bluuebunny/crossref_metadata_2025_split huggingface dataset:
Destruction of Organic Matter by Hydrogen Peroxide in the Presence of Pyrophosphate and Its Effect on Soil Specific Surface Area
Authors: Sequi Paolo , Aringhieri Roberto 
Published: July 2010

AbstractThe effectiveness of hydrogen peroxide in oxidizing soil organic matter was markedly increased by the presence of 0.1M sodium pyrophosphate at pH 7, with residual C after treatment being reduced up to 20 times lower compared to conventional soil peroxidation. “Electropositive” (Orange II) and external (N2) surface areas increased, whereas “electronegative” (cetyl pyridinium bromide) surface area values generally decreased after H2O2 treatment, supporting the assumption that metals released from organic matter may precipitate as hydroxide coatings that hinder further oxidation. Some soil sorption sites appear to be occluded by organic matter, so that changes in soil properties after peroxidation cannot be solely attributed to organic matter.
Information Provided on Humic Substances by E4/E6 Ratios
Authors: Chen Y. , Senesi N. , Schnitzer M. 
Published: July 2010

AbstractThe ratio of optical densities or absorbances of dilute, aqueous humic and fulvic acid solutions at 465 and 665 nm (E4/E6) is widely used by soil scientists for the characterization of these materials. While it has been suggested that the E4/E6 ratio is related to the degree of condensation of the aromatic carbon network, carbon content, and molecular weight of humic substances, little rigorous experimental evidence is available in the literature to confirm these hypotheses.The results of this investigation show that the E4/E6 ratio of humic and fulvic acid is: (i) mainly governed by the particle size (or particle or molecular weight); (ii) affected by pH; (iii) correlated with the free radical concentration, contents of O, C, CO2H and total acidity in as far as these parameters are also functions of the particle size or particle or molecular weight; (iv) apparently not directly related to the relative concentration of condensed aromatic rings; (v) independent of humic acid and fulvic acid concentrations, at least in the 100–500 ppm range. Our data show, in agreement with M. M. Kononova (1966), that E4/E6 ratios for humic and fulvic acids should be determined between pH 7 and 8. This can best be done by dissolving the humic material in 0.05N NaHCO3 solution at concentrations of 200–400 ppm.
Effects of pH Level on Yields and Compositions of Pearl Millet and Alfalfa in Soils with Differing Degrees of Weathering
Authors: Lanyon L. E. , Naghshineh‐Pour B. , McLean E. O. 
Published: July 2010

AbstractBulk samples of soils representative of widely differing degrees of weathering (Mollisols, Alfisol, Ultisols, and Oxisols) were collected. Aliquots of each were adjusted to different pH levels, fertilized, and cropped successively to one cutting of pearl millet (Pennisetum glaucum L. Willd.) and three cuttings of alfalfa (Medicago sative L.).As postulated, the trends in crop response to pH differed with crop and with degree of soil weathering. Pearl millet responded very little to increase in pH, except that with very highly weathered soils yields increased significantly up to pH 5.6 to 6.2 followed by a significant decrease at higher pH. Significant increases in alfalfa yields with increased pH were obtained on all soils. However, yields from some of the soils increased prograssively to the highest pH; others leveled off at an intermediate pH, and still others decreased at the highest pH. The latter generally occurred in the most highly weathered soils. Soil and plant analyses as well as visual symptoms suggested that toxic levels of Mn (all soils) and insufficient Ca and high Al (one soil only) were major causes of low alfalfa yields at low pH. Depressed yields of alfalfa in the highly weathered soils at higher pH levels may be related to low levels of available P.The yield response to soil pH vs. degree of weathering relationship was not as clear cut as postulated, but this may not be so much a shortcoming of the hypothesis as it is a consequence of the difficulty in selecting individual soils representative of the highest levels of soil classification, and of the effect of specific parameters important to crop response‐soil pH relationships which transcend such soil groupings.
Model Calculations for the Extraction of Soil Water by Ceramic Cups and Plates
Authors: van der Ploeg R. R. , Beese F. 
Published: July 2010

AbstractA numerical method is developed with which the flow of moisture towards suction units in soil can be evaluated. For a number of selected problems the unsaturated moisture flow equation is solved twice: (i) for radial flow towards a suction plate or suction cup; (ii) for vertical downwards flow under the same conditions, but without a suction unit in the soil. The calculations are performed for a flat soil without a plant cover. It is found that even for little vacuum, large differences may exist between the seepage rate as determined from a suction unit as compared to the seepage rate of the unextracted soil. It is also shown that the radius of influence of a suction unit, which extracts water continuously, can be several feet wide. It is concluded that in order to be reliable, data collected with suction units should be analyzed with care.
Experimental Studies of Wetting Front Instability Induced by Gradual Change of Pressure Gradient and by Heterogeneous Porous Media
Authors: White I. , Colombera P. M. , Philip J. R. 
Published: July 2010

AbstractThe stability of infiltration flows in Hele‐Shaw cells was examined. Flows were perturbed either by gradually increasing G, the pressure gradient behind the wetting front, or by heterogeneities in the cells. Two methods were used to increase G gradually through zero: (i) by allowing the air ahead of the front to be compressed by the flow, and (ii) by monotonically increasing the hydraulic conductivity of the cell with depth. In the other class of experiments, the flow was instantaneously perturbed by a step‐increase in conductivity at selected depths.It was found that Philip's (1975a, 1975b) stability analysis adequately predicted both the onset of instability and the wavelength of the initial disturbances. For quadratic increase in conductivity with depth the observed growth rate of disturbances was faster than expected from the linear theory.Examination of the data of Peck (1965) and Hill and Parlange (1972) showed that Philip's analysis is also adequate for coarse sands.
Effects of the Addition of Phosphorus and Inorganic Nitrogen on Carbon and Nitrogen Mineralization in Andepts From Colombia
Authors: Munevar F. , Wollum A. G. 
Published: July 2010

AbstractThis study tested the hypothesis that the level of available P in volcanic ash soils is a rate‐limiting factor for organic matter mineralization. Additions of calcium phosphate to give levels of P of 1,200 and 2,400 ppm significantly increased the amount of N mineralized and CO2 evolved as compared to soils not treated with P. Although the addition of glucose to these soils increased CO2 evolved, there was significantly more CO2 evolved in the presence of glucose and P than when glucose had been the only addition. Amendment of the soils with N did not have any significant affect on the rate of CO2 evolution. Both N and P additions stimulated N mineralization. The P×N interaction was also significant for C and N mineralization. It was concluded that available P is a rate‐limiting factor for organic matter mineralization in Andepts.
Influence of Soil Amendments on Potato Growth, Mineral Nutrition, and Tuber Yield and Quality on Very Strongly Acid Soils
Authors: Lee C. R. , MacDonald M. L. 
Published: July 2010

AbstractPotatoes (Solanum tuberosum L.) were grown in greenhouse soil pot cultures to evaluate soil amendments that might modify the fertility of very strongly acid Ultisols and improve potato production. Raising soil pH from 4.6 to either 4.9 or 5.2 with dolomitic limestone increased tuber yield and improved tuber quality. Superphosphate applied alone or in combination with dolomitic limestone also increased tuber yield. Tuber specific gravities were not improved with superphosphate alone, but only with combinations of superphosphate and dolomitic limestone. Cow manure applications increased tuber yield, but did not improve tuber specific gravity or quality. Manganese toxicity symptoms and potato leaf Mn content increased with cow manure applications. Magnesium sulfate alone or in combination with superphosphate was beneficial to potato tuber yield. Tuber quality was also improved with the combination of magnesium sulfate and superphosphate. The application of either potassium bicarbonate or Fe chelate did not improve potato growth, tuber yield, or quality. It was concluded that potato production on very strongly acid Ultisols can be improved either by raising soil pH to 4.9 with dolomitic limestone or by the application of Ca phosphate and Mg fertilizers without raising soil pH. Cow manure also improved potato tuber yield but did not improve tuber quality.
Hydrologic Response and Nutrient Concentrations Following Spring Burns in an Oak‐hickory Forest
Authors: Knighton M. Dean 
Published: July 2010

AbstractAnnual spring burns were applied for 1 to 3 years on a 25 to 50% slope in an oak‐hickory forest (Quercus—Carya) in southwestern Wisconsin. Overland flow and sedimentation did not increase, although no severe storms occurred during the study.Fires of light to moderate intensities, consumed most of the fresh litter and sometimes all of the fermentation layer. Mean weight of litter plus fermentation layers were significantly reduced (α = 0.05) from 15,800 kg/ha to 10,100 kg/ha by three annual burns. Bulk density, total pore volume, organic carbon content, and water permeability of the mineral soil were unaltered. Stems <5 cm in diameter at breast height were killed, but shrubs sprouted vigorously and herbaceous vegetation was not altered.Mean concentrations of both anions [PO4‐P and (NO3 + NO2)‐N)] and cations (Ca, Mg, K) in the soil leachate collected at 15‐cm depth appeared to increase after burning although the differences were small and highly variable. Significant changes (α = 0.05) in the concentration of both anions were measured through the growing season. Concentrations of (NO3 + NO2)‐N peaked 6 weeks after the mid‐April fires, which reflects increased nitrification following burning. Sodium concentrations were not affected by burning. Although it was increased by burning nutrient loss to deep leaching appeared to be approximately equivalent to, or less than, estimated annual input from precipation.
An Ultrasonic Nebulization Technique for Adding Aqueous Solutions Uniformly to Dry Soils
Authors: Mubarak A. , Woodriff R. , Olsen R. A. 
Published: July 2010

AbstractAn ultrasonic nebulizer has been successfully utilized to provide a relatively convenient laboratory means for wetting dry soil with aqueous solutions to any selected moisture or electrolyte content. The technique is believed to cause a minimum of alteration of the chemical and physical properties of the sample and causes aqueous solutions to become very uniformly distributed throughout all accessible zones.
Basaluminite and Alunite: A Possible Cause of Sulfate Retention by Acid Soils
Authors: Adams Fred , Rawajfih Zahir 
Published: July 2010

AbstractPure‐solution and soil‐solution experiments were conducted in which the solubility products of synthetic basaluminite and alunite in pure solutions were compared with the ion‐activity products of Al4(OH)10SO4 and KAl3(OH)6(SO4)2 in soil solutions of sulfate‐treated soil. Solution experiments were conducted in which 0.05M Al2(SO4)3 was titrated with NaOH, KOH, or Ca(OH)2 to an OH/AI mole ratio of 2.0. The initial precipitate was amorphous, with the chemical composition of basaluminite, Al4(OH)10SO4·5H2O. Aging the amorphous precipitates under different conditions transformed them to compounds of different composition and crystallinity: amorphous precipitate remained unchanged when aged in their mother solutions at 25°C; crystalline basaluminite formed in Ca mother solutions when aged at 50°C; crystalline alunite formed in Na and K mother solutions when aged at 50°C; crystalline alunite formed in K mother solutions that had been seeded with alunite or bentonite when aged at 25°C. The solubilities of the amorphous and crystalline precipitates were determined in dilute NaClO4 solutions and gave the following average calculated pKsp values: 116.0 for amorphous basaluminite; 117.7 for crystalline basaluminite; 79.7 for Na‐alunite; and 85.4 for K‐alunite. Similar Ksp values for basaluminite were found for soil solutions from a sandy loam soil that had been treated with different rates of K2SO4. However, the soil solutions were supersaturated with respect to alunite. When the SO4‐treated soil was subsequently treated with a high rate of KH2PO4, the soil solution remained supersaturated with respect to alunite, but became undersaturated with respect to basaluminite. It is proposed that sulfate retention by acid soils is a consequence of the solubility of basaluminite and/or alunite.
On the Use of the Langmuir Equation in the Interpretation of “Adsorption” Phenomena
Authors: Veith J. A. , Sposito Garrison 
Published: July 2010

AbstractA theoretical discussion in terms of molecular theory and the results of model experiments are employed to demonstrate that the conventional analysis of “anion fixation” data, through linear least squares regression of the points in a Langmuir plot, usually will not be sensitive enough to show the failure of the Langmuir equation whenever solubility product considerations are essential in the fixation reaction. The theoretical discussion points out that although the Langmuir equation is not restricted to two‐dimensional phenomena (i.e., adsorption), it cannot apply if the reacting anions must be present at some threshold concentration before fixation occurs. An analysis of model experiments on the reactions of OH‐ with Al‐ or Fe‐resin and of Cl‐ with Ag‐resin shows that secondary precipitation phenomena always result in a statistically significant, linear correlation of the variables in a Langmuir plot if the concentration of the reacting anions is much larger than the threshold value needed to initiate precipitation of the secondary solid phase. This condition generally can be expected to be met when anions such as o‐phosphate react with soils or soil constituents. Therefore, the Langmuir equation usually will appear to apply, on the basis of a statistical analysis, even when its applicability is impossible in principle. It follows that the Langmuir equation cannot be used statistically to determine whether adsorption or precipitation (formation of secondary minerals) is occurring during anion fixation reactions in soils and that the parameters in the Langmuir equation cannot be interpreted in terms of surface reactions without additional, independent evidence that only adsorption is involved in anion fixation.
Analysis of the Saturated‐unsaturated Hydraulic Conductivity in a Mixed Sodium‐Calcium Soil System
Authors: Russo David , Bresler Eshel 
Published: July 2010

AbstractA model is developed to diagnose the effect of Na/(Ca)1/2 ratios and soil solution concentrations on the hydraulic conductivity for an unsaturated soil. The model takes into account the porous nature and the electrical properties of the soil. Interactions between ions in the exchange phase and in the liquid phase are expressed quantitatively by the diffuse double‐layer theory. Experimental data on the effect of soil solution and soil‐water pressure on clay‐platelet organization and structure were considered in the model. A test is made of the sensitivity of the model to variations in the various input parameters. The model is found to be sensitive to the relationship between the number of platelets per clay particle, and the ESP of the soil. The diagnostic model is compared with experimental data for three soils of different texture. The model approximates the hydraulic conductivity function for many practical combinations of Na/(Ca)1/2 ratios and soil solution concentrations for the ranges of soil water content in which most of the water flow occurs.
Effect of Redox Potential on the Stability of Zinc and Copper Chelates in Flooded Soils
Authors: Reddy C. N. , Patrick W. H. 
Published: July 2010

AbstractStability of Zn and Cu chelates of EDTA and DTPA was studied under controlled redox potential‐pH soil conditions. The metal chelates ZnEDTA, ZnDTPA, CuEDTA, and CuDTPA were reacted with soil suspensions incubated at six different redox potentials (−200, −100, 0, +100, +300, and +500 mV) and at pH 7 for reaction periods varying from 2 to 192 hours.The redox potential has a very significant effect on the stability of all four metal chelates studied. The percentage of added Zn/Cu that remained in soil solution decreased with decreasing redox potential from +500 to −200 mV. Even though Zn and Cu chelates were stable at higher redox potentials, their stability decreased with time, apparently due to physical adsorption and microbial decomposition of metal‐chelate complex. At lower redox potentials, Zn and Cu chelates were found to be highly unstable. This instability was found to be mainly due to chemical fixation of added Zn and Cu, not due to physical/microbial decomposition of metal‐chelate complex. Iron, Mn, Ca, and Mg were found to be forming metal‐chelate complexes with EDTA and DTPA ligand molecules once Zn and Cu were removed from their metal‐chelate complexes.
Retention and Leaching of Nutrients in a Limed Ultisol Under Cropping
Authors: Juo A. S. R. , Ballaux J. C. 
Published: July 2010

AbstractThe response of maize (Zea mays L. Cv. TZB) to liming and the retention and leaching of Ca and other nutrient ions were studied in the greenhouse using an acid Ultisol from southern Nigeria. The soil was limed to various pH levels and maize was grown for 10 weeks. The largest growth response occurred when the soil pH was raised from 4.3 to 5.0 by liming (1.3 metric ton/ha). The highest yield was obtained when the soil pH was between 5.5 to 6.0.Substantial downward movement of Ca from the limed surface layer (0–15 cm) was noted, but these Ca ions were mostly adsorbed in the unlimed subsurface layer. The vertical distribution of exchangeable Ca in the limed soils followed a similar trend with pH, but was inversely related to exchangeable Al.Leaching losses of applied nutrient ions (Ca, Mg, K, NO3) during the 10‐week cropping period were relatively small. There was a significant increase in nitrate content in leachates when soil was limed above pH 7.0. Only 1% of the applied Ca was in the leachate while about 80% of the applied Ca was retained in exchangeable form when the soil was limed at a rate of 2 metric ton/ha.
Determination of Total Sulfur in Tidal Marsh Soils by X‐ray Spectroscopy
Authors: Darmody R. G. , Fanning D. S. , Drummond W. J. , Foss J. E. 
Published: July 2010

AbstractTwo X‐ray spectroscopy techniques, called additions and corrections, were developed for total S analysis of soils. The techniques are especially applicable to tidal marsh soils because of the wide range in organic matter contents of these soils and the importance of S in their genesis, classification, and management. Both methods involve basically the same equation: %S = (Sample counts/sec)/(counts/sec per %S), where c/sec is the sulfur Kα counts/sec (peak minus background). In the additions technique, the c/sec per %S is estimated by adding a known concentration of S as thiourea to a powdered soil sample and determining c/sec with and without addition. In the corrections technique, the c/sec per %S is based on the soil organic matter content, since c/sec per %S increases in a regular manner with increasing organic matter content. Results by the additions technique agreed well with values from Na2CO3 fusion analyses of tidal marsh soils and with Leco furnace analyses of powdered rock samples, and analyses by the corrections technique agreed well with those by the additions technique. When compared with National Bureau of Standards values for standard coals, however, total S contents were underestimated by the additions technique as employed, apparently at least partly related to a pyritic S form in the coals. Pyritic S gives less c/sec per %S than thiourea. An organoleptic “whiff” (aroma) method for field estimation of S in marsh soils is also described. “Whiff” values gave a highly significant correlation (r = 0.53) with surface soil S content as measured by the X‐ray additions technique. Maryland tidal marsh soils examined contained 0.10 to 96% organic matter and 0.02 to 5.44% total S.
Regional Distribution of Fluorine in Illinois Soils
Authors: Omueti J. A. I. , Jones Robert L. 
Published: July 2010

AbstractFluorine concentrations in 201 Illinois surface soils range from 70 to 618 mg/kg with an arithmetic average of 271 mg/kg or a geometric mean of 256 mg/kg. Interpretation of a cumulative frequency plot of the data on a probability‐log graph suggested that there were at least four populations of F in the state. Multiple regression analysis showed that clay content was the most highly associated variable (r = 0.924) with soil F. The only other significant variables, pH and clay by organic carbon interaction, accounted for 4 and 1%, respectively, of the variance. Variations in these three soil properties resulting from influences of topography, drainage, degree of weathering and soil development, vegetation, and parent materials were most closely associated with the observed distribution of F in Illinois soils.
Solution Activities of Aluminum and Silicon in Highly Weathered Soils that contain Gibbsite and Kaolinite
Authors: Weaver R. M. , Bloom P. R. 
Published: July 2010

AbstractSolution activities of aluminum (Al3+) and monosilicic acid (Si(OH)4) in dilute acid suspensions of six Brazilian Oxisols were measured over a period of 145 days. The steady state activity function of pH‐⅓pAl ranged from 1.86 to 2.69, while that of pSi(OH)4 ranged from 3.69 to 4.22. Although all of the soils contained kaolinite and gibbsite, the observed solute activity functions of pH‐⅓pAl and pSi(OH)4 deviated considerably from those expected for a thermodynamic equilibrium between gibbsite and kaolinite. It was found that the solution activities of Al and Si(OH)4 in these soils appeared to result from the dissolution of a surface aluminosilicate component (R) of variable composition‐{[Al(OH)3](1‐x)[SiO2]x}R rather than gibbsite and kaolinite.
The Shear Resistance of Root‐Permeated Homogeneous and Stratified Soil
Authors: Waldron L. J. 
Published: July 2010

AbstractMechanical reinforcement which stabilizes soil on slopes has been attributed to plant roots. To measure such reinforcement, direct shear tests were made on 25‐cm diameter root‐permeated soil columns. Roots of alfalfa (Medicago sativa), barley (Hordeum vulgare), and yellow pine (Pinus ponderosa), each increased the shear resistance of homogeneous and compacted layers of silty clay loam at 30‐cm depth. One‐year‐old alfalfa had a much greater reinforcing effect than pine trees 16 months after transplanting or barley at its maximum growth. Barley had a greater effect in the clay loam than pine, but its effectiveness decreased as depth increased from 15 to 30 to 45 cm. Alfalfa roots were more effective than either pine or barley roots in increasing the resistance to shearing between a dense gravel‐sand layer (simulating weathered rock) and the overlying soil, increasing shearing resistance to as much as 5 times that of fallow soil. A model is presented of soil reinforced by nonrigid roots. Calculations are given of slope safety factor increases from root reinforcement.