bluuebunny/crossref_metadata_2025 huggingface dataset:
Differential Sorption of Exogenously Applied Ferulic, p‐Coumaric, p‐Hydroxybenzoic, and Vanillic Acids in Soil
Authors: Dalton Barry R. , Blum Udo , Weed Sterling B.
Published: July 2010

Plant phenolic acids are found in soils and their importance has been implicated in various soil processes, including biochemical weathering of minerals, humus formation, interactions between plants (allelopathy), and nutrient availability to plants. P‐hydroxybenzoic, vanillic, p‐coumaric, and ferulic acids were added to soils at a rate of 5.15 mmol/kg, extracted with Mehlich III extractant immediately and on Days 1, 2, 4, 8, 16, and 32, and quantified by high‐performance liquid chromatography. The recovery of phenolic acids from Cecil (Typic Hapludults, clayey, kaolinitic, thermic), Portsmouth (Typic Umbraquualts, fine loamy, mixed, thermic), and White Store (Vertic Hapludalfs, fine, mixed, thermic) soils varied with soil type, horizon (A1 and B1), time, and type of functional group present on the aromatic ring. There was significant instantaneous sorption of all compounds in all soils; in A1 horizon materials, recovery decreased as soil organic matter increased. There was generally greater sorption of phenolic acids in the A1 horizon materials than in the B1 horizon materials of a particular soil type. Significant declines in recovery occurred with time for all phenolic acids in each type of soil, irrespective of horizon. The sharpest decline in recovery of phenolic acids from soils generally occurred within 2 d after addition of the compounds. The presence of methoxy groups and acrylic side chains on the aromatic ring of phenolic acids increased the “sorption” of these compounds in soils. Sorption of the phenolic acids by the various soils was generally in the order of p‐hydroxybenzoic ≤ vanillic <p‐coumaric < ferulic.
Soil Potassium Balance and Cumulative Cotton Response to Annual Potassium Additions on a Vermiculitic Soil
Authors: Cassman K. G. , Bryant D. C. , Higashi S. L. , Roberts B. A. , Kerby T. A.
Published: July 2010

Cumulative effects of annual K additions on cotton (Gossypium hirsutum L.) growth and soil K balance were examined in a field study on an irrigated, vermiculitic soil. In each of 3 consecutive yr, cotton ‘Acala SJ2’ was grown with 0, 120, 240, or 480 kg K ha−1 applied to the same treatment plots in a randomized complete block design with 10 replications. The relationship between seed cotton yield and petiole K concentration was similar across years (r2 = 0.61, P < 0.001), but slopes of the yield response to applied K increased each year; 2.6‐fold more seed cotton was obtained per unit K input in 1987 than in 1985. This cumulative response reflected a yield decline without K addition and increasingly higher yield with each additional input of 480 kg K ha−1. Two processes appeared to control this response. First, without K input, NH4‐extractable K+ in surface soil decreased 20% from August 1985 to August 1987. This decrease greatly exceeded the K removal by cotton, and we surmise that an 11% decrease in soil organic C content contributed to this phenomenon. Loss of cation exchange capacity associated with the loss of soil humus may shift K equilibria towards fixation at interlayer sites in vermiculite at the expense of external K pools extracted by NH+4. Second, with high levels of K input, apparent K uptake efficiency from applied K was 50% greater in 1987 than in 1985. Increased efficiency was attributed to the partial saturation of K fixation sites from previous K additions and thus a larger proportion of newly added K remained in plant‐available K pools. At the highest K addition level, 86% of the 1440 kg K ha−1 applied in the 3‐yr period was fixed beyond extraction by NH+4, and plants remained marginally K deficient. The existence of a cumulative response to applied K on vermiculitic soils would have a marked impact on the economics of K fertilization on cotton.
Tillage Effects on Nitrogen Recovery by Corn from a Nitrogen‐15 Labeled Legume Cover Crop
Authors: Varco J. J. , Frye W. W. , Smith M. S. , MacKown C. T.
Published: July 2010

The purpose of this study was to determine the effects of tillage on corn (Zea mays L.) total N uptake and recovery of N from 15N‐depleted legume residue. A conventional tillage (CT) variable was introduced into a 7‐yr‐old no‐tillage (NT) corn study in 1984 by moldboard plowing and disking half of each no N plot having either corn residue (winter fallow) or hairy vetch (Vicia villosa Roth.) cover. Prior to plowing each year, in situ hairy vetch vegetation was removed and replaced with fresh 15N‐depleted hairy vetch vegetation at a comparable rate. In 1984, final total N uptake by corn with vetch cover was 31 kg ha−1 greater with CT than with NT; however, no difference in grain yield occurred. This was a year characterized by limited precipitation during grain fill. In 1985, early season N uptake was greater with CT but there was no difference in final total N accumulated between tillage systems. Averaged across cover treatments, CT resulted in more grain yield than with NT. With vetch, corn N uptake in excess of that with corn residue averaged 60 kg ha−1 yr−1 across tillage systems. Recovery of vetch (15N (Nv) averaged over years was 32% with CT and 20% with NT. In both years this difference was established by 42 d after planting and the pattern of Nv recovery after this day was similar for both tillage systems. Residual recovery of Nv by corn the second year after application was greater with NT (7%) than with CT (3%). With vetch cover, extractable soil N levels were most elevated early in the growing season, particularly with CT in the 0.1‐ to 0.2‐m soil depth.
Field Techniques for Measuring Wetland Soil Parameters
Authors: Faulkner S.P. , Patrick W.H. , Gambrell R.P.
Published: July 2010

Delineating wetlands from nonwetlands in seasonally inundated ecosystems is often difficult and requires data on soil functions and attributes. Techniques (including equipment design, construction, and installation) for assessing wetland soil attributes have been developed that allow direct field measurements of soil O2 content, oxidation‐reduction potential, water‐table depth, and presence of ferrous iron. Soil O2 content is measured from diffusion chambers with a specially fitted polarographic probe. Redox potential is measured with permanently installed platinum electrodes and a voltmeter. Determination of water‐table depth may require piezometers in addition to unlined observation wells. The presence of ferrous iron can be detected with α, α,‐dipyridyl and indicates anaerobic conditions, although interpretation and extrapolation of results must be carefully made. These parameters are particularly diagnostic and results of field studies reveal their dynamic nature and utility in wetland delineation efforts.
Hydrological and Sedimentological Influences on Boroll Catenas, Central Saskatchewan
Authors: Pennock D. J. , Acton D. F.
Published: July 2010

The distribution of soils in a three‐dimensional catena is the result of the action and interaction of hydrologic and sedimentological processes. We examine the relative dominance of the two processes at three study sites in the Black Chernozem (Udic Boroll) soil zone in central Saskatchewan by comparing the distribution of surface soils and postglacial sediments to the present slope morphology and the reconstructed paleo‐slope configuration. Postglacial sedimentation was confined to convergent backslope and footslope configurations on the paleo‐surface and thick sola were associated with these elements. Soil characteristics on shoulder elements, divergent back slopes, and divergent footslopes were relatively unaffected by post‐glacial sedimentation, and the soil characteristics in these elements were in accordance with established differences in water movement in the landscape.
A Rapid Method for Analysis of Soil Macropore Structure. I. Specimen Preparation and Digital Binary Image Production
Authors: Moran C. J. , McBratney A. B. , Koppi A. J.
Published: July 2010

Previously the use of direct observation of soil pore structure in assessing tillage trials has been restricted by the slowness of specimen preparation and data generation. It is desirable that pore structure assessment be performed within a similar time‐scale required for other routine chemical and physical measurements. This would aid the interpretation of routine measurements and enhance the ability to make management decisions in the same growing season as sampling. A method developed for rapid analysis of soil pore structure is presented in two parts. In this paper, a new technique for production of an undisturbed planar face through soil with pore space in the field condition is described. Field impregnation with opaque epoxy resin, that will cure in moist soil, is followed by sawing, laboratory impregnation of the exposed face, and grinding back beyond the original surface to a smooth finish. Grinding is followed by digitization, and digital grey‐level image segmentation to produce a binary image. Methods of image production are described, explained, and illustrated. Samples of Vertisols from a tillage and fallow management trial are shown as examples of the technique. The method can be completed in 4 d for a single specimen. It is emphasized that high quality binary images should be used for image measurement. The discipline of mathematical morphology is used to ensure this quality. This paper finishes with production of high quality digital images that provide graphic illustration of the nature of the pore structure in the vertical plane under the different tillage treatments.
Modeling the Transport of Chromium (VI) in Soil Columns
Authors: Selim H. M. , Amacher M. C. , Iskandar I. K.
Published: July 2010

Miscible displacement experiments were conducted to describe chromium [Cr(VI)] mobility and interactions in six different soils. For Calciorthid, Webster, and Norwood soils Cr breakthrough curves (BTCs) indicated that the interactions with the soil matrix were similar to those for a nonreactive solute where no or small retardation of the equilibrium type was observed. These observations are in support of earlier kinetic batch results where little retention was observed for a wide range of Cr concentrations in these (high pH) soils. The BTCs from Olivier, Cecil, and Windsor soils indicated high Cr retention capacity as indicated by increased retardation, low peak concentrations, irreversible sorption and extensive effluent tailing during desorption (leaching). A nonlinear retention/release model is proposed for the purpose of describing Cr(VI) reactions during transport in soils. The model is incorporated into the convection‐dispersion transport equation for reactive solute in uniform soils. The model was capable of providing a good description of the Cr BTCs for all soils where model parameters were obtained using a nonlinear least squares (best fit) parameter optimization scheme. The model grossly underestimated effluent concentrations for Olivier and Windsor BTCs when independently measured retention/release rate coefficients from the batch data sets were used. Model predictions overestimated the amount irreversibly retained by Cecil soil. Model predictions indicated that a unique set of independently measured rate coefficients was not capable of providing an adequate description of Cr BTCs for these soils.
Role of Fungi in Stabilizing Aggregates of Sewage Sludge Amended Soils
Authors: Kinsbursky R. S. , Levanon D. , Yaron B.
Published: July 2010

The effect of sludge amendment on the percentage of water‐stable aggregates (WSA) of five soils with different physical and chemical properties was studied in an incubation experiment. A 5% sludge addition to soil incubated at 25 °C increased the per cent of WSA after 30 d in all of the soils. Bactericides were added to soil‐sludge mixtures to assess the role of fungi in the aggregation process. Bactericide addition resulted in the suppression of bacterial growth and a concomitant proliferation of fungal hyphae. The WSA was highly correlated with water‐soluble carbohydrates in all of the soils, and with hyphal length in two loessial soils. This suggests that cementing by fungal carbohydrates is a relatively more important binding mechanism than physical entanglement by mycelium in WSA formation of sludge‐amended soils. By using a soil washing technique, it was determined that fungi involved in stabilizing aggregates were indigenous soil saprophytes which replaced the native sludge fungal flora.
Preferential Microbial Reduction of Hematite Over Goethite in a Brazilian Oxisol
Authors: Macedo J. , Bryant R. B.
Published: July 2010

Research was conducted to evaluate Fe transformations in a hydrosequence of Oxisols from the Central Plateau of Brazil. The best‐drained member of the hydrosequence of soils selected for the study classifies as an Anionic Acrustox (Dark‐Red Latosol) and has codominant hematitic and goethitic iron oxide mineralogy and reddish hues (2.5 YR). X‐ray diffraction and chemical extraction techniques were used to make detailed analyses of the iron oxides. Peak positions for hematite are coincident with those reported for hematite without foreign ion substitution. Peak positions for goethite are shifted toward a lower d‐spacing, which corresponds to 34 mole % of AlOOH substituting for FeOOH. Soil samples from the Bo horizon were subjected to reducing conditions in the laboratory over a range of time periods, using sucrose as a source of energy to speed up the activity of the soil microorganisms. The observed changes in soil mineralogies confirm the preferential reduction and removal of hematite over goethite. Mineralogies and soil colors after reduction treatments are comparable to that of the Anionic Acrustox (Red‐Yellow Latosol) found in the wetter section of the hydrosequence. The results of this study support the hypothesis that differences in color and iron oxide mineralogy of soils in this hydrosequence are the result of the preferential reduction of hematite over Al‐substituted goethite in the presence of a seasonally high water table.
Fragipan Bonding by Silica and Iron Oxides in a Soil from Northwestern Italy
Authors: Marsan F. Ajmone , Torrent J.
Published: July 2010

An Aquic Fragiudalf developed from a fluvial terrace of Pleistocene age in northwestern Italy was investigated to determine the possible role of different compounds in fragipan bonding. Fragipan characteristics appeared only in yellow, goethite‐containing zones of the fragipan horizon but not in gray, essentially Fe oxides‐free zones. Citrate‐bicarbonate‐dithionite (CBD), but not acid oxalate, extracted more Si in the yellow zones than in the gray zones. These data, and the fact that citrate‐bicarbonate (CB) without dithionite extracted very little Si demonstrate that CBD extracted a Si compound specifically associated with the Fe oxides (mostly goethite). In the fragipan the ratio CBD‐extractable Si goethite reached a profile maximum suggesting that the Si compound associated with the goethite particles could, if present in sufficient amount, cement goethite particles together thus providing a framework to mechanically hold other soil particles; alternatively, that compound could bind goethite with other soil mineral particles. Although the amounts of CBD‐extractable Si were low, a simple calculation showed that they were clearly in excess of those needed to saturate the theoretical sorption capacity of goethite, giving a surplus of Si able to promote bonding. Selective extraction methods provided no evidence for implication of Al in bonding. Consequently amorphous silica could be the bonding agent.
Forest Soil Uniformity Along Toposequences in the Loess‐Mantled Driftless Area of Wisconsin
Authors: Frolking Tod A.
Published: July 2010

Forest soils in the loess‐mantled ridge and ravine topography of the Driftless Area of southwest Wisconsin show minimal effects related to hillslope gradient. Twelve undisturbed Fayette silt loam profiles (Typic Hapludalf, fine silty, mixed, mesic) that developed in Peoria loess and silty colluvium on slopes of 2 to 55% were examined to ascertain systematic differences as a function of slope. Climate, vegetation, parent material, and time of development were similar for the 12 profiles. Physical and chemical properties of the A and E horizons (including texture, pH, dithionite extractable Fe and Mn, and total P) do not vary significantly as a function of slope gradient. Of the B and C horizon properties measured, only Bt horizon pH, clay accumulation, and total P distribution show statistically significant variations with slope gradient. The Bt horizon pH decreases with increasing slope gradient (r2 = 0.63). Illuvial horizons show less clay accumulation in profiles on steeper slopes (r2 = 0.37). Total P content is higher throughout the B and C horizons of profiles on steep slopes (45%) compared to soils on level and moderate slopes (2–20%). Together these results indicate slightly less leaching of the subsoil on steep slopes. Exchangeable Ca/Mg, Fed, Mnd, maximum clay, and depth to maximum clay reveal no trends as a function of slope gradient. Soil conditions have favored infiltration and minimized surface erosion, leading to nearly uniform soil development in homogeneous parent materials on ridgecrests and sideslopes.
Application of Regionalized Variable Theory to Large‐Plot Field Experiments
Authors: van Es H. M. , van Es C. L. , Cassel D. K.
Published: July 2010

Spatial soil heterogeneity poses problems on field experiments which use large treatment plots, as in tillage research. Recent studies have established that many soil properties do not vary in a random manner, but often exhibit spatial dependence. Presently available methods to account for spatial effects either do not fully address these problems or they are too complicated to be widely accepted. The purpose of this study was to develop an experimental design which was based on the principles of regionalized variable theory. Using incomplete blocks of size two, the method estimates treatment effects by means of short‐distance comparisons; this prevents inflation of the error term due to spatial soil variability and eliminates biases caused by variable distances between plots. The analysis of variance for the method is simple and well established. A Monte Carlo simulation study using uniformity trial data was performed to compare the proposed method with a randomized complete block design. The study revealed that the use of incomplete blocks reduces the average error mean square by 44%, and the average coefficient of variation by 25% compared to using complete blocks. The proposed method was, on the average, 21% more efficient then a complete block design.
Runoff, Soil, and Dissolved Nutrient Losses from No‐Till Soybean with Winter Cover Crops
Authors: Zhu J. C. , Gantzer C. J. , Anderson S. H. , Alberts E. E. , Beuselinck P. R.
Published: July 2010

Soils are more vulnerable to erosion following cropping to soybean (Glycine max [L.] Merr.) than corn (Zea mays L.). This has been attributed to lower dry matter production, less residue cover, and soil‐loosening action by soybean roots. To augment soil cover, common chickweed (Stellaria media L.), Canada bluegrass (Poa compressa L.), and downy brome (Bromus tectorum L.) were grown as winter cover crops with no‐till soybean on natural rainfall erosion plots located on a poorly drained Mexico claypan soil (Udollic Ochraqualf). No‐till soybean without a cover crop served as the check. Winter cover crops significantly increased soil cover by 30 to 50% during the critical erosion period of late spring to early summer. Compared to the check, mean annual soil losses from the chickweed, downy brome, and Canada bluegrass were decreased by 87, 95, and 96%, and runoff was reduced 44, 53, and 45%, respectively. Dissolved NH+4 concentration in runoff from cover crops was 1.61 to 3.72 times more, and dissolved PO3‐4 was 1.61 to 2.86 times more than that of the check. However, runoff from the check plots had 96 to 117% greater concentration of dissolved NO‐3 than cover crop plots. Mean annual dissolved nutrient losses were decreased 7 to 77% by using winter cover crops. Thus, winter cover crops were very effective in reducing soil erosion and dissolved nutrient losses from no‐till soybean.
Moisture and Nutrient Status of Extremely Acid Umbrepts in the Black Mountains of North Carolina
Authors: Richter D. D. , King K. S. , Witter J. A.
Published: July 2010

Moisture and nutrient conditions are poorly characterized in soils at elevations >1500 m in the southern Appalachian Mountains. In the Black Mountains, high elevation soils are Typic and Lithic Haplumbrepts, with umbric epipedons that are extremely acid, organic‐rich, rocky, and unstable due to the steep slopes. Many of the Umbrepts in the Black Mountains have been disturbed by exploitative logging, repeated wildfires, and depredation by the balsam woolly adelgid (Adelges piceae Ratzeburg), each of which has caused major fluctuations in C, nutrient, and hydrologic cycles of soils and ecosystems. The objective of this study was to evaluate predictions based on climate, forest disturbance, and soil genesis: that these soils are rarely subjected to low water potential, that soil N mineralization rates are currently high, and that availability of soil nutrient cations is low. A water balance model appropriate for soils with average water‐holding characteristics indicated that, on a 6‐yr recurrence interval, plants deplete soil moisture to <‐0.2 MPa during low rainfall periods of one‐month duration. High rock contents (about 0.40 m3/m3 of soil volume in 40‐cm depth) limit soil water storage capacity, and make the spruce‐fir forests very dependent on regular rainfall supplies. Soil N appears mineralizable at moderately high rates, as indicated by three soil and plant indices of N availability, whereas plant availability of Ca and Mg appears marginal. Exchangeable Ca and Mg total only 6.4 and 3.4 kmolc/ha, respectively, in the surface 40 cm of mineral soil, low contents that indicate rapid rates of biogeochemical cycling of divalent cations in these ecosystems. The long‐term recovery of these soils from 20th century disturbances depends directly on the dynamics of soil organic matter, due to organic matter's susceptibility to disturbance and to its control over soil moisture and nutrient availability.
Effect of Application Method and Dicyandiamide on Urea‐Nitrogen‐15 Recovery in Rice
Authors: Norman R.J. , Wells B.R. , Moldenhauer K.A.K.
Published: July 2010

Field studies were conducted on a Crowley silt loam (Typic Albaqualf) to investigate the influence of split applications, subsurface placement, and the nitrification inhibitor (DCD) dicyandiamide (cyanoguanidine) on the plant uptake of 15N‐labeled urea by dry‐seeded rice (Oryza sativa L. ‘Newbonnet’). Fertilizer N topdressed in three split applications (TD3SA) resulted in the highest rice grain yields and highest percent recovery of fertilizer N in the rice plant. Fertilizer N applied all preplant with DCD resulted in slightly less grain yield, but similar total dry matter yield, total N uptake and fertilizer N recovery in the soil‐plant system as the TD3SA method. Fertilizer N applied all preplant without DCD was inferior to the other treatments. Subsurface preplant incorporation (SSPPI) of N resulted in greater fertilizer N uptake by the rice plant compared to broadcast preplant incorporation (BCPPI); but, this did not translate into more total N utilized or grain produced. It appeared that DCD, by maintaining more of the fertilizer N as NH4‐N, caused less fertilizer N to be lost via denitrification after flooding and may have enabled more of the fertilizer N to participate in the mineralization‐immobilization turnover cycle and exchange for soil N. Overall, DCD increased the uptake and yield effectiveness of preplant N in dry‐seeded rice cultivation.
Extraction Procedure for Determining Solution and Exchangeable Ions on the Same Soil Sample
Authors: Phillips I. R. , Bond W. J.
Published: July 2010

A procedure is described which allows the ionic composition of the soil solution and exchange phases to be measured on the same small soil sample. This procedure is based on existing methods which use a dense, water‐immiscible liquid to displace soil solution during high speed centrifugation. Exchangeable ions are then extracted by shaking the soil with 1.0 mol L−1 ammonium acetate (pH 7), after which the soil is oven‐dried and the water content determined. The solution extracted from the soil sample accurately represents the ionic composition of the equilibrium soil solution and the procedure does not affect the ionic composition of the exchange phase.
Dispersion of Three Andic Soils by Ultrasonic Vibration
Authors: Hunter Craig R. , Busacca Alan J.
Published: July 2010

A probe‐type ultrasonic vibrator was used to disperse, without chemical pretreatments, samples of three soils developed from volcanic ash. The efficiency of dispersion by ultrasonic vibration was evaluated using curves of percent clay or sand vs. vibration time along with electron micrographs of sand (50–2000 µm), coarse silt (20–50 µm), and clay (<2 µm) size fractions. Ultrasonic vibration for 900 s at an energy of 39.9 W/cm2 was sufficient to disaggregate the soils without significantly damaging primary sand‐ and silt‐sized glass shards or destroying imogolite threads in the clay fraction.
Water Transport in Unsaturated Nonisothermal Salty Soil: I. Experimental Results
Authors: Nassar I. N. , Horton Robert
Published: July 2010

This paper presents observed soil moisture redistribution within unsaturated soil in response to imposed boundary temperatures. Both salinized and solute‐free soil conditions are studied. Two different uniform initial soil water contents and solute concentrations are used for the salinized soil columns. Likewise, two different uniform initial soil water contents are used for solute‐free soil columns. High and low boundary temperatures are similar for all of the soil columns. Thus, the experiments are designed to directly observe the impacts of thermal, soil matric, and osmotic gradients on redistribution of soil water. In all cases, appreciable amounts of water move in the direction of decreasing temperature within the soil columns. This is not a general rule of soil water movement, but a result of the uniform initial water content, the presence of solute, and the imposed boundary temperatures under salinized soil, or the initial water content and the imposed boundary temperatures under solute‐free soil. For both solute‐free and salinized soils, the net amount of transported water to achieve steady‐state conditions is greater for low initial water content than for high initial water content. Therefore, the steady‐state variations in the soil moisture content increased by decreasing the initial moisture content. When the same initial water content is used for both salinized and solute‐free soils, the net water transported to achieve steady‐state conditions is greater for the solute‐free soil than for salinized soil. These observations indicate clearly that solute concentration affects soil water transport with unsaturated, nonisothermal conditions.
On the Estimation of Cation Exchange Parameters from Column Displacement Experiments
Authors: Kool J. B. , Parker J. C. , Zelazny L. W.
Published: July 2010

A procedure is presented for estimating cation exchange capacity (CEC) and exchange selectivity coefficients from miscible displacement experiments on undisturbed soil columns. The procedure provides an alternative to batch experiments and is applicable to scenarios involving either binary homovalent exchange or binary monodivalent exchange. Gapon's exchange equation is used in the latter case. Parameters are determined by nonlinear, least‐squares inversion of column effluent concentration histories. The procedure requires that hydraulic flux and total solution normality be kept constant. It is also assumed that ion exchange takes place instantaneously. When this assumption is violated, it is still possible to obtain a good description of the observed data, but the parameter estimates may be meaningless. The feasibility of estimating the dispersion coefficient in the advection‐dispersion equation along with the ion exchange parameters is evaluated. Results indicate that this is generally not possible for continuous injection experiments, but much better results are obtained for pulse injection experiments.
A Compact Constant‐Head Permeameter for Measuring Saturated Hydraulic Conductivity of the Vadose Zone
Authors: Amoozegar A.
Published: July 2010

Most procedures for determination of saturated hydraulic conductivity (Ks) of the vadose zone are difficult to perform and time consuming. Recent developments have shown that Ks can be determined by the constant‐head well permeameter technique with a few liters of water in less than 30 min using small‐diameter auger holes. A compact constant‐head (CCH) permeameter is designed for maintaining a constant height of water (>5 cm) at the bottom of a 4‐ to 10‐cm‐diam. hole in the unsaturated zone, and measuring the amount of water flowing into the hole. The main unit of the CCH permeameter is used for measuring Ks from the soil surface to a depth of 2 m. To determine Ks below 2‐m depth a special flow‐measuring reservoir, equipped with a portable pressure transducer, is connected to the device and inserted to the bottom of the hole. The CCH permeameter has a water‐holding capacity of 5 L, can be used on any landscape position without an external support, and can be easily transported in the field. The device has been tested in the laboratory and field, and is capable of delivering a maximum flow rate of 3 × 10−6 m3 s−1.
Determining Soil Salinity from Soil and Soil‐Paste Electrical Conductivities: Sensitivity Analysis of Models
Authors: Rhoades J. D. , Waggoner B. L. , Shouse P. J. , Alves W. J.
Published: July 2010

Models and relations used to determine soil salinity (ECe) in the field from measurements of bulk soil electrical conductivity (ECa), or from saturated soil‐paste electrical conductivity (ECp), and estimates of other influential soil parameters were analyzed to evaluate the degree to which salinity appraisal is affected by inaccuracies made in the estimates. Results show that the values of the parameters which can not be easily measured in the field (i.e., bulk density (ρb), particle density (ρs), clay percentage (% clay), and total and “immobile” volumetric soil water contents (θw and θws, respectively) can be estimated sufficiently accurately for the purposes of practical soil salinity appraisal.
Mechanisms of Dissolved Organic Carbon Adsorption on Soil
Authors: Jardine P. M. , McCarthy J. F. , Weber N. L.
Published: July 2010

The subsurface transport of inorganic and organic contaminants may be strongly related to the movement of dissolved organic carbon (DOC) through a soil profile. A variety of soil chemical and hydrologic factors control the mobility of the DOC, which may enhance or impede the transport of the associated contaminants. In this study, the sources of DOC adsorption on two proposed waste‐site soils are defined, and the chemical mechanisms operative during the adsorption process are specified. Adsorption isotherms for the two soils determined at constant pH, ionic strength (I), and temperature indicated that DOC adsorption increased with increasing soil profile depth. Different adsorption capacities were exhibited by the two soils, however, which was related to their contrasting indigenous organic matter contents and mineralogies. The adsorption of DOC by the soils was not a function of solution I (I = 0.001 to 0.1 mol L−1 using NaCl); however, DOC adsorption was dependent on solution pH, with maximum adsorption occurring at ≃4.5. Competitive ion‐exchange studies using Na2SO4 as an ionic‐strength adjuster suggested that a portion of the DOC was electrostatically bound to the soil via anion exchange. By using thermodynamic principles, the predominant mechanism of DOC retention by the soil was found to be physical adsorption driven by favorable entropy changes. This is supported by preferential adsorption of the hydrophobic organic solutes to the soil relative to the hydrophilic organic solutes.
Direct Determination of Aluminum and its Cationic Fluoro‐Complexes by Ion Chromatography
Authors: Willett I. R.
Published: July 2010

An ion chromatographic method was developed for the direct determination of monomeric Al (Al3+, and hydroxo‐, sulfato‐, oxalato‐, and fluoro‐ complexes). Separations were made in one run in 4 min with a 50 mm low‐capacity cation exchange column, and detected by postcolumn reaction with pyrocatechol violet. Three peaks corresponding with mono‐, di‐ and trivalent species were obtained. The last peak also included the hydroxo‐Al and sulfato‐Al species. The AlF2+ species could be determined directly, but AlF+2 coeluted with the monovalent oxalato‐ species. Citrato‐Al species were not detected because of the inability of pyrocatechol to decouple the complex in the time frame of the analysis. Concentrations of Al down to 2 µM could be determined with 200 µL injections. The results for 21 Al‐F solutions closely matched those predicted from a chemical equilibrium program. The method was applied to extracts of 10 soils and it was found that Al3+, including hydroxo‐Al species, and AlF2+ were dominant. Limitations to the application of the method to soils included coelution of AlF+2 with monovalent organic species that are able to be decoupled by pyrocatechol, and blockage of the column end frits by solutions containing more than 200 mg L−1 of humic acid. The ion chromatographic method is the first to directly determine AlF2+ and other well‐defined forms of monomeric Al. It is rapid and can be fully automated.
Residual Effects of Nitrogen Fertilization and Winter Cover Cropping on Nitrogen Availability
Authors: McCracken Daniel V. , Corak Steven J. , Smith M. Scott , Frye Wilbur W. , Blevins Robert L.
Published: July 2010

Long‐term management practices affect the reserve of mineralizable soil N, and so can influence the amount of supplemental N fertilizer required in crop production. This study was conducted to (i) evaluate the residual effects of long‐term N fertilization and winter cover cropping on corn (Zea mays L.) N nutrition, and (ii) examine the ability of selected soil indices to detect management‐induced differences in soil N availability. In 1986, N fertilizer and winter cover crops were eliminated from plots which, from 1976 through 1985, had received varying tillage treatments, N fertilizer additions, and either hairy vetch (Vicia villosa Roth), rye (Secale cereale L.), or no winter cover crop. A history of N fertilization increased corn yield and N uptake (by an average of 20.4 kg N/ha). A history of winter cover cropping with hairy vetch increased corn yield and N uptake (by an average of 28.0 kg N/ha). Rye cover cropping generally had small or inconsistent effects relative to no cover crop. Tillage generally had insignificant effects on corn yield and N uptake. Soil N availability indices were determined on surface samples (0–15 cm) taken 2 wk after corn planting. The anaerobic incubation provided a poor index of N availability. Total soil C and Kjeldahl N were affected by tillage, though not by cover crop or fertilization history, and were marginally correlated with crop response. The autoclave index was only slightly superior to total soil C and Kjeldahl N as a N‐availability index. The soil NO3‐N concentration was highly correlated with corn yield, and N uptake. Though this study was conducted for 1 yr at one site, results indicate that measurement of surface soil NO3‐N made shortly after corn planting can provide a valid index of the effects of past crop and soil management practices on soil N availability to corn.
Variability of the Cecil Map Unit in Appomattox County, Virginia
Authors: Thomas P. J. , Baker J. C. , Simpson T. W.
Published: July 2010

A study was initiated in Appomattox County in the southern Piedmont of Virginia to assess composition and variability of a Typic Kanhapludult map unit. Five delineations of the Cecil (clayey, kaolinitic, thermic Typic Kanhapludults) map unit, three to eight sites within each delineation, and three profiles within each site were randomly located in a two‐level nested sampling scheme. Soil physical, chemical, and morphological data were collected from the Ap, Bt, and BC horizons of each profile. Fifty‐eight percent of the 81 profiles met the criteria for the Cecil soil series. Seventy‐one percent of the profiles were taxonomically similar to Cecil. The remaining 29% were taxonomically dissimilar inclusions. Thus, the map unit name would be Cecil and the map unit description would include dissimilar soils. Taxonomic variability was reflected in variability of taxonomically important soil properties. Percent base saturation decreased with depth in the profile. Maximum clay distribution occurred in the Bt horizon and ranged from 25 to 75%. The solum exhibited large variation in thickness. Subsoil properties important to mapping (percent base saturation in the chemical control section, clay percentage in the particle‐size control section, and solum thickness) exhibited considerable variation within delineations but the variability was consistent from delineation to delineation. Intrusions of mafic material into the felsic crystalline system, from which Cecil and similar soils form, accounted for most of the variability in the soil properties.
Long‐Term Effects of No‐Tillage, Crop Residue, and Nitrogen Application on Properties of a Vertisol
Authors: Dalal R. C.
Published: July 2010

There is a paucity of information on the long‐term effects of crop residue management under no‐tillage culture on properties of clay soils in tropical and subtropical regions. The objective of this study was to compare the effects of 13 yr of conventional tillage vs. notillage, crop residue retained vs. burned, and no fertilizer N vs. application of 23 and 69 kg N ha−1 yr−1 on organic C content, total N, mineralizable N, pH, electrical conductivity, chloride, exchangeable sodium percentage (ESP), and aggregation index (undispersed fraction <20 µm silt + clay) in a fine‐textured Vertisol (650 g clay kg−1 soil). Highest concentrations of organic C and total N were found in the surface soil (0–0.1 m) with a combination of no‐tillage, crop residue retained, and fertilizer N. Mineralizable N followed similar trends. Soil pH to 0.3‐m depth and electrical conductivity to 1.2‐m depth were significantly lower under no‐tillage than under conventional tillage. Aggregation index of the surface soil (0–0.1 m), was higher under no‐tillage. The ESP was lowest in the surface soil (0–0.04 m) under no‐tillage with crop residues retained; the soil profile (0–1.2 m) under this treatment also contained far less NaCl‐equivalent salts (0.8 Mg ha−1) than under conventional tillage with crop residue burned (7.3 Mg ha−1). Available water and nitrate were lower in the surface soil but greater at depths (0.6–1.2 m) under no‐tillage than in tilled soil. Thus tillage and crop residue management can substantially affect soil organic matter and microbial activity in the surface layers, and water relations and salt movement to at least 1.2‐m depth, even in a fine‐textured Vertisol.
Effects of a Conditioner on Soil Physical Properties
Authors: Fitch Bryan C. , Chong S. K. , Arosemena J. , Theseira G. W.
Published: July 2010

Agri‐SC, a soil conditioner manufactured by Four Star Agricultural Services, Inc., Bluffton, IN, was applied to a fallow Stoy silt loam (fine‐silty, mixed, mesic Aquic Hapludalf) at rates of 0, 0.15, 0.30, and 0.60 L/ha for two successive years. After application, the following soil parameters were measured: organic matter content, mean aggregate diameter, porosity, 48‐h aeration porosity, sorptivity, saturated hydraulic conductivity, liquid limit, plastic limit, in situ infiltration and drainage rates, and soil water retention (up to 240 cm of suction). None of the soil properties differed significantly among treatments, but all decreased significantly the second year, except liquid limit. The detrimental effects to soil physical, hydrological, and rheological properties could be caused by the decreases in organic matter.
Predicting Douglas Fir Growth and Response to Nitrogen Fertilization in Western Oregon
Authors: Miller R. E. , McNabb D. H. , Hazard J.
Published: July 2010

The accurate prediction of which Douglas fir [Pseudotsuga menziesii (Mirb.) Franco] stands may or may not respond to N fertilization should improve the economics of the practice. Our objective was to determine the efficacy of various stand (site index, age, and relative density), climatic (total precipitation, average daily solar radiation), site (elevation, soil depth, and available water‐holding capacity), and soil‐test variables (anaerobically mineralized N, total N, organic matter, and C/N ratio) to predict relative and absolute response to a single application of 224 kg N ha−1 as urea. The core equation with stand variables accounted for 70% of residual variation in average annual volume growth. Predicting response of fertilized stands proved much less precise. The best core equation explained 37% of the residual variation for average percentage response in volume growth and explained less variation in absolute response in both volume and basal area. Of the site, climatic, and soil‐test variables, C/N ratio in the surface soil was the only one that significantly increased precision of the core equations. The best combined equation explained 46% of the variation in percent volume response. The anaerobic N mineralization test failed to make a significant contribution to the core equation and had a lower correlation with response than did the C/N ratio. Stand variables remain the most reliable predictors of fertilizer response in this region; any improvement from including soil data for N or organic matter is not justified because of their additional cost.
Burley Tobacco Response to Band Applications of N‐P‐K Fertilizer
Authors: Sims J. L. , Wells K. L. , Calvert J. R. , Schwamberger E. C. , Greer E. C.
Published: July 2010

Improved fertilizer management systems for hurley tobacco (Nicotiana tabacum L.) are needed to reduce the detrimental effects of large applications of fertilizer, such as fertilizer‐induced soil acidity and Mn toxicity. Field studies were conducted at several locations in Kentucky during 1980 to 1986 to examine the response of tobacco to rates and methods (band vs. broadcast) of application of N‐P‐K fertilizer. Response to banding N‐P‐K fertilizer varied widely among experimental sites and was related to level of NH4OAC‐extractable soil K. At low soil K levels, greater dry matter and cured leaf yields occurred most often for broadcast compared with banded fertilizer. These effects probably resulted from factors affecting the efficient use of K by the plant, including the greater numbers of roots in contact with fertilizer in broadcast treatments. At high soil‐test K levels, greater growth and yield occurred more often from band treatments (as opposed to broadcast). This probably resulted from a reduction in toxic Mn levels and fertilizer salt injury, and from a more favorable balance between K and other nutrients in band treatments. A linear regression revealed that yields from band and broadcast treatments were equal when initial soil‐test K measured 248 kg ha−1. In soils testing high in P and K, the content of plant Mn increased linearly with rate of N‐P‐K fertilizer in broadcast treatments, whereas it was unaffected by fertilizer rate when the fertilizer was banded.
Apparatus for Sampling and Controlling Gas Composition in Redox‐Controlled Soil Slurry
Authors: Guenzi W. D. , Hutchinson G. L. , Beard W. E.
Published: July 2010

Study of the production or consumption in soil of gaseous N compounds at near ambient concentrations requires unique apparatus and procedures. We used a soil slurry that is continuously flushed by a gas stream with controlled composition. Basic components of the system include a reaction chamber equipped to monitor and control slurry pH, Eh, and temperature, flow controllers for precise control of gas flow rates, a mixing chamber for blending inlet gases from different sources, a low‐volume manifold for collecting contamination‐free samples of inlet and exit gases, a dryer to selectively remove water vapor from the exit gases, and a large‐volume sample loop for collecting enough sample gas for NO analysis. The Eh control was accomplished using automated three‐way solenoid valves to select either O2 or an equal flow of inert gas to mix with the gas stream flushing the reaction chamber. Although the gas sampling and gas handling apparatus and procedures described here were designed for an Eh‐controlled soil slurry, we believe they could be easily adapted to other experimental systems that require trace gas sampling and control without contamination from ambient air.
Estimation of Statistical Moments of Spatial Field Averages for Soil Properties and Crop Yields
Authors: Bresler Eshel
Published: July 2010

Crop yield variability often results from spatial variability of soil properties. The quantities of practical interest are the spatial averages of these properties over the entire field domain. In this study, correlation scales and the conditional and unconditional first two moments of field averages were estimated, by the maximum likelihood (ML) and Conditional Multi‐Variate Normal methods and numerical approach, for four soil properties, two soil variables, and two crop‐yield components of three field crops. The results show the significant contribution of the conditional approach in reducing the variances of the spatial average yield and soil properties by about an order of magnitude. It is also observed that the estimated conditional expectations of the spatial averages are practically identical to the unconditional one, although the maps of the conditional expectation over the field differ from the maps of the unconditional one. The integral scales of crop yields were found to be roughly estimated from the integral scales of the related soil properties. The use of conditional probability as a practical tool for reducing prediction uncertainty and the potential of conditional analysis to help make practical decisions are demonstrated. The principal practical conclusion is that, although unconditional analysis may be much simpler than the conditional approach, the latter may be more advantageous.
Manganese‐Phosphate Solubility Relationships in an Acid Soil
Authors: Schwab A. P.
Published: July 2010

The chemistry of Mn and P is often complicated by apparent undersaturation with respect to mineral phases. The role of Mn phosphates in controlling the solubility of Mn and PO4 was studied in acid soils which had been fertilized annually for 40 yr with NH4NO3 and superphosphate. Soil pH ranged from 4.1 to 6.8 and available P varied greatly. Fresh, field‐moist soil samples were equilibrated with 0.01 M CaCl2 for 25 d and then analyzed for Mn and PO4 activities. A method was developed to measure redox potential reliably with a Pt electrode to allow calculation of Mn3+ activities. In previous studies, activities of PO4 in these soils were less than the solubilities of strengite (FePO4) and variscite (AlPO4), and Mn activities were less than Mn oxide solubilities. The measured activities of Mn3+ and PO3‐4 were consistent with the presence of MnPO4·1.5H2O but were undersaturated with respect to Mn(II) phosphates.