bluuebunny/crossref_metadata_2025_split huggingface dataset:
Soil Carbon Dynamics in a Mixed Deciduous Forest Following Clear‐Cutting with and without Residue Removal
Authors: Edwards N. T. , Ross‐Todd B. M. 
Published: July 2010

AbstractThe effect of two harvest intensities on soil carbon dynamics was determined for the first year following harvest of a mixed deciduous forest in Tennessee. Harvest procedures were clear‐cutting (all trees of all diameters cut) with only sawlogs removed (RL) and clear‐cutting with removal of all woody material except stumps (RR). There were no detectable differences in soil carbon pools between treated and control watersheds before harvest or 5 months after harvest. During the winter months immediately following harvest, CO2 efflux rates from the soil surface were greater in the intensively harvested watersheds than in the other watersheds. However, CO2 efflux rates were greater in the control watershed than in the harvested watersheds during the first growing season following harvest. This was apparently due to greater live root respiration in the control watershed because mineral soil respiration only (as determined by laboratory incubations) was greater in harvested watersheds than the control reflecting the higher soil temperature and moisture in the harvested watersheds. Annual soil respiration rates, predicted from laboratory measurements and field temperatures, were 92, 121, and 154 g CO2/m2 in the control watershed, RL watersheds, and RR watersheds, respectively. When extrapolated to a land area equal to that represented by the annual harvest of U.S. deciduous forests these rate increases amount to only ca. 0.006% of the annual carbon released from fossil fuel burning.
The Effects of Magnetite on Oxalate‐ and Dithionite‐Extractable Iron
Authors: Walker Ann L. 
Published: July 2010

AbstractSix soils from a chronosequence were chosen to test the effects of magnetite on using free Fe to estimate relative ages of soils. The acid‐ammonium oxalate and dithionite‐citrate‐bicarbonate methods were used to extract the free Fe from the samples. Iron values from these two extractions were compared for samples from which the magnetite was removed, from which the magnetite was not removed, and from the magnetite fraction itself. Visual examinations were also made of the untreated and treated magnetite grains. The oxalate solution releases Fe from magnetite in proportion to the amount of magnetite in the soil. The dithionite solution does not release Fe from magnetite, but releases Fe from hematite coatings and replacements on the magnetite grains. Large or varying magnetite concentrations can influence the amount of Fe released by either of these methods, and cause errors in estimations of relative age. Magnetite should be removed from the samples prior to treatment by oxalate extraction. Magnetite should be left in the samples to be treated by the dithionite extraction, but the concentration of magnetite in the soils should be noted. In order to get the best possible estimation of relative age using free Fe concentrations, the ratio of magnetite‐free oxalate to dithionite‐extractable Fe should be used.
Correlation of Clay Minerals and Properties of Soils in the Western United States
Authors: Nettleton W. D. , Brasher B. R. 
Published: July 2010

AbstractX‐ray diffraction (XRD) studies of about 2000 soil clays show that 1500 kPa water retention, in addition to Atterberg limits, cation exchange capacity, 33 kPa water retention, volume of water retained between 33 and 1500 kPa, and linear extensibility varies with kind of soil clay and the intensity of the XRD peak of the dominant clay mineral. Hence, knowledge of soil clay mineralogy is particularly useful for predicting the behavior of soils. In standard characterization work, however, determining the property of interest is usually more efficient than determining mineralogy and then estimating the property. Determining both is not necessary if their relationship is understood. In predicting the behavior of soils, identification of the dominant clay mineral is sufficient if that mineral is smectite. If the mineral is kaolinite or clay mica, somewhat greater accuracy of prediction of properties is possible if measurements of the relative intensities of the other clay minerals in the suite are also known.
Measuring Nitrogen Leaching with Ion Exchange Resin: A Laboratory Assessment
Authors: Schnabel R. R. 
Published: July 2010

AbstractA procedure using ion exchange resin to measure leaching losses of inorganic N in soils was tested in the laboratory. A 2‐cm thick bed of anion or cation exchange resin reduced the concentration of the percolating solutions to 1% of their initial concentrations until the resins were one‐third to one‐half N saturated. Greater than 90% of the nitrate adsorbed by anion exchange resin was recovered after 12 weeks of incubation indicating that N transformations were minimal.
Ion Exchange Resin Bag Method for Assessing Forest Soil Nitrogen Availability
Authors: Binkley Dan , Matson Pamela 
Published: July 2010

AbstractAn ion exchange resin bag technique was compared to six other methods for estimating N availability. Under a controlled greenhouse environment and with well‐mixed soils, the resin technique correlated well with more traditional N‐availability indices. However, resin bags on site in three forest stands yielded different N‐availability estimates than those in the greenhouse. This suggests that the resin bag method may be sensitive to on‐site conditions not discerned by more widely accepted laboratory techniques.
A Transient Method for Measuring Soil Water Diffusivity and Unsaturated Hydraulic Conductivity
Authors: Scotter D. R. , Clothier B. E. 
Published: July 2010

AbstractA method for measuring the unsaturated diffusivity of soil is described. It involves measurement of the matric potential transient at one end of a soil sample following a step change in the potential at the other end. Small potential steps can be used in contrast with the analogous outflow methods, because the difficult task of accurately measuring small flow rates is obviated. The analysis used to obtain the diffusivity from the potential data relies mainly on the delay in the transient and does not depend critically on its shape, thus avoiding the other major problem associated with outflow methods. With the use of the graphs provided, data analysis is simple. Measurement of the total outflow induced by each potential step allows the hydraulic conductivity to be calculated from the diffusivity. Measurements made on repacked soil during desorption and sorption showed no hysteresis in the hydraulic conductivity vs. water content relationship and agreed with independent measurements using a steady‐state method. Data for field soil cores are also presented. Differences in shape between the predicted and observed matric potential transients are discussed in terms of entrapped air.
Copper Adsorption by Soils Exposed to Desiccation Stress
Authors: Lehmann R. G. , Harter R. D. 
Published: July 2010

AbstractSoils undergo substantial physical, chemical, and biological changes during the process of drying. Because soils are usually dried before their use in the laboratory, it is important to understand these changes if laboratory results are to be related to field conditions. The effects of air‐drying (25°C) and over‐drying (105°C) moist soils and the effects of remoistening air‐dried and stored soils on copper adsorption are presented. Results indicate that oven‐dried soils adsorbed 3 to 10% less copper than air‐dried soils, which adsorbed 10% less than moist field soils. Remoistened samples, which were incubated for 1 month under aerated conditions, adsorbed an average of 12% more copper than air‐dried and stored soils. Remoistened soils, which were incubated without aeration under a layer of water, showed no significant deviation from adsorption onto air‐dried soils.
Infrared Dehydration Method for Determining Gypsum Content of Soils
Authors: Elprince A. M. , Turjoman A. M. 
Published: July 2010

AbstractA Mettler drying unit (Model LP12) and a top‐loading balance (Model PL60) were used for determining gypsum in soils. Plotting the rate of weight loss against time upon heating by infrared (IR) radiation (at 123 or 156°C) gave a dehydration curve made of two peaks. The first peak was due to soil moisture and the second to the crystal water of gypsum. Percent gypsum was determined by extrapolation the dehydration curve (vida infra) to rate = 0. The use of computer graphics in developing the curves made this method very rapid (about 15 min per determination). The reproducibility of the IR method (σ = 0.48) was better than the barium sulfate method (σ = 0.61) over the 2 to 58% gypsum range studies. The accuracies of the two methods were comparable and estimated to be ± 0.3% gypsum when the average of triplicate determinations was used and ± 0.5% gypsum with single determinations.
Nitrification and Denitrification of Nitrogen Fertilizers in a Soil Column
Authors: Khdyer I. I. , Cho C. M. 
Published: July 2010

AbstractNitrogen transformations occuring within reconstituted Wellwood soil profile samples packed in plastic columns (4.4 cm i.d.) and amended with urea or NO‐3‐N were investigated under isothermal (20°C) laboratory conditions. The surface of the soil column was open to the atmosphere and the bottom was closed. Samples of soil atmosphere were taken regularly through sampling ports located at several different depths and analyzed for N2, O2, and N2O with a mass spectrometer. A steady‐state O2 distribution within the column was established soon after packing, making the surface layer aerobic and the lower layer anaerobic. The depth of the aerobic layer was governed by the gas‐filled pore space of the column. Urea applied uniformly throughout the column was oxidized to NO‐3 within the aerobic layer. The concentration of NO‐3 was highest at the surface and decreased to almost zero near the aerobic‐anaerobic interface. Nitrate transported downward from the aerobic layer was denitrified near the interface. Ammonium in the anaerobic zone was stable in a column at 10.5% gas‐filled pore but gradually declined as incubation at 16.5% gas‐filled pore space progressed. Nitrate N applied to the aerobic layer was transported downward to the anaerobic layer and denitrified. The magnitude of denitrification was greater than that observed with urea possibly due to a higher flux of NO‐3 into the anaerobic layer. Nitrous oxide was observed near the aerobicanaerobic interface with both the NO‐3 treatment and urea (10.5% air porosity treatments). Dinitrogen was the only gaseous dinitrification product ohserved in the column at 16.5% air porosity amended with urea.
Soil Modification by Colonies of Black Meadow Ants in a New York Old Field
Authors: Levan Mary Ann , Stone Earl L. 
Published: July 2010

AbstractThe above‐ground mounds of the black meadow ant Formica fusca L. had an average weight of 8.7 kg and occurred at a density of 109/ha on a small study site in central New York. Both mound and a larger diameter soil column beneath are extensively channelled and result in a coarse fragment concentration or stone line at the 10‐ to 15‐cm depth. Channels extend to at least the 1.5‐m depth, and up‐ward transport of calcareous subsoil increases Ca and Mg concentrations and pH of the upper profile. In contrast, extensive replacement of the 0‐ to 10‐cm horizon with subsoil reduces its organic matter content by about 50%. Increased concentrations of extractable P and K in the mound and upper mound profile are attributed to exogenous sources. After abandonment the mound columns remain as near‐neutral nutritionally enriched microsites that may influence the course of old field succession.
Effect of Soil Texture on Critical Bulk Densities for Root Growth
Authors: Jones C. Allan 
Published: July 2010

AbstractPublished and unpublished data from 10 studies were analyzed to determine the effects of soil texture on critical bulk densities for rooting at near‐optimum soil water contents. Highly significant negative relationships were found between percentage clay or silt + clay and the bulk density at which rooting was at a maximum or the bulk density at which rooting was 0.2 of that maximum. Similar relationships were also found between percentage clay or silt + clay and (i) the bulk densities of soil layers classified as fragipans and (ii) the maximum bulk densities at which “many” roots are reported in U.S. Soil Conservation Service pedon descriptions. Thus, soil texture can be used to estimate bulk densities of fragipans and critical bulk densities at which root growth is severely affected at near‐optimal soil water contents.
Noncrystalline Clay Distribution in the Major Land Resource Areas of Mississippi
Authors: Nash V. E. , Pettry D. E. , Aide M. T. 
Published: July 2010

AbstractSelected horizons from 45 Mississippi soils have been examined for noncrystalline clay content as determined by 0.5M NaOH and 0.2M ammonium oxalate (pH 3). The soils represent the major soil resource areas of the state. Parent material varied in age from Cretaceous to Holocene. Only small amounts of amorphous clay were extracted from the weakly developed Inceptisols and Entisols, from calcareous soils of the Blacklands and from the alkaline Natraqualfs of the Coastal Plains. Under these nonacid conditions crystalline clay minerals are the more stable phase. The strongly developed Ultisols released large amounts of noncrystalline material with a low silica/alumina molar ratio. The low molar ratio is indicative of gibbsite; however, the large quantity of silica extracted suggests that silica may be adsorbed on the crystalline minerals.When only soils high in smectite are considered, the following trends in noncrystalline clay formation were observed. The silica/alumina ratio increases with smectite content. The quantity of noncrystalline clay increases with increased soil acidity. The poorly drained soils contain less amorphous clay indicating that smectite is the more stable mineral in this environment.Extraction of the clays with acid ammonium oxalate resulted in an average increase in cation exchange capacity of 14 cmol (½ Ca2+) kg−1 due to the removal of surface coatings blocking exchange sites.
Effect of Sesquioxide Coatings on Surface Charge of Standard Mineral and Soil Samples
Authors: Hendershot W. H. , Lavkulich L. M. 
Published: July 2010

AbstractIn nature, Fe and Al hydrous oxides often form the interface between crystalline soil minerals and the soil solution. To understand better the effect of these coatings on surface charge properties, standard minerals and cleaned C horizon samples were coated with either Fe or Al hydrous oxide and the point(s) of zero salt effect (PZSE) were measured by potentiometric titration. Five standard mineral samples (including illite, muscovite, kaolinite, microcline, and quartz) and three C horizon samples of mixed mineralogy were artificially coated with Fe and Al hydrous oxide material by precipitation of FeCl3 or AlCl3 solutions with the mineral and soil samples. The samples were then washed free of Cl‐ and aged. Uncoated samples and samples of pure sesquioxide material were prepared using similar procedures. Depending on the nature of the underlying surface, the addition of sesquioxide coatings to the samples changed the surface charge properties in different ways. In every case the buffering capacity of the samples was increased by the addition of the sesquioxide coatings. The uncoated samples that had relatively high buffering capacities had their surface charge properties changed more by the Al‐ than the Fe‐coating material. For example, the illite, muscovite, Memekay C horizon, and Marblehill C horizon all responded to the Al‐coating with a distinct shift of the PZSE to higher pH. The less reactive samples (kaolinite, microcline, quartz, and the Cox Bay C horizon) responded little to the Al coatings but showed a strong response to the Fe coatings. The results indicate that in a system containing both pH‐dependent and permanent exchange sites there is no effective means of separating the two components. Below the point of zero net charge (PZNC) of the coating material, the measured cation exchange capacity (CEC) will be decreased to a point below the permanent CEC by the coatings, whereas at pH values above this point the measured CEC will be increased. The PZSE of the pH‐dependent charge material cannot be measured separately by potentiometric titration; this method measures the PZSE of the samples as a whole. At any pH the CEC measured will be the result of a complex interaction between the two types of exchange sites.
Shape Factors for Seepage into Pits
Authors: Boast C. W. , Langebartel R. G. 
Published: July 2010

AbstractIn the field “pit‐bailing” method, saturated hydraulic conductivity below a water table is determined from the rate of rise of water in a pit. The relationship between the rate of rise and the soil hydraulic conductivity is expressed as a shape factor. Shape factors are presented here for pits with length/radius ratio ranging from 0 to 2, for pits ranging from empty to 0.9 full, and for impermeable‐barrier and very permeable source lower boundary conditions at various distances below the pit. The calculated shape factors are extrapolated to the situation of a pit in an effectively infinitely deep uniform soil. Shape factors for pits of a given fullness with a source or a semi‐infinite lower boundary condition are found to decrease and then increase as the length/radius ratio of the pit increases, reaching a minimum typically when this ratio is between 0.2 and 0.5 for the semi‐infinite case. This trend is investigated to determine whether it is due to calculation errors for extreme geometries or is due to real phenomena. That the trend exists is found by examining analytical solutions to two situations—a pit fully penetrating to an impermeable barrier and a disk in semi‐infinite space.
Statistical Analysis of Salinity and Texture Effects on Spatial Variability of Soil Hydraulic Conductivity
Authors: Bresler Eshel , Dagan G. , Wagenet R. J. , Laufer A. 
Published: July 2010

AbstractA statistical analysis that identifies the dominant factors responsible for the spatial variability of the saturated conductivity (Ks) in a selected field is presented. The variables are considered random functions of the space coordinates. Two types of stationarity are investigated: constant mean and stationary variogram (stationarity of order 2) and trend of the means (nonstationarity of the mathematical expectation) with stationary covariances. Linear models of statistical dependence were used. Elimination of factors of minor importance was based on correlation analysis. Electrical conductivity (EC) and percent sand were the most important independent variables, whereas Ks was the dependent variable. The analysis showed that soil salinity (EC) accounted for only 10 to 15% of the variability of Ks texture (percent sand) explained 25 to 45% of the Ks variability, and 10 to 15% of the variability was explained by the interaction between salinity and texture. Various soil factors other than salinity and texture accounted for 30 to 50% of the variability in Ks. Semivariograms and covariograms of Ks, EC, and percent sand did not have a sill because of a significant horizontal linear trend. Calculations showed that the trend accounted for about a half of the variability of the original data. Semivariograms and covariograms of a new population of residuals after extracting the trend gave values of the sills equal to the variances. The integral scale of the residuals of Ks and percent sand was estimated to be about 15 to 20 m, whereas salinity (EC) did not display a spatial structure. The results can be generalized for other studies with different values of variances and covariances of soil salinity and soil texture.
Redistribution of Exchangeable Calcium, Magnesium, and Aluminum Following Lime or Gypsum Applications to a Brazilian Oxisol
Authors: Pavan Marcos A. , Bingham F. T. , Pratt P. F. 
Published: July 2010

AbstractA greenhouse experiment was carried out with 16 columns of an undisturbed Oxisol that had sufficient subsoil acidity to restrict root growth of a wide variety of crop plants. The objective was to determine the effects of surface applied CaCO3, CaSO4·2H2O, and water on subsoil pH and exchangeable Al, Ca, and Mg. Eight soil columns were treated with CaCO3 or CaSO4·2H2O at rates equal to 0.25 and 1.50 × the lime equivalent (KCl‐extractable Al). The irrigation treatments consisted of trickle irrigation applied at 8.94 and 17.88 mm day−1 for 6 months. These treatments were superimposed on the amendment treatments. Observations included volume and composition of drainage water during the course of the experiment and chemical composition of the soil column by depth increments once the irrigation treatments were completed. Soil analysis included pH, cation exchange capacity (CEC), exchangeable cations, and composition of saturation extracts of soil. Effects of CaCO3 treatments were observed only in the upper 20 cm of the profiles irrespective of irrigation and fertilizer treatments. The CaCO3 treatments increased soil pH, CEC, and exchangeable Ca while decreasing exchangeable Mg and exchangeable Al; and CaSO4·2H2O treatments reduced the level of exchangeable Al and Mg throughout the 100‐cm depth profiles while increasing the level of exchangeable Ca. Soil pH and CEC were unaffected by the latter treatment. Based on the effectiveness of CaSO4·2H2O in reducing exchangeable Al and Mg while increasing exchangeable Ca, the combination of dolomitic lime and gypsum appears to be an appropriate amendment treatment for Oxisols with toxic concentrations of available Al.
Studies of Aged OH‐Al Solutions using Kinetics of Al‐Ferron Reactions and Sulfate Precipitation
Authors: Tsai Ping Ping , Hsu Pa Ho 
Published: July 2010

AbstractA series of OH‐Al solutions (0.02M in Al, NaOH/Al molar ratio = 1, slow neutralization) aged from 10 d to 55 months were all clear and had similar pH values and monomeric Al concentrations but reacted differently with sodium sulfate and with ferron. The addition of sodium sulfate yielded three kinds of basic aluminum sulfates: tetrahedral crystals of composition Na0.08 Al(OH)2.46 (SO4)0.31 · xH2O, x‐ray amorphous spherical particles of composition Al(OH)2.34 (SO4)0.33 · xH2O, and irregular‐shaped crystals of composition Al(OH)2.38 (SO4)0.31 · xH2O. The distribution of these sulfates is related to the aging of the parent OH‐Al solutions. The kinetics of Al‐ferron color development indicated that the OH‐Al polymers in the fresh solutions reacted with ferron rapidly, following a pseudo first‐order reaction (rate constant = 0.096 min−1). With increased aging, the rapidly reacting polymers slowly decreased, whereas another polymeric species that reacted with ferron slowly (rate constant = 0.00038 min−1) gradually developed. The results suggest that the polymers that reacted rapidly with ferron accounted for the formation of tetrahedral crystals and spherical particles, whereas those polymers that reacted slowly accounted for the formation of irregular‐shaped crystals.