bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fate of Fertilizer Nitrogen in the Rice Root Zone
Authors: Reddy K. R. , Patrick W. H. 
Published: July 2010

AbstractPoor N use efficiency by rice (Oryza sativa L.) in many regions of the world is due to the intensity of loss mechanisms functioning in the system. A study was conducted to determine the maximum potential loss of fertilizer 15N in a Crowley (Typic Albaqualfs) silt loam soil where conditions are favorable for both nitrification and denitrification in the root zone of rice. Nitrogen losses were measured in the rhizosphere (soil core with rice plants) and nonrhizosphere (soil core without rice plants) soil systems. The potential N loss in the system with plants was found to be 193 mg N m−2 d−1, while N loss due to the rhizosphere effect alone was 143 mg N m−2 d−1 (18% of the applied 15N). About 5% of the applied 15N was found to be lost due to upward movement of 15NH+4 into overlying flood‐water.
Characterization and Classification of Seaside—Salt‐marsh Soils on Virginia's Eastern Shore
Authors: Edmonds W. J. , Cobb P. R. , Peacock C. D. 
Published: July 2010

AbstractSalt marshes, historically, were considered to be of minimal value. Current concepts consider these marshes to have a very high biomass. This study was conducted to characterize soils in seaside salt marshes on Virginia's eastern shore and to classify them according to criteria in Soil Taxonomy and proposed amendments. Results indicate that salt‐meadow marshes, dominantly vegetated by saltmeadow hay (Spartina patens), contain soils with halmyric and nonsulfidic properties and aquic moisture regimes. Classification of these soils as members of the proposed Halmyraqualfs will necessarily broaden the definition of halmyric materials to include an aquic moisture regime and the definition of the argillic horizon to include sodium adsorption ratios (SARs) considerably >13. We propose that soils in these marshes with subsoil illuvial clay accumulations and SARs >13 be classified as members of Typic Natraqualfs even though they lack structure currently defined for natric horizons. Saltmarsh cordgrass marshes, dominantly vegetated by S. alterniflora, contain soils with halmyric and sulfidic properties, silty textures, and peraquic moisture regimes. Tidal mudflats, not vegetated by vascular plants, contain sediments that have halmyric, but dominantly nonsulfidic properties. These results indicate that conditions necessary for the formation and accumulation of sulfide minerals exists in the salt‐marsh‐cordgrass marshes and to a limited extent in the tidal mudflats and in the salt‐meadow marshes. Considerably more information concerning properties of all the soils in the study area is conveyed by the proposed halmyric great groups and subgroups than by taxa currently defined by Soil Taxonomy. Moist incubation of samples provides a convenient and economical method for evaluating soils and sediments as sulfidic materials. Results of this study support the need for the proposed amendments to Soil Taxonomy.
Pedogenesis on the Edwards Plateau, Texas: II. Formation and Occurrence of Diagnostic Subsurface Horizons in a Climosequence
Authors: Rabenhorst M. C. , Wilding L. P. 
Published: July 2010

AbstractFollowing reconnaissance efforts to minimize differences in parent materials, 15 pedons were sampled across the Edwards Plateau of Texas, which spans a pronounced moisture gradient. Care was taken to minimize differences in topography by choosing sites on relatively stable landscape positions. Statistically significant positive relationships exist between depth to bedrock or petrocalcic horizon and Thornthwaite's P‐E index. Negative relationships occur between carbonate contents and this index. Petrocalcic horizons are common and most strongly expressed in the dry western part of the study area, while argillic horizons are observed in the more humid eastern portion. High shrink swell activity in the argillic horizons (coefficient of linear extensibility [COLE] values 0.09–0.23) caused difficulty in distinguishing illuvial clay from stress oriented clay, both in the field and in thin section. Well‐oriented illuvial clay was best preserved within interconnected pores of sand and gravel size chert fragments.
Soils of the Mall in Washington, DC: I. Statistical Summary of Properties
Authors: Short J. R. , Fanning D. S. , McIntosh M. S. , Foss J. E. , Patterson J. C. 
Published: July 2010

AbstractTwenty profiles were examined in each of five transects along the length of the Mall in Washington, DC. The soils were formed in mixed, man‐deposited materials with lithologic discontinuities present in 95% of the profiles. Ninety‐nine percent of the profiles were within fine‐loamy and coarse‐loamy taxonomic families. B horizons were identified in 26% of the profiles based upon colors redder or stronger than those of underlying materials and/or the presence of soil structure, most commonly subangular blocky. Inorganic, manufactured artifacts were present in the particle size control section of 94% of the profiles. The loamy textures were conducive to compaction to high bulk densities of up to 2.03 Mg m−3. Mean bulk density values of 1.61 Mg m−3 for the surface horizon and 1.74 Mg m−3 at 0.3 m were found. The surface horizon had a mean particle density of 2.54 Mg m−3, and the mean particle density at 0.3 m was 2.59 Mg m−3. Pore space was limited, with a mean of 37% at the surface and 33% at 0.3 m. Pore space ranged from 21% to 50%. Data were statistically analyzed according to the position of the horizon from the soil surface. Mean pH of all horizons was 6.2 or higher, and mean pH of the surface horizon was 6.4; however, the pH of 27% of all samples was >7.0. Electrical conductivity was <0.57 dS m−1 in 80% of all surface horizons. Mean organic matter content was 19.7 g kg−1 at the surface, and tended to decrease with depth, although variation in this trend was observed. Mean cation exchange capacity was 11.2 cmol (NH+4) kg−1 in the surface horizon and tended to decrease with depth. Mean base saturation exceeded 88% in all horizons, with Ca as the dominant cation. Elevated levels of heavy metals were observed, with a mean Pb content of 184 mg kg−1 in the surface horizon. Enrichment of other metals was not as pronounced. Statistically fewer samples were required to estimate the mean for physical properties than for chemical properties. Only one sample was needed to estimate the mean particle density within 10% with a 95% confidence interval, whereas over 7000 samples were required to estimate the mean Ni content of the third horizon with a similar confidence interval.
Variability of Runoff and Soil Loss from Fallow Experimental Plots
Authors: Wendt R. C. , Alberts E. E. , Hjelmfelt A. T. 
Published: July 2010

AbstractThe amount of unexplained variation in runoff and soil loss studies often limits the interpretation of data. In this study, variability in runoff and soil loss from 40 essentially uniform experimental plots was examined for 25 natural rainfall events occurring during a 155‐d period. Plots had been maintained uniformly for the prior 3 yr and were kept fallow with periodic cultivation during the study period. Except for events producing low runoff and soil loss, event coefficients of variation were relatively constant for both runoff and soil loss at about 20%. Differences in runoff and soil loss among plots varied with event. Only minor amounts of observed variability could be attributed to any of several measured plot properties, and plot differences expressed by the 25 events did not persist in prior or subsequent runoff and soil loss observations at the site. The relatively large amount of unexplained variability shows that several replications of treatments are needed to confidently estimate mean runoff or soil loss for comparison purposes and that effects of factors having relatively minor effects on runoff or soil loss may be difficult to detect statistically. The fact that most variability is unexplained indicates important effects of factors or processes that are not currently understood.
Agronomic Potential of Eleven Phosphate Rocks from Brazil, Colombia, Perú, and Venezuela
Authors: Léon L. A. , Fenster W. E. , Hammond L. L. 
Published: July 2010

AbstractThe agronomic potential of 11 South American phosphate rocks was estimated by four laboratory methods (neutral ammonium citrate with two extractions, acid ammonium citrate [pH 3], 2% citric acid, and 2% formic acid) and by crop response data obtained from a greenhouse experiment with guinea grass (Panicum maximum Jacq.) on an acid (pH 4.9) Tropeptic Haplustox (Las Gaviotas) from Colombia. Standards for comparison included triple superphosphate (TSP) and phosphate rocks from the USA (North Carolina, central Florida, and Tennessee), Tunisia (Gafsa), and Israel (Arad). The relationship between laboratory reactivity values and crop response was evaluated following three cuttings of guinea grass at four rates of P application. Almost no yield was obtained without added P, and significant differences were observed between response curves of the P sources. Based on both solubility as measured by the four methods identified and crop response data, the 11 phosphate rocks were found to be segregated into four groups representing high (Bayovar), medium (Huila and Pesca), low (Sardinata, Patos de Minas, Lobatera, Araxá, and Abaeté), and very low (Catalão, Jacupiranga, and Tapira) reactivity. Solubility in neutral NH+4 citrate was found to be the most accurate of the chemical procedures tested. The relationship between yield and source solubility in neutral NH+4 citate showed that all of the sedimentary sources were more reactive than the igneous or metamorphic sources.
Influence of Thiosulfate on Nitrification of Ammonium in Soil
Authors: Janzen H. H. , Bettany J. R. 
Published: July 2010

AbstractAmmonium thiosulfate, a common nitrogen (N) and sulfur (S) source in fluid fertilizer formulations, has been reported to inhibit soil nitrification processes. A laboratory study was established to determine the degree and persistence of the inhibitory effect and to examine the agronomic potential of thiosulfate as a nitrification inhibitor. Thiosulfate applied to the soil was rapidly oxidized with a temporary accumulation of tetrathionate. The formation of nitrate (NO‐3) from applied ammonium (NH+4) was markedly suppressed at higher rates of applied thiosulfate. At the highest rate of thiosulfate application (100 mg S kg−1), relative inhibition of NO‐3 production over 22 d was 55% as compared to 57% for nitrapyrin, applied at 2 mg kg−1. Unlike nitrapyrin, thiosulfate inhibited the second nitrification reaction, the oxidation of nitrite (NO‐2) to NO‐3, and resulted in the accumulation of NO‐2 at concentrations as high as 42 mg N kg−1. This accumulation of NO‐2 may represent a serious drawback to the use of ammonium thiosulfate as a nitrification inhibitor under some conditions since NO‐2 is known to be toxic at relatively low concentrations.
Calcium‐Magnesium Exchange on Illite in the Presence of Adsorbed Sodium
Authors: Sposito Garrison , LeVesque C. S. , Hesterberg Dean 
Published: July 2010

AbstractBinary and ternary cation exchange experiments were performed with Na+, Ca2+, and Mg2+ on Silver Hill illite and on a soil illite suspended in 50 mol m−3 perchlorate at pH 7. The binary experiments indicated no preference for Ca over Mg on the specimen illite, but selectivity for bivalent cations over Na+ and for Ca2+ over Mg2+ on the soil illite. The ternary exchange data showed that, for both illites, there was no effect of adsorbed Na on the Ca‐Mg exchange isotherm at exchangeable sodium percentages from 0 to 30%, either for freshly‐prepared clay suspensions or for those aged up to 270 d in NaClO4. No significant differences in the total adsorbed metal charge (Qo) were observed among the binary and ternary exchange experiments, and Qo was independent of the degree of bivalent cation saturation (ECa or EMg) in the Na → Ca and Na → Mg exchange experiments on the soil illite. The Vanselow selectivity coefficient for Mg → Ca exchange on the soil illite decreased as ECa increased, showing a plateau near ECa ≈ 0.6 and dropping to 1.0 as ECa became equal to 1.0. This behavior was interpreted as evidence for at least two classes of surface complex involving Ca and Mg.
Comparison of Several Lime Requirement Methods on Coarse‐textured Soils of Northeastern Nebraska
Authors: Alabi K. E. , Sorensen R. C. , Knudsen D. , Rehm G.W. 
Published: July 2010

AbstractSoils of the eastern Sandhills of Nebraska are becoming progressively more acid as a result of the development of irrigation and subsequent use of high N fertilizer amounts for corn (Zea mays L.). Chemical determinations of lime requirement are expected to vary in their applicability to these poorly buffered, sandy soils. The objective of this research was to compare the abilities of selected chemical methods of determination of lime requirement to predict lime needs of sandy soils. The lime requirement values of 74 acid sandy soils from northern Nebraska were determined by eight methods. Correlation and regression were used to compare these values with those obtained by incubating the soils with varying amounts of lime in the laboratory. The validity of the CaCO3 incubation method as a standard method was confirmed by a Ca(OH)2 titration procedure. Most of the soils studied required <4492 kg of lime ha−1 to attain soil pH 6.5. The relationship between the values from chemical determination of lime requirement with those from incubation were essentially linear for all methods. Although the nature of the relationship as expressed in the intercepts and slopes of the regression curves and the precision varied among methods, values from all methods were correlated with lime requirement values from incubation. Determination of the correlations among methods showed that lime requirement values for each method were highly correlated with those from every other method included in the study. Correlation studies of lime requirement values for five methods with selected soil properties showed that no single property was correlated with all methods. However, soil pH, clay content, cation exchange capacity, and Mn and Al contents were correlated with values from at least one method.
Effects of Soil Moisture on Soil pCO2, Soil Solution Bicarbonate, and Iron Chlorosis in Soybeans
Authors: Inskeep William P. , Bloom Paul R. 
Published: July 2010

AbstractFour pot experiments were performed with five calcareous soils from western Minnesota (Haplaquolls and Calciaquolls) to determine the effects of soil moisture and soil temperature on Fe chlorosis in soybeans [Glycine max (L.) Merr.]. We used a factorial design with gravimetric moisture contents and bulk density values ranging from 0.22 to 0.44 kg kg−1 and 1.14 to 1.38 Mg m−3, respectively. Factor combinations of these levels resulted in ranges of volumetric moisture contents from 0.27 to 0.54 m3 m−3, air filled porosity fractions from 0.27 to 0.00, and soil matric potentials from <‐1500 to near 0 kPa. The soil pCO2 contents measured from gas wells in pots increased from 0.16 to 1.64 cmol mol−1 as a result of decreased gas diffusion when the air‐filled porosity decreased. With increasing soil moisture, soil solution HCO‐3 concentrations attained values as high as 10 mM. Total chlorophyll (ChlT) contents of Anoka soybeans decreased as soil moisture, soil pCO2, and soil solution HCO‐3 increased. The same response was not observed in all calcareous soils. Calcareous soils with lower amounts of clay sized CaCO3, lower soil solution Mg2+, and/or lower bicarbonate extractable P did not produce as severe a chlorosis with increased moisture. This suggests that clay sized CaCO3, Mg, or P may be additional stress factors associated with HCO‐3 induced chlorosis. High soil moisture treatments on a calcareous soil provided an effective soil screen for differentiating between susceptible and nonsusceptible soybean cultivars. Soil temperatures of 12 and 26°C produced more chlorosis at a given soil moisture than at 16 or 19°C. Soil temperature appears to be an additional stress factor, which might explain some of the variability in the incidence of Fe chlorosis under field conditions.
Statistical Evaluation of the Taxonomic Composition of Three Soil Map Units in Virginia
Authors: Edmonds W. J. , Lentner M. 
Published: July 2010

AbstractA consociation map unit is usually characterized by its central concept selected on the basis of mapping experience, by defining the central concept using morphological and laboratory data, and by assuming that ranges of soil properties defined for the taxon that encompasses the central concept and taxa that includes similar soils represent ranges delineated by the map unit. This study was conducted to statistically evaluate the dominant taxon or central concept as an indicator of map unit purity. Results indicate that the central concept of one of three map units studied had confidence intervals (CIs) that did not exceed limits defined for more than one taxon. Numbers of samples needed for 50% assurance of estimating means within 10% of their true value exceeded cost and time constraints for current soil characterization programs. Of the three map units studied, the highest probability of observing the stated composition was about 0.3 or 30% of the time. Therefore, descriptions of the patterns of occurrence of soils and observed ranges of properties within map units appear to provide more appropriate bases for predicting responses of soils to use and management for the three map units studied.
Simulation and Measurement of Evaporation from a Bare Soil
Authors: Lascano R. J. , van Bavel C. H. M. 
Published: July 2010

AbstractA numerical model was used to simulate evaporation, water, and temperature profiles for a bare soil over drying cycles of 8, 9, and 20 d using soil hydraulic characteristics and meteorological data as input. The model was also used to evaluate the effect of the thickness of the surface layer in the model on the simulated evaporation rates. The simulated values were compared to actual measurements made over the same period of time. The model predicted cumulative evaporation within 1 standard deviation (SD) of the measured values, and in 34 of 37 cases, predicted daily rates also within 1 SD of the measured means. The predicted water and temperature profiles were within 1 SD of the means measured. The accuracy of the model was further confirmed by its ability to predict soil surface temperature within 1.0°C and net radiation within 40 W/m2 of the measured values. The sensitivity of the simulated evaporation rates to the assigned thickness of the surface layer suggested that a value of 0.005 m was adequate under the conditions in which the model was tested. Hence, we conclude that the model is accurate to predict bare soil evaporation rates, as well as soil water and temperature profiles.
Analysis of Water Flow from Cylindrical Macropores
Authors: Smettem K. R. J. 
Published: July 2010

AbstractWater flow from cylindrical macropores of finite length is predicted using an approximate analysis derived previously for flow from a steady constant‐head uncased borehole permeameter in homogenous unsaturated soil. This analysis is appropriate in cases where the macropores fill rapidly and remain completely water filled. Under these conditions predicted macropore flow rates compared well to those obtained from measurements of flow into both “artificial” and natural macropores. The study emphasises the effect of pore continuity, with pore length exerting a dominant influence on the magnitude of macropore volume fluxes over the range of macropore diameters commonly encountered in agricultural soils.
Effects of Redox on Zinc Deficiency in Paddy Rice
Authors: Sajwan K. S. , Lindsay W. L. 
Published: July 2010

AbstractGreenhouse and laboratory experiments were conducted to determine if the pH and redox relationships associated with various soil moisture conditions could help to explain the increased incidence of Zn deficiency of rice (Oryza sativa L.) in submerged soils through greater solubilization of Fe and Mn. The soil used in these studies was Sycamore loam (Aeric Haplaqucepts). Increasing the moisture content of soils increased Fe and Mn concentration and decreased that of Zn in the plant tissue. Application of Zn increased Zn concentrations and decreased those of Fe and Mn in plant tissue. Depth and duration of flooding affected both pH and redox (pe + pH). After 20 days of continuous flooding, pH approached 7.0 and pe + pH approached to 4.0 at 2 cm below the soil‐water interface. Both pH and pe + pH decreased significantly with soil depth, reflecting greater accumulation of CO2 and depletion of O2. With alternate flooding and drying the pH fluctuated from 8.0 during drying to near 7.0 during flooding while pe + pH fluctuated from 15.0 during drying to approximatelyy 6.0 during flooding. Under controlled redox conditions in the laboratory, decreasing pe + pH from 14.99 to 4.00 decreased the Zn content of rice plants from 39 to 9 mg kg−1 while the contents of Fe increased from 140 to 339 and that of Mn from 226 to 919 mg kg−1. The findings reported herein support the hypothesis that Zn deficiency observed in the submerged paddy rice in this study can be partially explained by increased reduction and solubilization of Fe and Mn which had an antagonistic effect on the availability and uptake of Zn. It is also possible that increased HCO‐3 may also contribute to increased Zn deficiency. It is hypothesized that Fe dissolved at reduced microsites and subsequently reprecipitated as ferrosic hydroxide (Fe3[OH]8) in more oxidized zones. The higher solubility of Fe maintained by Fe3(OH)8 could depress Zn2+ solubility through formation of ZnFe2O4 or a similar franklinite‐like solid material.
Orthophosphate Solubility Transformations and Availability from Dual‐Applied Nitrogen and Phosphorus: Calcareous Soil
Authors: Hanson R. L. , Westfall D. G. 
Published: July 2010

AbstractHigher extractable P levels resulting from dual application (DApp) of ammoniacal‐N and ammonium polyphosphate (APP) have been postulated to be a function of pH changes in the fertilizer injection zone of acid to neutral soils. The objective of this study was to characterize the injection zone of DApp of NH4OH (to simulate NH3 application) and APP to a pH‐buffered calcareous soil (Weld sc1; Aridic Paleustolls). A previously studied acid soil, (Ascalon s1; Aridic Argiustolls), was used for comparison. The APP was applied to potted soil either alone or in DApp with NH4OH. The injection zone soils were sampled through time and analyzed for P solubility and NaHCO3‐P. Solubility of P remained constant or increased up to 10 d after application of DApp of APP and NH4OH to the calcareous soil. This treatment also enhanced NaHCO3‐P levels. Increased P solubilities and NaHCO3‐P levels were associated with slight pH decreases in the calcareous soil. This change in pH is postulated to be due to nitrification of the ammoniacal‐N; microsite pH change is undoubtedly much greater than what was measured in the whole soil mass and probably influenced P availability and solubility substantially.
Soil‐geomorphic Evolution of a Boroll Catena in Southwestern Alberta
Authors: Pennock D. J. , Vreeken W. J. 
Published: July 2010

AbstractThe geomorphic and pedological processes that have influenced the development of a Boroll catena in south‐western Alberta are examined using a combination of sedimentological and pedological techniques. Four geomorphic episodes are responsible for the sediments in the catena: the deposition of glacial till, two colluvial episodes, and a final eolian episode that deposited a thin mantle of sediment over the landscape. The vertical and lateral distribution of grain size fractions in the landscape is largely the result of these geomorphic processes. The vertical distributions of Fe and CaCO3 show some relict features from earlier phases of pedogenesis, whereas the organic C values appear to be related only to the present configuration of the landscape.