bluuebunny/crossref_metadata_2025_split huggingface dataset:
Apparatus for Extraction of Undisturbed Samples on Noncohesive Subsoils
Authors: Schuh W. M. 
Published: July 2010

AbstractA sampler was designed and tested for extracting 60‐ by 53‐mm (length by depth) undisturbed core samples from subsoils. The sampler consists of a sample cylinder “barrel,” and an “adaptor block” for fitting the barrel to the end of a 76.1‐mm o.d. hydraulic probe tube. Samples are taken by augering to the desired depth, and using the tube and sampler assembly to extract the sample. The tube and sampler assembly can also be used with a protective steel anvil to remove samples in shallow subsoils without a hydraulic probe. Samples on sands have been taken as deep as 2.5 m using the hydraulic probe, and as deep as 0.61 m using the anvil and maul method.
Determining Unsaturated Hydraulic Conductivity from Tensiometric Data Alone
Authors: Ahuja L. R. , Ross J. D. , Bruce R. R. , Cassel D. K. 
Published: July 2010

AbstractA simplified functions approach, presented earlier, for determining the unsaturated hydraulic conductivity of soil from only the field tensiometric data taken during steady infiltration and draining, along with steady infiltration rate, is evaluated further. The assumptions concerning the form of soil‐water characteristics used in the operational equations of the method are recast in an integral form. These assumptions, as well as the intermediate steps in the computation, are tested on the experimental data for shallow as well as deeper depths of two new soil types. One of these soil types has a complex layered profile with texture varying from sandy to clayey, and the other a relatively uniform sandy profile. The final hydraulic conductivities obtained are compared with the values determined by the more rigorous Darcian analysis of the data for three sites. The results show that the assumptions made in the simplified method approximately hold for these soils at the depths tested, as deep as 1.9 and 1.35 m, respectively. The unsaturated hydraulic conductivity values determined by the proposed method are reasonably close to those values obtained by the detailed Darcian analysis for all depths. Large fluctuations in the tensiometric data for certain depths resulted in a large scatter in the conductivity values obtained by the detailed Darcian method, as well as greater discrepancy between the two methods. Practical validity of the basic assumptions of the method and the final results, for shallow as well as depper depths of the new contrasting soil profiles, constitutes significant information that provides confidence in the simplified approach.
Rapid Nondestructive Bulk Density and Soil‐Water Content Determination by Computed Tomography
Authors: Anderson S. H. , Gantzer C. J. , Boone J. M. , Tully R. J. 
Published: July 2010

AbstractComputed tomography (Ct) is a promising tool that may help provide measurements needed to obtain finer resolution in soil‐water content and bulk density for water uptake studies or detailed investigation of root‐soil interactions. A need exists for a unified method to accurately predict soil bulk density and water content using output from CT. Research was conducted on soil collected from the A horizon of Mexico silt loam (Udollic Ochraqualfs) and the B2t horizon of Crider silt loam (Typic Paleudalfs) to evaluate the relationship between linear attenuation coefficients and volume fraction of soil solids and water. Air‐dry soil (<2 mm) was packed into polyvinyl chloride cylinders at densities between 1.2 and 1.6 Mg/m3 and CT slices or tomographs were taken before and after water was added. The relationship between attenuation coefficients and volume fraction of soil solids was linear for both of the soils evaluated. Parameter values for the Mexico soil compared favorably with those determined on previous data collected from Metea fine sandy loam (Arenic Hapludalfs). Differences in the parameter values for the Mexico and Crider soils were attributed to differences in Fe content. An experiment with Fe added to the Mexico soil was conducted that verified the effect of Fe content on the attenuation coefficients. Approximately 98% of the variation between the attenuation coefficients and volume fraction of soil water was accounted for by using linear regression relationships after correction for swelling. Results from this study indicate that it may be possible to develop a universal relationship for computed tomography data vs. soil bulk density and water content; however, more research is needed to characterize the influence of sample size on the calibration relationship.
Spatial Variability of Remotely Sensed Surface Temperatures at Field Scale
Authors: Yates S. R. , Warrick A. W. , Matthias A. D. , Musil S. 
Published: July 2010

AbstractBare soil surface temperatures (BST) and crop canopy temperatures (CCT) were collected from a 1‐ha field in central Arizona using an infrared thermometer to determine whether they were spatially correlated. The measurements were taken from a two‐dimensional random sampling pattern for selected dates and times to investigate the spatial and temporal distribution. Three measures of the correlation distance including two integral scales were calculated. Kriging, which produces the best linear unbiased estimator, was used to show the spatial pattern of the BST and CCT in the field on selected dates. The results indicate that the BST and CCT are spatially dependent random functions with integral scales that varied from 2 to 15 m for wet and dry conditions, respectively. The autocorrelation as the lagged distance approaches zero was greater than 0.4 except under wet soil conditions, where the autocorrelation for the CCT was found to be lower. The results are important because, to date, no geostatistical study has shown that the CCT is a spatially dependent random function.
Temperature Effects on Urea Diffusion Coefficients and Urea Movement in Soil
Authors: Sadeghi A. M. , Kissel D. E. , Cabrera M. L. 
Published: July 2010

AbstractUrea fertilizer is often applied at the soil surface, where it hydrolyzes and can form NH3. To quantify the volatilization of NH3, the molecular diffusion of urea into the soil must be described. The diffusion coefficient of urea in soil is related to its diffusion coefficient in water, which varies with temperature. We initially regressed the value of the urea diffusion coefficient in water from the international critical tables (ICT) on temperature for the range of 10 to 20 °C. Since surface soil temperatures often fall outside this range, additional values for the urea diffusion coefficients were needed. The capillary tube method of Phillips and Ellis was used to measure the diffusion coefficient of urea in water at temperatures ranging from 0 to 50 °C. The laboratory values obtained for the diffusion coefficient of urea in water were higher, by a factor of 1.5, than the ICT values. A comparison was made between measured values of urea concentration in columns of Richfield and Haynie soils and simulated values using regression equations based on laboratory results (new) and ICT data (old). The new regression equation allowed a better agreement between actual and simulated urea concentrations in soil.
Stimulated Denitrification in the Microenvironment of a Biodegradable Organic Waste Injected into Soil
Authors: Rice Charles W. , Sierzega Philip E. , Tiedje James M. , Jacobs Lee W. 
Published: July 2010

AbstractDenitrification and the associated processes of nitrification, mineralization, and respiration were studied in the zone around the injection slit in which two fermentation wastes were injected into soil. All processes were stimulated apparently due to the greater availability of N and C and the increased anaerobiosis caused by the greatly enhanced respiration. Under field conditions, denitrification rates as high as 4.9 and 2.3 µg cm−2 h−1 were measured from the cell waste and the spent growth medium, respectively. If extrapolated over the 73‐d period after application, the accelerated denitrification would remove over one‐half of the added N. The rate of CO2 production explained 31.4 to 46.8% of the variation in denitrification, whereas soil moisture explained only 3.6 to 18.9% of the variation. This suggests that respiratory activity created an anaerobic microenvironment making conditions favorable for denitrification. Under laboratory conditions, the loss of N due to denitrification of the cell waste could be reduced by 68% with surface incorporation rather than injection. This was probably due to the cell waste material being applied to a greater volume of soil, thus reducing both the temporal and spatial zones of anaerobiosis. Samples 5 cm away from the injection slit did not have enhanced denitrification rates nor NO‐3 concentrations, suggesting little lateral movement of the applied waste material. The enhanced denitrification response to cell waste C addition emphasizes the importance of respiratory O2 consumption by heterotrophs on denitrification. These results are expected to hold for any waste that is reasonably biodegradable and has a medium to low C/N ratio.
Phosphorus Supply Characteristics of 33 Soils as Influenced by Seven Rates of Phosphorus Addition
Authors: Kovar John L. , Barber Stanley A. 
Published: July 2010

AbstractSoil P supply to plant roots increases after addition of P fertilizer due to both the increase in soil solution P (Pl) and adsorbed P (Ps) that equilibrates rapidly with Pl. Little information is available on the effect of added P on the concurrent increase in Pl and Ps. The objective of this research was to investigate the relation between P added and increase in Pl and Ps of 33 soils. Surface soils collected from the U. S. and Canada were equilibrated moist for three weeks with seven rates of P ranging from 0 to 655 mg P kg−1. High rates of application occur where P is placed in a small fraction of the soil. Values for Pl were obtained from P analysis of displaced soil solution and values for Ps from a 24‐h extraction with anion exchange resin. For all soils relation of Pl, curvilinear with P addition, x, was described by Pl = axc + d. Values for c, the curvilinearity, varied from 1.03 to 3.15. There was a negative correlation between c and exchangeable Ca (r = −0.65*, significant at the 0.05 probability level) and soil solution P concentration before P addition, Pli, (r = −0.61*). Adsorbed P increased linearly with P addition for all soils, the slope of the relation varying from 0.35 to 0.86. The slope indicates the fraction of added P extracted with the anion‐exchange resin. There was a positive correlation between the slopes and the effective diffusion coefficients, De, for P in the soils (r = 0.47*). There was no significant correlation between c and the adsorption line slope. Development of methods for predicting the effect of added P on Pl and Ps will be useful in quantifying their increase in soil resulting from P addition.
Computer Simulation of Soil Sensitivity to Acid Rain
Authors: Levine Elissa R. , Ciolkosz Edward J. 
Published: July 2010

AbstractA two‐horizon (A and B) simulation model was used to determine the sensitivity of Pennsylvania soils to acid deposition. The model simulated changes in the soild phase of soils in humid, temperate climates undergoing acidification and cation leaching. The Pennsylvania State Univ. Soils Data Base, and precipitation data provided input to the model. Soils were grouped into sensitivity classes based on the amount of time required for bare, uncultivated, and unlimed soils to reach critical threshold values. Simulation results showed most Pennsylvania soils were either very sensitive or nonsensitive. Sensitive soils were already at the threshold values at the beginning of the simulation run. Nonsensitive soils contained sufficient buffer capacity to withstand present inputs of acid deposition for at least 90 yr. According to the model, changes in soil properties occur in the upper horizons first, and after a lag period, occur in the lower horizons. The number of exchangeable bases was the soil parameter most highly correlated with soil sensitivity due to the acid buffering ability of exchangeable cations. Adding CaCO3 to the simulation of slightly sensitive and very sensitive soils changed them to nonsensitive status by increasing the number of exchangeable bases available for buffering.
Soil Engaging Tool Effects on Surface Residue and Roughness with Chisel‐type Implements
Authors: Johnson Richard R. 
Published: July 2010

AbstractThe site specific nature of optimum tillage systems makes it desirable to provide versatility in tillage performance at a minimal cost. Chisel‐type implements are among the most flexible primary tillage machines, largely due to the range in options for soil‐engaging tools. The objective of this study was to evaluate surface residue and roughness from a full range of shovels, points, and sweeps on both a disk chisel and a chisel plow operated during fall tillage in corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] stubble. Effects of operating speed and depth were also examined. Changing soilengaging tools caused remaining spring residue to range from 44 to 59% in corn and from 22 to 54% in soybean stubble. Residue remaining generally ranked from high to low as follows: low crown sweep ≥ medium crown sweep > chisel point > high crown sweep > concave twisted shovels. Sweep and shovel width had only minor effects on surface cover, but similar soil engaging tools on a chisel plow left about 10% more surface cover than on a disk chisel. Soil engaging tools had less effect on roughness than residue. Twisted shovels left the roughest soil surface and sweeps left the smoothest surface. The chisel point left surface conditions smoother than twisted shovels but often not significantly rougher than sweeps. Shovel and sweep width as well as machine type (chisel plow vs. disk chisel) did not greatly affect surface roughness. Operating speeds of 5 to 9 km/h did not affect surface roughness, but reducing speed to 2.5 km/h increased residue and decreased roughness. Increasing operating depth of a disk chisel decreased surface residue, but had little effect on surface roughness.
Modeling the Losses of Soil‐applied Chemicals in Runoff: Lateral Irrigation versus Precipitation
Authors: Wallach Rony , Jury William A. , Spencer William F. 
Published: July 2010

AbstractThe differences between rainfall‐ and surface irrigation‐induced runoff are described in relation to the transfer of the surface‐applied chemicals from soil solution to surface runoff water in the absence of infiltration. The different processes inducing runoff are characterized by the residence time distribution (RTD) of the water in the system. The time‐dependent chemical concentration at the field outlet is affected by the RTD, even for the case of instantaneous equilibrium between chemicals in runoff water and soil solution. In this approach the water and chemical transport process in the field is represented by linear well‐stirred mixing cells in series, for which a general solution for the effluent concentration is available. The rainfall‐ and the lateral irrigation‐induced runoff processes, which are represented by complete mixing and plug flow models, respectively, form the two limiting cases for the actual chemical transport process by runoff. For each of these two extremes, mixing in the system is characterized by the parameter n, which is the number of cells in the series chosen to represent the actual transport process over the field.
Transfer of Chemicals from Soil solution to Surface Runoff: A Diffusion‐based Soil Model
Authors: Wallach Rony , Jury William A. , Spencer William F. 
Published: July 2010

AbstractA physically‐based diffusion and transport model is developed to describe chemical outflow concentrations during chemical removal from soil to overlying runoff water induced by continuous rainfall over the soil surface. In contrast to earlier models, movement from the soil to the runoff water is described as a liquid diffusion process to the surface, coupled to the runoff zone through a laminar boundary layer at the runoff interface with the soil surface. Within the soil, diffusion is moderated by equilibrium adsorption to solid surfaces characterized by a partition coefficient. The runoff concentration at the outlet is derived by treating the runoff zone as a wellmixed reactor, characterized by a residence time. The model was used to predict the results obtained in the experimental study of L.R. Ahuja and O.R. Lehman (1983) where infiltration was suppressed, with good agreement obtained between predicted and measured outflow concentrations when the model parameters were estimated independently using standard engineering equations from channel flow hydraulics. The model also predicted the final soil concentrations satisfactorily after runoff ceased.
Changes in Water‐extractability of Soil Inorganic Phosphate Induced by Sodium Saturation
Authors: Sharpley A. N. , Curtin D. , Syers J. K. 
Published: July 2010

AbstractThe effect of replacing indigenous exchangeable cations with Na on the subsequent release of inorganic phosphate (P) from 34 USDA‐SCS benchmark soils representing nine soil orders was investigated by sequential extraction with distilled water. Sodium saturation substantially increased the water extractability of P regardless of whether Ca‐P or sorbed P was the predominant form of inorganic P in the soil. On average, Na‐saturated soils released about 2.5 times more P than the untreated soils. Sequential chemical extractions were used to identify the sources of P extracted. In soils that had not been Na saturated, water‐extractable P appeared to originate largely from the NaHCO3‐extractable fraction. The additional P released following Na saturation was accounted for by a disappearance of Ca‐P compounds (HCl‐extractable) in soils where such entities were present or a decrease in the sorbed‐P fraction extracted by NaOH. The results indicate that the distribution of P between solid and solution phases is strongly dependent on the nature of the exchangeable cation population. These results have important implications to soil fertility and P availability in irrigated soils influenced by Na.
Potentiometric Determination of Potassium Q/I Relationships
Authors: Wang Jian , Farrell R. E. , Scott A. D. 
Published: July 2010

AbstractMethods of determining potassium quantity‐intensity (Q/I) relationships with ion‐selective electrodes (ISEs) were developed and evaluated with three Iowa soils. In doing so, soil suspensions and their filtrates were characterized with single‐ISE [ISE(S)] and dual‐ISE [ISE(D)] procedures, the ISEs were calibrated in terms of ion concentrations to obtain Q/I relationships based on concentration ratios (CR), and the results were compared with those obtained by conventional analyses of the filtrates by atomic absorption spectrometry (AAS). By using ISEs with filtrates from soil suspensions that were equilibrated for 18 h, it was established that the ISE(S) and ISE(D) methods yield essentially the same Q/I curves and related parameters as the reference AAS method. The potentiometrically determined CR values agreed particularly well with the AAS values that were based on Ca2+ plus Mg2+ because of the response of the Ca‐ISE to Mg2+. Subsequent experiments on the feasibility of using the ISE(D) procedure with the soil suspensions (to eliminate the filtration step) also yielded results that were in excellent agreement (no significant difference at α = 0.05) with those obtained by analyzing the filtrates. The time required for Q/I determinations was further reduced by using the ISEs with soil suspensions to which successive increments of KCl were added. This procedure, however, altered the shape and critical parameters of the Q/I curves. Clearly more information about the relevance of the different Q/I results is needed. The ISE methods provide a simple and rapid means of obtaining the necessary data.
Overwinter Transformations of Nitrate Derived from Soil and 15N‐Labeled Potassium Nitrate
Authors: Heaney D. J. , Nyborg M. 
Published: July 2010

AbstractTransformations of NO3‐N from fall through spring were examined in a Typic Cryoboralf and a Typic Argialboll in northcentral Alberta. Nitrogen‐15 labeled KNO3 (96% atom abundance) was applied at the rate of 2.4 kg N ha−1 to fallow and stubble plots in October and incorporated to a depth of 0.13 m. Isotopic analyses of NH4‐N, NO3‐N, and total‐N were performed on soil samples taken to a depth 0.60 m in November, January, March, and May. Analysis of November samples indicated apparent denitrification, immobilization, and release of 15N as NH4‐N occurred in both soils. Losses of NO3‐N occurred simultaneously with additions between November and January in 3 of 4 fallow‐stubble/soil combinations. Migration of soil water towards ice lenses in the surface 0.30 m suggested upward movement of NO3‐N took place as the soil froze. Between January and March, NO3‐N levels increased an average of 6.4 mg N kg−1 in the Cryoboralf while recovery of 15N was unchanged. In the Argialboll, NO3‐N levels remained constant from January to March. Lower recovery of 15N under fallow indicated that the NO3‐N pool remained active and losses were balanced by gains. In may recovery as NO3‐N accounted for only 1 to 24% of labeled N added in October. Immobilization accounted for 4 to 30%. Trace amounts of 15N were detectable in the 0.13 to 0.30‐m depth, but not in the 0.30 to 0.60‐m depth. Overwinter loss of labeled N from 0 to 0.60 m ranged from 55 to 86%. Processes affecting NO3‐N remained active between October and May, including periods during which soils were frozen throughout the 0 to 0.60‐m depth.
Early Stages of Mine Soil Genesis in a Southwest Virginia Spoil Lithosequence
Authors: Roberts J. A. , Daniels W. L. , Burger J. A. , Bell J. C. 
Published: July 2010

AbstractNatural topsoils in the Appalachian surface mining region are often more difficult to use and less desirable than alternative spoil materials. Parent material effects and initial pedogenic changes over 3 yr were observed in 5 mixes of sandstone (SS) and siltstone (SiS) spoils under grass vegetation. Spoil type controlled initial soil texture, but significant decreases in sand contents and increases in silt contents occurred in several spoil mixes within 2 yr. All mine soils studied were high (≥65%) in coarse fragments. Mine soils derived from spoils high in siltstone content were higher in coarse fragments, pH, extractable cations and iron, fine earth (<2 mm) water holding capacity, and electrical conductivity than sandstone mine soils. Dissolution and leaching, oxidation, and organic matter incorporation were dominant pedogenic processes influencing mine soil properties over the period of this experiment. Distinct surface A horizons formed within 3 yr. Water retention in the <2‐mm fraction increased over time in the surface (0 to 5 cm) of all spoil types except pure sandstone. Extractable Fe and total N increased between 1982 and 1984, while pH, and extractable Ca, Mg and P decreased in most spoil types. These changes reflect rapid pedogenesis in fresh unweathered parent materials in a humid environment.