bluuebunny/crossref_metadata_2025 huggingface dataset:
Sensitivity Analysis on the Comparison between the Gapon and Vanselow Exchange Coefficients
Authors: Evangelou V. P. , Phillips R. E.
Published: July 2010

The traditional nonthermodynamic Gapon exchange selectivity coefficient (KG) for Na‐Ca exchange has previously been shown in the literature to be in close agreement with the Vanselow coefficient (Kv) for Na equivalent fractions (NNa) in the exchange of <0.20. Furthermore, it has previously been shown for a heterogeneous group of soils that the traditional empirical ESP‐SAR relation (ESP = NNa × 100; ESP = exchangeable sodium percentage and SAR = sodium adsorption ratio) is indistinguishable from the ESP‐SAR relation predicted by the Vanselow equation for NNa <0.40. This study is a sensitivity analysis of the comparison between the Kv and KG for Na+ replacing Ca2+ in the exchange phase. It is carried out by mathematically deriving and graphically demonstrating the interrelationships between Kv and KG. These interrelationships are established on the basis that the Na‐Ca exchange system obeys ideal solid solution theory and thus Kv is reduced to a thermodynamic exchange constant. The results point out that generally, the greater the Kv, the greater the NNa range for which an apparent linear relationship between NNa and SAR is observed. This relationship, however, does not ensure that for the same NNa range the condition KG ≃ Kv is also met. The results show that as NNa approaches 0, KG = 0.50 Kv, and as NNa approaches 1, KG approaches infinity. The results also demonstrate that the condition KG ≃ Kv is dependent on the magnitude of Kv or KG for a limited NNa range, and it is independent of the magnitude of the cation exchange capacity (CEC). The condition KG ≃ Kv appears to have the potential to be met experimentally for Kv values in the range of <0.015 and up to a NNa value of approximately 0.60. At the larger Kv values (≫0.015), the condition KG ≃ Kv is less likely to be met because the absolute difference between Kv and KG is significant even at NNa values <0.20. The Kv, however, is always equal to the KG at NNa = 0.60. This cross‐over point is independent of the magnitude of Kv and CEC.
Crop‐water Production Functions for Sweet Corn and Cotton Irrigated with Saline Waters
Authors: Russo David , Bakker Derk
Published: July 2010

The effect of irrigation water quality (salinity) and quantity on the yields of sweet corn (Zea mays cv. Jubilee) and cotton Gossypium hirsutum L. cv. Acala SJ‐2) was studied in a sandy loam (Typic Torrifluvent) soil. For each of the irrigation water salinities of Co = 1.8, 3.6 and 6.7 dS/m (for corn) and Co = 3.6, 6.7, and 10.5 dS/m (for cotton), 10 amounts of irrigation water (Q) ranging from 0.15 to 2.7 times the class A pan evaporation (Eo) were applied via trickle irrigation. Root zone soil‐water matric potential, water content, and salinity were monitored, and corn and cotton yield components were measured. Time‐averaged root zone soil water content (θ) and soil salinity (EC), as well as crop yield components (Y) were affected by both Q and Co. Results of the analyses of the crop‐water production functions suggest that increasing the amount of irrigation water may compensate only in part for the adverse effects of the salinity of the irrigation water. For corn, using irrigation water of Co = 3.6 and 6.7 dS/m, maximum ear yields were reduced by 8 and 27%, respectively, relative to the maximum ear yield obtained using water of 1.8 dS/m. For cotton, using irrigation water of Co = 6.7 and 10.5 dS/m, maximum seed cotton yields were reduced by 6.5 and 30%, respectively, relative to the maximum seed cotton yield obtained using water of 3.6 dS/m. Analysis of the Y(θ, EC) relationship for each of the corn and the cotton yield components suggested that, due to the mutual effect of θ and EC on Y, the crop response to salinity curve is affected by θ and, in general, should be described by a nonlinear concave expression rather than by the piecewise linear expression of Maas and Hoffman (1977).
A Closed Tube Method for Measuring Gas Diffusion Coefficients
Authors: Tokunaga T. K. , Waldron L. J. , Nemson J.
Published: July 2010

A transient, closed tube method for measuring both ordinary gas diffusivities and porous media effective diffusivities is presented. The current method is suitable for measuring gas diffusivities in air‐dry systems over a range of temperatures. Gas concentrations are continuously monitored in a well‐stirred volume of a single end chamber, which is connected to a closed sample chamber during experiments. An analytic solution for this diffusion process is available in which, after a sufficient time, the diffusivity of the sample is obtained from the slope of the logarithm of dimensionless concentration excess versus time. The method was checked by comparing measurements of N2‐O2 gas diffusivities at 0, 30, and 60 °C to various previously reported values in the literature. The measured diffusivities fall within the uncertainties of these earlier works.
Soil Properties Affecting the Availability of Potassium in Highly Weathered Soils
Authors: Uribe E. , Cox F. R.
Published: July 2010

The interpretation of soil tests for K in highly weathered soils may be improved if the K buffering power is considered in addition to extractable K. This study was conducted to determine if cation exchange capacity (CEC) and humic matter (HM) should be included in the development of more meaningful K availability indices. Seventeen soils from the Coastal Plain, Piedmont, and Mountain regions of North Carolina and two soils from the Amazon Basin of Peru were studied. The buffering power tended to correlate positively with CEC, but that of soils high in HM was lower and less affected by CEC than that of the low‐HM soils, indicating a lower capacity to replenish K removed from the soil solution upon depletion of K. The K concentration in the equilibrium solution increased linearly with percent K saturation of the CEC, and high HM soils had a higher concentration of K in the equilibrium solution at any given percent K saturation than low HM ones. A larger portion of extractable K was found in solution as HM increased and CEC decreased. It was noted that high HM soils were behaving similarly to low CEC and low HM ones so the soils were grouped into two categories: (i) soils of low K buffering power, which are those with HM ⩾ 1.9% and a CEC ⩽ 4.6, and (ii) soils of higher buffering power, which are those with HM < 1.9% and CEC ⩾ 4.6. The use of this grouping should improve K fertilizer recommendations in highly weathered soils.
Prediction of the Calcium to Calcium Plus Magnesium Ratio in Soil‐Grown Winter Wheat Forage
Authors: Rossi N. , Nye P. H. , Grunes D. L. , Sanchirico C. A.
Published: July 2010

The purpose of the research was to predict the Ca/(Ca + Mg) ratio in soil‐grown winter wheat forage from a knowledge of (i) Ca/(Ca + Mg) in the soil solution, or from Ca/(Ca + Mg) calculated from exchangeable plus soluble ions in the soil, and (ii) Ca/(Ca + Mg) in the tops of plants grown in nutrient solutions of regulated Ca/(Ca + Mg). Winter wheat (Triticum aestivum L. ‘Centurk’) was grown in a controlled light‐temperature chamber and harvested after 10, 20, and 30 d. The same Ca/(Ca + Mg) ratios were used in both nutrient solution and soil experiments. In the nutrient solution experiment, the Ca level varied from 5.90 to 0.78 mM, while the Ca + Mg equalled 6 mM. In the soil experiment, the amounts of liming materials for the different treatments (in mg kg−1 of soil‐sand mixture) varied from 2 400 (CaCO3) + 0 (MgCO3) to 0 (CaCO3) + 2020 (MgCO3). Growth was similar in nutrient solution and in soil, and was unaffected by Ca‐Mg treatment. Concentrations of Ca and Mg in tops and roots were higher in the plants grown in nutrient solutions than in the soil‐grown plants. The observed and predicted Ca/(Ca + Mg) ratios in the tops agreed excellently. The concentrations of Ca and Mg at the root surfaces of the soil‐grown plants were calculated using diffusion, mass flow, and root absorbing power. The calculated valuves differed little from those found in the bulk of the soil solutions. Implications for Ca and Mg deficiency of grazing ruminants are discussed.
Compositional Differences in Organic Matter among Cultivated and Uncultivated Argiudolls and Hapludalfs Derived from Loess
Authors: Zhang Hailin , Thompson Michael L. , Sandor Jonathan A.
Published: July 2010

Twelve paired pedons were sampled to investigate the effects of vegetation and ∼120 yr of cultivation on Iowa soils. The study focused on organic matter in unfractionated and fractionated soil materials. Climate, parent material, time, and slope were held as constant as possible. Prairie‐derived mollic epipedons had higher organic C and total N contents than did forest‐derived ochric epipedons. Cultivated epipedons generally had lower organic C and total N contents than their uncultivated counterparts, but the C/N ratio was lowered markedly by cultivation only in the mollic epipedons. Although most of the organic C and total N was associated with the fine silt and coarse clay fractions of the uncultivated pedons, cultivation was associated with a relative shift of organic matter from the sand and silt fractions toward the fine clay fractions. Humic acid/fulvic acid ratios of organic matter in particle‐size fractions were always lower in the cultivated horizons than in the uncultivated horizons. The E4/E6 ratios of humic materials in the particle‐size fractions suggested that humic acids in mollic epipedons consisted of larger organic particles than those in ochric epipedons. Interpretations of the effects of cultivation on the soil organic matter must be made cautiously because of other agricultural influences on the uncultivated sites.
Using Regionalized Variables to Estimate Field Variability of Corn Yield for Four Tillage Regimes
Authors: Cassel D. K. , Upchurch D. R. , Anderson S. H.
Published: July 2010

In selecting an appropriate tillage system for a specific crop and field, it is desirable to choose one that maximizes yield for the field as a whole; however, various areas in a field often give different responses to the same tillage system. The theory of regionalized variables was used to evaluate corn [Zea mays L.] grain yield response to the following four tillage systems (tandem disking, tandem disking followed by bedding, in‐row‐subsoiling and bedding, and chisel plowing). These treatments were randomized, replicated three times, and stripped across the 198‐m‐long field of Norfolk soil (Typic Paleudults), which had a tillage pan and variable depth to B horizon. Grain was harvested in adjoining 15.2‐m‐long plots in each strip. Analysis of directional semivariograms for relative corn grain yield in the along‐the‐row direction, showed a different variance structure for each tillage treatment. Because only three separation distances were available to compute grain yield semivariance values in the across‐the‐row direction, a composite directional semivariogram in this direction was developed by combining relative grain yield‐semivariance values for all four treatments. A global semivariogram was constructed for each tillage treatment by combining the specific along‐the‐row semivariogram specific for each treatment with the composite across‐the‐row semivariogram, and was used to krige the relative corn grain yield for the entire field for each tillage treatment. Patterns of the kriged yields were appreciably different throughout the field for each tillage treatment. Corn grain yields, estimated using jackknife kriging at each location in the field where grain was harvested, compared favorably with the measured yields for all treatments.
A Method to Estimate the Probability that Subsoiling will Increase Crop Yields1
Authors: Vepraskas M. J.
Published: July 2010

Crop yield responses to subsoiling are determined by the amount and distribution of rainfall and soil properties. Because growing season rainfalls are not known in advance, the likelihood of subsoiling increasing yields at a given site can only be stated in terms of probabilities based on current soil properties and historic rainfall patterns. In this study, the probability that subsoiling would increase tobacco (Nicotiana tabacum L.) yield as compared to a nonsubsoiled treatment was estimated for 20 coarse‐textured soils in the southeastern USA where significant yield increases from subsoiling had been observed previously or were expected. Using data collected from 1981 through 1984 for yields of subsoiled and nonsubsoiled treatments, soil physical properties, and rainfall from the 20 sites, a regression model was first developed to describe yield differences between treatments on the basis of specific weekly rainfalls and the sand percentage and water retention of selected horizons. The regression model was then used to estimate yield differences between treatments using physical properties of each of the 20 sites and rainfall histories of two Coastal Plain locations for the years 1930 through 1986. For each rainfall history, the number of years that the estimated yield differences between treatments were ⩾300 kg ha 1(significant differences in yields at the 0.05 level) was tabulated for each site and divided by 57 to compute the proportion of years that subsoiling would have significantly increased yields in the soils considered. These proportions were assumed to be the probabilities that subsoiling would increase yields for a given rainfall history and set of soil properties. The estimated probability mean and standard deviation were 0.69 ± 0.12 across all 20 sites and both rainfall histories. This indicated that on the average, subsoiling would be expected to increase tobacco yield in approximately 7 out of every 10 yr. Probabilities were < 0.50 in only two sites that had relatively high water retention values. The probability values decreased as E‐B horizon water retention increased and Ap horizon sand percentage decreased. These results pertain to Costal Plain soils that had bulk densities ⩾ 1.63 Mg m−3 in either the Ap or E‐B horizon, and sand percentages ⩾ 73% in the Ap horizon.
Phosphorus Dynamics of Pinyon‐Juniper Soils following Simulated Burning
Authors: DeBano Leonard F. , Klopatek Jeffrey M.
Published: July 2010

The objective of this study was to determine the effect of a simulated prescribed fire on P compounds in a Lithic Ustochrept soil supporting a pinyon‐juniper woodland in Arizona. Soil, litter, and duff collected from beneath pinyon pine (Pinus edulis E.) and Utah juniper [Juniperus osteosperma (Torrey) Little] and adjacent interspaces were used to reconstruct laboratory microcosms in clay pipes that were burned when soils were wet or dry. Soil temperatures were monitored continuously throughout the microcosms during burning. Total, bicarbonate‐extractable (BEP), microbial, and organic P; phosphatase activity; and organic C were measured in the soil, litter, and duff before and immediately after burning and 45 and 90 d later. Soil texture, pH, and CaCO3 equivalents were also determined on unburned soils. Organic P and phosphatase activity were significantly higher in unburned juniper soils than under pinyon and interspaces. Total P and BEP were higher in unburned juniper litter than in pinyon litter. Organic P made up <35%, and BEP <5%, of total soil P. About 50% of total P was lost from the litter during burning. Burning significantly increased BEP in pinyon and juniper soils, but the increases were short‐lived and became statistically insignificant after 45 d. Phosphatase activity was significantly reduced in pinyon pine and juniper soils when burned dry. Burning over wet soils did not affect phosphatase activity or the concentration of P compounds.
A Method for Determining Sulfur‐34 Abundance in Soil and Plant Sulfur Fractions
Authors: Schoenau J. J. , Bettany J. R.
Published: July 2010

The variation in 34S abundance has been shown to be a valuable tool in studying S cycling in natural systems. Unfortunately, the measurement procedure is complicated, and the existing literature lacks sufficient information to allow the method to be easily duplicated. We describe a simple system for preparing SO2 for mass spectrometric analysis from different fractions of soil and plant S. The system employs a Johnson‐Nishita apparatus to convert soil S to Ag2S and a compact vacuum combustion system to convert Ag2S to SO2. Standard deviations of 0.1 to 0.4‰ were typical for soil and plant S fractions.
Transport of a Conservative Tracer in the Field Under Continuous Flood Irrigation
Authors: Jaynes D. B. , Rice R. C. , Bowman R. S.
Published: July 2010

A 5‐cm deep pulse of bromide‐tagged water was applied to four small field subplots and leached under continuously flooded conditions for 7 d. During leaching, solution samples were periodically withdrawn through suction samplers from seven depths within each subplot. Pore water velocities, vs, and dispersion coefficients, D, were calculated by fitting the one‐dimensional solution of the advection‐dispersion equation to the concentration vs. time curves from each sampler. Both vs and D were best described by a log‐normal distribution rather than a normal distribution. D values were very large compared to values reported for laboratory experiments, but similar to other field values measured under similar conditions. Neither vs nor D showed any significant correlation with depth or time, but the dispersivity (ratio of D to vs) did show a weak positive correlation with depth. The relationship between ln D and ln vs was linear with a slope near 1.0. However, when vs and D data measured in an earlier study under an intermittently dosed irrigation regime at the same site were included, ln D was no longer a simple linear function of ln vs. The ratio between the calculated pore water velocities and the velocities calculated from the surface flux divided by the average water content was equal to or slightly <1.0 for all depths >0.6 m. At depths <0.6 m the ratio was considerably >1.0, indicating that a fraction of the soil water was being bypassed or not participating in the leaching process. This result is in contrast to an earlier study conducted on this site when irrigated under a dosed irrigation scheme in which the ratio was consistently >1.0 at all depths.
Early Stages of Mine Soil Genesis as Affected by Topsoiling and Organic Amendments
Authors: Roberts J. A. , Daniels W. L. , Burger J. A. , Bell J. C.
Published: July 2010

Topsoil substitutes offer alternative reclamation options in many surface mining regions, particularly where native topsoil materials are of poor quality. The objective of this study was to measure effects of various amendments on mine soil properties and the early stages of pedogenesis. Treatments applied to 2:1 sandstone/siltstone spoil mixtures were inorganic fertilizer (control): 112 Mg ha−1 sawdust: 30 cm of local topsoil: and 22, 56, 112, or 224 Mg ha−1 of municipal sewage sludge. Morphologically distinct A horizons and transitional AC and C1 horizons developed in all pedons between 1982 and 1985, primarily due to plant rooting. The depth and nature of transitional AC and C1 horizons was strongly influenced by organic additions. Water availability after 3 yr was enhanced by sawdust applications. Mine soil pH decreased over time as basic cations leached, but sludge additions moderated the rate of decline. Organic C accumulation rates ranged from 700 to 1500 kg C ha−1 yr−1 and were accelerated by sludge additions. Soil total N generally increased as well, and both C and N accumulations were associated with A horizon formation. Extractable Fe increased significantly in the surface of all treatments over time. Sludge additions dominated mine soil chemistry for multiple seasons. Total cation exchange capacity (CEC) was greatly increased by sludge additions, but decreased significantly over time due to leaching of Ca and Mg. Changes in soil chemical and physical properties reflect rapid pedogenesis and effects of organic matter additions to mine soils. Organically amended spoils can equal or surpass native topsoil materials in forgage productivity.
Basal Mixing Zones in Loesses of Louisiana and Idaho: I. Identification and Characterization
Authors: Schumacher B. A. , Lewis G. C. , Miller B. J. , Day W. J.
Published: July 2010

The thickness and character of basal mixing zones in loess with different underlying materials and in different climates were studied in Louisiana and Idaho. Peoria loess in Louisiana is underlain by sandy braided stream deposits, clayey alluvium, and an older Sicily Island loess. In Idaho, materials underlying loess deposits include glacial till, basalt, Pliocene sediments, and a paleosol developed in loess. Multiple criteria, divided into primary and secondary indicators, were used in the identification of basal mixing zones. The primary indicators of basal mixing zones were field morphology and particle‐size distribution. Secondary indicators include total elemental analyses, clay mineralogy, CaCO3 equivalence, exchangeable cations and soil reaction listed in order of decreasing sensitivity. In Louisiana, basal mixed zones varied in thickness from 61 to 124 cm while in Idaho, basal mixed zones were between 8 and 40 cm thick.
Distribution and Characteristics of Windthrow Microtopography on the Cumberland Plateau of Kentucky
Authors: Cremeans D. W. , Kalisz P. J.
Published: July 2010

The abundance and characteristics of microtopography resulting from the uprooting of trees were examined on five landtypes on the northern Cumberland Plateau. Plots, 10 m by 25 m, were established at 180 locations on randomly‐oriented systematic grids located in 12 first‐order watersheds. The area and depth of soil disturbed were measured for each of the 524 uprootings encountered. In addition, all windthrow microtopography in a single representative hollow, 11.3 ha in area, was mapped and measured. Soil disturbance by uprooting was least on ridges, intermediate on side slopes, and greatest in coves and on lower north slopes. Percentage disturbance of the ground surface ranged from 0.4% on ridges to 2.4% in coves; number and mean area disturbed by individual uprootings ranged from 50 to 112 ha−1, and from 0.5 to 2.1 m2 along the ridge‐to‐cove gradient. The lower abundance of windthrow microtopography on ridges was attributed to a relatively high incidence of stem breakage vs. uprooting. Stem breakage seemed particularly common in scarlet oak (Quercus coccinea Muenchh.) which dominated ridges and south slopes. Observations made during the course of this study also suggested that concentrated subsurface water flow and concomitant decreases in tree stability may contribute to uprooting in coves and on lower slopes. Windthrow, viewed as a pedogenic process, clearly does not operate uniformly over this mountainous landscape.
Use of Acetylene Reduction for Estimating Nitrogen Fixation in Woody Debris
Authors: Hendrickson O. Q.
Published: July 2010

Both endogenous C2H4 formation and C2H4 arising from reduction of C2H2 must be accurately measured in N2 fixation studies using C2H2 reduction. Previous work with forest soil has shown that C2H4 formed in air is not an appropriate control for endogenous C2H4 formation. This study compared different controls for endogenous C2H4 formation during C2H2 reduction studies of woody logging debris. Amounts of C2H4 formed by decaying wood in the presence of C2H2 plus either of two noncompetitive inhibitors of C2H2 reduction (CO, (NH4)2SO4) were greater (p <0.01) than amounts of C2H4 formed in air. Ambient air controls therefore underestimated endogenous C2H4 formation, and would overestimate N2 fixation rates. Controls using (NH4)2SO4 were not suitable for routine use due to alteration of sample moisture content. With CO as an inhibitor, endogenous C2H4 formation averaged 23% of total C2H4 formed in the presence of C2H2 across a range of moisture contents. Field data on C2H4 produced by logging slash in the presence of C2H2 alone are discussed in light of these findings. In the future, C2H2 reduction studies of N2 fixation in decaying wood should employ CO controls for endogenous C2H4 formation.
Multivariate Statistical Analysis of Potassium and Chloride Redistribution from a Line‐source Sprinkler Experiment
Authors: Tillotson W. R. , Biggar J. W. , Nielsen D. R. , Shumway R. H.
Published: July 2010

Water treatment effects on K and Cl redistribution in a field soil were quantified using a particular multivariate analysis of variance method, profile analysis. A field experiment was conducted using the line‐source sprinkler system for the determination of water treatment effects on K and Cl redistribution through comparisons of K and Cl mean redistribution profiles. For a water treatment, the solute mean redistribution profile is obtained by averaging individual concentration‐with‐depth profiles from 25 field locations. Five water treatments covered a range of cumulative applied water and solute redistribution times equal to 110 to 450 mm and 27 to 305 d, respectively. Three of the water treatments resulted from the sprinkler system and two from rainfall. Soil profiles were sampled at depth intervals of 0 to 15, 15 to 30, 30 to 60, 60 to 90, and 90 to 120 cm. Samples were analyzed for water soluble K and Cl, and gravimetric water content. A logarithm transformation of the K and Cl data was sufficient for approximate population multivariate normality. Profile analysis identified the water treatment effects of parallelism among the ln K mean redistribution profiles, and symmetry and coincidence among the ln Cl mean redistribution profiles. Identification of specific effects among the mean profiles amounted to the determination of kinematic similarity in K and Cl redistribution. Comparisons of mean profiles corresponding to the depth variables were also analyzed. Profile analysis fills a void in the quantification of water treatment effects on solute redistribution not filled by other data analysis procedures.
Color, Organic Matter, and Pesticide Adsorption Relationships in a Soil Landscape
Authors: Fernandez R. N. , Schulze D. G. , Coffin D. L. , Van Scoyoc G. E.
Published: July 2010

Soil color, organic matter content, and adsorption of the pesticide diuron [3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea] were measured for the silt loam or silty clay loam Ap and Bt or Bg horizons of two toposequences of soils occurring within the same soil landscape in Tippecanoe Co., IN. Close linear relationships (r2 > 0.9) were obtained between Munsell value, organic matter content, and diuron adsorption. Color‐organic matter relationships within this landscape appear to be much better than previously reported relationships developed for soils over wider geographic areas. Sensors for measuring soil organic matter content as equipment moves across a field are more likely to be successful if they are calibrated on a field by field basis rather than utilizing relationships developed over a wide geographic area.
Soil Organic Carbon, Nitrogen, and Phosphorus Quantities in Northern Great Plains Rangeland
Authors: Aguilar R. , Heil R. D.
Published: July 2010

Soils were characterized in North Dakota rangeland along toposequences formed in sandstone, siltstone, and shale parent materials to evaluate quantities of organic C, N, P, and total P. Distribution of these soil constituents varied systematically with parent material and landscape position along the three toposequences, and generally increased upon moving downslope. The fine‐textured soils formed in shale had greater quantities of organic C, N, and total P than the coarser‐textured soils derived from sandstone and siltstone parent materials. Soils formed in sandstone had greater quantities of organic P on all landscape segments. Greater quantities of organic constituents on lower landscape segments were attributed to both greater vegetative productivity and accretion of soil organic matter through sediment deposition. Variable total‐P contents along the toposequences reflected changes in parent material and redistribution of sediments by erosion.
A Method for Measuring Incorporated Crop Residue and Associated Soil Properties
Authors: Allmaras R. R. , Pikul J. L. , Wilkins D. E. , Kraft J. M.
Published: July 2010

Controlled placement and depth distribution of crop residues are major objectives for tillage management. Appropriate methodology has provided quality information about surface placement, but the distribution of buried crop residue has not been readily measurable. A method was developed to measure dry bulk density (ρb), incorporated coarse organic matter (COM), and organic carbon (C) concentration using one soil sample. Cores, each 0.3‐m long, were taken with a specially constructed sampler (19‐mm diam.); each 0.3‐m core was separated into 20‐mm increments for subsequent analysis. After air‐drying, COM was estimated as that crop residue retained on a 0.5‐mm mesh sieve; C concentration measurements and an associated conservation‐of‐C algorithm were used to estimate COM because the incorporated crop residue could not be completely separated from contaminant soil. These ρb and COM had a CV of 5 and 20%, respectively. A depth function of ρb distinguished primary tillage from secondary tillage and traffic; a tillage pan produced by the moldboard base was usually detected by ρb. Moldboard plowing vs. sweep or chisel tillage consistently produced different depth distributions of COM; at least 85% of the COM was above 0.1 m when tilled with a chisel or sweep and >45% was below 0.1 m when moldboard plowed. Total COM in the profile ranged from 68 to 23% of that measured at harvest, respectively, 28 wk earlier in a wheat‐peas rotation and 82 wk earlier in a wheat‐fallow rotation. Long‐term use of a moldboard plow vs. a chisel or sweep for primary tillage produced consistently different profiles of organic C concentration.
Colorimetric Determination of Oxidizable Carbon in Acid Soil Solutions
Authors: Bartlett Richmond J. , Ross Donald S.
Published: July 2010

A simple and sensitive method is described that determines, colorimetrically, oxidizable organic matter in solutions from acid soils. It relies on measuring the loss of color by a Mn(III)‐pyrophosphate complex as Mn(III) becomes reduced by organic C in the presence of concentrated H2SO4. The method is applicable to 1‐mL samples containing 0.08 to 4.0 µmol of organic C and is practically free of interferences in aerobic solutions.
Automated In Situ Measurement of Unsaturated Soil Water Flux
Authors: van Grinsven J.J.M. , Booltink H.W.G. , Dirksen C. , van Breemen N. , Bongers N. , Waringa N.
Published: July 2010

A device is presented which, based on new operation principles, intercepts unsaturated soil water fluxes within an error of 10% and can yield samples for subsequent chemical analysis and calculation of convective solute fluxes. Operation is controlled by a microprocessor which automatically adjusts the vacuum imposed on a porous filter cloth such that identical matric potentials are maintained just above the cloth and at the same depth in the neighboring soil. Contact resistances and internal resistance of the device are implicitly corrected by adjustment of suction. Laboratory and field tests in a loamy sand under steady and transient flow conditions showed that cumulative water fluxes could be measured within 10% of those calculated from storage changes, and from numerical and analytical flow models.
Cultivation Effects on Carbohydrate Contents of Soil and Soil Fractions
Authors: Dalal R. C. , Henry R. J.
Published: July 2010

The distribution of monosaccharides in the acid hydrolysate of soil fractions and whole soils subjected to variable periods of cultivation (0–45 yr) were studied because carbohydrates constitute a substantial proporation of soil organic matter and affect soil aggregation, both of which are affected by cultivation. Monosaccharides in soil acid hydrolysates were analyzed as their alditol acetates by an improved procedure using 1‐methylimidazole as acetylation catalyst. Carbohydrate constituted from 8 to 16% of soil organic matter in virgin soils and generally increased with the clay content (18–78% clay). Of this, 27 to 43% of carbohydrate was present in the light fraction (<2 Mg m−3), which also contained proportionally more carbohydrate‐C than did total organic matter. Upon cultivation, the light fraction declined rapidly, resulting in substantial loss of carbohydrate, especially in clayey soils. In these soils, carbohydrate losses also occurred from sand‐size and silt‐size fractions but clay‐size carbohydrates were less affected. Glucose and galactose were normally the predominant monosaccharides in the acid hydrolysates of the soils and soil fractions. The effects of cultivation on the net amounts of carbohydrate‐C in the various fractions and the whole soil in the three soil series studied, were generally similar to those on the total organic C, showing thereby that carbohydrate fraction of the soil organic matter was no more liable than the total organic C.
Developmental Aspects of Water‐Repellency of Sandy Soils
Authors: Hubbell David H.
Published: July 2010

Increase in water‐repellency of some sandy soils has been reported to be induced by conditions of high relative humidity. Incubation studies in a closed system were used to study mechanisms by which a wettable soil and a Bacillus isolate from it were able to partially suppress the expected increase in water‐repellency, normally induced by high relative humidity, in some water‐repellent soils. Evidence indicates a volatile product(s) is responsible for suppressing increases in water‐repellency.
Independent Calibration of a Mechanistic‐Stochastic Model for Field‐scale Solute Transport Under Flood Irrigation
Authors: Jaynes D. B. , Rice R. C. , Bowman R. S.
Published: July 2010

Solute leaching at the field scale can show considerable variability because of variations in the hydraulic properties of the soil. A simple mechanistic‐stochastic model for predicting solute transport on this scale during intermittent flood irrigation is described and a method of calibrating the model independent of any leaching measurements is presented. The model assumes that the pore water velocity varies horizontally across the field but is uniform in the vertical direction. Explicit expressions for chemical diffusion and hydrodynamic dispersion are not included in the model. Instead, horizontal variations in the velocity serve to disperse the solute when measured on a field wide basis. The model requires knowledge of the probability density function for the velocity and estimates of the function parameters. These parameters were estimated from variations in infiltration rates measured within 63 ring infiltrometers and from water retention data. Model simulations of Br− leaching agreed well with most measured data for both position of the tracer peak and the degree of solute spreading, indicating that at least under flood irrigation, variations in infiltration as controlled by soil hydraulic properties explain most of the observed variations in Br− leaching over a field.
Single‐Column Ion Chromatography: IV. Determination of Arsenate in Soils
Authors: Mehra H. C. , Frankenberger W. T.
Published: July 2010

A method has been developed for the determination of arsenate (AsO3−4) in aqueous soil extracts by single‐column ion chromatography (SCIC) at trace levels. The eluent stream consisted of 6 mM p‐hydroxybenzoic acid (PHBA) at pH 7.0. Separation was carried out on a low‐capacity anion‐exchange resin column with the anion species being quantified by conductometric detection. Resolution between AsO3−4 and PO3−4 was Rs = 1.93. The method allows precise (RSD, relative standard deviation = 1.12 to 7.87%) trace amount measurement of AsO3−4 (detection limit, 0.092 mg L−1) in the presence of Cl, NO−3, PO3−4 and SO2−4. The AsO3−4 signal becomes masked limiting separation and detection when PO3−4 exceeds 30 mg L−1. Under the conditions described, arsenite (AsO3−3) was not detected. Analysis of aqueous soil extracts for AsO3−4 by SCIC agrees closely with those values obtained by atomic absorption spectrometry and inductively coupled plasma emission.
Salt‐induced Manganese Solubilization in California Soils
Authors: Khattak Riaz A. , Jarrell Wesley M.
Published: July 2010

The solubility of Mn in soil solution depends on soil pH, redox potential (Eh), amount and type of higher valency Mn oxides, and a variety of organic and inorganic soil constituents. Laboratory experiments were conducted to determine the extent of salt‐induced Mn release from a variety of California soils. To investigate the effect of salinity and time of incubation on Mn release, Redding (fine, mixed, thermic Abruptic Durixeralf) clay loam and Hanford (coarse‐loamy, mixed, nonacid, thermic Typic Xerorthent) sandy loam soils were saturated with 0, 75, and 150 mol m−3 NaCl‐CaCl2 solution (prepared on an isoequivalent basis) and incubated in a glasshouse for 0, 2, 4, 7, and 10 d. The Mn concentration in the soil saturation extract increased 2‐ to 4‐fold with time of incubation at all levels of salt solution and 7‐ to 16‐fold with increasing salt concentrations (ionic strength) at a given incubation time. Increases in [Mn] with time and increases in pH in the nonamended soil suggest reduction of Mn oxides while increases in [Mn] with increasing salt levels implicates the release of Mn into soil solution through reduction of Mn oxides, displacement by Na+ and Ca2+ and/or ligand (Cl−) complexation processes. In another experiment, Mn release by NaCl‐CaCl2 salinity was investigated in 20 California soils varying in pH, easily reducible Mn (hydroquinone + NH4OAc), total Mn (HF‐HNO3‐HClO4), and in total C concentrations. These soils were saturated with 0, 37.5, 75.0, 112.5, and 150.0 mol m−3 NaCl‐CaCl2 solution and extracted after 5 d of incubation in a glasshouse. Depending upon soil pH, easily reducible and total soil Mn levels, the [Mn] in soil saturation extracts increased from 10 to 4000 mmol m−3 for 150 mol m−3 NaCl‐CaCl2 levels over the nonsaline (deionized water) treatments. Although the order of magnitude of salt‐induced Mn release was high in soils low in pH and high in easily reducible Mn, a significant salt effect was noted for even high pH (above 7.0) soils. Multiple regression analysis showed that Mn solubility in salt‐amended soils was mainly related to soil pH, easily reducible and total Mn (R2 = 0.68***, significant at p < 0.001). This indicates that factors related to geochemical environments in which soils exist might explain the variations in Mn solubility in salt‐amended soils.
Residue Management Effects on Soil Temperature
Authors: Unger Paul W.
Published: July 2010

Soil temperatures are influenced by many factors, including surface residues. In turn, soil temperatures influence such factors as seed germination, plant growth, nutrient availability, insect populations, and pesticide degradation. Because of the increased use of conservation tillage involving surface residues, a better understanding of residue management effects on soil temperatures is needed. The objective of this study was to determine the effects of residue management practices on soil surface temperatures and on soil surface‐air temperature relationships for the southern Great Plains. Soil surface and air (at 2‐m height) temperatures were measured during the fallow period after winter wheat (Triticum aestivum L.) harvests in 1982 and 1983. Residue management treatments were disk, sweep, and no‐tillage (with standing or shredded residues). Minimum surface temperatures differed only slightly among treatments at different seasons of the fallow period (summer, fall, winter, spring). Maximum temperatures were highest with no‐tillage (standing residues) after dryland wheat in all periods, except in winter when they were highest with no‐tillage with shredded residues. Relationships between soil surface and air temperatures were highly significant (R2 = 0.931, P ≥ 0.001). The relationships developed from the 1983 to 1984 data were used to predict surface temperature from weather station air temperatures for the 1982 to 1983 period. Differences between observed and predicted mean temperatures were significant only for no‐tillage with standing residues in summer and fall and with shredded residues in spring. Normalized soil surface temperatures were affected more by season of the year than by residue management treatment.
Sequential Extraction of Iron, Manganese, Aluminum, and Silicon in Soils from Two Contrasting Watersheds
Authors: Arnseth R. W. , Turner R. S.
Published: July 2010

Soil samples from two contrasting forested watersheds on the U.S. Department of Energy Oak Ridge Reservation in Oak Ridge, TN, were chosen for selective extraction of organics, Fe, Mn, and aluminosilicates. The extracts were analyzed for Fe, Mn, Al, and Si, and the results were evaluated in terms of pedogenic processes. The clay mineralogy was determined on a subset of the samples. Differences between the watersheds were observed in clay mineralogy and in the vertical distribution of extractable Mn. Walker Branch soils, developed on Knox Group carbonates, exhibit vertical flow paths capable of transporting soluble Mn deep in the profile before precipitation. Physically separated zones of Mn and Fe precipitation are observed in Walker Branch cores wherein mid‐depth maxima in citrate‐bicarbonate‐dithionite (CBD)‐extractable Fe are not mimicked in the Mn‐specific extractable Mn profiles. Melton Branch soils, developed on shaly carbonates of the upper Maryville Limestone, with shaly residua persisting to the surface in some areas, retain a structure that obstructs vertical flow, forces lateral flow, and provides microenvironments for water stagnation. When these microenvironments experience periodic desiccation and oxidation, Fe‐ and Mn‐oxyhydroxides are precipitated and coprecipitated. Therefore, clay mineralogy reflected differences in parent material whereas differences in the distribution of extractable Mn‐oxyhydroxides probably reflect the distribution of soil microenvironments conducive to Mn accumulation and oxidation with implications for soil water flow patterns.
An Inexpensive, Portable System for Drilling into Subsurface Layers
Authors: MacDonald Lee H.
Published: July 2010

A relatively simple adaptation of rock drilling equipment to a portable two‐man power auger creates an inexpensive device capable of drilling 45‐mm diam. holes through both surface materials and moderately hard rock to a depth of at least 6 m. The equipment is portable and hence ideal for use in rugged terrain, but a local water source is required. The total cost for all the materials, including the power auger and water pump, is estimated at $1500. Drilling rates of 0.01 to 0.10 m min−1 were obtained in moderately hard to hard rocks in the Central Sierra Nevada of California, but the relatively low rotations per minute of a power auger suggest that drilling will be progressively less efficient in harder rocks. Use of this devise should allow more extensive investigations into the role of saprolites, fractured rock, and other subsurface layers in hydrologic and geomorphic processes.
Evaluation of Soil Recompaction by Transverse Wheeling of Tillage Slots
Authors: Blackwell P.S. , Jayawardane N. S. , Blackwell J. , White R. , Horn R.
Published: July 2010

Narrow, gypsum‐enriched slots are a technique for ameliorating texture‐contrast soils (Natrixeralfs) in Australia. It is expected that undisturbed soil adjacent to the slots will protect loosened soil within the slot from recompaction by wheel traffic. Vertical stresses in slots were compared to those in troughs formed by ripping, and to the stresses between slots and ripping troughs. Stresses were smaller in slots than outside, unless increased by downward movement of the whole slot contents. Inside troughs the stresses were similar to those outside. Macrostructure after zero, one, or four wheelings was also measured. There was more increase of density and loss of macroporosity in ripping troughs than in slots. However, the macrostructure in the slots could be seriously damaged after four consecutive passes over soil at water contents near the lower plastic limit. Thus gypsum‐enriched slots provide only a limited amount of protection from compaction and the amelioration technique needs to be associated with suitable techniques for the management of subsequent traffic.
Evaluation of Three Aluminum Assay Techniques for Excluding Aluminum Complexed with Fluoride or Sulfate
Authors: Alva A. K. , Sumner M. E. , Miller W. P. , Li Y. C.
Published: July 2010

Aluminon, 8‐hydroxyquinoline and ferron reagents are often used to measure Al in solutions. Since Al complexed with F‐ or SO2‐4 is less phytotoxic, in solutions containing these ligands an estimate of Al excluding that complexed with F‐ and/or SO2‐4 represents predominantly phytotoxic Al. In the present study, the capacity of the above reagents to exclude Al complexed with F‐ or SO2‐4 was evaluated in solutions containing 40 µM Al with 20 to 640 µM F‐ or 40 to 5120 µM SO2‐4 at pH 4.5. The effects of varying reaction time from 15 s to 30 min on the recovery of Al by the respective reagents was also investigated. The sum of predicted (by MINTEQ speciation model) concentrations of Al3+ and hydroxy‐Al monomers decreased to 45% or to 0.6% of total Al in solutions with 5120 µM SO2‐4 or 80 µM F‐. The concentration of Al measured by 8‐hydroxyquinoline (15‐ or 60‐s reaction) or aluminon (15‐s reaction) appeared to exclude entirely Al complexed with F‐. All three reagents, however, regardless of reaction time, failed to exclude Al complexed with SO2‐4. Therefore, 8‐hydroxyquinoline (15‐ or 60‐s reaction) aluminon (15‐s reaction) reactive Al would accurately represent phytotoxic Al in the presence of F‐, while ferron reagent is likely to overestimate the phytotoxic Al. In the presence of SO2‐4, however, all three reagents are likely to overestimate the phytotoxic Al.
Effects of Potassium and Lime Applied for Coastal Bermudagrass Production on Sandy Soil
Authors: Cripps R. W. , Young J. L. , Leonard A. T.
Published: July 2010

The deep sandy soils of eastern Texas are inherently low in available Ca and Mg. Also, Coastal bermudagrass [Cynodon dactylon (L.) Pers.] grown on these soils has exhibited K deficiency symptoms. This study was conducted to evaluate the effects of K fertilization and liming on (i) Coastal bermudagrass yield; (ii) plant tissue K, Ca, and Mg concentrations; and (iii) K, Ca, and Mg soil test values. The study was conducted on a Darco fine sandy loam (loamy, siliceous, thermic, Grossarenic Paleudults) from 1981 through 1983 using four rates of K fertilization (0, 140, 279, and 419 kg K ha−1 year−1) and six lime rates (0, 2.2, 3.6, 4.5, 9.0, and 18.0 Mg ha−1). Significant yield responses to both K fertilization and liming were observed in 1982 and 1983. Potassium fertilization resulted in increased plant K concentration and decreased plant Ca and Mg concentrations. Liming increased Ca and Mg concentrations. Maximum yields were obtained with K concentrations of about 22.0 g K kg−1 plant tissue. Increased plant K concentration did not depress Ca and Mg concentrations below 1.8 and 1.1 g kg−1, respectively. After 3 yr of K fertilization, soil test K values were increased only at the 419 kg K ha−1 rate. No yield response to liming was measured above 3.6 Mg lime Ha−1. At the conclusion of the study, soil pH and extractable Ca and Mg values in 3.6 Mg lime ha−1 plots were 5.3, 333 mg kg−1 and 30 mg kg−1, respectively.