bluuebunny/crossref_metadata_2025_split huggingface dataset:
Herbicide Treatment Effects on Properties of Mountain Big Sagebrush Soils after Fourteen Years
Authors: Burke I. C. , Reiners W. A. , Sturges D. L. , Matson P. A. 
Published: July 2010

AbstractSoil properties under stands of vegetation dominated by mountain big sagebrush (Artemisia tridentata ssp. vaseyana) and grass were examined 14 yr after spraying with 2,4‐dichlorophenoxy acetic acid (2,4‐D) to control sagebrush. Changes in only a few soil chemical properties were found after conversion to grassland. Phosphorus and K were apparently redistributed from depth to the surface 5 cm of soil by grass‐dominated vegetation. Conversely, surface concentrations of N were lower under grass vegetation than under undisturbed vegetation. No changes attributable to vegetation conversion were found for total C, Na, Mg, cation exchange capacity, base saturation, pH, bulk density, or potential net N mineralization rates at any depth. In situ net N mineralization rates at a 5‐ to 15‐cm depth were measured under and between shrubs for both vegetation conditions 15 yr after spraying. Nitrogen mineralization was similar from positions between and under former shrubs in converted (grass) vegetation, whereas in the sagebrush vegetation, mineralization rates were higher under live sagebrush plants than in interspaces between plants. Undershrub net N mineralization rates were higher under shrubs in the sagebrush vegetation than under former shrubs in the grass vegetation. Essentially, control of big sagebrush, in the absence of grazing, had no effect on site fertility. The spatial distributions of the elements and of their cycling, however, have been altered.
Improved Method for Separating Light‐ and Heavy‐Fraction Organic Material from Soil
Authors: Strickland T. C. , Sollins P. 
Published: July 2010

AbstractAn improved method is presented for separating whole soil into a mineral‐free organic fraction (light fraction) and an organomineral fraction (heavy fraction) by flotation in a dense inorganic salt solution. In the existing method, the heavy fraction is settled by centrifugation and the light fraction decanted. In the improved method, the light fraction is aspirated from the solution surface by suction after the soil suspension is allowed to settle. The improved method costs less, is more reproducible, and is practical in coarse‐textured soils where heavy fractions do not form stable pellets during centrifugation.
Soils, Soil Scientists, and Civilization
Authors: McCracken Ralph J. 
Published: July 2010

AbstractSeveral past civilizations have suffered and gone into eclipse or extinction due in greater part to lack of stewardship and/or knowledge of their soil resources. Since the middle of the 19th century, U.S. soil scientists have provided major findings, technological advances, and intellectual leadership for the development of a highly productive agriculture sector that has contributed to a vigorous, dynamic civilization. Our present civilization is being threatened by locally excessive soil erosion and other degradation of our natural resources, currently aggravated by rural economic problems. However, recent and current famines appear to be more closely related to economic and political factors than to deficiencies in soil resources. The quantity and quality of our global soil resources seem capable of supporting our civilization at least well into the 21st century, but local areas of hunger will continue due to local and regional economic conditions and various forms of political disruptions and repressions. Humans now have the capability of degrading and polluting soil, water, and air resources on a global scale—much too quickly. But technologies for monitoring and controlling these degradations and for increasing our productivity are now becoming available, or soon will be. The Soil Science Society of America collectively and its individual members have good opportunities for and real challenges in developing and applying soil science expertise toward solutions of the problems facing our civilization now and in the future. But more trained soil scientists will be needed to accomplish these contributions. The Society and its members need to assess what they can do by working together within their areas of interests and with scientists in other fields. May the next 50 years of the Soil Science Society of America be even more vigorous and productive than the first 50 years.
Kinetic Study of Citrate Effects on Orthophosphate Solubility in an Acidic, Montmorillonitic Soil
Authors: Traina Samuel J. , Sposito Garrison , Bradford Gordon R. , Kafkafi U. 
Published: July 2010

AbstractPrevious studies by the authors on the effects of pH, organic acids, ionic strength, and Ca on residual orthophosphate solubility in an acidic montmorillonitic soil (Typic Chromoxererts) were extended to include the variation of reaction time. The objective of the experiments was to determine the time dependence of the reactions and to elucidate further the mechanism of orthophosphate solubility in a montmorillonitic soil separate containing exchangeable Al and added citric acid, and suspended in 20 mol NaCl m−3. In the absence of added organic acids, soluble orthophosphate and Al3+ activities were found to be consistent with the presence of an amorphous hydroxy‐Al‐phosphate solid at elapsed t ≥ 24 h. Initial citrate concentrations of 10, 100, and 400 mmol m−3 resulted in citrate sorption by the soil separate and an increase in soluble orthophosphate and Al for t ≤ 1 h. Citrate sorption continued throughout the time course of the experiments. For 1 < t < 8 h, orthophosphate solubility was not affected by the initial citrate concentration. For 8 < t < 27 h, orthophosphate solubility decreased to constant levels. Soluble Al decreased for 1 < t < 30 h and then remained constant in the 10 and 100 mmol citrate m−3 treatments. The samples reacted with 400 mmol citrate m−3 exhibited a steady increase in soluble Al for the same time period. The time‐dependent changes in aqueous orthophosphate and Al were consistent with a previously proposed reaction describing organic ligand‐induced formation of an insoluble hydroxy‐Al‐phosphate. The time trends in the solution concentrations of Ca and Si were not affected by the addition of organic ligands nor were they related to the changes in soluble Al or orthophosphate.
Influence of Calcium and Magnesium Salts on Acid Soil Chemistry and Calcium Nutrition of Apple
Authors: Pavan Marcos A. , Bingham F. T. , Peryea F. J. 
Published: July 2010

AbstractField experiments were conducted in two Brazilian orchards to examine the effects of soil applications of calcitic lime (Ca‐lime), phosphogypsum, CaCl2, and magnesite (Mg‐lime) on soil chemistry and Ca nutrition of apple (Malus domestica Borkh. cv. Gala/MM 106). One orchard was on a low Ca, high Al Inceptisol; the second orchard was on a low Ca, low Al Oxisol. The resulting soil chemical changes were strongly influenced by the initial soil chemistry and the composition of the soil amendments. The effects of Ca‐lime, added at a rate calculated to neutralize the topsoil exchange acidity, were restricted primarily to the upper 20 cm of the soil, where it increased pH, increased total dissolved and exchangeable Ca, eliminated dissolved Al, and reduced exchangeable Al. Phosphogypsum, added at Ca rates equivalent to the Ca‐lime treatment, slightly reduced soil pH in the Inceptisol and slightly increased soil pH in the Oxisol. Phosphogypsum did not appreciably affect dissolved Al in the topsoil; however, it did reduce exchangeable Al but to a lesser degree than did Ca‐lime or Mg‐lime. Phosphogypsum increased exchangeable Ca and decreased exchangeable Al in the subsoil to a depth of 40 to 60 cm. Calcium chloride, added at Ca rates equivalent to the Ca‐lime treatment, produced dissolved and exchangeable Ca increases similar to the phosphogypsum treatment; however, soluble and exchangeable Al were increased and pH slightly decreased throughout the soil profiles. Mg‐lime, added at an acidity‐neutralizing rate equivalent to the Ca‐lime treatment, produced results similar to Ca‐lime except that soluble and exchangeable Mg rather than Ca were increased in the topsoil. Apple tree root densities were enhanced in the soil layers that were made simultaneously high in exchangeable Ca and low in exchangeable Al by the soil amendments. The trees with the more extensive root systems had higher leaf Ca concentrations and produced more and larger fruit. The Ca concentrations in these larger fruit were not reduced by fruit expansion, suggesting enhanced Ca supply from the soil
Interrill Soil Erosion Processes: II. Relationship of Splash Detachment to Soil Properties
Authors: Bradford J. M. , Ferris J. E. , Remley P. A. 
Published: July 2010

AbstractSoil erodibility is often estimated using predictive equations based on easily measurable soil parameters. However, most predictive equations are valid for a limited group of soils and do not account for temporal changes in surface conditions. The objective of this study was to identify those soil properties that affect interrill splash and to develop an interrill detachment model based on both static and dynamic soil properties. Twenty soils ranging in texture from sand to clay were exposed to laboratory simulated rainfall with an intensity of about 63 mm/h. The development of a surface seal decreased infiltration rate, splash, wash erosion, and increased soil strength, as measured with a fall‐cone device. The best predictor of soil splash for the surface sealed condition was a combined kinetic energy/fall‐ cone strength (KE/τ) and total silt content term, and of total soil loss, a KE/τ and coarse silt content term. Comparing results from this study with previously reported studies, we conclude that for improvement of laboratory based indices, greater attention must be given to dynamic soil properties such as the soil's resisting force to raindrop impact and surface flow.
Microbial Reduction of Structural Iron(III) in Smectites
Authors: Stucki Joseph W. , Komadel Peter , Wilkinson Henry T. 
Published: July 2010

AbstractOctahedral Fe(III) in the crystal structures of three different smectites was reduced to Fe(II) by actively growing microorganisms indigenous to the clay. The smectites were SWa‐1 ferruginous smectite from Grant County, Washington; API 33a, Garfield Nontronite; and API 25, Upton montmorillonite. Bacterial growth was supported by incubating clay suspensions at room temperature in a nutrient broth solution consisting of peptone and beef extract. Some samples were first sterilized (by autoclaving), then seeded with bacteria that had been isolated previously from the SWa‐1 sample. The effect of O2 on microbial reduction of Fe(III) was also tested. Results revealed that, in all three clays, about 0.30 mmol Fe(III)/g clay was reduced to Fe(II) by bacteria in a 28‐day period. The specific organism responsible for Fe reduction has yet to be classified, but it was more efficient in samples that had not been purged of O2, and it appears to be indigenous to the SWa‐1 clay.
Sand‐sized Kaolinized Feldspar Pseudomorphs in a California Humult
Authors: Southard R. J. , Southard S. B. 
Published: July 2010

AbstractDeeply weathered soils forming on andesitic mudflows are common in the foothills of the Sierra Nevada of California. Many of these soils (Humults) have oxidic mineralogy based on extractable Fe and gibbsite detected by x‐ray diffraction and differential thermal analysis. Thermal analysis and differential thermal analysis of whole soil samples reveal kaolin and gibbsite percentages greater than clay percentages obtained by particle‐size analysis. X‐ray diffractometry of the fine (0.1–0.25 mm) and coarse (0.5–1.0 mm) sands shows fractions dominated by kaolin throughout the profile. Halloysite predominates in the saprolite; kaolinite increases in abundance toward the soil surface. Gibbsite is present in the surface and upper argillic horizons. Observation of the fine sand fraction with a polarizing light microscope reveals highly weathered feldspar grains with very low birefringence. Scanning electron micrographs of coarse and fine sands show pseudomorphic replacement of feldspar by halloysite resulting in discrete sand‐sized grains wherein simple albite twins are preserved. Energy dispersive analysis by x‐ray of unweathered feldspars produces Si/Al count ratios of 6:1 and indicates the presence of K and Ca in the feldspar structure. Analysis of the surfaces and interiors of kaolinized feldspar grains shows Si/Al count ratios of 2:1 and an absence of K and Ca, demonstrating that the feldspars are completely altered to kaolin by desilication and loss of hydrolyzable cations. The alteration appears to be crystallographically controlled because the original feldspar crystal morphology is preserved.
Air Encapsulation During Infiltration
Authors: Constantz Jim , Herkelrath W. N. , Murphy Fred 
Published: July 2010

AbstractA series of field and laboratory experiments were performed to measure the effects of air encapsulation within the soil's transmission zone upon several infiltration properties. In the field, infiltration rates were measured using a double‐cap infiltrometer (DCI), and soil‐water contents were measured using time‐domain reflectometry (TDR). Before half of the infiltration experiments, CO2 was injected through the DCI into the soil to reduce the amount of air encapsulation in the soil's transmission zone. For a gravelly loam as steady infiltration rates were approached, the average volumetric water content was 0.38 cm3 cm−3 for control experiments and 0.43 cm3 cm−3 for CO2 experiments. The average steady infiltration rate was 0.42 cm min−1 for the control experiments compared to 4.40 cm min−1 for the CO2 experiments. For a sandy loam as steady infiltration rates were approached, the average volumetric water content was 0.43 cm3 cm−3 for control experiments compared with 0.45 cm3 cm−3 for CO2 experiments. The average final infiltration rate was 0.09 cm min−1 for the control experiments compared with 0.42 cm min−1 for the CO2 experiments. In the laboratory, infiltration experiments were performed using repacked soil columns (15‐cm i.d. by 140 cm long), again using TDR and CO2 flooding. For a medium sand as steady infiltration rates were approached, the average volumetric water content was 0.29 cm3 cm−3 for the control experiments and 0.36 cm3 cm−3 for the CO2 experiments. The average steady infiltration rate was 0.25 cm min−1 for the control experiments and 1.23 cm min−1 for the CO2 experiments. For a loam as steady infiltration rates were approached, the average volumetric water content was 0.45 cm3 cm−3 for the control experiments and 0.50 cm3 cm−3 for the CO2 experiments. The average steady infiltration rate was 0.02 cm min−1 for the control experiments and 0.10 cm min−1 for the CO2 experiments. These results suggest that a significant portion of the total encapsulated air resided in interconnected pores within the soil's transmission zone. For the time scale considered, this residual air caused the effective hydraulic conductivity of the transmission zone to remain at a level no greater than 20% of the saturated hydraulic conductivity of the soil.
Specific Cadmium Sorption in Relation to the Crystal Chemistry of Clay Minerals
Authors: Ziper Craig , Komarneni Sridhar , Baker Dale E. 
Published: July 2010

AbstractThree possible locations on clay minerals exist where Cd can be sorbed by ion exchange. These are the external planar, interlayer, and edge surfaces. In this study, montmorillonite, kaolinite, vermiculite, and biotite minerals were used to separate these sorption sites. The vermiculite and biotite were fractionated into five size fractions ranging from <2 to 1000 µm. The relative effect of one surface type on the others was enhanced by further structural manipulations by K+ or Li+ treatments on the vermiculite and montmorillonite. Equilibrium adsorption and desorption of Cd was measured using 109Cd at 0.02 µCi/mL for isotopic dilution to a concentration range of 10−9 to 10−5 M in a 0.005 M CaCl2 background. The mineral concentrations were defined for a constant cation exchange capacity (CEC) or constant external surface area. The results using these different phyllosilicates suggest that the edge and high charge density planar sites (as in biotite) contribute the greatest influence. Generally an increase in the edge to planar surface area ratio with decreasing particle size, or the increase in edge to interlayer surface area ratio by either K+ or Li+ treatments, resulted in an enhanced sorption of Cd. These results suggest that CEC alone is not an accurate measurement to predict Cd sorption behavior for layer silicates. The concentration range used in this study allowed a full inspection of specific and nonspecific Cd‐clay interaction. Equilibrium desorption was used to infer the specific or nonspecific Cd‐clay interaction type. The structural manipulations such as K and Li fixation in vermiculite and montmorillonite, respectively, showed that edge sites retained Cd specifically. The high charge density edge and planar sites of biotite also desorbed Cd the least, suggesting the role of high charge density in specific Cd retention.
Seasonal Pore Water Dynamics in Marshes of Barataria Basin, Louisiana
Authors: Feijtel T. C. , DeLaune R. D. , Patrick W. H. 
Published: July 2010

AbstractSediment redox potential (Eh), interstitial pore water pH, sulfate, carbonate, and trace metals were measured monthly from August 1984 to August 1985, in a salt, brackish, and freshwater marsh in Barataria Basin, LA. The salt marsh was characterized by low Eh during the summer and fall, resulting in pyrite formation. Early spring oxidation of the sediments created extreme acid conditions, indicating that pyrite was oxidized completely to sulfate. Brackish and freshwater marshes exhibited a much greater seasonal variability, with strong vertical redox fluctuations. In the freshwater marsh, both Fe2+ and Mn2+ were controlled by temporal pH changes and were relatively independent of oxidation‐reduction phenomena, suggesting a possible organic control mechanism. However, in the brackish marsh, Fe2+ concentrations were governed by pH (r = −0.74** significant at the 0.01 probability level) and Eh (r = 0.65**) changes, indicating that Fe2+ concentrations were likely controlled by pyrite formation and oxidation. Ion activity product calculations indicated that iron and manganese phosphates and carbonates were unlikely to form in Barataria Basin marshes. However, iron and manganese sulfide supersaturation occurred in all three marshes. Brackish marshes were found to contain significantly higher pyrite concentrations (1.4% w/w), than salt (0.69% w/w) and freshwater (0.66% w/w) marshes. The dynamic pyrite cycling in Louisiana salt marshes, resulted in a low pyritic pool, characterized by single, fine grained euhedral crystals. Pyritic Fe represented 23% of the total Fe accumulation flux in the salt marsh, and 34% in the brackish marsh.
Microbial Colonization and Decomposition of Corn, Wheat, and Soybean Residue
Authors: Broder M. W. , Wagner G. H. 
Published: July 2010

AbstractDecomposition studies were conducted on corn (Zea mays L.), wheat (Triticum aestivum L.), and soybean (Glycine max L.) residue with emphasis on quantitative determination of the microbial populations colonizing the residues and identification of the predominant fungi isolated from the residues. The study was conducted over a 2‐yr period in a Mexico silt loam (Udollic Ochraqualf) at Sanborn Field in Columbia, MO. Plant residues were placed in a porous net and buried in the field. At intervals these sacks were exhumed, washed, and the washings were plated on rose bengal and soil extract agars. The residue was dried and weighed to determine decomposition rates. The predominant fungi were isolated and identified. Microbial determinations were conducted on soil samples taken from the same plots. Of the three residues, soybean had the most rapid rate of decomposition, losing 68% of its total organic matter over the course of 32 d compared with 42 and 47% for corn and wheat residue, respectively. Despite a more rapid rate of decomposition in wheat in comparison with corn residue at 32 d, after 756 d in the soil corn retained 15% of its original organic matter in comparison with 18% for wheat. Bacterial and actinomycete populations were consistently higher on soybean residue in comparison with corn and wheat residue; however, fungal populations were consistently highest on corn residue and lowest on wheat residue. Size of microbial populations from soil were similar for the three plots over the course of the study. Aspergillus, Penicillium, and Trichoderma were the three predominant genera isolated from the residues. Aspergillus niger was consistently isolated at high levels from corn residue, and A. clavatus was isolated frequently, but at low levels from wheat residue. Penicillium spp. were isolated from residues mainly during drought conditions and during the latter stages of decomposition. Trichoderma spp. were isolated at their highest levels during the second summer of the decomposition study, but were found at substantially lower levels during the third summer. Myrothecium spp. was isolated consistently from soybean residue but only during the latter stages of the decay process.
Soil Organic Matter Turnover in Long‐term Field Experiments as Revealed by Carbon‐13 Natural Abundance
Authors: Balesdent J. , Wagner G. H. , Mariotti A. 
Published: July 2010

AbstractCultivation of C‐3 (Calvin cycle) plants after turning under a native prairie of grasses possessing C‐4 metabolism (Hatch‐Slack cycle) allows partitioning of soil organic matter as to origin. Contrasting natural 13C abundance for the two different contributing kinds of plant residues provides an in situ labeling of the soil organic matter. A study to exploit this approach used soil from a long‐term experimental field. Samples were collected under different continuous crops and at different dates and were analyzed for total C and for natural isotope composition of C. The results demonstrated an initial rapid loss of prairie C, suggesting the presence of an easily mineralizable component that was exhausted in 30 to 40 yr. The extent of this was dependent upon the type of cultivation. A pool of stable organic matter of prairie origin persisted under all systems during the approximate 100 yr of cultivation, which was no less than 50% of the current level. The half‐life, under cultivation, of the easily mineralizable compartment was shown to be 10 to 15 yr. Mechanical fractionation of soil mineral particles and associated organic matter showed a heterogeneity with regard to stability. The clay fraction included both the most stable C, and some labile C, whereas clay associated with fine silt demonstrated a turnover that suggested slow replacement of the whole of the fraction. The overall results demonstrate the potential value of long‐term field experiments for studying soil organic matter turnover by the natural 13C abundance technique.