bluuebunny/crossref_metadata_2025_split huggingface dataset:
Single Column Ion Chromatography: III. Determination of Orthophosphate in Soils
Authors: Karlson U. , Frankenberger W. T. 
Published: July 2010

AbstractA chromatographic procedure was developed to determine orthophosphate in aqueous soil extracts by single column ion chromatography (SCIC) with conductimetric detection. The eluent stream consisted of 1.5 mM phthalic acid adjusted to pH 2.7 with formic acid. The method allows precise (RSD = 1.1‐3.3%) measurements of trace amounts of orthophosphate (detection limit = 0.3 µg L−1) in the presence of high background levels of Cl‐ and NO‐3. Analysis of orthophosphate by SCIC closely agrees to those values obtained with an AutoAnalyzer based on the Mo blue chromophore reaction. Under the chromatographic conditions described, elution of orthophosphate occurred at 6 min while Cl‐ and NO‐3 had respective retention times of 11 and 20 min. Single column ion chromatography proves to be a rapid and routine method for determination of orthophosphate with greater sensitivity than the conventional colorimetric methods.
Relation Between Potassium Fixation and the Oxidation State of Octahedral Iron
Authors: Chen S. Z. , Low P. F. , Roth C. B. 
Published: July 2010

AbstractSamples of the <2‐µm fractions of five pure smectites and six soil clays were reduced by sodium dithionite in the presence of a potassium citrate‐bicarbonate buffer. Subsequently, they were freed of excess electrolyte by dialyzing them in a deoxygenated, 10−3 M KCl solution. Subsamples of the resulting clays were used to determine Fe2+/total Fe, the ratio of ferrous Fe to total Fe; mw/mc, the mass ratio of water to clay, at a swelling pressure of 0.3 MPa; KT, the total K; KE, the exchangeable potassium; and KF, the fixed K. Identical samples of the same smectites and soil clays were subjected to the same experiments except that they were treated with sodium sulfate instead of sodium dithionite. Hence, they remained in the oxidized state. Then the differences in the experimental results for the reduced and oxidized samples were determined. For the several samples, it was found that ΔKF, the change in KF, was proportional to Δ(mw/mc), the change in mw/mc. Also, it was found that ΔKF was an exponential function of 1/ΔFe2+, where ΔFe2+ is the change in Fe2+, but that the constants in this function were different for the pure smectites than for the soil clays. From these findings it was concluded that K+ fixation is enhanced by the reduction of octahedral ferric Fe in the clay crystal and that the difference between the pure smectites and soil clays was attributable to nonsmectite minerals in the latter.
Response of Turfgrass to Various Nitrogen Sources
Authors: Landschoot P. J. , Waddington D. V. 
Published: July 2010

AbstractNitrogen sources with different properties and release characteristics are used to meet a variety of fertility management needs in turfgrass culture. Our objective was to determine the response of turfgrass to various urea‐formaldehyde reaction products; two particle sizes of oxamide; experimental sulfur‐coated ureas (SCU); products containing combinations of N sources; and an experimental composted sewage sludge. Nitrogen sources included for comparative purposes were isobutylidene diurea (IBDU); commercial SCU products; soluble sources; and Milorganite. In this 2.5‐yr study, 25 N source treatments were evaluated on ‘Merion’ Kentucky bluegrass (Poa pratensis L.) using 196 kg N ha−1 yr−1, split into two equal applications. Turf response was measured by weekly color ratings, weekly clipping yields, and N uptake for six growth periods during 2 yr. Urea‐formaldehyde reaction products containing no water‐in‐soluble N (WIN) gave results similar to those of conventional soluble N sources, while products containing WIN caused less initial color and growth responses, but gave a slight residual effect in the third year of use. Nitrogen uptake for powdered ureaform (66% of N as WIN) and the suspension FLUF (20% of N as WIN) was 44 and 75%, respectively, of that obtained with Formolene (0% WIN). Major differences in color and growth were found for the different particle sizes of oxamide, with the fine (<0.25 mm) material providing a faster release and less residual effect than the coarse (1‐3 mm) material. Turf fertilized with coarse oxamide responded similarly to that fertilized with coarse IBDU (0.7‐2.5 mm). Commercial SCU and fine particle SCU made with curtain granulated urea (94% of particles between 1.14 and 2.38 mm; dissolution rates: 6 and 15%) had pronounced residual effects, especially in the spring prior to fertilization. The experimental composted sewage sludge was inferior to Milorganite as a source of N for use on turf. N uptake with the compost treatment was only 32% of that obtained with Milorganite. Turf response from combinations of N sources generally reflected the amount and type of N source present. All N sources except the sludge compost were effective for turfgrass fertilization. Selection of an N source or combination of sources for turf fertilization should be dependent on quickness and duration of response desired, rate and frequency of applications, and various economic factors.
Copper Activity in Soil Solution: II. Relation to Copper Accumulation in Young Snapbeans
Authors: Minnich M. M. , McBride M. B. , Chaney R. L. 
Published: July 2010

AbstractSoil solution Cu2+ activity measured in soil saturation extracts was compared with Cu accumulation in young snapbeans (Phaseolus vulgaris L.). Copper was supplied through sewage sludge mixtures of varied Cu concentrations and through Cu‐salt additions to the soil. Treatments were a factorial combination of four levels of Cu additions and four levels of total sludge additions. Soil and sludge pH values were limited to pH 5.0 to 5.5. Plant yield differences were minor. Data are reported showing the relationships of root, shoot, and total plant Cu contents with Cu2+ activity, with DTPA‐extractable Cu, with soluble Cu, and with sludge Cu concentration. The Cu source (sludge vs. salt) produced distinctly different curves in most every case. Sludge treatments demonstrated nonlinear relationships of Cu activity vs. Cu accumulation; these were fit with exponential functions. Higher shoot Cu concentrations occurred with the Cu salt treatments. Higher root Cu levels occurred at lower Cu2+ activity values with sludge as the Cu source. This probably reflects the superior ability of the sludge to replenish or maintain the Cu supply in soil solution. Total soluble Cu was not related to plant Cu. The proportion of Cu in the sludge was closely linked with shoot Cu (r2 = 0.94); root Cu levels also reflected the proportion of Cu in the sludge, but higher sludge rates resulted in increased root Cu. Increased labile, soluble, Cu‐organic complexes with increased sludge rates would explain both the observed differences between salt and sludge treatments and the positive correlation of root Cu and sludge rate. Physiological control of Cu translocation within the plant is implicit in this reasoning. Continual monitoring of soil solution ion activity or a buffering index is needed to improve predictions of plant ion uptake.
A Pedogenic Chronology for Kilbourne Hole, Southern New Mexico: II. Time of the Explosions and Soil Events Before the Explosions
Authors: Gile Leland H. 
Published: July 2010

AbstractBecause tuff was emplaced as a result of explosions that produced Kilbourne Hole, soils formed in the tuff should provide important clues concerning time of the explosions. Pedogenic carbonate of illuvial origin was used to estimate the age of a soil in the tuff. Age was estimated by calculating the amount of pedogenic carbonate in a soil column 1 m2 in horizontal cross section, and by comparing this amount with the amount of carbonate in a soil with estimated age in the nearby Desert Soil‐Geomorphology Project. The amount of pedogenic carbonate for a soil in the tuff is 73 kg m−2. The Desert Project soil is estimated to be about 11000 yr old and has 34 kg m−2 of pedogenic carbonate that accumulated at a rate of 3.1 kg m−2 kyr−1. Using the same rate of carbonate accumulation, the soil in the tuff dates from about 24 000 yr BP and the explosions that produced Kilbourne Hole and the associated tuff are thought to have taken place at about that time. A lava flow preceded the explosions that produced Kilbourne Hole, but a time of sedimentation and soil formation occurred between the two events as evidenced by a postlava, pre‐tuff deposit in which a soil formed. This deposit is attributed to a localized cycle of sedimentation initiated by presence of the lava. The combined ages of the soil in the tuff and the soil in the post‐lava, pre‐tuff deposit are believed to represent the approximate age of the lava. Based on carbonate amount and morphology, the lava is estimated to be about 0.1 million yr old. This contrasts with the most recently obtained K‐Ar date of 0.53 ± 0.03 million yr for the lava. The amount of pedogenic carbonate in desert soils has potential for widespread application as a chronological tool and as a cross‐check for other dating techniques. However, lack of agreement on the age of soils at chronological benchmarks can indicate that some of the dates obtained by chronological extrapolation should be considered tentative, including the date obtained in this study.
Exact Desorptivities for Power Law and Exponential Diffusivities
Authors: Lisle I. G. , Parlange J.‐Y. , Haverkamp R. 
Published: July 2010

AbstractThe desorption of water from a soil is analyzed for a soil‐water diffusivity function obeying a power or an exponential law, and precise numerical values for desorptivity are found. An effective reduction in the number of parameters allows the cumulative desorption for various boundary conditions to be calculated from a short table of results. For the power law case, desorptivity for arbitrary initial water content can be obtained from tabulated values by a simple scaling transformation. A similar scaling transformation yields the exponential desorptivity for arbitrary initial and surface water content. An approximate desorptivity formula of Parlange is discussed, and found to give an accuracy within 2.5% over the whole parameter range. In general, the present results should be useful to assess numerical and analytical procedures.
Effect of Exchangeable Cation and Electrolyte Concentration on Mineralogy of Clay Dispersed from Aggregates
Authors: Ali O. M. , Yousaf M. , Rhoades J. D. 
Published: July 2010

AbstractThe type of clay dispersed from aggregates of various arid land soils as influenced by sodium adsorption ratio (SAR) and electrolyte concentration was evaluated in Ca‐Na and Mg‐Na systems. It was observed that, in general, in the case of Fallbrook I, Fallbrook II, Pachappa, and Arlington soils, all the common clay minerals (kaolinite, clay mica, vermiculite, and montmorillonite) dispersed whenever disaggregation occurred inrrespective of SAR and electrolyte concentration levels. In Bonsall soil, kaolinite and mica clays were apparently more dispersive than montmorillonite, which, in turn, was more dispersive than mixed layer clays in Ca‐NaCl solutions. More intense x‐ray diffraction peaks were obtained, in general, in the Mg‐Na system compared to the Ca‐Na system.
Clay Dispersion and Hydraulic Conductivity of Some Salt‐Affected Arid Land Soils
Authors: Yousaf M. , Ali O. M. , Rhoades J. D. 
Published: July 2010

AbstractCumulative clay dispersion from four arid land soils are compared with their relative hydraulic conductivities as affected by electrolyte concentration and sodium adsorption ratio (SAR). As electrolyte concentration decreased and SAR increased, clay dispersion increased and hydraulic conductivity decreased correspondingly. Threshold relations between electrolyte concentration and SAR associated with clay dispersion of 5 g of clay per kilogram of soil corresponded well with hydraulic conductivity threshold relations. This correspondence between clay dispersion and sodicity‐related reductions in soil hydraulic conductivity can be utilized to provide an index based on clay dispersion for screening soils for their sodicity hazard sensitivity and for predicting reductions in soil hydraulic conductivity related to soil and water sodicity.
Phosphorus and Potassium Uptake by Corn in Conservation Tillage Systems
Authors: Mackay A. D. , Kladivko E. J. , Barber S. A. , Griffith D. R. 
Published: July 2010

AbstractIn conservation tillage systems surface application of P and K fertilizers and the annual return of corn residue to the soil surface can result in the stratification of these two nutrients in the topsoil. The extent to which this changes P and K uptake patterns of corn (Zea mays L.) has not been investigated. The objectives of this field study on a Chalmers silty clay loam (Typic Haplaquoll) were to compare the degree of stratification of P and K after 9 yr under conventional, no‐till, and ridge till systems, and to use this data along with root measurements in a model to calculate P and K uptake patterns by corn under these three tillage systems. Under conventional tillage Bray P1‐P and exchangeable K were distributed evenly throughout the topsoil (0–275 mm). Stratification of P and K, however, had occurred in the ridge till and no‐till systems after 9 yr. Of calculated P and K uptake from 30 to 47 d after planting, only 18 and 23%, respectively, came from the upper 75 mm under conventional tillage, compared with 52 and 58%, respectively, under no‐till for the same period. From 30 to 77 d, 39 and 52% of calculated P and K uptake, respectively, was from the upper 75 mm under no‐till compared with only 28 and 26%, respectively, under conventional tillage. Some deep placement of fertilizer P and K may be desirable after several years of continuous no‐till cropping, to provide P and K to roots growing deeper in the soil.
Diffusion of Strontium and Chloride in Compacted Clay‐based Materials
Authors: Robin M. J. L. , Gillham R. W. , Oscarson D. W. 
Published: July 2010

AbstractThis study examines the effect of pore solution composition and temperature on the measured and calculated diffusion coefficients (Dm and Dc, respectively) for Sr2+ in a compacted mixture of bentonite (50 wt%) and sand. Dm for Sr2+ and Cl‐ in the soil was determined at a dry bulk density of ∼1.7 Mg m−3 using deionized water (DW) and two synthetic groundwater solutions (SGW) with ionic strengths of 0.27 and 1.4 mol L−1 to saturate the soil, and at 25, 60, and 90°C. The Dc for Sr2+ was calculated from Dc = Doτ/(1 + ρbKd/θv), where Do is the diffusion coefficient of Sr2+ in free solution; τ is a tortuosity factor, obtained for the compacted soil from Cl‐ diffusion experiments; ρb is the dry bulk density; θv is the volumetric moisture content; and Kd is a distribution coefficient that accounts for the interaction of Sr2+ with the soil. Both Dm and Dc for Sr2+ increased with an increase in the ionic strength of the saturating solutions and with an increase in temperature. The Dm values were, however, always greater than Dc values by a factor of 6.2 to 8.0 for DW and 1.3 to 1.8 for the SGW with an ionic strength of 1.4 mol L−1. This difference is believed to be the result of obtaining Kd values in solutions that differed significantly from the pore solution of the compacted soil. Nevertheless, the results indicate that Dc values, which are often more convenient and less time‐consuming to obtain than Dm values, can at least be used to establish relationships and trends between the diffusion rates of some contaminants in clay‐based materials and the properties of these materials.
Microbial Role in Immobilization and Subsequent Mobilization of Cadmium in Soil Suspensions
Authors: Chanmugathas Pushparany , Bollag Jean‐Marc 
Published: July 2010

AbstractThe effect of microorganisms on the fate of Cd in soil suspensions was investigated. Samples of four soil types were suspended in growth media amended with Cd(NO3)2 (20 mg/L) and incubated aerobically or anaerobically at 28 ± 1°C. At various time intervals, aliquots were withdrawn, and Cd concentrations (total and free Cd2+) and pH were determined in the supernatant. The results of the short‐ and long‐term studies indicated that in all soils tested the extent of Cd disappearance (total and free Cd2+) in nonsterile soil supernatants was significantly greater than in the corresponding sterile controls. However, during the subsequent long‐term 8‐week aerobic incubation, a significant amount of Cd (including free Cd2+) was released into solution of nonsterile suspensions, while no increase in Cd concentration was observed in the sterile suspensions. Under anaerobic conditions, a continued disappearance of Cd from the non‐sterile soil supernatants was observed during an incubation period of up to 24 weeks. Under aerobic conditions, the pH of the nonsterile soil suspensions decreased to approximately pH 5.5, whereas the pH remained approximately 8.0 during anaerobic incubation. The rate and degree of Cd immobilization or mobilization was also dependent on the soil types used. Of the four soils tested, Morrison (Ultic Hapludalfs) sandy loam from a coniferous forest site exhibited the highest degree of Cd mobilization, accounting for up to 100% of total Cd immobilized. Our results suggested that soil microbial activity is responsible for both binding of Cd to and its subsequent release from soil.
Soluble Organic Nitrogen Losses Associated with Recovery of Mineralized Nitrogen
Authors: Smith S. J. 
Published: July 2010

AbstractThe extent and subsequent availability of soluble organic N in soil mineralization extracts were determined using initially air‐dry soil samples. Involved were eight Southern Plains agricultural soils comprising five soil orders. The major losses of soluble organic N occurred during the initial leaching prior to incubation, and are attributed to factors not directly associated with the mineralization procedure (e.g., freshly decomposed plant residues, pretreatments, etc.). Often, these losses were as high or higher than initial values for inorganic N. Thereafter, the organic N losses represented, on average, only about 5% or less of the inorganic N produced in surface soil samples during 84 d of aerobic mineralization. This was the case for both indigenous and fertilizer‐incorporated N. Subjecting the soluble organic N in the mineralization extracts to subsequent aerobic, anaerobic, or autoclave procedures indicated no excessive N availability. Distribution of the soluble organic N components in the extracts did not differ greatly from that of soil. In general, soluble organic N losses were not a major factor associated with recovery of mineralized N.
Chemical, Spectroscopic, and Biological Characteristics of the Organic Matter in Particle Size Fractions Separated from an Aquoll
Authors: Catroux G. , Schnitzer M. 
Published: July 2010

AbstractSamples from the surface horizon of a cultivated Aquoll were ultrasonically dispersed and separated into particle size fractions. Humic acids (HAs) were extracted from the whole soil and each particle size fraction. Residual humic acids (RHAs) were obtained from the residue of each HA extraction by treating with HCl‐HF and reextracting. Chemical analyses showed that the fine silt fraction had the highest C and N contents. Although δ15N values and proportions of mineralizable N increased with decreasing particle size, C/N ratios decreased. Mineralizable N appeared to be related to both the total N content and the characteristics of the minerals with which the organic matter was associated. Nitrogen in sand and silt fractions was more resistant to mineralization than in clay fractions. Extractions with 0.5 M NaOH removed more of the C and N from the fine‐clay fraction than from the whole soil or any of the other fractions. Carbon‐13 nuclear magnetic resonance (NMR) spectra showed that HAs extracted from clays were more aliphatic than HAs extracted from larger particle sizes. The major aliphatic components in the clay size fractions appeared to be alkanoic and hydroxyalkanoic acids. Compared with HAs, RHAs, were more homogeneous, contained fewer proteinaceous materials and carbohydrates, were more aromatic, richer in phenolic OH and CO2H groups, had higher molecular weights, and contained more free radicals.
Influence of Sample Size on Measurement of Soil Denitrification
Authors: Parkin T. B. , Starr J. L. , Meisinger J. J. 
Published: July 2010

AbstractThe influence of sample size on the magnitude and variability of soil denitrification was studied by collecting soil cores, ranging in size from 1.7 to 5.4 cm in diameter, from no‐till and conventionaltill corn plots. Estimates of natural denitrification rates were obtained by incubating intact soil cores with C2H2 and monitoring gaseous N2O production. In addition, maximum denitrification potential was determined by monitoring N2O production in anaerobic slurries amended with glucose, NO‐3 and C2H2. Natural rate estimates were highly skewed and approximated lognormal distributions. The spatial variability of denitrification was characterized by large variation at small distances of <10 cm and only weak spatial dependence at distances of 10 to 100 cm. Studies of the effect of sample size on denitrification suggest that soil cores >4.2 cm in diameter yielded the most reliable estimates of natural denitrification rates. Using a computerized random resampling technique, we estimated that approximately 10 to 15 kg of soil was necessary to obtain a representative soil mass for estimating natural denitrification rates. The results of this study are consistent with the hypothesis that the source of variability associated with the natural denitrification rates is the patchy distribution of denitrifying “hot spots” in soil. Some implications associated with the application of classical statistical methods to lognormal data are also discussed.
Physical Properties of a Typic Haplaquoll Under Conventional and No‐Tillage
Authors: Culley J. L. B. , Larson W. E. , Randall G. W. 
Published: July 2010

AbstractConservation tillage, particularly no‐till (NT), for corn (Zea mays L.) production on poorly drained soils in the U.S. Corn Belt often produces lower yields. Cone index (CI), bulk density (ρb), shrinkage, hydraulic conductivity (Ks), and water release charcteristics were all measured in a Typic Haplaquoll under NT and conventional tillage (CN) to characterize soil physical factors possibly related to the lower yields. Measurements in the interrows indicated that wheel traffic, associated only with crop establishment (planting and herbicide spraying), eliminated the benefits of lower CI and greater Ks associated with primary and secondary tillage. Cone index was a more sensitive indicator of these trafficking effects than was ρb. With the exception of the surface layer (0.0–0.1 m) of untracked interrows, Ks values under NT, as measured in vertically oriented soil cores, exceeded those in CN profiles. Because these tillage effects were not observed when Ks was measured in situ using a permeameter that integrated horizontal and vertical components of Ks, the high Ks measurements from cores were probably produced by flow in vertically oriented macropores although interfacial flow between sample ring and soil cannot be discounted. Untracked NT and CN surface layer macroporosities amounted to 5 and 0% of total porosity, respectively. Macropores did exist below the surface of the tilled layer, but they were susceptible to destruction by wheel traffic. However, tillage did not affect tile drain performance.