bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bulk Density of a Sandy Loam: Traffic, Tillage, and Irrigation‐Method Effects
Authors: Meek B. D. , Rechel E. R. , Carter L. M. , DeTar W. R. 
Published: July 2010

AbstractModern crop production creates a cycle between soil compaction caused by traffic and alleviation of this condition by tillage or natural processes such as freezing and thawing. The objective of this study was to evaluate important management practices as they relate to changes in bulk density of a tilled sandy loam soil. Practices evaluated were irrigation method, time between tillage and traffic, tire pressure and wheel load of applied traffic, and controlled traffic. Relationships among bulk density, penetration resistance, and infiltration rate were determined. Experiments were conducted in the San Joaquin Valley of California, on a sandy loam soil (Entisol) with an organic‐matter content of <1%. After tillage, settling and trafficking of a soil resulted in rapid changes in its bulk density until a new equilibrium was reached. Tire pressure of 408 kPa and wheel weight of 2724 kg applied at moisture contents near field capacity resulted in a bulk density of 1.92 Mg m−3, compared with a value of 1.67 for no traffic. The time interval between tillage and traffic did not affect final bulk density. Drip irrigation, which did not saturate the soil, resulted in a bulk density of ≈0.1 Mg m−3 lower than flood irrigation, which saturated the soil surface. Wheel traffic in the furrow resulted in only small changes in the bulk density within the row. When tillage did not occur between cropping seasons, traffic caused high bulk densities in the furrow but only small changes in the row. An increase in bulk density from 1.7 to 1.89 Mg m−3 decreased the infiltration rate by four times and increased resistance to penetration at the end of the season by three times. Knowledge of how management practices affect bulk density can aid growers in reducing recompaction following tillage.
Transport in a Horizontal Flow Chamber
Authors: Sadeghi Ali M. , Starr James L. 
Published: July 2010

AbstractA better understanding is needed of the factors that control the fate of chemicals that move laterally in shallow groundwater within fields to tile lines and drainage ditches and from fields to nearby streams or estuaries. A chamber was designed and used to simulate shallow groundwater flow in the field. The chamber, made of Plexiglas with dimensions 120 by 60 by 60 cm, was filled to a depth of 30 cm with sand. A multiport arrangement of 10‐mm‐diam. holes on a 5 by 5 cm grid on both end walls of the chamber provided a combination for quite uniform solute application at the inlet side, and allowed sampling simultaneously from all ports at the outlet side. As a first approximation, the flow and transport were assumed to be one dimensional, and a convective‐dispersive solute‐transport model was applied to the Cl breakthrough data of each of the 50 outlet ports in order to quantify the spatial distribution of the dispersion‐coefficient values at the outlet plate. Based on the inconsistency observed between measured and estimated pore‐water velocities and dispersion coefficients of each of the 50 outlet ports, it appears that the one‐dimensional model is not appropriate to adequately characterize transport parameter in this horizontal flow system.
State‐Space Approach to Spatial Variability of Crop Yield
Authors: Wendroth Ole , Al‐Omran A. M. , Kirda C. , Reichardt K. , Nielsen D. R. 
Published: July 2010

AbstractSpatial crop yield variability complicates interpretation of field experiments if there is no information available about the spatial variability structure of the soil. Our objective was to determine, using a state‐space approach, the underlying process in a soil that caused spatial yield variability of a N2‐fixing crop and a nonfixing crop. On a heterogeneous soil, ryegrass (Lolium multiflorum L.) and alfalfa (Medicago sativa L.) were cropped on neighboring transects. Dinitrogen fixation, calculated with either the difference method or the 15N isotope dilution method and averaged across the transects, did not differ. But, as we examined locations along the transect, differences in amount of fixed N calculated by each method became apparent. Yields of both crops showed different variability structures along the transects. Local effective soil N content was related to local N uptake from soil and to soil symbiotic N2 fixation of alfalfa. In order to conclude this, the spatial distribution of the soil volume taken by stones in this partially rocky soil had to be considered. In stochastic (state‐space) models based on spatial dependence between observations, crop yield, effective soil N, and N2 fixation were identified as first‐order autoregressive processes moving through the transect. In other cases, state‐space models were useful tools for spatial interpolation of plant yield, except for large yield alterations between neighboring plots along a transect. This study showed that the spatial variability structure of yields could be explained from located field observations combined with state‐space models.
Genesis of Natriborolls (Solonetzic) in a Closed Lake Basin in Saskatchewan, Canada
Authors: Heck R. J. , Mermut A. R. 
Published: July 2010

AbstractMorphological and chemical characteristics of seven soils (Aquents and Borolls), crossing four successive terraces, were studied to understand the genesis of Natriborolls (Solonetzic) and associated soils in a closed lake basin in the Saskatchewan prairies. Formation of these terraces may be associated with major climatic changes during the Holocene. Based on zirconium/quartz ratios and field observations, frequent lithological discontinuities were identified in the profiles. These discontinuities have influenced the morphology and chemistry of the soils. Differences between the lake water and underlying artesian aquifer reflect the influence of more soluble and weatherable minerals in the basin's deposits. The concentration and composition of soil solutions, the degree of carbonate dissolution, and the amounts of gypsum changed with increasing elevation. The sequence of anion leaching observed was: Cl‐ > SO2‐4 > HCO3‐ (or CO2‐3). Lateral capillary flow from the lake is the major mechanism of salination, but a limited redistribution of efflorescent salts by wind also occurs in the basin. Due to the high inherent shrink‐swell potential of the parent material, prismatic structure has formed at an early stage of profile development. Morphology of the soils on the younger terraces suggests that the eluvial horizons developed after the formation of the prismatic structure. The preservation of solonetzic morphology (stable columnar structure), despite changes in salinity, is attributed to the fine texture of the soil.
Alternative Soil Water Release Parameters for Distinguishing Tillage Effects
Authors: Powers William L. , Baer Jonathan U. , Skopp J. 
Published: July 2010

AbstractTillage effects on the water‐holding characteristics are frequently difficult to evaluate. This may partially be due to the insensitivity of the parameters selected to make the comparisons. This study was initiated to evaluate alternative parameters for assessing tillage effects on water‐holding characteristics. Corn (Zea mays, L.) was planted on a Crete silt loam soil (fine, montmorillonitic, mesic Pachic Argiustoll) which was subjected to conventional and no‐till management for four consecutive years. Water‐release data were obtained from undisturbed soil cores taken from the surface soil three times during the 1989 growing season and at harvest. The following parameters were calculated: the air‐entry value, ψe; the pore‐size distribution index, d; the transformed air‐entry value, c; the zeroth ordinary moment or porosity (OMO), the first ordinary moment or mean pore size (OM1), the second central moment or breadth of the pore‐size distribution (CM2), and the skewness (SKW) of the pore‐size distribution; and four volumetric fractions. Except for ψe and the volume fraction of pores with radii between 1.5 and 15 µm, VF3, all parameters showed an effect of tillage treatments at the 90% confidence limit as determined by an F test. Only the CM2 showed a significant effect of time. The above parameters were also calculated from data on three Iowa soils. For these data, two additional parameters, OMO and VF3, did not show a difference between selected tillage treatments. Stepwise discriminant analysis selected only OM1 as a discriminator for the data from the Crete soil, but several combinations of OM1, OM2, d, and VF3 were selected when the Iowa soil and Crete soil data were combined. Our recommendation for a single characterization of the pore‐size distribution is moment analysis.
Polymers' Effects on Infiltration and Soil Erosion during Consecutive Simulated Sprinkler Irrigations
Authors: Levy G. J. , Levin J. , Gal M. , Ben‐Hur M. , Shainberg I. 
Published: July 2010

AbstractImpact energy of water drops from overhead sprinkler irrigation can cause seal formation, and an increase in runoff and in soil erosion. The effects of low concentrations (5, 10, and 20 g m−3) of two polymers, an anionic polyacrylamide (PAM) and a cationic polysaccharide (PSD), on soil permeability and erosion from a grumusol (Typic Chromoxerert) and a loess (Typic Haploxeralf), were studied during five consecutive irrigations of 60 mm each. The polymers were added to the irrigation water during the first three consecutive irrigations, and thereafter the soils were subjected to two additional irrigations of water only. During the first three irrigations, the final infiltration rates (FIR) of the soils were significantly higher than those of the untreated samples (control). In the subsequent two irrigations with water only, the FIR values of the treated samples decreased to values similar to those of the control. The low residual effect of the polymers was explained by erosion of the thin treated layer and an insufficient amount of the polymers. A lower concentration of PAM (10 g m−3) was needed for optimal effect on the FIR and cumulative infiltration, compared with PSD (20 g m−3). For the optimal treatments, infiltration parameters were generally higher in the PAM‐ than in the PSD‐treated soils. Soil losses in all the PAM treatments were significantly lower than those in the PSD treatments. Both polymers stabilized soil aggregates, but PAM also cemented aggregates together and increased their resistance to erosion.
Depth Profiles of Electrical Conductivity from Linear Combinations of Electromagnetic Induction Measurements
Authors: Cook P. G. , Walker G. R. 
Published: July 2010

AbstractWithin the past 10 yr, frequency‐domain electromagnetic (FEM) induction techniques have become more and more widely used in soil science and hydrology. Each measurement of apparent electrical conductivity represents a depth‐weighted average of soil electrical conductivity. However, the depth weighting corresponding to each measurement may be very different from that required by the user. The simultaneous use of multiple measurements (with different depth weightings) should allow some aspects of the depth distribution of electrical conductivity to be inferred. We illustrate a method for obtaining linear combinations of FEM measurements to estimate the soil electrical conductivity within the depth interval of interest. The method relies on the simple fact that the measurement‐system response is linear, so that a linear combination of apparent‐conductivity readings corresponds to a linear combination of response functions. One can seek a linear combination of response functions that has desirable characteristics. This sets up an optimization problem that can be solved by standard methods, which avoids difficulties encountered with layered inversions to resolve nonlayered systems. The approach was applied to GEONICS EM31, EM34, and EM38 instruments in three examples: (i) single frequency measurements at vertical and horizontal dipole configurations, (ii) frequency measurements using the EM34 at all six possible configurations, and (iii) frequency measurements using the EM38 held at varying heights above the ground. The derived linear combinations were applied to field data from southern Australia. Soil conductivity profiles predicted using linear combinations showed good agreement with profiles measured with a conductivity probe.
Dynamic Simulation of Phase Changes in Snowpacks and Soils
Authors: Grant R. F. 
Published: July 2010

AbstractPhase changes of water in snowpacks and soils are controlled mainly by the short‐term dynamics of energy exchange with the atmosphere. The accurate reproduction of the exchange processes is thus necessary to the reproduction of freezing and thawing, and of consequent water movement, in ecosystem simulation models. In the model used for this study, energy exchange between the atmosphere and the surfaces of single‐layered snowpacks and multiple‐layered soils were calculated from recorded meteorological data and from measured physical properties of snowpacks and soils. The consequent absorption and transmission of energy through the snowpack and soil media were used to estimate the dynamics of phase changes in the snowpack and soil water. The hourly behavior of the model allowed it to reproduce, to within 50 W m−2, the diurnal patterns of energy exchange recorded over a melting snowpack and, to within 1 °C, the diurnal soil temperatures recorded at depths of 0.05 and 0.15 m in a thawing soil profile. The seasonal behavior of the model allowed it to reproduce overwinter patterns of accumulation and disappearance of a snowpack to within 50 mm, and those of maximum and minimum daily soil temperatures at depths of 0.05 and 0.15 m to within 1 °C. Models that function at this level of detail are useful in estimating the effects of slope, aspect, residue cover, and other surface characteristics on snowmelt and soil warming. With higher spatial resolution in parameterizing snowpack functions for hydraulic and thermal conductivity, these models may be used to represent multilayered snowpacks.
Electrophoretic Mobility of Illite and Micaceous Soil Clays
Authors: Lebron I. , Suarez D. L. 
Published: July 2010

AbstractExamination of the colloid chemistry of clays may provide an increased understanding of the structural stability of soil clays under field conditions. Electrophoretic mobility (EM) gives specific information about the net charge of a particle at the shear plane. An evaluation was made of the effect of the important water quality variables, electrolyte concentration, sodium adsorption ratio (SAR), and pH on the EM of Silver Hill illite and three micaceous soil clays. Increases in electrolyte concentrationg enerally increased the mobility of the colloidal particles, contrary to double‐layer prediction. The EM behavior is thus not explained by the commonly used double‐layer theory of infinite plates; however, results can be explained if this double‐layer theory is extended to consider charge spillover into clay particle edges and changes in variable edge charge. The EM increased faster when the SAR increased from 5 to 20 (mmol L−1)0.5 than at higher values of this parameter. These results are in agreement with tactoid formation and demixing theory previously developed by others for smectites. The EM for micaceous soil clays and specimen Silver Hill illite was more sensitive to changes in pH as the electrolyte concentration increased. These results are consistent with observations on variable‐charge minerals where variable charge increases with increasing ionic strength. Removal of organic matter increased the EM in the pH 4 to 10 range studied.
Diffusion of Kjeldahl Digests for Automated Nitrogen‐15 Analysis by the Rittenberg Technique
Authors: Liu Y. P. , Mulvaney R. L. 
Published: July 2010

AbstractNitrogen‐isotope analysis by the Rittenberg technique requires N in the form of NH4. Conversion of organic N to NH4‐N is normally accomplished by the Kjeldahl method, which involves digestion with concentrated H2SO4. A diffusion method recently developed for isotope‐ratio analysis of inorganic N in soil extracts was modified for use with Kjeldahl digests. An aliquot of the digest (to 20 mL) containing 50 to 150 µg of N was neutralized by overturning a vial with 2 mL of 20 M NaOH in a 118‐mL specimen container sealed with a screw‐top lid, and the NH3 liberated was collected for 6 d at room temperature in a 7‐mm‐diam. glass‐fiber disk acidified with 10 µL of 1 M H2SO4. For automated Rittenberg analysis of the diffused NH3‐N by mass spectrometry, the glass disk was tranferred to a plastic sample tray (96 samples per tray), treated with 10 µL of 28.9 M (concentrated) HF, and dried in a desiccator over anhydrous CaSO4. Studies showed that diffusion was complete (>97%) and that, when correction was made for isotopic dilution by natural‐abundance N in reagents, isotope‐ratio analyses of diffused N (0.2–4.2 atom % 15N) were in close agreement with analyses using conventional steam‐distillation and concentration techniques.
Crop and Tillage Rotations: Grain Yield, Residue Cover, and Soil Water
Authors: Wagger M. G. , Denton H. P. 
Published: July 2010

AbstractInformation regarding crop yield response for different tillage and rotation systems is needed to determine regional or local suitability for a given production system. Our objective was to determine the effects of continuous and alternating tillage sequences in corn (Zea mays L.) monoculture and corn‐soybean [Glycine max (L.) Merr.] rotation on residue cover, soil water, and grain yield. Continuous conventional tillage (CT), continuous no‐tillage (NT), or CT and NT alternating every other year were evaluated during a 5‐yr period on a Rion (fine‐loamy, mixed, thermic Typic Hapludult)‐Pacolet (clayey, kaolinitic, thermic Typic Kanhapludult) sandy clay loam complex at a Piedmont location and an Eunola sandy loam (fine‐loamy, siliceous, thermic Aquic Hapludult) at a Coastal Plain location. The 5‐yr average NT corn grain yield was 27% (1.15 Mg ha−1) higher than CT at the Piedmont location, but only 4% (0.32 Mg ha−1) higher at the Coastal Plain location. Continuous NT at the Piedmont location also resulted in higher corn yields 2 out of 4 yr compared with NT following CT. The increase in corn yield with NT was associated with greater soil water availability, primarily attributed to surface residue cover from corn stover fostering greater infiltration on a crust‐prone soil. Soybean yield during the 5‐yr period was 5% higher with NT at the Piedmont location and unaffected by tillage at the Coastal Plain location. In general, crop rotation had no effect on corn yield at either location. Results indicate that continuous NT should be the system of choice on this upland Piedmont soil.
Alternative Farming System Effects on Profile Nitrogen Concentrations on Two Iowa Farms
Authors: Karlen D. L. , Colvin T. S. 
Published: July 2010

AbstractThere is a general lack of quantitative data to assess alternate farming systems. Our objectives were to quantify long‐term (20‐yr) effects of conventional and alternative farming practices on soil NH4‐N, NO3‐N, and total‐N concentrations. Contiguous soil map units of Clarion loam (fine‐loamy, mixed, mesic Typic Hapludoll), Nicollet loam (fine‐loamy, mixed, mesic Aquic Hapludoll), Canisteo silty clay loam (fine‐loamy, mixed [calcareous], mesic Typic Haplaquoll), and Webster silty clay loam (fine‐loamy, mixed, mesic Typic Haplaquoll) were identified and used to compare long‐term farming system effects. Sixty‐four soil profile cores averaging 4.5 m in depth were collected from a 16‐ha conventional field and from a 16‐ha alternative field in April 1989 following a year in which total precipitation was ≈30% below normal (588 vs. 848 mm). In autumn 1990, 32 cores averaging 3.0 m in depth were collected from each of two other 16‐ha conventional and alternative fields just north of those sampled in 1989. Farming practice significantly affected total‐N, NH4‐N, and NO3‐N concentrations measured at the various sampling depths, but differences were small and inconsistent. Corn (Zea mays L.) grain yields averaged 9093 kg ha−1 in the conventional field and 8977 kg ha−1 in the alternative field in 1989. Comparing conventional and alternative fields, total aerial N accumulation 6 wk after planting averaged 203 and 123 mg plant−1, ear leaf N concentration averaged 26.6 and 20.6 g kg−1, and total N removed by corn grain averaged 91.6 and 85.7 kg ha−1. All measured differences were generally within the 95% confidence interval, and neither system was consistently better. We conclude that well‐managed conventional and alternative farming systems do not differ in their risk for groundwater N pollution in central Iowa.
Fractal Description of Macroporosity
Authors: Brakensiek D. L. , Rawls W. J. , Logsdon S. D. , Edwards W. M. 
Published: July 2010

AbstractMuch interest has been generated in the application of self‐similar power laws and fractal geometry principles to the description of soil properties. Fractal geometry is here proposed as a descriptor of macroporosity. Data on macropore counts‐sizes were used to investigate this possibility. The fractal Sierpinski carpet was assumed to compute two‐dimensional areal porosity. A tentative conclusion is that macropore count‐size distributions can be described by the carpet generator and the areal porosity can be calculated.
Catalytic Decomposition Kinetics of Aqueous Hydrogen Peroxide and Solid Magnesium Peroxide By Birnessite
Authors: Elprince A. M. , Mohamed W. H. 
Published: July 2010

AbstractPeroxides are used as O2‐generating agents. The decomposition of H2O2 (aq) or MgO2(s) in the presence of synthetic birnessite [δ‐MnO2(s)] as a catalyst was observed by measuring the volume of O2(g) given off. The experimental data fit a first‐order kinetic law and the mechanism proposed by Habes and Weiss can explain the experimental results obtained for the decomposition of H2O2(aq). The applicability of the proposed mechanism involving H2O2(aq) was based on the following: (i) the activation energy was relatively high (82 ± 3 kJ mol−1); (ii) the rate constant (k) was pH dependent, indicating that H+ and OH‐ ions were formed in the process; (iii) a linear relationship (and not logarithmic) between k and the ionic strength indicated a reaction between an ion and a neutral molecule; and (iv) using birnessite with different fractional coverages of Co indicated that the reaction was heterogeneously catalyzed by Mnz+1/Mnz active centers. Regarding MgO2(s) decomposition, the experimental data obtained at pH 7.6 followed a rate law derived from a shrinking‐core model for fixed‐size particles. The rate of the reaction was controlled by diffusion through the Mg(OH)2(s) product layer rather than by chemical reaction at the core surface. Compared with ionic peroxides, MgO2(s) could be a potential O2‐generating agent for generating O2(g) during a relatively long period of time.
Noninvasive Time Domain Reflectometry Moisture Measurement Probe
Authors: Selker John S. , Graff Lynette , Steenhuis Tammo 
Published: July 2010

AbstractTime domain reflectometry (TDR) has been shown to be a widely applicable method for determination of moisture content in soils and other geological and engineering materials. All TDR probes used to date have required penetration of the sample under study, which severely limits the utility of the method. We demonstrated that, by simply placing the probe wires against the surface of a sample and recalibrating the dielectric vs. moisture content response, the TDR method may be used to obtain moisture content without sample penetration. This expands the range of applicability of the TDR technique to such critical areas as hard rock drill cores and pavement measurements, as well as endurated soils. An example of such a noninvasive probe is shown to have the accuracy of previous probe designs (i.e., ± 2% m3 m−3 moisture content), without requiring penetration of the sample, with additional advantages including the ability to miniaturize the probe.