bluuebunny/crossref_metadata_2025 huggingface dataset:
Engineering Properties of Soils as Related to Mineralogy and Particle‐Size Distribution
Authors: Harris W. G. , Zelazny L. W. , Parker J. C. , Baker J. C. , Weber R. S. , Elder J. H.
Published: July 2010

Relationships between engineering properties and mineralogical and particle‐size variables were determined for samples from B and C horizons of selected soils. Measurements were made of internal friction (φ), California bearing ratio (CBR), and compression index (Cc). Particle size was determined by pipette analysis and mineral weight fractions were estimated on a clay, silt, sand, and whole‐soil basis using X‐ray diffraction and fluorescence, differential scanning calorimetry, and petrographic grain count analyses. Values of φ and CBR decreased with increasing whole soil phyllosilicate content (kg/kg) and decreasing particle size. Compressibility increased with increasing whole soil phyllosilicate content and decreasing particle size. Correlation coefficients between engineering parameters and most mineral weight fractions for isolated size fractions were low, but interactions between mineralogical and particle size variables were significant. Multiple linear regression models relating φ, CBR, and Cc to soil variables were highly significant, and R2 values for models were high. Interactions of transformed particle size and mineralogical variables were strong contributors in φ and CBR models. Signs of regression coefficients were consistent with the hypothesis that strength decreases and compressibility increases with decreasing particle size and increasing phyllosilicate content.
Comparison of Models for Determining Stability Constants of Metal Complexes with Humic Substances
Authors: Fitch Alanah , Stevenson F. J.
Published: July 2010

Several recent approaches for determining apparent stability constants of metal complexes with humic and fulvic acids are shown to represent graphical modifications of the basic equation relating the formation function of binding (v = sites bound/macromolecule concentration) to stability constants for the system v = ΣnjKj(M)/Σ[1 + Kj (M)], where Kj is the stability constant for binding at class j, nj is the number of binding sites of class j, and (M) is the free metal ion concentration. They include the Scatchard [v/(M) vs. v], reciprocal [1/v vs. (M)], and double reciprocal [1/v vs. 1/(M)] plots. Another approach is shown to have the same form as the Hill plot, which is based on an assumption of positive cooperativity. Comparison of the various models using a common set of experimental data revealed that approaches based on an assumption of linearity yield poor estimates for stability constants. Of the various models, the Hill plot is the least reliable.
Zinc and Copper Sorption and Fixation by an Acid Soil Clay: Effect of Selective Dissolutions
Authors: Cavallaro N. , McBride M. B.
Published: July 2010

Copper and zinc sorption‐desorption studies were carried out over a range of pH values using clay fractions separated from two horizons of an acid soil from New York. In the pH range of high sorption, as much as 95% of the sorbed metal could not be desorbed by several washes with 0.05M CaCl2 and thus was considered fixed. Sorption and fixation of Cu and Zn increased rapidly above pH 4 and 5, respectively, for the whole soil clays. Following removal of the oxide fraction by oxalate and citrate‐dithionite extractions, sorption and fixation were reduced considerably at pH values below the onset of hydrolysis of the metals in bulk solution, indicating a significant role of the oxides in metal retention. Citrate‐dithionite extraction was more effective than oxalate in reducing Zn sorption and fixation, suggesting a significant influence of the more crystalline iron oxide fraction. These extraction procedures had less effect on the ability of the clays to sorb and fix Cu. Treatment of the clays by hypochlorite to remove organics tended to either enhance or have little effect on sorption and fixation of Cu and Zn. It is concluded that microcrystalline and noncrystalline oxides in the clay fraction of this soil, representing < 20% of the clay by weight, provide reactive surfaces for the chemisorption of Cu and Zn. At low pH, adsorption at these surfaces may be the dominant mechanism of heavy metal immobilization, especially in the subsoil horizons.
Identification of Two Dominant Serotypes of Rhizobium trifolii in Root Nodules of Uninoculated Field‐Grown Subclover
Authors: Demezas D. H. , Bottomley P. J.
Published: July 2010

Analysis of the protein profile patterns by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS‐PAGE) of 30 isolates of Rhizobium trifolii obtained from root‐nodules of uninoculated field grown plants of subclover (Trifolium subterraneum L.) cv. ‘Mt. Barker’ showed that 12 and 9 isolates were represented by two different protein profile patterns (gel types). Serological analyses performed using antisera raised to one isolate of each gel type showed that although the two isolates, 1‐01 and 2‐01, shared a common antigenic determinant, they were distinguishable by their reactions in whole‐cell somatic agglutination and gel‐immune‐diffusion tests. Forty‐nine of the sixty isolates collected from nodules in the establishment year, and 56 of 90 isolates collected the following year were antigenically identical to either one or the other of the two parent isolates. Sixteen of the one hundred fifty isolates cross‐reacted strongly with both antisera in whole‐cell somatic tube agglutination and gel‐immune‐diffusion assays while only 23 of the 150 isolates were antigenically unrelated to either 1‐01 or 2‐01. All of the 22 isolates of serotype 1‐01 collected in the establishment year possessed the same gel type, wheres 19 of 27 isolates of serotype 2‐01 had the same gel type as the parent isolate, 2‐01. The majority (18 of 22) of isolates of serotype 1‐01 were superior symbiotic effectiveness while the majority (17 of 19) of isolates of serotype 2‐01 possessing the same gel type were of inferior effectiveness.
Prolificacy in Corn: Its Effects on Nitrate and Ammonium Uptake and Utilization
Authors: Pan W. L. , Kamprath E. J. , Moll R. H. , Jackson W. A.
Published: July 2010

Corn (Zea mays L.) genotypes differing in prolificacy were evaluated for N uptake and utilization from NO‐3 and NH+4 sources. Five single‐cross hybrids which differed in capacity to produce more than one ear per plant were field grown to maturity on a Dothan loamy sand (plinthic Paleudults), with two different N sources, calcium nitrate, or urea plus nitrapyrin. The two N sources were applied at two rates, each in multiple applications throughout the growing season. This minimized (i) the magnitude of nitrification within the urea treatments, and thereby enhanced the supply of N in the NH+4 form to the plants grown under the urea treatment, and (ii) differences in N availability due to differential leaching rates of NH+4 and NO‐3. At the low N supply there was little difference in N uptake or grain yield between the two N sources. At the high N supply, genotypes that produced > 1.5 ears per plant absorbed more N from the urea treatment and produced more dry matter during ear development. These increases were associated with an enhanced grain yield over the comparable NO‐3 treatment. Fully prolific plants demonstrated greater remobilization of N from vegetative tissue to grain. However, they also showed a lesser capability to absorb N during ear development, particularly from the NO‐3 source. The latter trait may have limited yields as indicated by the enhanced grain production in these genotypes when grown with a NH+4 source.
Characteristic Variations in Spectral Reflectance of Selected Eroded Alfisols
Authors: Latz K. , Weismiller R.A. , Van Scoyoc G.E. , Baumgardner M.F.
Published: July 2010

Soil cores taken at incremental depths from a Typic Hapludalf were examined to investigate the relationships among the chemical, physical, and spectral reflectance properties which occur as the proportion of various horizons change in the soil samples. Results of these studies were compared to soil samples taken from selected Typic Hapludalfs in Indiana which represented various degrees of natural erosion. Two important properties affecting the spectral reflectance of these soils were the organic matter and iron oxide contents. High organic matter contents tend to cause the reflectance to be low and give a concave character to the spectral response in the 0.5‐ to 0.8‐µm region. High iron oxide content along with the reduction in organic matter tends to cause an increase in the overall spectral response; however, the presence of iron oxides causes a leveling off of the spectral response in the 0.8‐ to 1.1‐µm region. Intermediate contents of organic matter and iron oxide affect the spectral response relative to their proportions within the soil sample. These distinctive reflectance characteristics can be related to the severity of erosion. Comparison of laboratory data to simulated Landsat data suggests that satellite multispectral scanner data can be useful in detecting eroded soils. Separability of erosion classes for the Alfisols studied was best determined by observing the slope of the simulated Landsat plots between 0.75 and 0.95 µm, bands 3 and 4. As the severity of erosion increases, the slope of the plot decreases in this region.
Stored Available Soil Water and the Fallow/Recrop Decision—Critical Level Approach
Authors: Goos R. J. , Johnson B. E. , Sobolik F. J. , Schneider R. P.
Published: July 2010

The amount of stored soil water at seeding has long been appreciated as a critical factor in the success of annual spring wheat (Triticum aestivum L.) production in the semiarid region of the Northern Great Plains. Stored available soil water at seeding, growing season precipitation, and grain yield data from 53 spring wheat experiments in western North Dakota were analyzed by both multiple regression and an interaction chi‐square approach. Soil types were generally fine‐loamy, mixed Typic Haploborolls or Argiborolls. Regression equations explained to little of the variability of the data to be useful in drawing practical guidelines for future fallow/recrop decisions. The results suggest that stored soil moisture data are better analyzed by the interaction chi‐square test, the results of which provide easy‐to‐interpret guidelines for making future fallow/recrop decisions. For example, for a minimum acceptable recrop wheat yield of 1350 kg/ha, the following critical levels were defined: stored available soil water at seeding less than 6.4 cm, crop failure is likely and summerfallow is advised; stored available soil moisture 6.4 to 9.4 cm, approximately equal odds of crop failure or success; stored available soil moisture > 9.4 cm, crop success is likely and recropping is advised.
Effects of Fresh and Decomposing Corn Plant Residue Extracts on Corn Seedling Development
Authors: Yakle G. A. , Cruse R. M.
Published: July 2010

Early corn (Zea mays L.) growth is frequently reduced in tillage systems that leave large amounts of corn residue on or near the soil surface. This effect may be due, in part, to the release of phytotoxic chemicals from the residue during rainfall or microbial breakdown. Laboratory experiments were conducted to investigate the activity of corn residue phytotoxins after movement through soil by using a corn seed bioassay for measurement. Corn seeds were germinated in tap water solutions extracted from corn residues that had been incubated with or without soil for 0, 15, or 30 d under wet, poorly aerated conditions. The extracted corn residue solutions were then either filtered or not filtered through columns of sterilize soil before being used to germinate the seeds. The corn seedlings were grown without light for 7 d in a growth chamber maintained at 22°C. A tap water check treatment was included in the study. Extracts of corn residue incubated without soil resulted in 39% as much root growth as did the check treatment. Incubation of the residue with soil reduced the inhibitory effects of the extracts, as did filtration of the corn residue extracts through the sterilized soil columns. The results suggest that phytotoxins extracted from corn residues incubated with soil were inactivated in the soil by microbial breakdown. Phytotoxins, however, were able to move through the sterilized soil columns without significant alteration of their inhibitory properties.
Use of Pressurized Vials for Loading Sample Loops in Soil Gas Analyses
Authors: Stealey T. E. , Hern J. L. , Harner E. J.
Published: July 2010

A technique was developed using small (3 mL) evacuated glass vials for soil gas sample storage and loading of gas chromatographic sample loops. Vial volume was reduced 2 mL by inclusion of glass beads. The vials were pressurized with 3.2 mL sample and used directly for loop loading via a specially contructed vial guide. Time course determinations on stored samples of C2H2 and Kr indicated leak losses of 0 to 0.2% d−1 when compared to the ideal technique of exhaustive loop purging from a standard gas tank. The low cost, reusability, and known vacuity of the vials, as well as the elimination of a transfer stop from storage container to a syringe prior to injection into a gas chromatograph, should favor their use in agronomic field and laboratory studies where numerous samples of the smallest possible volume must be taken.
Ion Products and Solid‐Phase Activity to Describe Phosphate Sorption by Soils
Authors: Blanchar R. W. , Stearman G. K.
Published: July 2010

Solution equilibria and regular solid‐solution concepts were combined to relate phosphate solubility to amounts of added phosphate in eight acidic Missouri soils. Phosphate sorption studies were done by shaking KH2PO4 solutions with soil for 16 d and measuring pH, Eh, electrical conductivity, Ca, Mn, Al, Fe, and P contents of the solution. These data were used to compute ion products and to estimate the activities of solid‐phase phosphate minerals. It was shown that solubility relationships for the reaction of H2PO4 with Al(OH)3 could be interfaced with estimates of solid‐phase activities and used to predict phosphate in solution as a function of a soil constant (C), soil pH, and the amount of phosphate added. Activities for the equilibrium equation,

p(H2PO4) = 10.50 − pH − p[Al(OH)3] + p(AlPO4),

were estimated. The value of p[Al(OH)3] was determined from the data to be a linear function of pH, 2.41 − 0.42 pH, for soils used in this study. The value of p(AlPO4) was determined by statistically fitting observed p(AlPO4) and Padded to a polynomial equation similar in form to the one for a regular solid solution:

p(AlPO4) = C − 9.4 × 10−3 (Padded) + 6.9 × 10−6 (Padded)2,

with r2 = 0.96. Values of p(H2PO4) were calculated from pH and Padded by these combined equations, and compared with measured p(H2PO4) with an r2 of 0.96. The system was shown to have solubility features similar to those described for a regular solid solution. Combining solution equilibria and regular solid‐solution concepts was useful in providing a chemical basis for interpreting phosphate sorption by soils.
Distribution of Applied Nitrogen in Soil—Pensacola Bahiagrass Components as Indicated by Nitrogen‐15
Authors: Impithuksa V. , Blue W. G. , Graetz D. A.
Published: July 2010

The fate of fertilizer N applied to coarse‐textured soil‐plant systems is not well understood. To determine the effects of N rates and seasonal N applications on plant response and recovery of applied N from these soils, three field experiments with 15N‐enriched fertilizer were superimposed in 1976 on nontracer N experiments on Myakka fine sand (sandy, siliceous, hyperthermic Aeric Haplaquods), Ona fine sand (sandy, siliceous, hyperthermic Typic Haplaquods), and Astatula sand (hyperthermic, uncoated Typic Quartzipsamments) planted to Pensacola bahiagrass (Paspalum notatum Flugge). At each site, a split‐plot experimental design was used with two N rates (100 and 200 kg ha−1) as main plots and three seasonal N applications as subplots. Forages, stolon‐root masses, and soils were analyzed for total N and 15N concentrations. In 1976, forage yields and 15N‐labeled fertilizer N contents were larger at the higher N rate, but were not affected by seasonal N applications. Recovery of fertilizer N in forage was 36, 31, and 29% for the Myakka, Ona, and Astatula soils, respectively. An average of 48% of the total N in forage was from the fertilizer. Mineralization of immobilized N from previous fertilizations probably did not account for the large amount of nonfertilizer N in the forage. Recoveries of fertilizer N in stolon‐root masses were 11, 11, and 16%; recoveries in soils were 28, 13, and 11%; and recoveries in soil‐plant systems were 74, 54, and 54% from the Myakka, Ona, and Astatula soils, respectively. Denitrification was suspected as an important N loss mechanism from the poorly drained Myakka and Ona soils, and leaching was likely dominant from the well‐drained Astatula soil; however, soil‐solution samples collected from depths of 60 and 120 cm in these soils showed no evidence of N leaching. Not more than 5% of the 15N‐labeled fertilizer applied in 1976 was recovered in forage produced in 1977. At the end of 1977, total fertilizer N accounted for was essentially the same as at the end of 1976. Two important results were the relatively large amounts of nonfertilizer N in forage, especially in 1976, the year of 15N‐labeled fertilizer application, and the relatively high percentage of fertilizer N retained in these three sandy soils. In 1983, 7 yr after fertilization with labeled N, there was little change in labeled N in the soil compared to 1977.
A Soil Test for Nitrogen Availability to Corn
Authors: Magdoff F. R. , Ross D. , Amadon J.
Published: July 2010

A soil test for N availability to corn (Zea mays L.), NO‐3‐ to 30cm when plants are 15 to 30 cm tall, was evaluated on a wide range of soils at 33 locations in Vermont and one in New York state. The NO‐3‐N present at the time of sampling is a result of an integration of all the soil and weather factors that have influenced the availability of N prior to the time for sidedress fertilizer application. There was a typical response relationship between soil test NO‐3‐N and corn silage yield on plots that only received limited amounts of starter N fertilizer at planting. The Cate‐Nelson procedure for NO‐3‐N vs relative yield (yield without sidedress N/yield with sidedress N) indicated that there was a greater probability of response to N fertilizer when NO‐3‐N was less than 36 kg ha−1 than at higher soil test values. The currently used N fertilizer recommendation procedure is based on estimates derived from cropping history, yield goal, soil type, and manure management information provided by farmers. Compared with the current method of estimating N fertilizer needs, recommendations based on the NO‐3‐N soil test call for much less N fertilizer application and are more accurate in separating sites with varying response probabilities. As a routine laboratory procedure, the proposed test has numerous advantages over other N availability procedures. However, special procedures are needed, including rapid soil treatment after sampling (to eliminate N transformations), sampling the soil at a different time than for the usual soil test, and a rapid sample turnaround time in the laboratory.
The Relationships of Landsat Digital Data to the Properties of Arizona Rangelands
Authors: Horvath E. H. , Post D. F. , Kelsey J. B.
Published: July 2010

Pedon descriptions, vegetation transect information, and Landsat digital data were obtained for 110 sites on the Tonto National Forest in central Arizona. Using the field and satellite data, 33 variables were evaluated and prediction models were generated using stepwise multiple regression techniques. The following six factors explained 84% of the variability within the sum of the values for the four Landsat spectral bands: sum of brush and forest crown densities, elevation, surface color, rock type, cobbles on the surface of the site, and grass cover. Seven factors explained 81% of the variability for the ratio of Bands 4 plus 5 to Bands 6 plus 7: percent clay in the surface horizon, percent fragments > 2 mm in the surface horizon, the sum of forest and brush crown densities, pH of the surface horizon, color of the surface horizon, litter cover, and site aspect.
A Simple Colorimetric Measurement for Humic Acids in Spodic Horizons
Authors: Holmgren G. G. S. , Holzhey C. S.
Published: July 2010

An organic buffer, 2‐amino‐2‐methyl propanol neutralized to pH 10 with 4M acetic acid, was investigated as an extractant for soil organic matter. The color of the humic acid fraction of this extract proved to be a distinctive marker of spodic horizon organic matter. Both the humic acid and fulvic acid fractions were quantified by a simple comparator used to classify color in natural waters. The fulvic acid color was functionally related to aluminum in the extract and also to aluminum in the pyrophosphate extract. If the extract contained iron, it was associated with the humic acid color, although humic acid color could be present without iron. The humic acid color was present only in those soils with pH < 4.5. Data are presented to demonstrate the ruggedness of the procedure with respect to variations of extraction time and of the soil/solution ratio.
Relation of Organic Carbon to Soil Properties and Climate in the Southern Great Plains
Authors: Nichols J. D.
Published: July 2010

The proportion of Mollisols in the Southern Great Plains ranges from 1% to > 90% of counties with completed soil surveys. A study was made on data from 65 pedons spaced as equally as possible across the area. All of the soils studied had grassland vegetation, were on uplands, were not excessively wet, and did not have high shrink‐swell potential. Stepwise multiple regression analyses were made on percent organic carbon vs. percent clay, percent silt, base saturation, mean annual precipitation, and mean annual temperature. Results indicate a significant relationship between organic carbon and clay with a lesser relationship with precipitation. The other variables did not improve the predictive equation.
Using Clay Mineralogy to Infer Sources of Suspended Clay and Silt in a Watershed: Quantitative Approach
Authors: Hsieh Y. P.
Published: July 2010

A functional procedure for using clay mineralogy to infer sources of suspended clay and silt in a watershed is presented. The information could lead to estimation of soil loss from various parts of a watershed, if the dispersion factor of the source soils can be evaluated. The suspended clay and silt carried by the Gallatin River and its tributaries were used to illustrate the methodology. Clay mineralogy of the clay and silt is expressed as the relative percent peak heights of minerals from the x‐ray diffractogram. The percent peak heights of these minerals are found reproducible (CV = 6%), and additive in nature. Analysis of variance reveals that clay mineralogy is significantly different among the tributaries of the Gallatin River. The results of discriminant analysis substantiated that clay mineralogy can be a signature of the suspended clay and silt carried by the Gallatin River and its tributaries. The Q‐mode factor analysis technique was applied to “demix” the suspended clay and silt of the main stream into its source components. The results of Q‐mode factor analysis indicate that clay and silt carried by the Gallatin River was mainly from Taylor Fork (92%) on 7 May 1971. The source of clay and silt in Taylor Fork was further traced back to its upper‐stream above Wapiti Creek (90%). The source of suspended solids in West Fork varied according to the sampling dates. On 27 May 1971, the north and south branches contributed almost equal parts of that to West Fork, while on 8 June 1971, the south branch contributed the majority (84%) of clay and silt to West Fork. The proposed method of sediment tracing by clay mineralogy is relatively simple and economical compared to the conventional stream monitoring methods. More important, it provides an independent alternative to the conventional methods of soil erosion assessment in a watershed.
A Portable Tool for Obtaining Soil Cores in Clayey or Rocky Soils
Authors: Tuttle C. L. , Golden M. S. , Sirois D. L.
Published: July 2010

A portable tool was designed to collect soil samples, root cores, and bulk density cores on remote forest sites. Use of the designed tool allowed soil cores to be collected repeatedly from a study plot with minimal site disturbance. Cores 7.62 cm in diameter and up to 45.0 cm deep were collected and analyzed. Up to 10 cores per hour can be obtained by a two‐man crew. Over 1000 cores were collected before maintenance of the tube was needed. Bulk density cores collected with the designed tool were not significantly different from cores collected using standard 7.62 cm rings.
A Generalized Solution to Infiltration
Authors: Warrick A. W. , Lomen D. O. , Yates S. R.
Published: July 2010

A generalized solution to the moisture flow (Richards') equation is developed for infiltration. The equation is expressed in terms of dimensionless time, depth, and water content. The reduced form applies for the hydraulic functions of van Genuchten or of Brooks and Corey as well as to other scaled forms and the solution utilizes the procedure of Philip. Answers are presented in concise tables which, in principle, allow for finding moisture profiles, wetting front, intake rate and cumulative intake for a variety of soils and for varying initial water contents. For application, specifically measured hydraulic conductivities can be best‐fitted to the forms used here or generalized empirical values can be used from the literature. Thus, either specific or generic parameters may be used, depending on availability for a given problem.
Statistical Relationship between Apparent Dielectric Constant and Water Content in Porous Media
Authors: Ansoult M. , De Backer L. W. , Declercq M.
Published: July 2010

A theoretical relationship between the apparent dielectric constant (Ka) and the water content (θr) of porous media is presented. The dielectric effect of the porous medium is investigated at the microscopic scale of the probable path of an electric charge. This path is a function of the environment of the charge. Only one parameter, the number of degrees of freedom of the charge is necessary to describe the heterogeneity of the porous medium. The results of this model generally agree very well with recently published experimental data.
Water Relations of Saturated Bentonite: Some Effects of Temperature and Solution Salt Concentration
Authors: Smiles D. E. , Barnes C. J. , Gardner W. R.
Published: July 2010

Transient flow (constant pressure desorption) and equilibrium pressure membrane experiments were used to determine some water relations of bentonite pastes in the range of water content (volume of water per unit volume of solid) from 6 to 33. The pastes were prepared in equilibrium with three different sodium chloride concentrations (3.25 m mol L−1, 16.8 and 119 m mol L−1), and the experiments were performed at temperatures of 277, 293, and 306 K. It was found that for each solution salt concentration, the moisture characteristic was effectively temperature independent, and the effect of solution concentration was qualitatively, but not quantitatively, in agreement with electrical double layer theory. In the transient flow experiments, both the cumulative outflow (expressed as a function of the square root of time) and the water content profiles (determined by destructive sampling and expressed as a function of material distance divided by square root of time) revealed clear temperature dependence. This effect is wholly accounted for by the temperature dependence of the kinematic viscosity of water. The observations lead us to infer that temperature dependence, over and above effects on viscosity, in the moisture characteristic and flow properties in unsaturated soils arises not in double‐layer effects, but in effects on the air water interfaces in these systems.
Significance of Iron Oxides and Calcium Carbonate Particle Size in Phosphate Sorption by Calcareous Soils
Authors: Ryan J. , Curtin D. , Cheema M.A.
Published: July 2010

Though many soil components are involved in reactions whereby soluble fertilizer P is converted to less soluble and therefore less available forms, the relative influence of each phase in this process is not clearly defined. While both crystalline and amorphous Fe oxides readily react with P in noncalcareous soils, the contribution of these forms to P sorption in calcareous soils has received little attention. Thus, in this study, samples of 20 mainly calcareous Lebanese soils, ranging widely in relevant properties, were equilibrated for 6 d with 25 mL P solutions ranging from 12.5 to 62.5 mg kg−1. The data did not conform to the conventional Langmuir isotherm. Correlations and regression coefficients with actual P rentention from solution indicated an involvement of oxalate Fe, but there was no effect of CaCO3 particle size. Removal of Fe prior to equilibration had an inconsistent effect on P retention. The P behavior of calcareous soils may be modified by Fe oxides in such soils.
Determination of Exchangeable Bases in Soils by Ion Chromatography
Authors: Basta N. T. , Tabatabai M. A.
Published: July 2010

A simple, accurate, and precise ion chromatographic (IC) method for determination of exchangeable bases in soils was developed. It involves extraction of the bases with neutral 1M ammonium acetate (NH4 OAc), followed by ignition of the soil extract at 400°C for 30 min, dissolution of the residue in 5 mM HCl, and determination of exchangeable bases by using a Dionex Model 10 IC. The IC method is based on separation of the cations by a separator column containing a low‐capacity, cation‐exchange resin in the H+ form and converting the various cations to their corresponding hyroxide forms by a suppressor column in the OH‐ form. Solutions of 5mM HCl and 2.5 mM HCl + 2.5 mM m‐phenylenediamine dihydrochloride are used as the eluents for determination of monovalent and divalent exchangeable bases, respectively. Electrical conductivity is used as the mode of detection. Results showed that the average exchangeable K in 10 soils by IC, atomic absorption spectrophotometry (AA), and flame photometry (FP) were 0.49, 0.47, and 0.47 cmol(i)/kg soil, respectively. The corresponding average exchangeable Na values were 0.09, 0.09, and 0.08 cmol(i)/kg soil. The average exchangeable Ca values of the same soils by IC and AA methods were 13.5 and 13.5 cmol(i)/kg soil. The corresponding exchangeable Mg values were 3.50 and 3.54. The IC method has excellent sensitivity, with detection limits of 0.1, 0.05, 0.1 and 0.03 mg L−1 of K, Na, Ca and Mg. respectively. With the IC method, K and Na can be determined simultaneously in 6 min, or Ca and Mg can be determined in 7 min. A single operator can perform about 40 analyses of monovalent or divalent bases in a normal working day.
Acetylene Decomposition in Soils
Authors: Terry Richard E. , Duxbury John M.
Published: July 2010

AcetyIene (C2H2) is useful in studies of nitrogen fixation and denitrification in soils. The objective of this study was to determine the soil environmental conditions under which microbial decomposition of acetylene occurs. Samples of Collamer sicl, Timpanogos cl, and Pahokee muck were exposed to carbon‐14 labeled acetylene in the laboratory. Less than 2.5% of the added gas was metabolized during the first 7 d of incubation, whether the soils were incubated aerobically or anaerobically. Adaptation to acetylene metabolism was observed in the two mineral soils during the second 7‐d period of aerobic incubation but adaptation did not occur during 42 d of anaerobic incubation or during a 21 d aerobic incubation of the Pahokee muck. Acetylene metabolism in soil samples adapted to acetylene utilization was stimulated by the addition of 10 mg N kg−1 soil of ammonium, nitrite, or nitrate. Addition of ≥ 100 mg N kg−1 soil of nitrate or nitrite or 1,000 mg N kg−1 soil of ammonium had a substantial inhibitory effect on acetylene utilization. The order of inhibition was ammonium < nitrate < nitrite. The addition of alfalfa, a source of readily available carbon, slowed microbial adaptation to acetylene decomposition and resulted in lower rates of transformation in the Collamer soil.

Adaptation of soil microorganisms to acetylene utilization in the Collamer soil occurred in situ at a rate similar to laboratory incubation experiments. The ability of microorganisms in the soil to metabolize acetylene was maintained for at least 42 d after exposure of field plots to the gas was discontinued.
Factors Related to Urea Hydrolysis in Soils
Authors: Reynolds C. M. , Wolf D. C. , Armbruster J. A.
Published: July 2010

The use of urea as a nitrogen source for crop production has increased in recent years. Because the hydrolysis of urea to ammonia and carbon dioxide is mediated by the enzyme urease, efficient use of urea requires an understanding of factors that influence urea hydrolysis in soil. The purpose of this research was to relate the rate of urea hydrolysis to chemical, physical, and biological properties for soils in pasture and in cultivation. For each of 22 soils in Kansas, Missouri, and Oklahoma, samples were collected from paired fields, one in pasture and one in cultivation. The samples were taken from both 0 to 2.5 cm and 0 to 15 cm, and urea hydrolysis rates were measured in field‐moist and air‐dried samples. Urea hydrolysis rates in air‐dried soils ranged from 1 to 149 µg urea g soil−1 h−1 and from 1 to 117 µg urea g soil−1 h−1 in field moist soils. For each soil, the greatest urea hydrolysis rate was in the 0 to 2.5‐cm depth of pasture samples. The urea hydrolysis rate for each soil was greater in pasture samples than in samples from cultivated fields. For samples from cultivated fields, urea hydrolysis rates in both field‐moist and air‐dry samples were positively correlated with total nitrogen (TN) and organic carbon (OC). Only in the field moist soils were urea hydrolysis rates correlated with TN and OC in the soils from pastures. Urea hydrolysis rates in the 0 to 2.5‐cm depth of pastures exhibited the greatest change from field‐moist to air‐dry conditions. Rates generally decreased with drying, but did remain constant or increased with drying in some cases. Both the greatest rates and the greatest variation in urea hydrolysis rates between field‐moist and air‐dry soils were observed in the surface 0 to 2.5 cm samples from pastures.
Fractionation of Inorganic and Organic Phosphorus in Virgin and Cultivated Soils
Authors: Sharpley A. N. , Smith S. J.
Published: July 2010

Amounts of phosphorus (P) in inorganic and organic pools were determined for three noncalcareous and five calcareous surface soils (0–150 mm) which had been cultivated for at least 15 yr, and their virgin analogues, to ascertain if relative pool sizes or soil P fertility are being changed by cultivation and associated fertilizer application. The soils were representative of major agricultural areas of the USA, with total P concentrations ranging from 200 to 1920 mg kg−1 (approximately 50% inorganic P) and P applications from 0 to 90 kg ha−1 yr−1. P forms in the pools and extractants used were as follows: inorganic P; loosely‐bound (1.0M NH4Cl), nonoccluded (0.5M NH4F + 0.1M NaOH), occluded (citrate‐dithionite‐bicarbonate + 0.5M NH4F + 0.1M NaOH), and Ca bound (1.0M HCl) (calcareous soils only): organic P; labile (0.5M Na HCO3), moderately labile (1.0M H2SO4 + 0.5M NaOH), moderately resistant (0.5M NaOH/HCl soluble), and resistant (0.5M NaOH/HCl insoluble). Distribution of inorganic P in virgin noncalcareous soils was, on average, 2% loosely‐bound, 52% nonoccluded, and 46% occluded. Cultivation resulted in an increase in nonoccluded and decrease in occluded P. Average distribution in the virgin calcareous soils was 2% loosely‐bound, 11% nonoccluded, 9% occluded, and 78% Ca‐bound, with no significant change in pool size with cultivation observed. On average, organic P in the virgin soils was 7% labile, 48% moderately labile, 33% moderately resistant, and 12% resistant, with no significant change in relative amounts due to cultivation. A mounts of fertilizer P applied and organic P mineralized and immobilized in stable inorganic P pools during cultivation, were related to P sorption index of the soils. The conversion of organic to inorganic P may be reversed by management practices allowing a build up of soil organic matter. Since little change in amounts of loosely‐bound inorganic and labile organic P was observed during cultivation, the more stable pools may represent a better estimate of long‐term soil fertility.
Soil pH Buffering Revisited
Authors: Magdoff F. R. , Bartlett R. J.
Published: July 2010

The buffering relationships of a wide variety of Vermont soils were investigated by adding either acid (H2SO4) or base (CaCO3). Soils were found to be very well buffered above pH 7 and below pH 4. When amendment added is expressed on an organic matter (OM) basis [mmol (H+ or 1/2 CaCO3) g−1 OM] and the check treatment is transposed to a common curve, all soils appear to follow a similar relationship (a unified buffer curve). Thus, OM appears to strongly influence the degree of pH buffering of Vermont soils. For practical purposes, pH buffering of soils in the pH 4.5 to 6.5 range is linear with added amendment. However, the change in slope of the unified buffer curve indicates that of the entire pH range soils may be least well buffered between pH 5 and 5.6. The low degree of pH buffering in this range may be due to a high degree of cation exchange capacity (CEC) buffering. The pH vs. percent base saturation (%BS) relationship has been misinterpreted as being the same as a pH vs. lime addition titration curve. In a soil without appreciable exchangeable Al, the %BS is essentially the soil's CEC at its current pH expressed as a percent of the CEC at pH 8.2. Ranges in pH where the %BS increases only slightly may be zones of low pH buffering.
Soybean Shoot and Root Growth and Phosphorus Concentration as Affected by Phosphorus Placement
Authors: Borkert C. M. , Barber S. A.
Published: July 2010

Effect of P placement on shoot and root growth and their relation to recovery of applied P is important for economic crop production. Few studies have investigated the effect of varying the P‐fertilized soil volume on soybean (Glycine max L. Merr.) root growth, P uptake and soybean yield. The objective of this research was to investigate the effect of localizing P in decreasing volumes of soil on soybean seedling root morphology and distribution, and P uptake in order to determine the placement giving maximum plant growth. An experiment with soybeans grown in Raub silt loam (Aquic Argiudoll) was conducted in 3‐L pots in a controlled climate chamber. Adding the same amount of P per pot (60 mg/kg soil) in decreasing volumes of soil stimulated root length in the fertilized portion while the root radius became smaller in this zone. The relation between soil volume fraction fertilized with P and fraction of total root length in the fertilized soil could be described by y = x0.70 (r2 = 0.96), where x is the proportion of the soil volume treated with P and y is the predicted proportion of the total root length in the P‐treated soil. Shoot P concentration increased as the volume of fertilized soil was reduced to 0.125 but did not increase further as fertilized soil volume was reduced to 0.0625. Also, maximum shoot dry weight was obtained when 0.125 of the soil was P fertilized and did not increase further as P‐treated soil volume was reduced to 0.0625.
Genesis of Cambic and Argillic Horizons in Two Northern Utah Aridisols
Authors: Southard R. J. , Southard A. R.
Published: July 2010

A study of the mineralogy and morphology of two northern Utah Aridisols (Camborthid and Haplargid) formed from ancient Lake Bonneville sediments revealed small but important differences between the two soils in the degree of weathering and soil development. The B horizons of both pedons meet the argillic horizon textural requirement. An incipient argillic horizon was identified in the Haplargid on the basis of thin, discontinuous pore argillans observed with a scanning electron microscope. The Camborthid Bw horizon is a cambic horizon, as indicated by partial removal of carbonates, development of structure, and lack of illuviation argillans. The Camborthid is calcareous throughout, and interlayering of mica‐smectite in the clay fractions is extensive. Stronger weathering in the Haplargid is inferred from the nearly complete removal of carbonates from surface horizons and more complete alteration of mica to smectite (i.e., less interlayering). The argillic horizon has formed in about 9000 yr under the influence of at least two pluvial periods. The cambic horizon formed in an environment at least as dry as at present, and it is still calcareous after about 6000 yr. The scanning electron microscope is a valuable tool for inferring soil‐forming processes from soil fabric morphology, especially in weakly‐developed horizons.
Effect of Disturbed Soil Thickness on Soil Water Use and Movement under Perennial Grass
Authors: Merrill S. D. , Smith S. J. , Power J. F.
Published: July 2010

Previous research has shown that plant growth on minespoil of lower plant productivity is dependent upon thickness of soil replaced. Sodium‐affected strip‐mine spoils are a significant reclamation problem in the northern Great Plains. The purpose of this work was to develop understanding of plant growth response to soil thickness over sodic minespoils by measurement of water movement, water use, and root growth. Soil water storage and use were measured in each of three growing seasons under crested wheatgrass (Agropyron desertorum) grown on 0.25‐, 0.5‐, 0.75‐, and 1.0‐m thicknesses of disturbed soil. Soil profiles were constructed from Haploboroll topsoil (0.2 m for all treatments), placed over varying thicknesses of subsoil (B and C horizon materials), which in turn was placed over sodic (Sodium adsorption ratio = 30) drag‐line spoil at a semiarid, steppe‐land site in western North Dakota. Forage yield was 2‐ to 3.5‐fold greater on 1.0 m soil thickness than on 0.25 m. Both total soil water potentials and root weight densities were similar in minespoil and in subsoil at the same profile depths. Root water uptake was much less from the minespoil (mean saturated hydraulic conductivity (HC) = 1 × 10−3 cm/d) than from subsoil (mean HC = 0.2 cm/d). Low HC per se appeared to be the dominant factor limiting sodic minespoil as a plant growth medium because low HC resulted in less use of stored soil water from minespoil compared to subsoil. Depletion from a 120‐cm profile was 0.2, 3.3, 7.9 and 9.8 cm for 0.25‐, 0.50‐, 0.75‐ and 1.0‐m soil thickness, respectively. Relative differences in evapotranspiration (ET) between the 0.25‐m and 1.0‐m soil thickness treatments were much less than yield differences, reflecting progressively reduced water use efficiency with less soil thickness.
Effect of Slope and Rainfall Intensity on Erosion from Sodium Dispersed, Compacted Earth Microcatchments
Authors: Evett Steven R. , Dutt Gordon R.
Published: July 2010

Knowledge of erosion in microcatchment systems is needed for the design of water harvesting systems. This study was therefore conducted on the effects of microcatchment slope and length on runoff and erosion rates under natural rainfall. Two replicates of a two factor experimental plot design, including 1, 5, 10 and 15% slopes and 3 and 6 m lengths, were built on a gravelly sandy clay loam using 11.2 Mg/ha of NaCl mixed into the surface 2 to 5 cm of soil followed by compaction with a 6‐Mg roller after a heavy rain. Most of the erosion was from interrill erosion. Length (m) and storm energy, E, (MJ/ha) had no significant effects on erosion. The effects of slope, s, (m/m) and maximum 30 min rainfall intensity, I30, (mm/h) were significant at the 0.1% level for the 11 storms studied. These effects were significantly different from those in the USLE (Universal Soil Loss Equation), which underpredicted erosion at low slopes. The best fit equation was A = (0.0595s0.998 + 0.0068)I301.86 where A is the estimate of erosion (Mg/ha). The sodium treated surface layer is estimated to last up to 20 yr under our conditions if slopes are kept to 5% or lower on these microcatchments of less than 6m length.
Changes In Solum Chemistry Following Clearcutting of Northern Hardwood Stands
Authors: Snyder K. E. , Harter R. D.
Published: July 2010

To assess the role of the soil in retaining nutrients after clearcutting, the sola beneath three even‐aged pin cherry (Prunus pensylvanica L.)‐birch (Betula alleghaniensis Britton and B. papyrifera Marsh.) stands were analyzed for post harvest changes in Ca, Mg, K, pH, organic carbon, titratable acidity, and loss‐on‐ignition. A 93‐year‐old second‐growth northern hardwood stand served as the preharvest comparison. The stands were located in central New Hampshire. The sites were selected to reduce influences from such external parameters as elevation, aspect, physiographic position, and parent material. Within each site, morphologically matched pedons of a single soil series were sampled. Mineral soil analysis indicated that organic matter may be translocated into the upper mineral horizon following the post‐harvest initiation of surface decomposition. A large influx of Ca, Mg, and K into the mineral soil was associated with this decomposition. Potassium concentrations showed a rapid increase throughout the solum soon after harvesting. Following an assumed reduction in counter ion leaching, Ca and Mg accumulation was apparent, particularly in spodic horizons high in soil organic matter. Exchangeable nutrient levels remained two to three times higher at the 30 yr post‐harvest relative to the preharvest site.
Micromorphological and Submicroscopical Features Related to Pyrite Oxidation in an Inland Marine Shale from East Central Saskatchewan
Authors: Mermut A. R. , Curtin D. , Rostad H. P. W.
Published: July 2010

The micromorphology and submicroscopy of a soil mapped within the Arborfield Association in east central Saskatchewan, which is derived from Cretaceous marine shale, were investigated. Qualitative analysis of well‐formed monomineralic crystals in the oxidation zone by energy dispersive analysis of x‐ray (EDAX) system attached to transmission electron microscope (TEM) confirmed them to be jarosite in which most of the monovalent cation positions were occupied by sodium with minor quantities of Potassium (natrojarosite, Na(K)Fe3(SO4)2(OH)6). They occur as void natrojarositans, neonatrojarositans, and quasinatrojarositans. Persistence of natrojarosite in some aggregates within the upper Cgk and Cg horizons with high pH is attributed to the low solubility of this mineral. A comparison of the size, shape and distribution of pyrite and natrojarosite suggest that natrojarosite is essentially formed by crystallization from solution rather than in situ replacement of pyrite. Ferric glaebules in the form of nodules and concretions, found only in the upper part of the profile, were characterized as the ultimate development phase of pyrite oxidation. Stabilization of iron as glaebules leaves the sodium and sulphate in the soil solution. These are generally the major soluble ion species in saline soils in Saskatchewan. Presence of planar voids (craze and skew planes) and their orientation pattern, especially in the lower part of the profile, were ascribed to the poor drainage conditions, which is an important factor affecting the persistence of pyrite and natrojarosite in the profile studied.
A Spot Test with Toluidine Blue for Allophane and Imogolite
Authors: Wada Koji , Kakuto Yasuko
Published: July 2010

Toluidine blue is adsorbed on negatively charged colloids and exhibits a characteristic color change from blue to purplish red (metachromasis). A procedure to test the metachromasis for the soil was developed and tested for Chile and Ecuador soil samples containing and not containing allophane and imogolite. The results show that the absence of the metachromasis can be used for the test of allophane and imogolite.