bluuebunny/crossref_metadata_2025_split huggingface dataset:
General Criteria for the Validity of the Buckingham‐Darcy Flow Law
Authors: Sposito Garrison 
Published: July 2010

AbstractA detailed, first‐principles study is undertaken on the exact equation of linear momentum balance for water in an unsaturated soil. First, it is shown that an approximate momentum balance equation, presented originally by Raats and Klute, can be used to demonstrate unequivocably that the flow of water through a rigid, homogeneous, isotropic, unsaturated soil will obey the Buckingham‐Darcy law within 10−12 to 10−5 sec after a gradient in the total potential of soil water has been applied. Next, an exact equation of motion for the Fourier component of the water mass flux density vector is derived using standard methods in nonequilibrium statistical mechanics. This exact equation is employed to deduce the general physical criteria required for the Raats‐Klute equation to be an accurate expression. The results of the investigation lead to the conclusion that the Raats‐Klute equation will be accurate if: (i) the water mass density and mass flux density vector constitute a complete set of strongly coupled, macroscopic dynamical variables; and (ii) the time scale over which these two variables change significantly is much longer than that over which any other dynamical quantities vary. If these two conditions are met, then, according to statistical mechanics, the flow of water through unsaturated soil will be described accurately over all macroscopic time intervals by the Buckingham‐Darcy law.
Liming and Lime‐Phosphorus‐Zinc Interactions in Two Nigerian Ultisols: I. Interactions in the Soil
Authors: Friesen D. K. , Juo A. S. R. , Miller M. H. 
Published: July 2010

AbstractInteractions of lime, phosphorus (P), and zinc (Zn) in two coarse‐textured Ultisols from southeastern Nigeria were examined by means of factorial soil incubation and phosphate sorption experiments.In both soils, liming reduced exchangeable aluminum (Al) saturation from 45% to < 5% at pH 5.0 and soil solution Al concentration to < 1.0 µg/ml also near pH 5.0. There was no significant lime‐P interaction on active Al levels, indicating a lack of any ameliorating value of P on Al toxicity. Adsorption isotherms showed that liming reduced P adsorption in both soils at equilibrium solution concentrations of approximately 0.2 µg P/ml or higher, but at lower concentrations the effect became inconsistent. Soil incubation studies indicated that the concentration of P in soil solution (null‐point estimate) was first reduced by lower rates of lime then increased when soils were limed to approximately pH 6.0 or higher.Zinc activity in soil solution declined sharply when soils were limed to pH above 5.0, but was unaffected by P applications within the pH range studied (pH 4.3 to 7.2).
Hydrodynamic Dispersion During Constant Rate Absorption of Water by Soil
Authors: Smiles D. E. , Perroux K. M. , Zegelin S. J. , Raats P. A. C. 
Published: July 2010

AbstractAn analysis of hydrodynamic dispersion accompanying constant flux absorption of KCl solution by an initially relatively dry soil, is developed for the case when the hydrodynamic dispersion coefficient is pore water velocity‐independent. It is shown that in this process both the water content and the soil water salt concentration are uniquely defined by θ(X,T) and C(X,T), where X = vox and T = vo2t are space and time‐like coordinates, and vo is the constant surface flux of water.Quasi‐analytical methods based on the flux‐concentration relation predict θ(X,T) while an error‐function solution, based on a material coordinate Q labeling parcels of water, predicts the salt profile.The analysis is demonstrated using a chemically inert sandy soil. The results show that during transient, unsaturated flow a simple piston‐flow model described the process over a range of water contents. The method may be extended to explore dispersion in structured and chemically reactive soils.
Predicting Crop Responses on High‐Potassium Soils of Frigid Temperature and Ustic Moisture Regimes
Authors: Skogley Earl O. , Haby Vincent A. 
Published: July 2010

AbstractResults of 13 years of field research throughout Montana have demonstrated a relatively high rate of crop yield response to K fertilization when included in an N‐P‐K fertilizer program. Correlations between crop response to fertilizer K and ammonium acetate‐extractable K have been too low for this method to be used as a soil test. Alternative extraction methods or proposed soil test techniques were investigated in search of a useful relationship. These included saturated paste extraction, equilibrium extraction with dilute solutions, extraction with HEDTA or DTPA, ion‐exchange resin extraction, combination resin—ammonium acetate extraction, percentage‐K saturation of the CEC, and free energy of exchange relations for various ionic ratios. No adequate soil test relationship was identified in these studies.Soils of the northern Great Plains—Intermountain region are relatively high in extractable K and have frigid (cool) temperature regimes and ustic (semi‐arid) moisture regimes. Under these conditions, chemical measurements which relate to the quantity of K in soil apparently do not have an adequate cause‐and‐effect relationship in the availability of K to plants.
Numerical Analysis of a Chronosequence, Including the Development of a Chronofunction
Authors: Sondheim M. W. , Singleton G. A. , Lavkulich L. M. 
Published: July 2010

AbstractMultivariate techniques were applied to 11 chemical and physical properties of soil samples collected along a prograded beach chronosequence, located on the west coast of Vancouver Island, British Columbia. The samples were taken from three horizons at each of seven sites. The 21 samples were considered as independent observations. Application of principal component analysis with a normal varimax rotation gave highly interpretable results. The first component was readily identified with podzolic pedogenic processes, whereas the second component appeared to relate closely to sea spray input. A nonlinear optimization procedure was used to fit the first principal component to an empirical equation incorporating a logistic term for time and an exponential term for depth. A correlation coefficient value of 0.99 was obtained. The notion of a pedogenic damping depth analagous to a thermal damping depth is suggested.
Spatial Variability of Crop Yield as a Stochastic Soil Process
Authors: Bresler Eshel , Dasberg S. , Russo D. , Dagan G. 
Published: July 2010

AbstractIn a heterogeneous field in which the soil water properties vary, the yield of a crop may also differ from point to point. Using actual field variability data of irrigated peanut (Arachis hypogaea L.) yield, of soil water properties, and stochastic approaches, effects of spatial variability of soil water on the crop yield distribution and on the spatial correlation structures are evaluated. Values of total dry matter yield (YT) [together with two additional crop yield components pods (Yp) and hay (Yh)], soil water content [before (θb) and after (θa) irrigation], and saturated conductivity, Ks, were used to estimate distribution types (normal or lognormal) and their moments. The two‐point autocorrelation functions of YT, Yp, Yh, θa, θb, and Ks, were calculated and used to estimate their integral scales (J). The calculated J‐values for Ks, θa and θb, and YT are 25, 21, and 13 m, respectively. These results and calculations of the cross correlations between crop yield and soil water components were used to establish an approximate relationship between the crop yield and the soil water variables regarded as random spatial variables.
Effects of Skid Roads on Diameter, Height, and Volume Growth in Douglas‐fir
Authors: Wert Steve , Thomas Byron R. 
Published: July 2010

AbstractThis study was conducted to measure the effects of tractor logging which occurred in 1947 upon the productivity of a subsequent stand of Douglas‐fir (Pseudotsuga menziesii [Mirb] Franco) and to assess the degree and extent of residual soil compaction. The 4.33‐ha study area was categorized into skid roads, transition zones (3 m on each side of the skid roads), and undisturbed areas. Volume of every tree over 5 cm diameter breast height (dbh) was estimated by the tarif method. Forty trees in each category were measured for age‐growth relationships. Soil bulk densities were measured with a two‐probe nuclear densiometer.Total tree volumes per hectare for skid roads, transition zones, and undisturbed areas were 34.1, 97.2, and 128.9 m3; stand densities were 693, 974, and 1,180 stems/ha, respectively. Growth reductions in the skid roads and transition zones resulted in an overall volume loss of 11.8% for the total area.An analysis of covariance showed that there was no significant difference in the slope of the tree height‐age regression lines for each of the three categories. However, there was a highly significant difference in the adjusted height means between trees from skid road and those in the other two categories. Trees growing in the skid roads took 4.1 years longer to reach breast height than those growing in the undisturbed areas. After 32 years, 25% of the entire study area was still heavily compacted (bulk density > 1.20 g/cm3). Recovery from compaction has occurred in the surface 15 cm.
The Quantitative Assay of Minerals for Fe2+ and Fe3+ Using 1,10‐Phenanthroline: II. A Photochemical Method
Authors: Stucki J. W. 
Published: July 2010

AbstractA photochemical method for measuring Fe3+ and total Fe in minerals is described. The method determines Fe2+ concentration by measuring the Fe(phen)32+ (phen = 1,10‐phenanthroline) complex formed during HF‐H2SO4 digestion of the mineral. To measure Fe2+ accurately in the presence of Fe3+ from the mineral, the sample digestion and analysis are performed under red light to prevent photochemical reduction of the ferric‐phen species. Total iron is measured by converting any Fe3+ in the digestate to Fe(phen)32+ by photochemical reduction using a fluorescent lamp. This procedure avoids the problems associated with adding chemical reducing agents to iron‐phen solutions. The calibration curves were linear up to 8‐µg Fe/ml with a lower detection limit of 0.011 µg/ml. The absorptivities of the calibration curves were 0.1852 ± 0.0017 and 0.1960 ± 0.0018 ml/cm‐µg for Fe2+ and total Fe, respectively. Ferric iron in the mineral samples was calculated by difference.
Effect of Field Variability in Soil Hydraulic Properties on Solutions of Unsaturated Water and Salt Flows
Authors: Russo David , Bresler Eshel 
Published: July 2010

AbstractUsing actual field variability data and the stochastic approach, effects of spatial variability of soil hydraulic properties on the predictions of water and salt flow distributions, and of correlation structure, are evaluated. The governing water and salt flow equations are solved numerically using actual field data of soil hydraulic conductivity and differential water capacity. These data, which had been obtained previously from measurements made in 30 different locations in a field, were the same as those obtained from a Monte‐Carlo simulation that considered the correlations between the parameters of the hydraulic functions. Simulated values of pressure head (h), water fluxes (q), wetting front positions (Zf), and solute concentration (c) for each of the 30 locations in the field were used to estimate distribution types (normal or log‐normal) and its moments, for h, q, Zf, and c. The two‐point autocorrelation functions of pressure head, wetting front, and solute concentration have been calculated and used to estimate the integral scales of h, Zf, and c. Distances in the field in which the horizontal flow components were negligibly small compared with the vertical flow components were calculated and found to be in the order of 10 cm and larger. Field dispersion of solutes was calculated from the simulated salt distribution results. Values of field scale dispersivity were estimated to be larger than the pore scale dispersivity and to increase with soil depth. An “equivalent” uniform porous medium, which was defined at the soil surface, exists for large infiltration time when a unit hydraulic gradient may be assumed.
Areal Variation and Chemical Modification of Weathered Shale Infiltration Characteristics
Authors: Luxmoore R. J. , Spalding B. P. , Munro I. M. 
Published: July 2010

AbstractSpatial variability of infiltration into a weathered shale subsoil were evaluated at a site proximal to one used for shallow land burial of low‐level radioactive waste at Oak Ridge National Laboratory. Double‐ring infiltrometers were installed at 48 locations on a 2‐ by 2‐m grid after the removal of 1 to 2 m of soil (Litz‐Sequoia association, Typic Hapludults). Infiltration rates were measured before and during the 0‐ to 20‐ and 239‐ to 259‐day periods following treatment with solutions of NaOH, KOH, NaF, NaAlO2, and Na2SiO3 at rates of 151 equivalents/m2. None of these chemical treatments significantly altered infiltration rate, indicating that chemical modification of soil exchange properties may be achieved without inducing hydrologic disturbance in these subsoils. A semivariogram analysis of infiltration data showed that areal variability was random; any spatial patterning must therefore occur at a smaller scale than 2 m. The frequency distribution of infiltration rate fitted a lognormal model with a geometric mean of 2 cm per day and a coefficient of variation of 130%.
Super Slurper Effects on Crust Strength, Water Retention, and Water Infiltration of Soils
Authors: Hemyari Parichehr , Nofziger D. L. 
Published: July 2010

AbstractThe effect of hydrolyzed starch polyacrylonitrile graft copolymer, commonly called “super slurper,” at rates of 0.0, 0.025, 0.05, 0.1, 0.2, and 0.4% by weight on the crust strength, water retention, and infiltration of selected soils was determined. The strengths of simulated crusts were measured for all the treatments. Infiltration rates were measured in the laboratory for untreated soils and soils treated with 0.4% super slurper. Water retentions were measured for all treatments by use of pressure plate and pressure membrane apparati.Super slurper decreased crust strength and infiltration and increased water retention. The crust strengths of a sandy loam, a loamy sand, and a clay loam soil were reduced 84, 75, and 54%, respectively, by the addition of 0.4% super slurper. Infiltration rates were also reduced. Sorptivities for a sandy loam, clay loam, and loamy sand soil, treated with 0.4% super slurper, were reduced 38, 18, and 11%, respectively. Loamy sand and sandy loam soils treated with super slurper retained more water than the untreated soils. Super slurper had little effect on water retention in the clay loam soil.
Ammonia Losses from Surface‐Applied Urea and Ammonium Fertilizers as Influenced by Rate of Soluble Calcium
Authors: Fenn L. B. , Matocha J. E. , Wu E. 
Published: July 2010

AbstractPrevious research has shown that applying large amounts of soluble Ca with urea and NH4 fertilizers depressed ammonia (NH3) losses extensively. This paper reports effects of varying amounts of Ca on reduction of this loss. Ammonia loss was progressively less with increasing Ca/N ratios. In the greenhouse, a Ca/urea‐N equivalent ratio of 0.25 reduced NH3 losses to 11% of applied N. In the laboratory, this ratio reduced NH3‐N losses to 42% of applied N; without Ca, N losses were 75%.Soluble Ca was effective in reducing NH3 losses from urea when surface applied to both acid and calcareous soils. Increased acidity from the application of soluble Ca salts on acid soils reduced the amount required to reduce NH3 losses. Soluble Ca applied with (NH4)2SO4 (AS) and NH4NO3 (AN) also reduces NH3 losses from calcareous soils. Reduction of NH3 losses from AN was due solely to lowered soil pH values. However, reduction of NH3 loss from urea and AS was possibly due both to CaCO3 precipitation and soil pH depression.
Corn and Cotton Root Growth in Response to Soil Impedance and Water Potential
Authors: Bar‐Yosef B. , Lambert J. R. 
Published: July 2010

AbstractThe equation dL/dt = C · L, which relates root elongation rate (dL/dt) to root length capable of growth (L), was tested on split root systems of corn and cotton under controlled laboratory conditions. Evidence is presented for the validity of the equation for the various parts of the root system when the growth period was up to 50 days. While the equation held, C, the specific root growth rate, was affected by soil impedance and water potential (ψ), varying between 0.02 and 0.15 per day for the cotton and between 0.03 and 0.28 per day for corn. When the various parts of the root system were under the same soil density (d) and different ψ, C varied with ψ according to a bell‐shaped relationship. When d was different, C decreased monotonically with increasing d values.The flux of water uptake by cotton and corn had a peak at a matric potential between −0.13 and −0.20 bar and was about 0.02 and 0.03 ml cm−1 root day−1, respectively.
Predicting Nitrogen Mineralization in Chaparral Soils
Authors: Marion G. M. , Kummerow J. , Miller P. C. 
Published: July 2010

AbstractNitrogen mineralization is a key process in supplying N for plant growth in terrestrial ecosystems. The objectives of this study were to evaluate N mineralization in chaparral soils and to evaluate an N mineralization simulation model.The chaparral soils contained 0.4 to 54 ppm potentially mineralizable N, which is considerably less than typical agricultural soils (generally > 100 ppm potentially mineralizable N). The quality of the organic matter with respect to N mineralization (N mineralization/total N) was low for chaparral soils relative to agricultural soils; this may be due to soil toxins (allelopathic compounds) or a highly resistant organic matter in chaparral soils. The potentially mineralizable N was highly correlated to total soil N (r2 = 0.82) but poorly correlated to C/N ratio (r2 = 0.07).The simulation model is based on laboratory soil N mineralization curves developed from long‐term soil incubations with adjustments for field soil temperature and moisture. Because of temperature and moisture limitations, simulated field N mineralization rates were only 3 to 27% of optimal rates; environment is as important as substrate quantity and quality in estimating field N mineralization. The simulation model estimates of annual N mineralization in two chaparral stands agreed to within ± 10% with independent estimates of N mineralization developed by solving a system N balance equation. The proposed N mineralization model should be useful for estimating annual soil N availability, which is an important step in developing N fertilizer prescriptions for intensively managed lands.
Selection of Variables to be Used in Statistical Analysis of Field‐Measured Soil Water Content
Authors: Cassel D. K. , Nelson L. A. 
Published: July 2010

AbstractInterpretations and inferences drawn from soil water content measurements collected in agronomic field studies are dependent upon the particular method of data analysis. The purpose of this study was to examine alternative approaches for analyzing soil water content data measured by neutron attenuation. Data from tillage studies conducted at two locations on the Atlantic Coastal Plain were used to demonstrate and compare the methods of data analysis. Analysis of variance was performed on the field‐measured data (total soil water content measured by neutron attenuation) and on either six or eight relevant soil water variables derived from them. Derived variables included (i) the net change in total water content between successive measurement dates; (ii) a transformed soil water content; and (iii) six variables derived using bulk density and 15 bar soil water contents to provide estimates of plant‐available water.The total soil water content variable has a coefficient of variation (C.V.) of about 12%, and the cost of collecting data and analyzing it is relatively low. Differences in total water content between successive dates have C.V.s generally about 100%. Requiring the measurement of the 15 bar percentage and bulk density values, which allows plant‐available water to be calculated, increases the costs of data collection. Incorporation of this information into the water variables results in data which have a C.V. of about 30%. In field experiments, the investigator should select the appropriate soil water variable only after examining the relative costs, expected C.V.s, and the anticipated use of the data.
The Swelling of Clay: III. Dissociation of Exchangeable Cations
Authors: Low Philip F. 
Published: July 2010

AbstractValues of ζ, the zeta potential, were determined for 34 different Namontmorillonites by electrophoresis. These values were used in the equations of diffuse double‐layer theory to obtain the corresponding values of σ', the surface charge density at the outer limit of the Stern layer. In addition, data on cation exchange capacities and specific surface areas were used to calculate the corresponding values of σ, the surface charge density at the particle surface. From the respective values of σ′/σ, it was found that < 2% of the exchangeable cations were dissociated. This low degree of dissociation was confirmed by using double‐layer theory and experimental data from another study. Then a representative value of σ′ was used in the appropriate equations to obtain data from which a theoretical curve of the swelling pressure, Π, vs. interlayer distance, λ, was constructed. Comparison of this curve with the experimental curve of Π vs. λ indicated that double‐layer repulsion makes a relatively small contribution to Π. The necessary conclusion is that Π develops primarily because of surface‐water interaction.
Transport of Sediment Nitrogen and Phosphorus in Runoff through Cornstalk Residue Strips
Authors: Alberts E. E. , Neibling W. H. , Moldenhauer W. C. 
Published: July 2010

AbstractA rainfall simulator study was conducted on a Sidell silt loam (Typic Arguidolls, fine‐silty, mixed, mesic) in northwest‐central Indiana to evaluate the effectiveness of different lengths and percentage covers of cornstalk residue strips in reducing total nitrogen and available phosphorus discharges associated with the sediment. A 2.7‐m long residue strip with 50% surface cover reduced nutrient discharges by about 70% when the nutrient loads entering and leaving the residue strip were compared. Reductions in sediment and nutrient discharges with increasing length and percentage cover of the residue strips were almost proportional.The sediment was separated by sieving and gravity sedimentation into 10 size fractions ranging from > 2 to <0.002 mm in diam. About 50% of the sediment entering the residue strips was composed of particles >0.05 mm. The 2.7‐m long residue strip with 50% surface cover filtered out most of the particles >0.05 mm. As a result, 85% of the sediment leaving this residue strip was in the <0.035‐mm size fractions.Nutrient concentrations of the fractions >0.21 mm entering the residue strips were higher than those concentrations of the 0.05‐ to 0.01‐mm fractions entering the strips. Nutrient concentrations of the fractions <0.21 mm and >0.01 mm increased as the sediment moved through the residue strips, with the effect being related to residue length and percentage cover. Residue reduced the transport capacity of runoff below its sediment load, which caused the denser particies within these size fractions to be deposited. The less dense particles that were not deposited were composed of a greater proportion of small silt and clay primary particles, which increased the nutrient concentrations.