bluuebunny/crossref_metadata_2025 huggingface dataset:
Predictability of Recreational Impact on Soils
Authors: Marion Jeff L. , Merriam L. C.
Published: July 2010

Biophysical measurements were taken on 96 paired campsites and controls in the Boundary Waters Canoe Area Wilderness of north‐eastern Minnesota. Multiple regression analysis was used to identify and evaluate factors affecting changes in bulk density, organic horizon thickness, and exposed soil associated with campsite use. The best predictors of change in bulk density were campsite age, mineral soil organic content, organic horizon thickness, and offsite bulk density. Offsite organic horizon thickness and level of use were the best predictors of change in campsite organic horizon thickness. Level of use and campsite age were the best predictors of amount of exposed soil. Bulk density and exposed soil continued to increase with campsite age, even though all sites included in the study were > 5 yr in age. Other studies have not found this relationship. This information can be used to assist managers in selecting recreation site locations and appropriate site management techniques.
Hydroxylamine and Ammonium Oxalate Solutions as Extractants for Iron and Aluminum from Soils
Authors: Ross G. J. , Wang C. , Schuppli P. A.
Published: July 2010

A comparison was made of acid hydroxylamine and acid ammonium oxalate methods for extracting Fe and Al from three clay mineral (chlorite) samples and 27 soil samples. Although the hydroxylamine solution was more acid than the oxalate solution, the hydroxylamine extraction did not increase dissolution of the chlorites markedly. It was concluded that overnight hydroxylamine extraction at room temperature using a 1:250 soil‐to‐solution ratio can be used as an alternative method to the 4‐h oxalate extraction method with the 1:40 soil‐to‐solution ratio commonly used in soil studies. This conclusion was based on the following reasons: (i) the results from both methods were comparable for nearly all samples; (ii) hydroxylamine solutions were more easily analyzed than oxalate solutions by atomic absorption analysis; (iii) overnight hydroxylamine extraction at room temperature required no specialized heating baths with compatible shaking equipment and is therefore suitable for most laboratories.
Inspectional Analysis in the Theory of Water Flow through Unsaturated Soil
Authors: Sposito Garrison , Jury William A.
Published: July 2010

Conventional inspectional analysis is applied to the one‐dimensional Richards equation to provide a unified classification scheme for three macroscopic scaling approaches which have been used to describe soil water flow phenomena under laboratory or field conditions. It is shown that the scaling parameters and similarity groups developed in an inspectional analysis of the Richards equation depend on the boundary and initial conditions imposed as well as on the special physical hypotheses invoked. Nielsen similarity analysis is based on a zero‐flux boundary condition and the assumption that the hydraulic conductivity, soil water diffusivity, and matric potential are exponentional functions of water content. Warrick similarity analysis, on the other hand, is formulated independently of the boundary and initial conditions while adopting three scaling parameters to define reduced forms of the water content, hydraulic conductivity, and matric potential. Field experiments have shown that two of these parameters often are correlated. Macroscopic Miller similarity analysis is based on the physical postulate that water transport through unsaturated soil is governed by viscous flow and capillary forces. It differs from the classical Miller similar media concept in that it requires a scaling parameter for the volumetric water content and makes no direct reference to the geometric structure of a soil at the pore scale.
Analysis of Soil Water Content and Temperature Using State‐space Approach
Authors: Morkoc F. , Biggar J. W. , Nielsen D. R. , Rolston D. E.
Published: July 2010

Several statistical methods have been developed to smooth or interpolate observations taken spatially and temporally. Most of these methods require that the observations manifest stationarity, meaning that the expected value of the observations is constant over the domain considered. The authoregressive moving average method requires the above condition but can also be used to estimate missing observations. The exponential smoothing method is available for nonstationary time or space series but generally requires evenly spaced observations. The state‐space model can be used for smoothing or estimating and forecasting a relatively short, nonstationary series of observations. A first order state‐space model was used here to estimate the missing observations of 0‐ to 5‐cm gravimetric soil water content. This was accomplished using joint analysis of observed water content and soil surface temperatures from a sorghum field irrigated by two line source irrigation system. The parameters of the model indicated the degree of spatial correlation between the two measured parameters. The expectation maximization algorithm and Kalman smoothed estimators were used to estimate the first order state‐space model parameters by maximum likelihood.
Kinetics of Post‐reclamation Boron Dissolution
Authors: Peryea F. J. , Bingham F. T. , Rhoades J. D.
Published: July 2010

The <0.25‐mm particle size fractions of four natively high boron (B) soils were reacted in suspension with a B‐specific exchange resin. By separating the resin from the suspension after selected times of reaction, four subsamples of each soil were obtained, representing increasing degrees of reclamation. The subsamples were reacted with deionized water and release of residual B to the supernatant was measured as a function of time. The data for each soil subsample were plotted according to an integrated form of the Elovich reaction rate equation. The release of B from the soils closely conformed to a linear function of the natural logarithm of time. Linear regression analysis was used to calculate the reaction rate constants for each treatment. The rate of post‐reclamation B dissolution and the equilibrium concentrations of regenerated B were inversely related to the amount of B removed from each soil during reclamation.
Mechanisms for Boron Regeneration
Authors: Peryea F. J. , Bingham F. T. , Rhoades J. D.
Published: July 2010

The ability of reclaimed natively high B soils to re‐establish elevated soluble B concentrations has been termed “boron regeneration”. Potential mechanisms for this phenomenon were qualitatively examined. Soil samples reclaimed in columns contained appreciable concentrations of residual, potentially reactive B and Cl−. Reclamation by multiple batch extraction removed 100 percent of the Cl−; however, the soils could not be completely reclaimed of B. Boron regeneration was observed in both column and batch reclamation systems, while Cl− regeneration occurred only in the column systems. The data suggest that two mechanisms may account for B regeneration. Post‐reclamation release of B from residual sparingly soluble or desorbable B‐containing sources is confirmed by the batch and column experimental results. The column data suggest that portions of the soil were bypassed by the leaching solution during reclamation. By analogy with Cl− behavior, post‐reclamation diffusion of B from bypassed to leachable pores also contributes to the B regeneration phenomena.
Predicting the Most Efficient Phosphorus Placement for Soybeans
Authors: Borkert C. M. , Barber S. A.
Published: July 2010

The effect of placement of P fertilizer on P uptake and plant growth has been predicted for corn (Zea mays L.) but not soybeans [Glycine max (L.) Merr.]. The objective of this paper is to predict the effect of P placement on soybeans and compare it with predictions made earlier for corn. Data for operation of the model were obtained from a pot experiment reported in an earlier paper. Calculations were for soybeans, cv. Century, growing on Raub soil (fine silty, mixed, mesic, Aquic Argiudolls). Calculations were made for P rates of 30, 60, 120, 240, and 480 mg kg−1 each with fractional volumes of soil fertilized ranging from 1.0 to 0.01. Predicted P uptake was converted to predicted plant weight using an experimental relation between P uptake and plant weight. The placement giving the greatest predicted P uptake interacted with P rate. At each P rate as P was mixed with an increasing volume of soil, predicted P uptake reached a maximum and decreased. The greatest predicted P uptake occurred when P was placed in 0.04 of the soil volume when the P rate was 30 mg kg−1, 0.10 when the rate was 60 mg kg−1, 0.20 when the rate was 120 mg kg−1, and 1.0 when the rate was 240 mg kg−1. The results were comparable to those obtained with corn.
Use of By‐product Gypsum to Alleviate Soil Acidity
Authors: Oates Kenneth M. , Caldwell A. G.
Published: July 2010

By‐product gypsum has been accumulating in large mounds in southern Louisiana for over 25 yr and little has been utilized. The objective of this study was to determine if large applications of byproduct gypsum could be used to alleviate soil acidity. A column leaching experiment was conducted using an acid subsoil amended with 5.0 gypsum equivalents of phosphogypsum, hydrofluorogypsum, or pure gypsum. In addition, several rates < 5.0 were used for the pure gypsum. Soybeans (Glycine max L.) var. ransom were then grown in a greenhouse experiment on an acid subsoil amended with 5.0 gypsum equivalents of phosphogypsum, hydrofluorogypsum, or pure gypsum. (One gypsom equivalent is defined as 4.2 cmol (+) kg−1.) Results of the column leaching experiment showed that both by‐ product gypsums removed more Al from the soil than did pure gypsum. They also removed Al at a faster rate than pure gypsum. Hydrofluorogypsum was the most effective. It removed 81% of the KC1‐extractable Al and increased the soil pH from pH 4.9 to pH 5.3. The increased effectiveness of the by‐product gypsums was shown to be due to the fluoride impurity. The Al removed by pure gypsum increased linearly as described by the regression equation of Al leached = −0.0137 + 0.276 (gypsum equivalent) [R2 = 0.99] Soybeans grown on soil amended with by‐product gypsum and leached had significantly higher plant weights than soybeans grown on nonleached amended soil.
Morphology of Late Holocene Soils at the Lubbock Lake Archeological Site, Texas
Authors: Holliday Vance T.
Published: July 2010

Three soils have been identified in late Holocene deposits at the Lubbock Lake site, a well‐ stratified archaeological locality on the Southern High Plains. The soils have been informally named and their ages firmly established by radiocarbon dating. The soils formed in quartzose, sandy loam to sandy clay loam, dominantly eolian sediments with illite and mixed‐layer illite‐smectite clay mineralogy and lesser amounts of smectite and kaolinite. The Lubbock Lake Soil formed in material deposited between 5000 and 4500 yr BP and has had 4500 yr to form or, where buried, 3500 yr. The soils exhibits mollic and ochric (buried) epipedons, cambic and argillic and, in some positions, a partically gleyed B horizon, and Stage I or II, often multiple, calcic horizons. It is classified as either a Calciustoll, Haplustoll, Haplustalf, or Ustochrept. The Apache Soil formed in sediments deposited from 800 to 450 yr BP and is 450 yr old where not buried and 200 yr old where buried. The soil usually has a mollic epipedon but in some buried situations it is ochric. The B horizon is normally cambic but sometimes qualifies as argillic. Secondary carbonate accumulation, sometimes qualifying as calcic, commonly attains a Stage I morphology. The Apache Soil is classified as either an Ustochrept, Haplustoll, Calciustoll or possibly minimally developed Haplustalfs. The Singer Soil formed in sediments deposited from 250 and 100 yr. BP, allowing 100 yr for soil formation. The soil has an ochric epipedon and either a C, Bw, or a cambic horizon. Weak Stage I carbonate horizons are common but never qualify as calcic. The Singer Soil is classified as an Ustorthent. These three soils define a chronosequence that will allow a study of pedogenesis in Holocene sediments in a semiarid environment. The discovery of soils elsewhere on the southern High Plains of similar age, parent material, and landscape setting to the Lubbock Lake Soil and possibly the two younger soils, indicate that these late Holocene soils will be useful stratigraphic markers and dating tools.
Sulfate Adsorption Relationships in Forested Spodosols of the Northeastern USA
Authors: Fuller R. D. , David M. B. , Driscoll C. T.
Published: July 2010

Soil SO2−4 adsorption has important implications in the study of acidic deposition effects on terrestrial and aquatic systems, because this process results in the release of alkalinity or prevents leaching of H+ and cations. Forested Spodosols of the northeastern USA have generally been considered poor adsorbers of SO2−4, in part due to the interfering effects of soil organic matter. Soils from both the Adirondack Mountains, NY and the Hubbard Brook Experimental Forest, NH (Typic and Lithic Haplorthods and Aquic Fragiorthods, respectively), however, contained SO2−4 in Bs horizons predominately in an insoluble (nonwater‐extractable) form and were capable of adsorbing additional SO2−4 given higher SO2−4 concentrations than currently found in situ. Concentrations of insoluble SO2−4 in Bs horizons ranged from 0.3 to 2.1 × 10−3 mol SO2−4 Kg−1 by H2PO−4 extraction. Fractionation of free Fe and Al suggest that both elements were present largely in organically complexed forms. Insoluble SO2−4 was highly correlated with several forms of free Fe and Al, but crystalline Fe and organic Al content appeared to explain most of the variability in SO2−4 adsorption capability. These soils may not presently be accumulating SO2−4 through the adsorption process on an annual basis. Their SO2−4 adsorption capability, however, indicates that the adsorption process may well buffer seasonal variations in SO2−4 concentration or serve as a net source or sink of SO2−4 subsequent to conditions which either influence concentrations of SO2−4 in the soil solution (eg. atmospheric inputs) or affect the adsorbent phase.
Layer Charge Evaluation of Expandable Soil Clays by an Alkylammonium Method
Authors: Senkayi A. L. , Dixon J. B. , Hossner L. R. , Kippenberger L. A.
Published: July 2010

The interlayer charge of five reference smectites (hectorite, saponite, two montmorillonites, and a nontronite) and clay samples from strongly acidic smectitic soils of Alabama, Mississippi (Ultisols), and Texas (Alfisol) were investigated by an alkylammonium method (AAM). The total layer charge of the reference smectites based on the chemical formula ranged from 0.31 to 0.50 mol(−) per O10(OH)2. The interlayer charge density by AAM linearly increased with increasing total charge. Nontronite had the highest tetrahedral charge and exhibited the highest interlayer charge density. A qualitative distinction of soil clay samples containing low charge and high charge smectite or vermiculite was based on the d‐spacings of the complexes formed by a single alkylammonium compound. Changes in relative peak intensities indicated that the low charge smectite increases whereas the high charge smectite decreases with profile depth. The low charge smectite in these soils appears to have been mostly inherited from the underlying Tertiary and Cretaceous sediments whereas the high charge smectite appears to be a weathering product of the mica present in these sediments.
Use of Peltier Coolers as Soil Heat Flux Transducers
Authors: Weaver H. L. , Campbell G. S.
Published: July 2010

Peltier coolers were modified and calibrated to serve as soil heat flux transducers. The modification was to fill their interiors with epoxy. The average calibration constant on 21 units was 13.6 ± 0.8 kW m−2 V−1 at 20°C. This sensitivity is about eight times that of the two thermopile transducers with which comparisons were made. The temperature coefficients of the Peltier cooler transducers avg −0.034 kW m−2 V−1 °C−1, whereas those of the two thermopile transducers were only 25% as large, relative to their calibration constants. The thermal conductivity of the Peltier cooler transducers was 0.4 W m−1 °C−1, which is comparable to that of dry soil. The cost of an unmodified Peltier cooler is around $20.
Zeta Potential and Surface Area of Calcium Carbonate as Related to Phosphate Sorption
Authors: Amer Fathi , Mahmoud A. A. , Sabet Violette
Published: July 2010

Orthophosphate (OP) sorption by eight reagent‐grade CaCO3 samples and a natural limestone, as influenced by the surface area and zeta potential (ZP), was investigated in the absence and presence of pyrophosphate (PP) as a crystal growth inhibitor. Reacting the nine CaCO3 samples for 24 h with 1 mmol OP L−1 indicated a rapid 0.08‐h adsorption reaction and a 2‐h induction period that preceded OP precipitation. The amount of adsorbed OP was proportional to the CaCO3 surface area which ranged from 250 to 12 780 m2 kg−1 and accounted for 92.8% of the variation in OP adsorption. The surface area was generally proportional to the ZP, as five CaCO3 samples were positively charged with ZP values ranging from 17.7 to 25.3 mV, three samples were noncharged, and only limestone was negatively charged with a ZP of −6 mV. The ZP decreased with OP adsorption and again increased after OP precipitation. Addition of PP did not interfere with OP adsorption, but inhibited OP precipitation during the 24‐h reaction period by extending the induction period, and markedly reduced the ZP. Negativity of the CaCO3 particles per se was not considered the main factor in retarding P precipitation, as polyacrylamide was very effective in lowering ZP but had no effect on OP sorption. The added PP was also subject to adsorption by the CaCO3 and, therefore, the amount of PP needed for inhibiting growth of the calcium phosphate crystals depended on CaCO3 reactivity as well as on OP concentration.
Sodium‐Calcium‐Magnesium Exchange on Silver Hill Illite
Authors: Sposito Garrison , LeVesque C. S.
Published: July 2010

Binary and ternary cation exchange reactions involving sodium (Na+), calcium (Ca2+), and magnesium (Mg2+) on Silver Hill illite suspended at pH 7 in a 50 mol m−3 perchlorate background were investigated. The binary exchange experiments indicated a preference of the clay mineral for Ca and Mg over Na and for Ca over Mg. The principal ternary exchange data, on the other hand, indicated no selectivity difference between Ca and Mg in the presence of adsorbed Na at a nominal exchangeable sodium percentage (ESP) of 25. No differences among the values of the total adsorbed metal charge (Qo) were observed in a set of binary and ternary Na→M (M = Ca and/or Mg) exchange experiments carried out at the same time. There was, however, a systematic increase in the value of Qo on a time‐scale of months in Na‐illite suspended in NaClO4. The increase in Qo was produced by adsorbed Na+ that could be displaced by ammonium (NH+4) but not by Ca2+ or Mg2+ ions. The quantity of this “quasi‐exchangeable” Na present in the principal ternary exchange experiments was determined to be about 13% of the value of Qo, an amount concluded to be sufficient to cover the high‐energy exchange sites on the illite and thereby relegate Ca‐Mg exchange to sites having relatively low selectivity differences, as observed experimentally.
Determination of Nitrate in Soil Extracts by Dual‐wavelength Ultraviolet Spectrophotometry
Authors: Norman Richard J. , Edberg Jeffrey C. , Stucki Joseph W.
Published: July 2010

A rapid method is described for determining nitrate concentration in a soil extract solution based on its UV absorbance at 210 nm. The interference of nonnitrate species is accounted for by subtracting an empirically‐determined multiple of the absorbance of the extract solution at 270 nm from its absorbance at 210 nm. The value of the multiplication factor, R, is calculated from the 210: 270 nm absorbance ratio of the extract solution after it has been treated with Raney‐Nickel catalyst to remove nitrate. The method was tested using 10 Illinois soils. The composite value of R for these soils was 3.05 ± 0.22. This value, as well as each individual value of R for the respective soils, was used to calculate the nitrate concentration. The results were then compared to one another and to results obtained by the steam distillation method. Correlation among these various methods was very high, giving values of r2 of 0.9987 and 0.999. Large errors occurred when no correction for nonnitrate species was made.
Lime Induced Magnesium Stress in Corn: Impact of Magnesium and Phosphorus Availability
Authors: Grove J. H. , Sumner M. E.
Published: July 2010

Previous research has indicated that lime additions to soils with variable surface charge resulted in reductions in measures of “exchangeable” Mg. The potential loss of Mg from “plant available” soil phases was evaluated in two greenhouse trials. These experiments were conducted in 1979 and 1980 to evaluate the potential for Mg nutritional problems in corn [Zea mays (L.) Merr.] grown on a Bradson clay loam (Typic Hapludults) over a wide range in soil pH and plant available P and Mg. Bulk soil samples were taken from each of three lime rate treatments in a field trial last amended with dolomite in 1967. In the first experiment three levels of lime and P were imposed in a complete factorial combination on each bulk sample. In the second experiment, the bulk soil sample with the lowest native level of extractable Mg was amended with eight rates of lime and two rates of Mg in a complete factorial combination. Increased Mg availability was associated with increased tissue Mg concentrations and shoot dry matter productivity. Added lime generally decreased extractable soil Mg, tissue Mg, and shoot dry matter. Applied P reduced “overliming” stress in the first experiment. Magnesium, P, and Zn were implicated in the nutritional stress associated with lime induced yield depressions.
Uniformity of Nitrogen‐15 Enrichment in Different Plant Parts and Subsequent Decomposition Monitoring of Labeled Crop Residues
Authors: Wagger M. G. , Kissel D. E. , Smith S. J.
Published: July 2010

In order to accurately evaluate the N mineralization from decomposing crop residue, residue should be uniformly labeled, i.e., it should contain a relatively constant atom % 15N in all N compounds within the plant. Our objective in this study was to estimate the uniformity of 15N labeling by comparing the 15N content of different plant parts of winter wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench]. Labeling with 15N was accomplished by applying a single, highly enriched but low rate of N to the soil early in the growth stage of the respective crops. Small enclosed microplots were used for incorporating the 15N enriched fertilizer into the initial crop and for following decomposition in subsequent years. At crop maturity, recovery of the initial K15NO3 application avg. 71.9% for all soil texture‐crop combinations. Data from the 15N labeling study indicated that relatively uniform enrichment of various plant parts was obtained when K15NO3 was applied to the soil at the jointing and eight‐leaf stages for wheat and sorghum, respectively. On average, atom % 15N values for all plant parts ranged from 6.962 to 8.171 and 2.801 to 3.274 for winter wheat and sorghum, respectively. These results imply that segregation of 15N‐labeled plant material into various plant parts for use in subsequent crop residue decomposition experiments is unnecessary.
Automated Analysis of Nitrite, Nitrate, and Ammonium Nitrogen in Soils
Authors: Markus D. K. , McKinnon J. P. , Buccafuri A. F.
Published: July 2010

Automated procedures are presented for determining NO‐2‐N, NO‐3‐N, and NH+4‐N in various soil testing programs. An AutoAnalyzer system equipped with a microprocessor‐based controller and data handler was employed in the study. The new system, through its drift, gain, and carryover correction features, provides improvement in accuracy and precision of results. Further, the new system also has the potential for more rapid chemical determination. The evaluation of accuracy and precision of NO‐3‐N and NH+4‐N analyses, studied in standard solutions and determined with the automated system at 60, 90, and 120 h−1 sampling rates, is presented. Results of NO‐2‐N, NO‐3‐N, and NH+4‐N analyses in nutrient solutions of hydroponic culture, as well as in extracts of mineral soils and peat‐based greenhouse substrates, determined with the automated procedure at the 90 h−1 sampling rate, are also presented. Moreover, the total N content and cation exchange capacity of mineral soils determined by NH+4‐N analysis with the AutoAnalyzer at the 90 h−1 sampling rate are also shown. Analyses performed by automated procedures are compared with those obtained by a nonautomated colorimeter for all samples used in the study. Nitrite nitrogen and NO‐3‐N were determined by hydrazine reduction, and NH+3‐N was determined as indophenol in both the automated and nonautomated procedures. Also, the threshold concentration levels of interfering ions determined in aqueous standard solutions of NO‐2‐N, NO‐3‐N, and NH+4‐N are presented.
Mineralization of Nitrogen from Nitrogen‐15 Labeled Crop Residues Under Field Conditions
Authors: Wagger M. G. , Kissel D. E. , Smith S. J.
Published: July 2010

The management of crop residues and their contribution to the supply of plant nutrients is intimately tied with N cycling in the soil. Any attempt to utilize crop residues to the fullest extent requires an understanding of how the system functions. The objective of this research was to determine the extent and rate of N mineralization from 15N‐labeled winter wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] residues. In addition, the influence of soil texture and fertilizer N on net N mineralization also was evaluated. Nitrogen mineralization from decomposing crop residues was followed by means of plant and soil sampling during subsequent cropping seasons. Plant N uptake and soil inorganic N data showed that 12 to 15% of wheat residue N and 12 to 33% of sorghum residue N were mineralized after one cropping season. Net mineralization differences between crop residues may be attributed to both the C/N ratios and chemical composition of these plant materials. Soil texture and the addition of fertilizer N mainly influenced the initial rate of mineralization, particularly with the wheat residue. There was also evidence of N immobilization of the recently mineralized 15N followed by remineralization later in the growing season for wheat and sorghum residues decomposing in the medium‐textured soils. This immobilization occurred during a period of rapidly increasing soil temperatures. On avg, 79% of the mineralized wheat residue N and 82% of the mineralized sorghum residue N were utilized by wheat and sorghum plants, respectively. Based on these results, the greatest proportion of N mineralized from decomposing wheat and sorghum residues appears to coincide with plant N demand by the subsequent crop, irrespective of differences between C/N ratios of these residues or soil texture.
Use of Soil Survey Data for Regional Soil Water Simulation Models
Authors: Wösten J. H. M. , Bouma J. , Stoffelsen G. H.
Published: July 2010

A detailed soil survey of an area of 650 ha was used to obtain basic soil physical data for a simulation model of the water regime in the unsaturated zone. Nine major soil horizons were defined for the entire survey area in terms of pedological classification and easily measurable characteristics such as texture, structure, organic matter content, and bulk density. In these horizons multiple measurements of hydraulic conductivity and moisture retention curves were made, yielding average curves. Statistical comparison of the curves showed that only five of the nine major soil horizons were different from a soil‐physical point of view. Next, representative soils for the mapping units were transformed into soils composed of a characteristic sequence of some of these five horizons. In this way a simulation map, containing data to be used for simulation of the soil water regime, was formed from the soil map. For a sample area of 125 ha the simulation map contained 41 delineated areas as compared to 110 delineations on the soil map. Sixty independent test borings indicated 80 ± 6% purity comparing borings and the legend of the simulation map. A simulation run for one pedon with the model SWATRE showed excellent agreement between measured and calculated actual evapotranspiration for the years 1976, 1977 and 1978. Major soil horizons, rather than individual points of observation, were used in this study as carriers of soil physical information, allowing extrapolations based on a limited number of measurements.
Acidification Sources in Red Alder and Douglas Fir Soils‐Importance of Nitrification
Authors: Van Miegroet H. , Cole D. W.
Published: July 2010

Precipitation, throughfall, forest floor, and soil leachate samples were monitored continuously in 1981 and 1982 in a N‐poor Douglas‐fir [Pseudotsuga menziesii (Mirb.) Franco] forest and a red alder (Alnus rubra Bong.) forest growing adjacently on a glacial soil in western Washington. The purpose of the study was to quantify the relative importance of atmospheric vs. natural sources of H+ input to forest soil acidification, and to determine the role of N transformation processes in the overall H+ balance of soils with different N status. Rainwater samples had an avg pH of 4.7 and annual H+ deposition via precipitation averaged 320 mol H+ ha−1 yr−1. This was modest compared to internal H+ production associated with HCO‐3 and NO‐3 formation. In the soil under alder cover, which was naturally enriched in N through symbiotic N2‐fixation, nitrification released up to 4500 mol H+ ha−1 annually to the solution percolating through the upper part of the soil profile. In the N‐poor soil no nitrification could be observed and N transformation processes had a minor influence on the soil H+ balance. The main internal acidification source in this case was H2CO3 dissociation releasing 420 mol H+ ha−1 yr−1. In both instances, soil solutions appeared well buffered against these external and internal acidification sources, and few H+ leached below the 40‐cm soil depth.
Embryonic Halloysites in Ecuadorian Soils Derived from Volcanic Ash
Authors: Wada Koji , Kakuto Yasuko
Published: July 2010

A unique mineral association that represents embryonic stages of halloysite formation in weathering of andesitic volcanic ash was found in three Ecuadorian soils which did not contain allophane. This mineral association consisted of more or less poorly ordered halloysites and a “1.0‐nm mineral”. The more poorly ordered halloysite was nearly x‐ray amorphous and showed infrared (IR) absorption bands which were characteristic of halloysite but poorly resolved. It was dissolved congruently (Si/Al ratio = 1.0–2.0) by hot M/3 sodium citrate solution and incongruently (Si/Al ratio = 0.37–0.40) by 0.2 M ammonium oxalate‐oxalic acid (pH 3.0). The 1.0‐nm mineral and the less poorly ordered halloysite were not dissolved by these reagents. The former was not distinguished from the latter on the IR spectra and both had a Si/Al ratio of, or close to, 1.0. The 1.0‐nm mineral showed, however, a broad 1.0‐nm reflection not only at 25 but at 300°C and even at 550°C. Embryonic halloysites varied in morphology from thinly spread flakes to elongated, rolled thick plates, and spherical particles. Soils containing the more poorly ordered halloysites with Si/Al ratios of ca 1.5 to 2.0 and 1.0 showed a low and a fairly high “Al reactivity”, respectively. It was inferred that embryonic halloysites have formed in base and silica rich environments. Structural schemes of the 1.0‐nm mineral and the more poorly ordered halloysite were discussed.
A Suction Apparatus for Orienting Clay Minerals Onto Porous Ceramic Tiles
Authors: LaManna John M. , Bowers Fred H.
Published: July 2010

A new design is presented for an apparatus that makes oriented mounts for the x‐ray study of clay minerals. The apparatus can be easily fabricated by drilling and tapping holes into a metal plate and adding standard screws, nuts, pipe fittings, and plastic funnels. The main advantages of this design are (i) ease of fabrication, (ii) the ability to deposit clay cakes of almost any diameter onto tiles of almost any shape or size, and (iii) the incorporation of a relatively large sample reservoir that will hold enough suspension to allow the operator to perform other tasks while the tiles are being prepared.
Field Calibration and Validation of Solute Transport Models for the Unsaturated Zone
Authors: Jury William A. , Sposito Garrison
Published: July 2010

Data from two solute transport field experiments, one obtained from soil solution samplers and the other from soil coring, are used to illustrate the parameter estimation problem for two models describing area‐averaged vertical transport of mobile solutes. The two models, the lognormal transfer function model (TFM) and the convection dispersion equation (CDE), were selected because of their simplicity and because they represent different hypotheses for the governing mechanisms determining longitudinal solute spreading on the field scale. The two parameters of each model are estimated using three calibration procedures: sum of squares optimization, method of moments, and maximum likelihood. The three calibration procedures yield different estimates for the parameters using a given data set, and different trends in parameter variation at different depths or times in a given experiment. Calculated uncertainty in the parameter estimates was high enough that no conclusion could be drawn about which model better described the data from the solution sampler experiment, but the TFM provided a better description of the coring experimental data after calibration than the CDE. It was concluded that future experiments on field scale solute transport through the unsaturated zone will have to monitor movement below 5 m in order to yield a data set suitable for distinguishing between different models.
A Simple Method for Combining Soil Properties that Show Variability
Authors: Addiscott T. M. , Wagenet R. J.
Published: July 2010

A method is shown by which variable soil properties expressed by distributions may be combined to estimate a variate that is derived from them through some functional relationship. The probability distribution (normal, log‐normal, or any other form) of the input for each property is divided into sections, each having the same number of observations. The section medians for each property are then combined through the functional relationship in all combinations of section and property to generate a population of values for the required variate without presupposing any particular type of distribution for it. The method gave estimates of unsaturated hydraulic conductivity, K(θ), that agreed with those from the Taylor series method (Rao et al., 1977) and additionally showed a marked increase in the variance of K(θ) as the volumetric moisture content, θ, decreased. Because the method generates a population of θ values, it could be further shown that as θ decreased, K(θ) became less well described by a log‐normal distribution. It can be used for nondifferentiable functions and, as is demonstrated for water flux calculations, functions whose inputs are log‐normally distributed but which cannot be expressed in logarithmic form. Although the method is not equivalent to the Monte Carlo procedure, it gave estimates of water flux that differed little from those given by Monte Carlo simulations.
Ionic Transport in Soil with Ion‐exchange Reaction
Authors: Cho C. M.
Published: July 2010

A mathematical model describing the transport of two ions in an exchange material such as soil, was described. Concentration profiles of displacing ion, A, and an ion being displaced, B, were obtained using the numerical solution of the two simultaneous transport equations of A and B. The variations in the concentration distributions were investigated by varying the selectivity coefficient of ion exchange reactions, valences of A and B, the magnitude of incoming concentration, and cation exchange capacity under constant flow rate of soil solution and dispersion coefficient. The results of the analyses indicated that the concentration distributions of displacing and displaced ions within a soil column can be related to the selectivity coefficient of the ion exchange reaction, exchange capacity, and concentration of the displacing ion. As the ion exchange selectivity coefficient became large, the front of the displacing ion became sharper and the maximum concentration of the displaced ion became greater. The depth of penetration of the displacing ion was not great since the ion effectively replaced the native ion that resided on the exchanger phase. For divalent‐monovalent exchange, the cation exchange capacity, selectivity coefficient, and concentration of the displacing solution played a role in determining the shape of the distribution curves of displacing and displaced ions.
Kinetics of Calcite Dissolution as Affected by Carbon Dioxide Partial Pressure
Authors: Amrhein C. , Jurinak J. J. , Moore W. M.
Published: July 2010

Research was conducted to determine the effect of CO2 on the kinetics of soil mineral dissolution. It was found that in soils or overburden materials in which CaCO3 is the dominant weatherable mineral, the kinetics of dissolution was not a simple diffusion controlled or first‐order reaction. In these calcareous systems, the transfer of atmospheric CO2 to solution was an important rate limiting step in the kinetics of dissolution. At higher PCO2 values the dissolution of calcite was modeled by three simultaneous reactions on the surface of the calcite. It is postulated that the CO2 attack consists of an adsorption of CO2(aq) on the calcite surface followed by hydrolysis of the CO2 to H2CO3. The hydrolysis is apparently catalyzed by the calcite surface because the aqueous hydrolysis, CO2(aq) + H2O → H2CO3, occurs too slowly for the observed rate of reaction.
Estimating Net Nitrogen Mineralization from Carbon Dioxide Evolution
Authors: Gilmour J. T. , Clark M. D. , Sigua G. C.
Published: July 2010

The ability to estimate net N mineralization from C decomposition data has the potential to improve our understanding of N dynamics in soil systems. It was the objective of this study to study this relationship using substrates with varying decomposition rates and C/N ratios. Five substrates including sewage sludge, alfalfa (Medicago sativa L.), clover (Trifolium sp.), bermudagrass [Cynodon dactylon (L.) Pers.] and ryegrass (Lolium multiflorum Lam.) were incubated in Crowley silt loam (Typic Albaqualfs) or Captina silt loam (Typic Fragiudults) soil at known soil temperatures and moistures. Concurrent CO2 evolution and soil inorganic N concentrations were measured periodically. A significant linear relationship between N mineralization and CO2 evolution was found experimentally for each substrate. A computer simulation model was developed which used first order kinetics for conversion of substrate C to CO2. Substrate C mineralization rate constants, substrate C/N ratios and microbial efficiency were primary inputs, while substrate, biomass, and soil organic matter were the major compartments of the model. Microbial efficiency was defined for any C pool undergoing decomposition as the ratio of assimilated C to assimilated C plus dissimilated C. An important feature of the approach was the introduction of a fraction with a C/N ratio of protein that decomposed very rapidly for those substrates where initial N mineralization was large while CO2 evolution was small. Model predictions of both CO2 evolution and net N mineralization were in good agreement with experimental results.
Effects of Potassium and Magnesium Applied for Corn Grown on an Irrigated Sandy Soil
Authors: Rehm G. W. , Sorensen R. C.
Published: July 2010

While the sandy soils of the Nebraska Sandhills and bordering areas are inherently low in N, P, and S, the levels of K and Mg in many soils are considered to be marginal. This study was conducted to evaluate the effects of repeated application of K and Mg on: (i) grain yield of corn, (ii) concentration of K and Mg in plant tissue, and (iii) soil test values for K and Mg. This study was conducted in north‐central Nebraska from 1979 through 1982 at a site that was marginal with respect to K and Mg. The soil was classified as a Valentine loamy fine sand (Typic Ustipsamments, mixed, mesic). Twenty treatment combinations from a 92 complete factorial were selected to fit a central composite factorial design and replicated 3 times. Selected rates of K (0, 34, 67, 101, 134, 168, 202, 235, 269 kg ha−1) and Mg (0, 5.6, 11.2, 16.8, 22.4, 28.0, 33.6, 39.2, 44.8 kg ha−1) were broadcast and incorporated before planting. Whole corn plants were collected from each plot when plants were 40‐ to 60‐cm tall and the leaf opposite and below the ear was sampled each year. These tissue samples as well as samples of grain were analyzed for K and Mg. Grain yields were measured each year. The application of both K and Mg had no significant effect on yield throughout the study. Although the concentrations of K and Mg were marginal as indicated by routine soil test procedures, this soil was apparently able to supply adequate K and Mg for corn production. Soil test values for K and Mg increased linearly with the rate applied. A yearly application of 33 kg K ha−1 was satisfactory for maintaining the initial level of soil test K. The K concentration in both whole plant and ear leaf tissue increased linearly with rate of K applied. In general, the K concentrations in the ear leaf tissue were in excess of the published critical level of 19 g kg−1. The Mg concentration in the plant tissue increased linearly with rate of applied Mg but decreased curvilinearly as the rate of K was increased. The Mg levels were substantially higher than published critical levels.
Energy Dissipation for Water Drop Impact into Shallow Pools
Authors: Ferreira Alfredo G. , Singer Michael J.
Published: July 2010

The literature reports that the presence of a shallow layer of water over the soil during a rainfall event is associated with more soil loss than the sum of the soil loss produced by rainfall and overland flow separately. The mechanism for this increase in raindrop effectiveness is not fully understood. We photographed, at 1000 frames s−1, the splashes of 3.2‐mm diam drops that were falling at close to terminal velocities into static water. During impact crater closing, soil from the pool bed was lifted. Energy calculations showed that the kinetic energy during crater closing generally reached a larger value than during crater opening. This may be responsible for the lifting of soil particles that were disaggregated during drop impact and crater formation and explain why a shallow water layer over the soil surface increases the erosive efficiency of raindrops.
Increases in Extractable Ions in Infertile Aquults Caused by Sample Preparation
Authors: Gilliam F. S. , Richter D. D.
Published: July 2010

Effects of sample preparation on dilute acid‐extractable ions were measured for paired unground field‐fresh and ground air‐dried soil samples taken from three depths at two sites in the coastal flatwoods of South Carolina. Concentrations of most extractable ions for the two preparation methods correlated closely. However, grinding and air‐drying increased extractable NO‐3 concentrations by 6 to 10 times, NH+4 and PO3‐4 2 to 3 times, and base cations up to 2.5 times. Ion releases from grinding and drying soils in the laboratory are related to soil organic matter and to field changes in soil moisture depletion.
Manganese Deficiency in Soybeans as Affected by FeEddha and Low Soil Temperature
Authors: Moraghan J. T.
Published: July 2010

Soybeans [Glycine max (L.) Merr.] developed an interveinal chlorosis, which eventually turned into a yellow‐green mottling on older leaves, when grown on certain calcareous soils treated with FeEDDHA. It was hypothesized that the problem was due to Mn deficiency, the intensity of which is known to be accentuated in soybeans at low soil temperatures. The influence of FeEDDHA, a foliar application of MnSO4, and soil temperature on growth of soybeans on a Glyndon loam, Aeric Calciaquolls, was studied under green‐house conditions. Increasing the FeEDDHA concentration from 0.2 to 2 mg of Fe kg−1 decreased dry matter yield at 15 but not at 24°C. The higher rate of FeEDDHA also caused a leaf chlorosis that was much more intense at 15 than at 24°C. The yield depression and the chlorosis were overcome by a foliar application of MnSO4. Soybean plants grown with the higher rate of chelated Fe contained 8 and 20 mg Mn kg−1 at 15 and 24°C, respectively, after 43 d. It was concluded that the chlorosis observed in soybeans growing on the calcareous soil was due to Mn deficiency induced by FeEDDHA and low soil temperature.
Transport of Cadmium by Organic Solvents Through Soil
Authors: Sheets P. J. , Fuller W. H.
Published: July 2010

Solutions of 0, 50, and 100% 2‐propanol and ethylene glycol in water containing 1 mM Cd were perfused through soil columns of river sand, Anthony sl (coarse‐loamy, mixed [calcareous], thermic Typic Torrifluvents), or Davidson c (clayey, kaolinitic, thermic Rhodic Paleudults) at two initial soil moisture contents (air dry and water saturated) to determine if organic solvents have the potential to alter the rate of Cd movement through soils as compared with water alone. Soils adsorbed less Cd from ethylene glycol than from water. Cadmium breakthrough was rapid and Anthony sl and river sand adsorbed <6 µmol Cd g−1 when leached with Cd‐enriched 2‐propanol. The 2‐propanol increased Cd adsorption compared to water in the Davidson c. Cadmium adsorption increased with increasing 2‐propanol concentration in the Davidson c but decreased with increasing 2‐propanol concentration in the River Sand and Anthony sl. No consistent trends occurred with increasing ethylene glycol concentration. Davidson c and river sand adsorbed significantly more Cd at 95% confidence levels from 2‐propanol when initially air dry, while Anthony sl adsorbed more Cd when initially water saturated. Initial soil moisture content did not significantly affect ethylene glycol transport of Cd at the 95% confidence level.
Structural Characteristics of a Fungal Melanin and a Soil Humic Acid
Authors: Schnitzer M. , Chan Y. K.
Published: July 2010

A melanin produced by Hendersonula toruloidea and a soil humic acid were characterized by a number of chemical (elemental and functional group analyses, carbohydrate content, amino acid, amino sugar, and NH3 analyses) and spectroscopic methods (IR and 13C NMR) before and after 6 M HCl hydrolysis. The following distinct differences were observed between the two materials: (i) phenolic components were prominent in the untreated and hydrolyzed melanins but not in the corresponding soil humic acids (HA); (ii) the melanin contained more complex unidentified N than did the soil HA; and (iii) following hot acid hydrolysis, the melanin was more aliphatic but considerably less aromatic than the soil HA. Hot acid hydrolysis, by removing practically all of the proteinaceous materials and carbohydrates from the two materials, made it possible to focus on the structural chemistry of the residual materials.