bluuebunny/crossref_metadata_2025_split huggingface dataset:
Statistical Modeling of the Variability of Selected Colo Soil Properties
Authors: Collins M. E. , Fenton T. E. 
Published: July 2010

AbstractForty‐seven soils representing the Colo soil series (fine‐silty, mixed, mesic Cumulic Haplaquolls) as mapped on 0 to 2% slopes in the Upper Midwest were described and sampled to determine selected physical, chemical, and morphological properties to use in statistical modeling. The soils were sampled in Iowa (35 pedons), Nebraska (4), Missouri (4), Illinois (2), and Minnesota (2), and studied in the following groups: all Colo pedons, by master horizon, and by the presence or absence of postcultural sediments (PCS). The groups were statistically analyzed by using means, ranges, standard deviations, coefficients of variation, correlation coefficients, and multiple regression equations. The objectives of this study were to (i) characterize the Colo soil throughout its geographic range; (ii) stratify the data to study the relationship between selected soil physical, chemical, and morphological properties; and (iii) develop statistical regression models using several soil chemical and physical properties of one soil series. Ranges in soil properties such as particle size, hydrogen‐ion activity, and total carbon (TC) content are restricted by the limits of the official series used as guides in mapping. Therefore, these properties did not have as wide a range as other soil properties studied‐available, total (TP), organic (OP), and inorganic phosphorus (IP) or organic carbon/organic phosphorus (OC/OP) and organic phosphorus/total phosphorus (OC/TP) ratios which are not defined for the series. The Colo samples were stratified according to master horizon designations. TC, OP/TP, OP, and OC/OP means were highest in the A horizon and decreased with increasing depth in the profile. Soil properties used to define the series had a narrower range (e.g. particle size, TC amount) than other soil properties especially in the A horizon. Forty‐five percent of the pedons sampled had some evidence of PCS. The sand, silt, clay, and TC means were similar for those soils with or without PCS as were IP, OC/OP, and OP/TP. The ranges differed but were not as great as anticipated. If less than 50 cm thick, PCS should not be considered part of the mollic epipedon. Still all the soils studied had a mollic epipedon greater than or equal to 91 cm thick. Morphologically, the majority of the Colo soils described had an A‐B‐C horizon sequence. A B horizon was described to indicate “structural” alteration of original material. Alluvial‐derived soils are reported to be in an early stage of development and, therefore, should have little alteration of the original material. As indicated by some of the Colo soil properties, this assumption is not necessarily correct. As a result of this study, the genesis of some soils derived from alluvial sediments in the Upper Midwest is better understood.
Extraction of Radiostrontium Coprecipitated with Calcium Carbonate in Soil
Authors: Spalding B. P. 
Published: July 2010

AbstractThe fraction of soil 90Sr coprecipitated with calcium carbonate (CaCO3) was determined by extraction into 0.1M hydrochloric acid (HCl)‐0.5M potassium chloride (KCl) after an initial extraction with either 1M ammonium acetate (NH4OAc) or 1M KCl to remove soluble salts and exchangeable cations. This procedure was tested on soil samples supplemented with 85 g CaCO3/kg containing coprecipitated 85Sr. The 85Sr and calcium (Ca) in this Ca(85Sr)CO3 behaved identically in the extraction sequences. In the absence of soil, about 95% of the Ca(85Sr)CO3 dissolved into the 0.1M HCl‐0.5M KCl following the KCl extraction. In the presence of soil, a significant amount of both 85Sr and Ca remained undissolved in this extractant but were subsequently removed by extraction with 8M HNO3. Ammonium acetate, however, extracted more Ca and 85Sr from Ca(85Sr)CO3, with or without soil, than did KCl. The extraction procedure was also applied to a group of 16 90Sr‐contaminated soil and streambed sediment samples which contained from 0 to 7.9 g carbonate‐carbon/kg (0 to 66 g CaCO3/kg). The amount of Ca + Mg extracted by 0.1M HCl‐0.5M KCl, following KCl extraction, was well correlated with but slightly lower than the amounts expected for a complete dissolution of the CaCO3. Pre‐extraction with NH4OAc, rather than KCl, dissolved significantly more CaCO3 resulting in a lower estimate of the soil CaCO3. Several soil samples, taken from a radioactive waste burial trench that had received sodium carbonate (Na2CO3) treatment injections, revealed that up to 98% of the total 90Sr was observed in a CaCO3 phase. Untreated soils typically exhibited 80 to 95% of their 90Sr in a cation exchangeable form, i.e., extractable by either NH4OAc or KCl.
Transient Microsite Models of Denitrification: I. Model Development
Authors: McConnaughey P. K. , Bouldin D. R. 
Published: July 2010

AbstractPast models of denitrification are reviewed. None of these models include a description of anaerobic volume and transient solute diffusion to and away from zones of N reduction. In this paper, models describing denitrification in the anaerobic zone of a saturated homogeneous soil are presented. The models consider the reduction sequence: nitrate (NO−3) → nitrite (NO−2) → nitrous oxide (N2O) → dinitrogen (N2). Anaerobic volume was described by an approximate solution to a moving boundary problem. Transient diffusion of NO−3, NO−2, N2O, and N2 was allowed throughout the saturated soil, while reduction of the nitrogenous species occurred only in the anaerobic region. Four types of reaction terms were considered, resulting in a zero‐order model, a Michaelis‐Menten model with differential rates of reduction, a Michaelis‐Menten model with NO−3 and NO−2 inhibition of N2O reduction, and a competitive inhibition model. The use of an operational Vmax which reflects electron donor availability was proposed.
A Comparison of NH4HCO3‐DTPA, NaHCO3, CaCl2, and Na2‐EDTA Soil Tests for Phosphorus
Authors: Labhsetwar V. K. , Soltanpour P. N. 
Published: July 2010

AbstractThe NH4HCO3‐DTPA soil test of Soltanpour and Schwab was developed for simultaneous determinations of availability indices for P, K, Zn, Fe, Cu, Mn, and other elements. In this paper NH4HCO3‐DTPA was compared with NaHCO3, CaCl2, and Na2‐EDTA soil tests for P in a greenhouse study. Five rates of P: 0, 50, 100, 150 and 200 mg kg−1, were applied to 11 Colorado soils and yield response of alfalfa (Medicago sativa L.) to P was measured. Phosphorus levels in soil extracts were measured using inductively coupled plasma spectrometry. The NH4HCO3‐DTPA extracts also were analyzed for P colorimetrically. The inductively coupled plasma spectrometric method gave higher values (1.7 mg kg−1 on the average) for P than the colorimetric method probably due to inclusion of organic P. The Nelson and Anderson analysis of variance method indicated that all tests were equally effective in separating soils that required fertilizer P from non‐responding soils with r2 values of 0.52, 0.50, 0.60, and 0.50, for NH4HCO3‐DTPA, NaHCO3, CaCl2, and Na2‐EDTA soil tests, respectively. However, the NH4HCO3‐DTPA is more economical because it is designed to extract other elements simultaneously, thereby saving considerable time. The r2 value was 0.58 for colorimetric method. The greenhouse critical levels of P were 9.4, 27.6, 0.46 (0.23 mg L−1 in solution), and 36.8 mg kg−1 for NH4HCO3‐DTPA, NaHCO3, CaCl2, and Na2‐EDTA soil tests, respectively.
Silicate and Phosphate Influence on Kaolin‐Iron Oxide Interactions
Authors: Golden D. C. , Dixon J. B. 
Published: July 2010

AbstractInteractions between kaolin and iron oxide minerals are important in understanding the physical properties of highly weathered soils. This study shows that anions (silicate and phosphate) play a major role in determining the type and strength of particle associations, both during and after the formation of the iron oxide minerals in soils. The presence of silicate as an adsorbed anion on kaolinite inhibited iron oxide cyrstallization from ferric hydroxide gel and facilitated an intimate coulombic association between fine positively charged iron oxide particles and kaolin minerals whereas adsorbed phosphate did not affect the crystallization of iron oxide or the kaolinite iron oxide association. Mossbauer spectroscopy was used to demonstrate the existence of strong attractive forces between fine iron oxide particles and the kaolinite surface. The specific adsorption of silicate ions by associated kaolinite‐iron oxide systems, disrupted the attractive forces between kaolinite and iron oxides and effectively dispersed the system in most cases. This was taken as an evidence for the existence of coulombic type attractions. Attractions which could not be disrupted by silicate treatment were observed in cases where goethite was formed by the oxidation of Fe2+ ions in the presence of kaolinite and halloysite.
A Mechanistic, Numerical Model of Sedimentation, Mineralization, and Decomposition for Marsh Sediments
Authors: Morris James T. , Bowden William B. 
Published: July 2010

AbstractThis paper describes a computer model that relates measured nutrient profiles to organic matter diagenesis in marsh sediments. Processes included in the model are sedimentation of exogenous and endogenous organic and inorganic matter, decomposition, above‐ and belowground biomass and production, and N and P mineralization. The shape of organic nutrient profiles in marsh sediments is controlled by the relative rates of nutrient mineralization and inputs of organic and inorganic matter. Sediment inputs were specified for a freshwater, tidal marsh on the North River, Massachusetts, and the model was solved for nutrient mineralization rates by fitting the model to observed nutrient profiles. Model calculations of net annual N and P export from a 1‐m sediment column, 9.6 to 17.5 g N m−2 yr−1 and 1.19 to 2.02 g P m−2 yr−1, were sensitive to small changes in estimates of belowground production and the fraction of organic material that is refractory, constants in the model that are poorly known for marsh ecosystems. These export rates are about 55 to 78% and 71 to 85% of the annual sediment inputs of organic N and P, respectively. The fate of nutrients exported from the sediment was not specified, but it could include plant uptake, denitrification, and net loss to the adjacent tidal river. The model demonstrates that mature marshes with deep sediments recycle proportionally more of the nutrients required by primary producers than young marshes with shallow sediments. Model calculations indicated that the greatest changes in C, N, and P occur in the upper 2 cm of sediment. Labile organic C decomposed most rapidly which caused the relative concentrations of organic N and P to increase. Below this thin surface zone C loss became negligibly small, but there was a gradual decline in concentrations of organic N and P as they continued to mineralize slowly within the upper 60 cm of sediment. Apparently, only refractory C, N, and P compounds remained below the 60‐cm depth. The predicted ratio of N/P loss from sediment ranged from 8.2 N/1 P to 9.55 N/1 P (g/g) and was constant over depth; this compares to a ratio of about 11 N/1 P in litter of the dominant macrophytes. This model is sufficiently general as to be useful in studies of sediment formation and nutrient cycling in other systems.
Illuvial Band Formation in a Laboratory Column of Sand
Authors: Bond W. J. 
Published: July 2010

AbstractExperiments are described in which thin clay bands were formed by illuvial processes in a laboratory column of fine sand containing <1% clay. It is hypothesized that band formation resulted from dispersion of clay in the sand and its subsequent deposition, which was triggered by layers of small pores within the sand column, and/or by exceeding the maximum possible suspension concentration. The results permit a number of comments to be made about the occurrence and formation of illuvial clay bands, as well as precautions that should be taken when carrying out water flow experiments in sandy soils.
Manganese Phosphate Equilibrium Relationships in Soils
Authors: Boyle F. W. , Lindsay W. L. 
Published: July 2010

AbstractSolubility diagrams were developed using log K° values for MnHPO4·3H2O, Mn3(PO4)2·3H2O, Mn5H2(PO4)4·4H2O and MnPO4·1.5H2O. The latter mineral was found to be more stable than hydroxyapatite and thus capable of controlling soil‐solution P at pH values <7.2 and pe + pH values between 13.5 and 17. Controlled redox cells were used to maintain suspensions of several soils at fixed redox levels above pe + pH = 13.5. After 28, 56, 84, and 140 d, samples were taken, and the clear filtrates were analyzed. The activities of Mn2+ and H2PO‐4 were calculated by speciating total Mn and P in solution. Ionic activity products were calculated and compared to the activity products of pure Mn phosphates. This study helps to explain the beneficial effects of phosphate in alleviating Mn toxicities and the importance of Mn phosphates as reaction products of Mn and P fertilizers in soils.
Organic Oxidation and Manganese and Aluminum Mobilization in Forest Soils
Authors: Pohlman Andrew A. , McColl John G. 
Published: July 2010

AbstractA kinetic model is presented that describes the initial and rapid redox processes between polyhydroxyphenolic acid and soil or manganese oxide suspensions. The rate constants derived by the model were similar in magnitude in both suspensions for the organic reductants studied. Polyhydroxyphenolic acids with para‐ and ortho‐OH groups were rapidly oxidized by manganese oxides with spectral evidence suggesting that the reaction leads to polymeric humic products by way of benzoquinone derivatives. In contrast, polyhydroxyphenolic acids with meta‐oriented phenolic‐OH groups were not oxidized by soil or by manganese oxide suspensions within the 120‐min reaction period, presumably because these compounds were not capable of being oxidized to benzoquinone intermediates. The oxidative process was also accompanied by formation of Mn2+ both from soil and from manganese oxide suspensions. The rate of Mn2+ formation by gallic acid from Challenge A horizon soil suspensions containing a total of 3.6 × 10−4 mol L−1 Mn content was comparable to the rate from birnessite suspensions containing a total of 2.5 × 10−4 mol L−1 Mn content. The appearance of Mn2+ in soil suspensions within the reaction period was attributed mainly to reduction rather than clelation by the organic reductants or their products of oxidation. Dissolution of soil Mn also occurred by 2,5‐dihydroxybenzoic, and 3,4‐dihydroxybenzoic acids, but not by 2,6‐dihydroxybenzoic and 3,5‐dihydroxybenzoic acids. Humic products formed from oxidation by Mn were quite effective chelators of Al. The rates of Al dissolution by humic products from Blodgett A horizon soil in suspensions were comparable to the rates in the original organic acids, and were 3 to 6 times faster in dissolving Al than mineral acid at comparable pH levels. The parallel behavior in reactivities of both soil and manganese oxide suspensions towards polyhydroxyphenolic acids suggests that manganese oxides are being reduced in both systems.
Volcanic Glass Influence on Selected Soil Properties in Western Nebraska
Authors: Uzochukwu G. A. , Lewis D. T. 
Published: July 2010

AbstractVolcanic glass exerts an influence on surface area, water‐holding capacity, and cation‐exchange capacity. This study was conducted to quantify the volcanic glass in the Mitchell (coarse‐silty, mixed [calcareous], mesic Ustic Torriorthent) and Tripp (coarse‐silty, mixed, mesic Aridic Haplustoll) soils in western Nebraska and to determine the influence of glass on cation‐exchange capacity, surface area, and water retention at 1.5 MPa. These properties are important in understanding soil response to management practices. Surface area and water retention at 1.5 MPa increased with depth in the soils. The increasing water retention at 1.5 MPa with depth was associated with volcanic glass, which might indicate more amorphous material in the clay fraction. The ratio of water retention at 1.5‐MPa tension to clay (g/kg) determined by standard analysis was greater than 0.6, suggesting that clay should be estimated by calculation (water content at 1.5 MPa × 2.5) for Mitchell and Tripp soils.
Factors Affecting Zinc Uptake in Cropping Systems
Authors: Hamilton M. A. , Westermann D. T. , James D. W. 
Published: July 2010

AbstractZinc availabilities can change with different cropping management practices. The objective of this study was to identify some of the causative factors associated with previous crops contributing to Zn uptake differences in a subsequent crop. Field studies over 3 yr evaluated the Zn availability after four precropping treatments: bean (Phaseolus vulgaris L.), corn (Zea mays L.), wheat (Triticum aestivum L.), and fallow, across two Zn fertilization rates (with and without 11 kg Zn ha−1 as ZnSO4), using the ‘Viva’ bean as a test crop. Soil samples taken before and after the test crop were analyzed for extractable P, Zn, Cu, Mn, and Fe, and organic matter. Soil respiration during the test crop was periodically estimated the last cropping year. Whole plant samples estimated nutrient concentration and uptake. Soil Zn extracted by diethylenetriaminepentaacetic acid (DTPA) was increased by Zn fertilization but not affected by precropping treatments. Zinc uptake by bean was significantly higher after precropping with corn and lower after fallow regardless of Zn fertilization. Uptake differences were most pronounced during early plant growth. Phosphorus and Cu uptake varied with treatment in a similar pattern as Zn uptake, and were positively correlated with each other. Zinc uptake was also positively correlated with soil organic matter and negatively correlated with soil P. Soil respiration rate was significantly lower after the fallow treatment compared with other precropping treatments. Vesicular‐arbuscular mycorrhiza (VAM) colonization in the test crop roots was higher after corn and lower after fallow regardless of soil Zn concentrations. Colonization was positively correlated with Zn, P, and Cu uptake during early plant growth. The VAM colonization, soil respiration, and DTPA‐extractable Zn were selected by a stepwise regression procedure as the important variables affecting Zn uptake during early plant growth. These results emphasize the importance of the soil's biological activities on Zn availability and may help explain some field observations where chemical soil tests appear to fail.
Effect of Soils on the Behavior of Immobilized Enzymes
Authors: Gianfreda Liliana , Bollag Jean‐Marc 
Published: July 2010

AbstractThe use of immobilized enzymes, such as oxidoreductases and hydrolases, in contaminated soils offers a simple, efficient, and inexpensive method for solving pollution problems in the soil environment. Investigations on the behavior of a laccase (from the fungus Trametes versicolor), a peroxidase (from horseradish [Armoracia rusticana P. Gaertner, Meyer & Scherb.]), and an acid phosphatase (from wheat [Triticum aestivum L.] germ) were conducted in the presence of sand, various soils, and soil‐sand mixtures. The enzymes were either free or immobilized on three natural supports (a montmorillonite, a kaolinite, and a silt loam soil). On immobilization, laccase and peroxidase retained high activities, whereas immobilized acid phosphatase showed reduced activity. The affinity of laccase and peroxidase for their substrates remained practically unchanged (similar Michaelis constant [Km] values) and higher Km values (low substrate affinity) were obtained for immobilized acid phosphatase. By increasing the amount of soil in the soil‐sand mixtures or the content of organic matter in soil, an inhibitory effect on the activity of free and immobilized enzymes was observed. The reusability of immobilized laccase and peroxidase, both in the absence and presence of soil, was evaluated by repeated incubation cycles with 2,4‐dichlorophenol. After several incubation cycles, the immobilized enzymes retained different activity levels. Furthermore, in the presence of soils, the inhibitory effect decreased after each incubation cycle, indicating that the observed inhibition was, at least in part, due to soluble soil components easily extracted with the buffered substrate solution. Our results indicate that immobilized enzymes introduced into the soil environment have catalytic activity, but their performance is affected by organic or inorganic soil constituents.
Genotypic Variation in Promotion of Rice Dinitrogen Fixation as Determined by Nitrogen‐15 Dilution
Authors: Shrestha R. K. , Ladha J. K. 
Published: July 2010

AbstractRice (Oryza sativa L.) genotypes capable of stimulating associative N2 fixation (NFS) are desirable to reduce dependence on fertilizer N. A pot experiment was conducted during the 1993 dry season to assess differences in NFS among 70 genotypes of diverse origin and growth duration and to validate the use of 15N enrichment of mineralized soil N as reference for N2 fixation measurement. The soil used had a stable 15N enrichment that was obtained by incubating and frequent mixing with (15NH4)2SO4 (6.3 kg N ha−1) in submerged condition for 6 wk. The 15N enrichment of soil NH+4‐N dropped exponentially, showing an initial rapid decline to half of the original level within 2 wk, followed by a slower, nonsignificant rate of decline after 5 wk. Whole plant 15N atom % excess was inversely correlated with growth duration and ranged from 1.78 in Oking Seroni (late genotype) to 2.45 in PTB‐18 (early genotype). It was, therefore, necessary to compare NFS among genotypes of the same growth duration. Enrichment was lowest in the roots, suggesting this as the site of active N2 fixation; it was highest in the shoot and intermediate in grain. Nitrogen derived from air (Ndfa) estimated using 15N enrichments of mineralized soil N and reference rice genotype correlated highly (r = +0.998**). Percentage Ndfa ranged from 1.5 to 21.0, with an average of 10.2. Yelsulbyeo, Pankaj, and Oking Seroni had the highest Ndfa among early, medium, and long growth duration genotypes, respectively. Genotypes with high Ndfa, grain yield, and N uptake are Oking Seroni, IR29337‐36‐3, OR‐142‐99, and Pankaj.