bluuebunny/crossref_metadata_2025_split huggingface dataset:
Morphology, Mineralogy, and Genesis of a Hydrosequence of Oxisols in Brazil
Authors: Macedo J. , Bryant R. B. 
Published: July 2010

AbstractResearch was conducted to establish the genetic relationship between soil color patterns and natural drainage characteristics in a hydrosequence of Oxisols formed in Tertiary/Quaternary sediments of the Cerrado (Savanna) Region of the Central Plateau of Brazil. The soils classify as Acrustox and Plinthaquox in Soil Taxonomy and as Dark‐Red Latosols, Red‐Yellow Latosols, and Hydromorphic Laterite in the Brazilian classification scheme. In addition to standard soil characterization analyses, x‐ray diffraction and sodium citrate‐bicarbonate‐dithionite extractions were used to determine soil mineralogy. Precipitation was recorded and weekly positions of the water table at sampling sites were measured in observation wells for a period of 1 yr. Kaolinite, gibbsite, quartz, and Fe oxides are the dominant minerals in all sites. Relative amounts of these minerals show similar desilication trends with depth at all sites in the hydrosequence. Well‐drained soils with water tables >3 m had reddish hues (2.5YR or 5YR) indicating an oxidizing environment and a codominant hematite and goethite Fe mineralogy. The upper organic rich solum at sites with seasonally high water tables (<2 m) had yellowish hues (10YR or 7.5YR) and a dominantly goethitic Fe mineralogy. In the deeper perennially saturated zones of all profiles the matrix color has reddish hues (2.5YR or 10R) and a dominantly hematitic Fe mineralogy. Stratigraphic, geomorphic, and pedogenic evidence supports the hypothesis that soils having reddish (2.5YR or 10R) hues and codominant hematite and goethite Fe mineralogy formed in a prior environment, then underwent changes in Fe oxide mineralogy in response to changes in hydrology brought about by landscape evolution and climate change. The organic rich upper sola of soils having a seasonally high water table show color adjustment to yellowish (10YR or 7.5YR) hues and dominantly goethitic Fe mineralogy.
Virgin Hardwood Forest Soils of the Southern Appalachian Mountains: I. Soil Morphology and Geomorphology
Authors: Daniels W. L. , Everett C. J. , Zelazny L. W. 
Published: July 2010

AbstractLittle is known about the characteristics of undisturbed soils in the eastern USA, since few exist. Eight sites with virgin forest soils formed under southern Appalachian hardwood vegetation were studied in the Joyce Kilmer Memorial Forest, an unlogged watershed in western North Carolina. Sites ranged in elevation from 720 to 1200 m with only two on <50% slopes. Generally, soils were quite deep and highly weathered because of high rainfall (>200 cm), weatherable feldspathic parent material, and no accelerated erosion. Average solum depth was 90 cm, while depth to metasandstone bedrock was typically >1.3 m. Deeply weathered saprolites were commonly encountered. Soils on northerly aspects had thick umbric epipedons and more organic matter than soils on south‐facing slopes. Organic matter contents of A1 horizons ranged from 45 to 170 g/kg and surface horizons contained moderate coarse and medium crumb structure. Most soils had cambic horizons and clay contents that decreased with depth. Argillic horizons were present only at low elevations on south‐facing slopes. While the majority of soils were formed in colluvium, significant amounts of deep soils in residuum occurred on sideslopes and appeared stable. The present‐day land‐forms appear to be significantly influenced by periglacial activity. Windthrow appears to have mixed the surfaces of these soils. Due to their decreasing clay content with depth, oxidic mineralogy, and low CEC, these soils resemble tropical forest soils.
Virgin Hardwood Forest Soils of the Southern Appalachian Mountains: II. Weathering, Mineralogy, and Chemical Properties
Authors: Daniels W. L. , Zelazny L. W. , Everett C. J. 
Published: July 2010

AbstractEights undisturbed soils derived from feldspathic meta‐sediments in the Joyce Kilmer Memoiral Forest were studied. Gibbsite was common throughout all soils, and inceased in aboundance in the clay fraction with depth. The clay content in most soils decreased with depth, with intergrade 2:1 type minerals occurring as the dominant phyllosilicates in surface horizons. Kaolinite was low in all soils, but was more abundant in south‐facing soils. Gibbsite abundance was not aspect dependent. The silt fractions contained appreciable quantities of weathered 2:1 type minerals similar in type to the clays. The coarse sand fractions wee almost entirely quartz, while the fine sands contained quartz, weathered 2:1 minerals, and feldspars. The CEC of the mineral surfaces in these soils was extremely low. Soil CEC was almost entriely derived from organic matter, and was typeically <3 cmol/kg in subsurface horizons. Levels of exchangeable Ca and Mg, acid extractable P, and total‐N were very low below surface horizons. These soils have weathered in a wet (>200 cm precipitation) temperate environment and resemble some tropical soils. Erosion could severely damage the natural productivity of these soils. The addition of oxidic mineralogy classes to certain Inceptisol families is recommended.
Application of a Conceptual Model to Irrigation Water Requirement and Salt Tolerance of Crops
Authors: Bresler Eshel 
Published: July 2010

AbstractA theoretical model describing crop yield response to water quantity and quality under irrigation conditions is generalized to obtain soil‐water‐salt regimes, water requirement, and salt tolerance curves. Theoretical results show that under continuous irrigation conditions steady water and salt regimes may be achieved only when application water quantities exceed seasonal class A pan evaporation (E0) by >50%. The effects of water quantity and soil salinity on crop yield and the shape of the response curves to electrical conductivity of saturated paste extracts are similar for measured data and simulated results. In both, salt tolerance curves of wet irrigation regimes (irrigation quantity >E0) have maximum relative yield (YR) of one, while for dry irrigation regimes (irrigation quantity <0.8. E0), YR <1.0. Explanation of salt tolerance curves is attempted.
A Cumulative Mass Coordinate to Determine Water Profile Changes in Variable Volume Soil
Authors: McGarry D. , Malafant K. W. J. 
Published: July 2010

AbstractA method for calculating changes in soil water of variable volume soil using a cumulative mass coordinate is demonstrated. Water content on a mass basis is plotted against mass per unit area of soil solids rather than against depth, lines are fitted, and changes in soil water in zones of gain or loss are calculated from areas between lines. A second method is presented that assesses the need for the cumulative mass coordinate by demonstrating its relation to profile depth. Application of the methods is demonstrated through a worked example using field data taken from an experiment on a Typic Pellustert (Australia).
Significance of Potassium Chloride pH of Calcareous Soils
Authors: Moore T. J. , Loeppert R. H. 
Published: July 2010

AbstractThe use of high ionic‐strength media for determination of soil pH has been limited primarily to acid soils. In this study, the theoretical and practical significance of the pH of calcareous soils suspended in 1 M KCl was investigated. Solutions from suspensions of 24 soils in 1 M KCl were analyzed for pH, Ca, Mg, Na, K, and alkalinity, and equilibrium relations were evaluated. In addition, the equilibrium relations of standard calcite samples were investigated in 1 M chloride solutions at different Ca to K ratios. Suspensions of calcite were in equilibrium with respect to CaCO3; however, soil suspensions were supersaturated (Ω = 1‐3). The KCl pH values of calcareous soils were inversely related to both the Ca concentration of the KCl extract and the cation exchange capacity (CEC) of the soil. The role of K+ was to displace Ca2+ from the cation exchange complex. Increased Ca in the KCl extract resulted in a decrease in pH, as predicted from the equilibrium relations of calcite. The use of KCl pH with calcareous and acid soils is analogous in that the pH reflects CEC and the cationic composition of the exchange complex. As with acid soils, the KCl pH of calcareous soils may provide valuable precursory information concerning the chemical properties of the system.
Determination of Fe(III) and Fe(II) in Oxalate Extracts of Sediment
Authors: Phillips Elizabeth J. P. , Lovley Derek R. 
Published: July 2010

AbstractA method was developed to determine the concentrations of oxalate‐extractable Fe(III) and Fe(II) in sediments. Sediment was extracted in acid ammonium oxalate under N2. Iron(II) in the extract was determined with ferrozine. Iron(III) in the extract was reduced with hydroxylamine‐hydrochloride, and total Fe in the extract was determined with ferrozine. Oxalate‐extractable Fe(III) was calculated as the difference between Fe(II) and total Fe in the extract. Iron(II) was not oxidized, and Fe(III) was not reduced during the extraction. For an accurate estimate of oxalate‐extractable Fe(III), fresh samples had to be analyzed, because air‐drying or freeze‐drying the samples oxidized Fe(II) to oxalate‐extractable Fe(III). With a minimal increase in analytical effort, the method yields far more information on Fe geochemistry than the standard aerobic oxalate extraction method.
Effects of Carbon Source on Immobilization and Chemical Distribution of Fertilizer Nitrogen in Soil
Authors: Kelley Kenneth R. , Stevenson Frank J. 
Published: July 2010

AbstractThree C sources (glucose, a phenolic glycoside, and catechol) were added to soil along with 15N‐labeled (NH4)2SO4 in an incubation study to determine effects of aliphatic and phenolic substrates on transformations of fertilizer N. Microbial utilization of the C substrates resulted in a rapid depletion of available mineral N, with maximum immobilization of soil and tracer N after 6, 10, and 20 d in the glucose‐, phenolic glycoside‐, and catechol‐amended soil, respectively. A close relationship was observed between clay‐fixed nonexchangeable 15NH+4 and KCl‐extractable (exchangeable + soluble) 15NH+4 during incubation (r2 = 0.91**). The nonexchangeable 15NH+4 was readily released and immobilized during microbial utilization of the added substrates. Availability ratios indicated that the immobilized 15N at the point of maximum incorporation into the microbial biomass was from 3.5 to 8.0 times as susceptible to mineralization as the native soil N. Net mineralization of 15N was accompanied by a decrease in amino acid‐15N, an indication that synthesis and decomposition of microbial protein were closely related to the level of available mineral N. Higher levels of acid‐insoluble 15N in the phenolic glycoside‐ and catechol‐amended soil were attributed to condensation reactions involving amino compounds and substrate‐derived polyphenols. Overall, microbial transformations were more important than substrate effects in determining the distribution of immobilized 15N after 120 d of incubation.
Silica in Duric Soils: II. Mineralogy
Authors: Chadwick O. A. , Hendricks D. M. , Nettleton W. D. 
Published: July 2010

AbstractOpal‐A and opal‐CT were identified by x‐ray diffraction as the primary pedogenic silica minerals in two central Nevada duric soils. Opal‐A was also present in the form of allogenic volcanic glass. Pedogenic microcrystalline quartz was not identified. Saturated paste extracts contained > 60 mg L−1 Si(OH)4 and opal‐A precipitation is likely during soil dehydration. Opal‐CT precipitates from soil solution once silica concentrations have been reduced through adsorption, precipitation, and/or increased solution ionic strength, or it may be produced by transformation from opal‐A by mineral aging processes. High concentrations of silica in soil solution favor opal formation in preference to deposition of microcrystalline quartz.
Spatial Variability of Soil Salinity in Furrow‐irrigated Torrifluvents
Authors: Miyamoto S. , Cruz I. 
Published: July 2010

AbstractDistribution characteristics of salinity and sodicity in furrow‐irrigated fields have not been adequately evaluated. This study examined the pattern of salt accumulation within crop beds and its spatial variation along or across crop rows, mainly for developing sampling guides for routine salinity appraisal. Soil samples were collected at spacings ranging from 1.5 to 6 m in four furrow‐irrigated fields of the middle Rio Grande Basin and were analyzed for salinity of the saturation extract and in selected cases for the sodium adsorption ratio (SAR). Salinity varied two to sixfold within the row lengths of 110 to 190 m, and its variation generally increased with increasing sampling depth and numbers of irrigation. The analyses of autocorrelation showed that salinity readings were spatially dependent at one of the four tested fields, and the distance of dependence reached 46 m. This field showed a gradual change in soil texture (from silty clay loam to silty clay), and provided a semivariogram conforming to a generalized linear model. When samples were collected from an area consisting of a single soil type or when salinity values were stratified by soil type, the distance of dependence decreased to <15 m. The frequency distribution of both salinity and sodicity within the same soil type followed a normal distribution with the standard error of estimates of mostly <8%. The sampling sites required to obtain a mean value within 15% of the true mean ranged from 3 to 11 per test row when sampled at 0‐ to 0.20‐m depth prior to preplant irrigation, and the required number increased with increasing sampling depth and numbers of irrigation. For routine appraisal of salinity in the fields similar to examined here, soil samples can be collected on the basis of soil type, and salinity data can be analyzed by conventional statistics with a reasonable assurance that salinity values are spatially independent.
Simulating the Effects of Soil Depth and Climatic Factors on Corn Yield
Authors: Swan J. B. , Shaffer M. J. , Paulson W. H. , Peterson A. E. 
Published: July 2010

AbstractSimulation models are needed to estimate crop yield responses to climate and soil water storage. Measured corn yields (Zea Mays L.) from a tillage‐residue management study on the Univ. of Wisconsin Lancaster Exp. Stn. were compared to simulated yields determined using the Nitrogen‐Tillage‐Residue Management (NTRM) simulation model. Data collected at the site from 1982 to 1985 on crop, soil, climate, and management charactertistics were utilized in the model. A significant interaction effect on corn yield was observed between climate and soil‐water‐holding capacity of individual plots. In 1983, 1984, and 1985 corn yields increased as soil depth to red clay residuum increased; in 1981 and 1982 corn yield had little relationship to soil depth to residuum. The observed differential effect of soil depth to residuum on corn yield under different years' climatic conditions necessitated the use of a simulation model to estimate corn yield accurately in a given year and to express the probability of obtaining a given yield level. Frequency distributions for grain yield were determined for specific soil depths to residuum. Grain yield was determined as a function of soil depth for specific probability levels based on simulated site‐specific daily climatic values generated for a 100‐yr period.
Relationship Between Microbial Biomass Nitrogen and a Nitrogen Availability Index
Authors: Myrold David D. 
Published: July 2010

AbstractThis study examined the microbiological basis for the anaerobic N mineralization assay, a technique that has been widely used in studies of N availability in forest soils. It was hypothesized that N mineralized using the anaerobic incubation method came mainly from killed microbial cells, similar to the flush of N obtained from the chloroform fumigation‐incubation method for determining microbial biomass. Soil samples, representative of a wide range of forest types in Oregon, were analyzed for the amount of NH+4 released after a 7‐d anaerobic incubation and by the standard chloroform fumigation‐incubation method. A second experiment was done using the same soils treated with 15NH4Cl, and the isotopic labeling of the NH+4 released by both methods was determined. There was a highly significant correlation between both the amount and atom % 15N of NH+4 released by the two procedures (r2 = 0.81 and 0.82, respectively). These results suggest that the anaerobic N mineralization assay measures N released primarily from the microbial biomass.
Energy and Water Balance of a Sparse Crop: Simulated and Measured Soil and Crop Evaporation
Authors: Lascano R. J. , van Bavel C. H. M. , Hatfield J. L. , Upchurch D. R. 
Published: July 2010

AbstractDryland crops grown in semiarid environments often do not completely cover the soil, leaving a portion of the soil surface exposed to a condition of rapid soil‐water evaporation. Quantitative separation of soil evaporation and crop transpiration is important if cultural practices or cultivars are to be evaluated. This study was designed to evaluate a combined energy and water balance model, ENWATBAL, to describe the concurrent heat and water fluxes in a row crop. Inputs to the model include soil and plant variables and daily weather data. Measurements were made for a period of 74 d over a cotton (Gossypium hirsutum L.) canopy during 1985 on an Olton soil (fine, mixed, thermic Aridic Paleustolls) at Lubbock, TX. Data collected included soil‐water content, soil temperature, root distribution, soil evaporation with microlysimeters, and leaf area index, for both an irrigated and a dryland plot. The values for daily evaporation and evapotranspiration calculated with the model were within 1 standard deviation of the measured values. Cumulative evaporation and evapotranspiration from the model agreed with measured values within 7% for the dryland and 8% for the irrigated plot. Estimated soil‐water and temperature profiles also agreed closely to measured values. Soil evaporation was found to be 30% of evapotranspiration, for both the irrigated and the dryland plot. The ENWATBAL model provides a reliable method of evaluating the effects of management practices and crop selection on the water‐use efficiency of crop production in a semiarid area.
Effect of Solution Composition on the Rate and Mechanism of Gibbsite Dissolution in Acid Solutions
Authors: Bloom P. R. , Erich M. S. 
Published: July 2010

AbstractThe rate of dissolution of gibbsite was measured as a function of H+ concentration and anion concentration. The anions examined were nitrate, sulfate, and phosphate and the pH range used was 1.5 to 4.0. Rates of gibbsite dissolution were low and comparable to reported dissolution rates for feldspars. In the presence of nitrate and sulfate the dissolution reaction was first‐order with respect to H+ below pH 2.5. In phosphate there was no dependence of the rate on H+. Above pH 3.5 in nitrate the reaction order with respect to H+ approached zero. The order of the reaction with respect to anion concentration was about 0.6, 0.4, and 0.9 for nitrate, sulfate, and phosphate, respectively. The rate dependence of gibbsite dissolution on H+ and anion concentration suggested that the mechanism of dissolution, as well as the rate, is a function of solution composition. In solutions containing ions not specifically adsorbed (e.g., NO‐3 and SO2‐4), proton attack of the surface is the rate‐determining step. In solutions containing phosphate, anion attack predominated, and the rate of the reaction is not dependent on pH.
Selenite Adsorption on Alluvial Soils: II. Solution Composition Effects
Authors: Neal Rosemary H. , Sposito Garrison , Holtzclaw K. M. , Traina S. J. 
Published: July 2010

AbstractThe adsorption envelope for selenite on two alluvial soils from the San Joaquin Valley, California, was investigated with respect to variations in solution composition. Sodium‐saturated soil pastes were mixed with solutions containing sulfate, phosphate, and Ca ions in a background electrolyte of 50 mol NaCl m−3. The effects of increasing chloride concentration were investigated at 100 mol NaCl m−3. No discernible change in the amount of selenite adsorbed was found as a result of increased chloride concentration or through the addition of 16 mmol Na2SO4 kg−1. In contrast, an initial concentration of phosphate comparable to that of selenite resulted in a decrease of selenite adsorbed by approximately one‐half. The addition of 100 mol CaCl2 m−3 resulted in significant increases in selenite adsorption on both soils above pH 5, which could be attributed to precipitation or an increase of surface charge through Ca adsorption.
Influence of Exchangeable Calcium on Phosphate Retention by Weakly Acid Soils
Authors: Smillie G. W. , Curtin D. , Syers J. K. 
Published: July 2010

AbstractThe extractability of P from two weakly acid soils that had been amended with three forms of P [KH2PO4, single superphosphate (SSP), and Chatham Rise phosphorite (CRP)] was investigated in an incubation study under field conditions. In a sequential extraction sequence with water, P release from soils incubated for 9 and 27 weeks with KH2PO4 and SSP declined with increasing extraction number. In contrast, P extracted from CRP‐treated soils increased, indicating a slow dissolution of phosphate rock. Washing with 0.1 M NaCl to remove exchangeable Ca resulted in a large increase in P extracted subsequently with water, regardless of whether sorbed P (as in KH2PO4‐ and SSP‐treated soils) or particulate Ca phosphate (as when CRP was added) was the source of the extracted P. A high proportion (up to 80%) of the added P could be recovered by water extraction when exchangeable Ca was replaced by Na. Significantly, P recovery did not decrease with time of contact between soil and P as it did before exchangeable Ca was replaced with Na. The removal of exchangeable Ca accelerates the dissolution of Ca phosphates by creating a sink for Ca. The results obtained suggest that sorbed P may enter into chemical association with Ca, possibly at metal oxide surfaces, and that this interaction with Ca constitutes an important P retention mechanism in acid soils that contain adequate exchangeable Ca.
Analysis of Factors Controlling Soil Organic Matter Levels in Great Plains Grasslands
Authors: Parton W. J. , Schimel D. S. , Cole C. V. , Ojima D. S. 
Published: July 2010

AbstractWe analyzed climatic and textural controls of soil organic C and N for soils of the U.S. Great Plains. We used a model of soil organic matter (SOM) quantity and composition to simulate steady‐state organic matter levels for 24 grassland locations in the Great Plains. The model was able to simulate the effects of climatic gradients on SOM and productivity. Soil texture was also a major control over organic matter dynamics. The model adequately predicted aboveground plant production and soil C and N levels across soil textures (sandy, medium, and fine); however, the model tended to overestimate soil C and N levels for fine textured soil by 10 to 15%. The impact of grazing on the system was simulated and showed that steady‐state soil C and N levels were sensitive to the grazing intensity, with soil C and N levels decreasing with increased grazing rates. Regional trends in SOM can be predicted using four site‐specific variables, temperature, moisture, soil texture, and plant lignin content. Nitrogen inputs must also be known. Grazing intensity during soil development is also a significant control over steady‐state levels of SOM, and since few data are available on presettlement grazing, some uncertainty is inherent in the model predictions.