bluuebunny/crossref_metadata_2025_split huggingface dataset:
Water Extraction by Single Plant Roots
Authors: Hainsworth J. M. , Aylmore L. A. G. 
Published: July 2010

AbstractApplication of computer assisted tomography to x‐ray attenuation measurements has been used to study the drawdowns in soil‐water content associated with single plant roots. Drawdowns have been measured at different depths along radish (Raphanus sativus cv long scarlet) roots growing in soil at two different initial water contents while the plants were subjected to either a high or low transpirational demand. This novel approach has provided the most detailed observations of this type yet obtained, particularly by a nondestructive technique. Soil resistance to water flow is clearly of significance even at the high soil‐water potentials used since it has been observed to markedly influence water uptake. Comparisons between these experimentally determined drawdowns and those predicted by an analytical approach indicate that this model does not adequately describe the extraction process. In particular, the assumption that a plant root acts as a uniform absorbing cylinder along its length is clearly erroneous. While a numerical model gives a closer fit to the experimental data, it is clear that improvements in the physical concepts on which this is based are necessary to accurately describe the position and shape of the drawdowns.
Solution Aluminum Anomalies Resulting from Various Filtering Materials
Authors: Jardine P. M. , Zelazny L. W. , Evans A. 
Published: July 2010

AbstractCommercially available filter papers and membranes of varying composition were examined for their effect on solution Al. This investigation was conducted in order to assess the impact of filter materials on environmental water samples and solubility studies. Many of the filter materials in equilibrium with unneutralized and partially neutralized AlCl3 removed a significant portion of Al from solution (0‐87% of added Al). The loss of solution Al resulted from the negative charge and/or residual anion content of the filter material. Filter discs that resulted in large losses of solution Al generally had high levels of F‐, PO3‐4, and/or SO2‐4 and had an appreciable cation exchange capacity. Removal of residual salts from uncharged membrane filters essentially eliminated any loss of Al from solution. Potentiometric titration analyses of the equilibrium Al solutions indicated marked titration curve distortions for several filter materials, which was related to their residual contaminants.
Effect of Corn, Sugarbeets, and Fallow on Zinc Availability to Subsequent Crops
Authors: Leggett G. E. , Westermann D. T. 
Published: July 2010

AbstractField observations indicated that Zn deficiency of beans (Phaseolus vulgaris L.) was sometimes more severe than expected when grown on fallowed soil that was low to marginal in available Zn. The objectives of this study were to determine the effects of fallow, sugarbeets (Beta vulgaris L.), and corn (Zea mays L.) on Zn availability to subsequent crops grown on a Portneuf silt loam (Durixerollic Calciorthids, coarse silty, mixed, mesic). The sugarbeet and corn plant tops and sugarbeet roots were removed, and 11.2 kg Zn ha−1 was applied on one‐half of each plot before fall plowing 25‐cm deep. Beans, sweet corn, or potatoes (Solanum tuberosum L.) were planted the following spring. Whole plant samples of beans and sweet corn and potato stems, leaflets, and petioles were sampled for chemical analyses during the growing season. All bean plants were Zn deficient when grown after fallow or sugarbeets but not after corn or where Zn fertilized. Potatoes and sweet corn did not show any Zn deficiency symptoms or any growth responses to Zn fertilization. The average zinc concentration in beans (vegetative development stage, V3) following corn was 20.5 mg kg−1 compared with 12.5 mg kg−1 following fallow or sugarbeets without Zn fertilization. The average Zn uptake by beans (V3) following corn was 1.3 g ha−1 compared with 0.6 g ha−1 after fallow or sugarbeets without Zn fertilization. The Zn uptake after corn was even greater than where 11.2 kg Zn ha−1 was applied to fallow or sugarbeets (1.3 vs. 0.9 g Zn ha−1). Enhanced Zn availability following corn persisted throughout the growing season and into a second bean crop, although at a decreased level. Similar trends occurred with potatoes and sweet corn. Soil DTPA‐extractable Zn was not significantly different after fallow, sugarbeets, or corn. These results indicate that Zn deficiency in sensitive crops may be alleviated or prevented depending upon the preceding crop grown, and that factors not measured by DTPA can significantly influence Zn availability.
Use of Rayleigh Scatter for Determining X‐ray Mass Absorption Coefficients
Authors: Beavers A. H. , Olson Ken R. 
Published: July 2010

AbstractX‐rays impinging upon matter are both scattered and absorbed. As the mass absorption coefficient (µM) of the soil sample increases more x‐rays are absorbed and less are scattered. X‐ray absorption is directly related to the atomic number of the element present and the scatter is inversely related to the atomic number of the elements making up the sample. Since some x‐ray tubes, such as W, have severe limitations using the Lα Compton scatter for determining (µM), we have found that the Rayleigh (unmodified) x‐ray scatter is as precise as the Compton scatter (MoKα) and has many advantages. Any x‐ray tube can be used and the Rayleigh scatter is linear with respect to (µM) over a range of two theta settings, making possible the determination of both µM and the true background from one measurement. X‐ray mass absorption coefficient µM can be used to characterize the homogeneity and changes of soil with depth. Each soil studied had a characteristic line expressing the relationship between mass absorption coefficient and soil depth. The maximum value of µM appeared to reflect the maximum of soil mass including weathering productions such as clay, Fe, and bases. For all soils, the maximum value of µM appeared to be one or two subhorizons below the maximum clay and cation exchange capacity values. The subsoil tends to have a higher capacity to absorb x‐rays than either the topsoil or parent material.
A Method to Verify the Presence of a Trend in Studying Spatial Variability of Soil Temperature
Authors: Davidoff B. , Lewis J. W. , Selim H. M. 
Published: July 2010

AbstractA method for estimating the drift function and assessing the significance of possible trends in spatial observations was developed. This method takes as many data points as possible within each lag distance, is less sensitive to “outliers,” and nearly all observations obtained by it have their contribution in calculating the drift function. Our method, as well as the “cancellation method,” were examined on temperature data collected at a depth of 0.05 m at 0.68‐m intervals along an 80‐m long transect. Tests based on the cancellation method falsely indicated the presence of a significant trend in the temperature data. No trend was indicated by our method, which has more statistical validity than the cancellation method. The decision to detrend or not has a marked impact on the interpretation of the data as attested to by the semivariograms and autocorrelograms of the original and detrended data. Detrending of the data resulted in a loss of information about the spatial dependence of temperature observations.
Boron Adsorption on California Soils
Authors: Goldberg Sabine , Glaubig R. A. 
Published: July 2010

AbstractBoron adsorption on 15 arid zone soil samples was investigated both as a function of equilibrium B concentration (0–100 g m−3) and as a function of solution pH (5.5–11.5). Boron adsorption as a function of equilibrium B concentration could be described by the Freundlich adsorption isotherm over the entire concentration range studied and by the Langmuir adsorption isotherm over a limited concentration range. Boron adsorption increased from pH 5.5 to 8.5, exhibited a peak in the pH range 8.5 to 10, and decreased from pH 10 to 11.5. The adsorption maximum was highly correlated with both specific surface area and clay content. It was assumed that B adsorbs by ligand exchange with hydroxyl groups at the edges of clay particles and Al and Fe oxide minerals. The constant capacitance model was able to describe B adsorption on the soil samples. While the fit was generally good, the chemical significance of one of the surface complexation constants is uncertain for a few soil samples. An average set of surface complexation constants could be used to predict B adsorption on most of the soil samples studied.
Role of Soil Organic Matter in the Effect of Acid Rain on Nitrogen Mineralization
Authors: Stroo Hans F. , Alexander Martin 
Published: July 2010

AbstractThe effect of soil organic matter on the influence of acid rain on microbial processes was studied in columns containing samples from the O horizons of two forest soils and mixtures of those horizons with sand. Simulated acid rain at pH 3.5 reduced the percentage of inorganic N present as NO‐3 when the organic matter level was below about 0.1 g/g soil, and the percentage decreased with decreasing organic matter levels. The effects of acid rain on N mineralization and NO‐3 formation in Adams (Typic Haplorthods) soil were similar. Nitrogen mineralization was increased in Croghan (Aquic Haplorthods) soil by simulated acid rain when the organic matter content was high, and the degree of stimulation decreased with lower organic matter levels. Dissolved organic C levels were initially decreased by treatment with simulated acid rain in all soil mixtures, but the amounts in soil solutions from acid rain‐treated soils recovered with time to similar or greater levels than in the control soils. The recovery was more rapid in Croghan than Adams soil. Increasing organic matter contents in soil mixtures also decreased the magnitude and duration of acid rain‐induced changes in pH of soil solution and levels of dissolved organic C.
Effects of Land Clearing and Subsequent Management on Soil Physical Properties
Authors: Alegre J. C. , Cassel D. K. , Bandy D. E. 
Published: July 2010

AbstractLarge scale, mechanized land clearing is common in the humid tropics even though little attention has been given to defining and solving soil problems that may be created. The purpose of this study was to evaluate various combinations of land clearing method, burning of vegetation, post clearing tillage, and soil management on soil physical properties of a forested Ultisol in the Amazon basin. Land clearing methods used were (i) slash, (ii) bulldozer clearing with a straight blade, and (iii) bulldozer clearing with a shear blade. Specific effects associated with clearing were mechanization, bulldozer blade type, burning, disking, and chiseling. Post clearing soil management systems isolated effects of bedding, liming, and fertilization. Soil physical properties were measured before clearing and 14, 29, and 98 weeks after clearing. Compaction increased bulk density (ρb) of the 0‐ to 15‐cm depth for all clearing methods, but ρb of the 15‐ to 25‐ depth increased by 0.1 Mg m−3 only for the bulldozer cleared treatments. Soil texture of the 0‐ to 15‐cm depth was not altered by land clearing. Gravimetric water content at soil matric potentials < −2 kPa was greatest for the straight blade cleared soil. The infiltration rate 14 weeks after clearing decreased 37, 96, and 90% for soil cleared by slash, straight blade, and shear blade, respectively, as compared to initial conditions. Chisel plowing and disking the newly cleared land increased the infiltration rate compared with straight blade without chiseling. Detrimental changes in soil physical properties caused by clearing were minimized when post clearing management practices of bedding, fertilization, and liming were adopted.
Concurrent Sorption of Phosphate and Zinc, Cadmium, or Calcium by a Hydrous Ferric Oxide
Authors: Kuo S. 
Published: July 2010

AbstractConcurrent sorption of phosphate and Zn, Cd, or Ca by a hydrous Fe oxide sample was investigated by enclosing sparingly‐soluble Zn‐phosphate, Cd‐phosphate, or Ca‐phosphate in dialysis tubings and equilibrating with the oxide up to 2 yr in 0.1 mol L−1 NaNO3 solution at room temperature (296 ± 2 K). The ability of the oxide to concurrently sorb phosphate and Zn, Cd, or Ca was evident from their amounts present in the oxide, as well as from x‐ray analysis and microprobe mapping of the elements sorbed on Fe‐oxide particles. The selectivity of the oxide for the metals increased int he order Ca < Cd < Zn, and was apparently not affected by the absolute amounts of phosphate sorbed. No obvious complementary effect of metal sorption on phosphate sorption, or vice versa, was observed. Aging the oxide up to 1 or 2 yr in the presence of metal and phosphate adversely affected only the sorption of Ca but not the sorption of Zn, Cd, or phosphate. Therefore, it is likely that the affinity determines whether or not a sorbate, once sorbed, can be excluded from the oxide undergoing aging or changes in its crystallinity. Two simplified equations were tested for their ability to fit the sorption of the metals and phosphate by the oxide, with sorbate concentration, pH, and available sites as dependent variables. The good fit of Zn, Cd, and phosphate sorption data to the equations suggests that phosphate and the metal are being sorbed on specific sites.
The Effect of Adsorption on Sulfate Leaching
Authors: Bolan N. S. , Scotter D. R. , Syers J. K. , Tillman R. W. 
Published: July 2010

AbstractMovement of sulfate (S) through repacked columns of soil with high and low S adsorption capacity was studied in the laboratory. Differences in movement could be explained by the shape of adsorption isotherms which were determined from batch‐type experiments. 35S was found to be a suitable tracer to study the movement of applied 35S. For step‐function changes between 0, 3.12, and 6.24 mol m−3 in the concentration of the applied S solution, different breakthrough curves (BTC) were found for the rising and falling limbs. Also the higher the concentration of S in the applied solution, the earlier the added S appeared in the effluent. The BTC obtained agreed well with those calculated from numerical solution of the dispersion‐convection equation, assuming a Freundlich adsorption isotherm and instantaneous reversible adsorption. However, after leaching of a pulse of S added to the surface soil, the observed S distributions in soil columns were not well described by theory. The discrepancies were largest when the soil containing the added pulse of S was incubated prior to leaching. Possible reasons for this lack of agreement are discussed.
Alteration of Sulfur‐34 Natural Abundance in Soil by Application of Feedlot Manure
Authors: Chae Yeh Moon , Krouse H. Roy 
Published: July 2010

AbstractThe 34S/32S abundance ratios (δ34S) of four forms of S present in cattle feedlot manure and at various depths in profiles of a soil receiving different rates of manure were determined. Whereas the δ34S values for all S forms in manure were similar (−2.8–3.6) they differed markedly among different forms of soil S (+1.6 for Raney Nireducible S to +6.2 for HI‐reducible S). Effects of manure applications on the isotopic composition of S were observed for most S forms only at the soil surface or in shallower horizons. In contrast, the δ34S values and concentrations of C‐bonded S indicated penetration of manure S down to or near the water table, particularly in the profile which had received a high rate of manure application. The NO‐3‐‐N distribution in the soil profiles showed that manure NO‐3‐‐N had also moved down below the water table. Therefore, it is concluded that C‐bonded S is the best form for tracing the down‐ward movement in soils of S‐bearing compounds in manure.
Calcium Carbonate Supersaturation in Soil Solutions of Calciaquolls
Authors: Inskeep William P. , Bloom Paul R. 
Published: July 2010

AbstractWe found that soil solutions of Calciaquolls in western Minnesota were up to 40‐fold oversaturated with respect to pure calcite. Selective dissolution of soil calcites and x‐ray diffraction showed that the Mg content of these calcites ranged from 1 to 10 mole % MgCO3. This amount of Mg substitution cannot explain the degree of oversaturation observed in the soil solutions. X‐ray peak broadening and scanning electron microscopy (SEM) was used to determine the size and shape of soil calcites. The mean size of soil calcite crystallites was approximately 0.04 to 0.09 µm. Surface energy relationships predict that soil calcites of this size would have solubility products (−log Ksp) near 8.3, not low enough to explain the observed supersaturation. Energy dispersive analysis of x‐rays (EDAX) and SEM observations of these samples showed that the larger soil calcites (0.5–20 µm) were irregularly shaped and did not exist as independent crystals, and were associated with other aluminosilicate solid phases. Soil suspensions of Calciaquolls prepared at 10‐fold oversaturation remained oversaturated for 40 d. Adding pure calcite seeds to soil suspensions and soil solution supernatants induced some precipitation, but the solutions remained oversaturated, attaining CaCO3 ion activity products (−long IAP) ranging from 7.6 to 7.9. These results suggest that the metastable condition of supersaturation is a result of inhibition of the calcite precipitation process by water‐soluble organic components, which are adsorbed and block potential crystal growth sites.
Agronomic Effectiveness of Bayovar Phosphate Rock in Soil with Induced Phosphorus Retention
Authors: Hammond L. L. , Chien S. H. , Easterwood G. W. 
Published: July 2010

AbstractA greenhouse experiment was conducted with soil from the A horizon of an acid Mountview silt loam (Typic Paleudult) to measure the relative influence of soil P retention capacity on P availability from Bayovar (also known as Sechura) phosphate rock (Peru) with that from triple superphosphate (TSP). The P retention capacity of the soil was adjusted by application of variable quantities of freshly prepared amorphous Fe gel. The P sources were incorporated into the treated soil at rates to supply 0, 150, and 300 mg total P kg−1 soil. Corn (Zea mays L.) was grown as a test crop. The Fe gel treatments significantly increased the P retention capacity of the soil and resulted in significant reductions of both dry matter production and P uptake with both P sources. The effectiveness of the phosphate rock, however, tended to decline to a greater extent than that of TSP with increasing P retention capacity. These results suggest that, contrary to popular opinion, the effectiveness of phosphate rock relative to soluble P fertilizer may be less on soils with high P retention capacity than on soils with the same pH but with lower P retention capacity for short‐term crops such as corn.
Distribution of Applied Anhydrous Ammonia in Soils and Germination Hazard to Winter Wheat
Authors: Jacobson J. S. , Westerman R. L. , Claypool P. L. 
Published: July 2010

AbstractCurrent changes in residue management systems for winter wheat (Triticum aestivum L.) include anhydrous NH3 injection combined with herbicide application, planting, and other field operations. The feasibility of NH3 application during planting is dependent upon potential NH3 toxicity to germinating seeds. A laboratory experiment was conducted to study anhydrous NH3 movement in soils by injecting 124 and 180 mg N as NH3 into a Hollister clay (fine, mixed, thermic Pachic Paleustolls), Grant silt loam (fine‐silty, mixed, thermic Udic Argiustolls), and Norge clay loam (fine‐silty, mixed, thermic Udic Paleustolls) at 0.124 and 0.181 water (kg kg−1) contents. Soil samples were taken 1, 7, and 14 d after N application. Soil NH+4‐N and calculated NH3(aq) concentrations following NH3 injection generated a normal distribution curve with N concentrations highest near the injection point and decreasing with increasing distance. Calculated NH+4 diffusion coefficients decreased with time and water content and were soil dependent. Field studies were conducted in 1983 to determine the potential germination hazard from NH3 applied at 0, 56, 112, 168, 224, and 280 kg N ha−1 while planting, and in 1984 to winter wheat planted 0, 1, 3, 5, 6, and 7 d after applications of 0, 100, and 200 kg N ha−1. Stand counts, forage NO‐3‐N concentration, and yield were not influenced by NH3 applications during planting in 1983, but grain N concentration increased linearly up to 24.1 mg g−1 with 280 kg N ha−1. In the 1984 experiment, increasing NH3 rates did not decrease seedling stand, even though analysis of soil samples reflected increased soil pH and soil NH+4‐N concentration. Anhydrous NH3 placement at a sufficient distance from newly seeded rows will ensure the success of systems which include NH3 injection in conjunction with other field operations in residue management systems.
Experimental Evaluation of Two Operational Standard States for Montmorillonite in Metastable Hydrolysis Reactions
Authors: Peryea F. J. , Kittrick J. A. 
Published: July 2010

AbstractTwo conventions have been used to represent smectite formulas in mineral hydrolysis reactions: exchangeable cations are either included in (monophase structure) or excluded from (charged structure) the Standard State phase designation. Replicate mixtures of K‐saturated Belle Fourche montmorillonite, kaolinite, goethite, and magnesite were taken through a series of consecutive equilibrations with 0.01, 0.1 or 1.0 M KCl solutions using low solution/solid ratios. Apparent chemical equilibrium with respect to magnesite was used as an indication of system‐wide meta‐equilibrium. Following equilibration, the aqueous phases were recovered by immiscible displacement. Total soluble K, Mg, Si, pH, and ambient CO2 were measured. The solutions were chemically speciated using an ionassociation computer model. Hydrolysis reactions were developed based on the two smectite standard state phase designations. Reaction equilibrium constants and Gibbs free energies of formation (ΔG°) for montmorillonite were calculated. In the case of the monophase structure model, these parameters were functions of exchangeable cation composition. The mean ΔG° (montmorillonite) values for the charged structure and monophase structure models differed in absolute value but were equally precise. These results suggested that a characteristic metastable equilibrium was obtained in the experimental system. Justification for the selection of one convention over the other must be based on criteria other than precision.
Prediction of pH Errors in Soil‐water Extractors Due to Degassing
Authors: Suarez D. L. 
Published: July 2010

AbstractMoisture samples taken from the unsaturated zone with soil water extractors undergo degassing and an upward shift in pH. The measured pH values from commercially available extractors are usually sufficiently in error that they cannot be used in a quantitative manner. A model has been developed that predicts the extent of CO2 degassing and the resulting pH error. Using this model measured pH values can be corrected back to in situ soil water pH provided that precipitation has not occurred in the extractor. Extractors are classified into two groups—single chamber and multichambered. The extractors are evaluated for both operation under constant vacuum (open to the source) and decreasing vacuum (evacuated and then sealed). Analysis of the data and model predictions indicates that the major factor controlling the pH error is the ratio of liquid volume to total extractor volume. Additional factors exerting major influence are the initial extractor gas composition and the total pressure in the extractor when sampled. Variations in soil solution composition and differences in soil CO2 concentrations in carbonate buffered systems had a major effect on pH values but a negligible effect on the extractor induced pH error. Under typical field conditions the multichambered extractor is predicted to give the most satisfactory results; the pH errors were sufficiently small that no corrections for degassing were necessary.