis, commonly grows in Aridisols; mountain big sagebrush, A. t. ssp. vaseyana, commonly lives in Mollisols at a higher average elevation; and basin big sagebrush, A. t. ssp. tridentata, occurs in deep soils of either order. This study evaluated some physical and chemical characteristics of surface and subsurface soil horizons of soils occupied by each subspecies in four widely spaced Oregon locations. Most soil chemical characteristics showed no significant differences between subspecies. Interaction between location and subspecies often indicated that analysis should proceed at each individual location. The Frenchglen location had the greatest elevational differences between sites and also had most statistically significant soil differences between subspecies. Many of the measured characteristics are interrelated and differences in them probably are influenced by elevation‐related variation in climate. Surface horizons of Frenchglen, A. t. ssp. vaseyana sites had lower pH, base saturation, and exchangeable Na+ and higher organic matter, cation exchange capacity, and water retention at −1.50 MPa than surface horizons of A. t. ssp. wyomingensis sites. Fewer surface soil characteristics of A. t. ssp. tridentata sites were significantly different. In deeper soil horizons at Frenchglen, A. t. ssp. vaseyana sites had lower pH and base saturation than A. t. ssp. tridentata sites.
Resistant and Exploratory Techniques for Use in Semivariogram Analyses
Authors: Hamlett J. M. , Horton R. , Cressie N. A. C. 
Published: July 2010

Abstract“Traditional” statistical analyses based on the assumption of independent observations are being replaced by spatial analyses that take account of correlations between neighboring observations. Geostatistics is one approach; it characterizes the spatial relationships of data via the variogram, which is in turn used for kriging (optimal, unbiased linear interpolation). Exploratory data analysis techniques, relying on resistant measures, graphical tools, and robustness ideas, can be used to help “model” the spatial structure of data. Data should fulfill certain stationarity conditions before computing and interpreting the semivariogram. Data of soil‐water pressure potential are analyzed by straight‐forward techniques that assure the data meet the implicit assumptions of stationarity (of the mean and the variance) and at least symmetry. Stem‐and‐leaf plots and plots of mean vs. variance (or for a more resistant analysis, median vs. interquartile range squared) are used to assess the variance stationarity and data distributions. Median‐based techniques (rather than polynomial modeling and generalized least‐squares fitting of drift) are used to remove drift along both grid directions. Then the spatial structure is exposed through computing and interpreting semivariograms of the modified data.
Effect of Mineral Weathering on the Response of Sodic Soils to Exchangeable Magnesium
Authors: Alperovitch N. , Shainberg I. , Rhoades J. D. 
Published: July 2010

AbstractThe clay dispersivity and hydraulic conductivity (HC) properties of three California soils were studied as a function of exchangeable Na and electrolyte concentration in Na/Ca and Na/Mg systems. Soils that are relatively stable chemically are concluded to be the most sensitive to low levels of exchangeable Na and to the “specific” effect of exchangeable Mg when leached with distilled water. The results agree with the hypothesis that the susceptibility of soils to HC decreases produced by exchangeable Na and exchangeable Mg depends on their rates of mineral dissolution. Exchangeable Mg reduces the dissolution rates of noncalcareous soils and increases soil susceptibility to exchangeable Na under conditions of low electrolyte concentrations.
Comparison of Inoculant and Indigenous Rhizobial Dinitrogen Fixation in Cowpeas by Direct Nitrogen‐15 Analyses
Authors: ElHassan G. A. , Focht D. D. 
Published: July 2010

AbstractSoil that contained 15N enriched organic matter (0.461 % 15N) was used to determine competitiveness of six strains at different logarithmic inoculum densities against indigenous rhizobia and against a previous surviving inoculant (strain P132). Analyses of N content of plant tissues by direct 15N technique showed that cowpeas (Vigna unguiculata L. Walp.) were capable of deriving 60 to 98% of shoot N from N2 fixation. The two fast‐growing strains (176A26 and 176A28) were poorer competitors and fixed less N2 compared to the other slow‐growing strains. Inoculum density had no effect upon yield response of cowpeas, but inoculation with strains P132, 401, and 22A1 effected greater seed yield, shoot dry matter, total N, and percentage of N derived from fixation (86‐98%) than other strains and the uninoculated control (60‐73%). By contrast, N2 fixation and yield parameters in inoculated cowpeas were not significantly different from inoculated controls that contained residual P132 from a previous inoculum study. The higher hydrogen uptake (Hup) efficiency of nodules containing residual P132 (98 ± 2%) facilitated presumptive identification of P132 (100% ± 0 Hup efficiency axenically) as the surviving and infecting inoculant strain since nodules infected by indigenous rhizobia had lower Hup efficiencies (88 ± 2%).
Chloride, Soil Solution Osmotic Potential, and Soil pH Effects on Nitrification
Authors: Roseberg R. J. , Christensen N. W. , Jackson T. L. 
Published: July 2010

AbstractLaboratory incubation studies designed to measure chloride (Cl‐), soil solution osmotic potential, and soil pH effects on nitrification of added NH+4 were conducted in order to help explain effects of Cl‐containing fertilizers and liming on soil NH+4 and NO‐3 concentrations measured in field experiments. Samples of an Aquultic Argixerolls (pH 5.5, 6.0, 6.4, and 6.7) and a Xeric Haplohumults (pH 4.9, 5.5, and 6.2) were amended with 100 mg NH+4‐N kg−1, maintained at −10‐kPa matric potential and incubated at 25°C. Ammonium was added as either NH4Cl or (NH4)2SO4 salt solutions with four osmotic potential levels ranging from −96 to −692 and −90 to −669 kPa, respectively. Osmotic potential gradients were obtained by adding KCl to the NH4Cl solutions and K2SO4 to the (NH4)2SO4 solutions. At 0, 3, 9, 14, and 28 d, samples were extracted with 2 M KCl and analyzed for NH+4, NO‐3, and NO‐2. At 15 d, soil solutions were recovered by centrifugation and analyzed for Al, Ca, Mg, K, Na, Mn, NH4, NO3, PO4, SO4, Cl, pH, and osmotic potential. Soil solution osmotic potential was lower in soils amended with Cl‐ than with SO2‐4 salt solutions. In both soils, nitrification was inhibited by Cl‐ and by decreasing soil solution osmotic potential. Chloride inhibition of nitrification was greatest (⋍30%) at low soil pH (4.9‐5.5) but disappeared or decreased markedly in magnitude above pH 6.0 to 6.2. Because of soil solution osmotic potential and pH by Cl‐ interaction effects, inhibition of nitrification would be expected to be greatest where Cl‐containing fertilizers are applied in a band on moderately acid (pH 5.0‐5.5) soils.
Relationships between Root Length of Soybean and Calculated Activities of Aluminum Monomers in Nutrient Solution
Authors: Alva A. K. , Edwards D. G. , Asher C. J. , Blamey F. P. C. 
Published: July 2010

AbstractAluminum species composition in solution is largely dependent on solution pH. Effects of Al on root length of soybean [Glycine max (L.) Merr.] were studied in solution culture using an incomplete factorial design comprising varying pH levels of 4.0, 4.2, 4.4, 4.6, 4.8, and 5.0 and added Al concentrations of 10, 15, 20, 25, 30 and 40 µM. These treatments caused calculated sum of activities of monomeric Al species (Σ aAl mono) in solution to vary from 4.4 to 33.8 µM. The range in calculated activities of each of the Al monomers was 0.4 to 16.1 µM for Al3+, 0.3 to 2.8 µM for Al(OH)2+, 2.5 to 19.3 µM for Al(OH)+2, 0.1 to 4.4 µM for AlSO+4, and 0.02 to 0.22 µM for Al(OH)03. At a given concentration of added Al an increase in pH was associated with a decrease in calculated Σ aAl mono in solution and an increase in root length. Relative root length of soybean was highly correlated with calculated Σ aAl mono in solution (R2 = 0.910). Among the individual Al monomers, relative root length was most highly correlated with calculated activity of Al(OH)2+ (R2 = 0.870), followed by AlSO+4 (R2 = 0.674), Al(OH)+2 (R2 = 0.621), and Al3+ (R2 = 0.590). No significant correlation was found between root length and calculated activity of Al(OH)03. Reinterpretation of data from other studies with soybean, subterranean clover (Trifolium subterraneum L.), alfalfa (Medicago sativa L.), and sunflower (Helianthus annuus L.) also revealed that root growth was most highly correlated with activity of either Al(OH)2+ or Al(OH)+2. In a majority of cases the relationship between root growth and activity of Al3+ was relatively poor.
Differentiation of Spodosols and Andepts in a Western Washington Soil Climosequence
Authors: Nettleton W. D. , Goldin A. , Engel R. 
Published: July 2010

AbstractFive Spodosols were sampled on mountain slopes about 20‐km southwest of Mount Baker in the Cascade Range of western Washington. The soils have formed in colluvium derived from Darrington phyllite and an admixture of 1 to 30 dag tephra kg−1. Four of the pedons form a climosequence on steep, south‐facing slopes. The fifth is at the foot of the mountain, on an east‐facing slope, and is more weathered than one would have predicted from its low elevation. The three pedons sampled above 700 m have horizons that meet the chemical criteria for Spodosols. These three, as well as the fourth of the climosequence, have silt‐size pellets and cracked coatings. The fifth, at low elevation, has a horizon that meets both the chemical and morphological criteria for Spodosols. All of these pedons have one or more horizons that have the high NaF pH, high 15‐bar to clay and CEC to clay ratios, and the smeary feel characteristic of horizons that contain amorphous material. However, unlike Andepts these pedons have E horizons that contain crystalline silicate clays, mostly smectite, have low NaF pH, and lack the smeary feel. Except for the fourth pedon of the climosequence, the pedons meet the humic acid color criteria recently proposed for Spodosols. Some of the B horizons have >2 dag kg−1 of (NH4)2C2O4 extractable Al and ≥1.5 dag kg−1 of 4 M KOH extractable Al, but are not thick enough for the soils to be placed in the proposed Andisols.