bluuebunny/crossref_metadata_2025 huggingface dataset:
Calcium‐supplying Characteristics of Two Gypsum Materials on Southeastern Coastal Plain Soils
Authors: Keisling Terry C. , Walker Milton E.
Published: July 2010

Field studies were conducted on two soils to study the manner in which finely and coarsely divided gypsum materials supplied Ca to the soil depth where peanut (Arachis hypogaea L.) fruit absorb Ca. The finely divided material was characterized chemically as CaSO4 · 2H2O, approximately 72% CaSO4 or 20.2% Ca and physically as having 88% of the particles < 0.25 mm in diameter. The coarsely divided material was characterized chemically as CaSO4, approximately 92% CaSO4 or 26.5% Ca and physically as having 82% with particle diameters < 4.2 mm, but > 0.5mm. Each material was applied at three rates in randomized complete block experiments. At approximately 3‐week intervals, composite soil samples were collected at the 0‐ to 5‐, 5‐ to 10‐, and 10‐ to 15‐cm depths and extracted with acid (0.05N HCl + 0.025N H2SO4) extractant which was analyzed for Ca.

The amount of Ca transported to a given soil depth was found to be related to the magnitude, order, and frequency of rainfall events. Generally, several small rainfall events resulted in accumulation of Ca near the soil surface, whereas, larger rainfall events resulted in a reduced Ca concentration near the soil surface for both materials. The fine gypsum material was found to be more effective in supplying Ca to the soil depth where peanut fruit are absorbing it early in the growing season than the coarser material.

Dissolution of gypsum sources consisting of different particle sizes and subsequent transport of Ca into the fruiting zone of peanuts was not always closely related to the total amount of rainfall. Either the finely or coarsely divided gypsum could supply more Ca to the fruiting zone depending on the rainfall pattern.
Thermodynamics of Potassium‐Calcium and Magnesium‐Calcium Exchange Reactions on a Kaolinitic Soil Clay
Authors: Udo E. J.
Published: July 2010

Thermodynamic parameters derived from experimental results were determined for the potassium‐calcium and magnesium‐calcium exchange reactions on a kaolinitic soil clay separated from the B horizon of a strongly weathered soil profile. The clay samples were equilibrated at 10° and 30°C with a mixed solution of KCl and CaCl2 for the K‐Ca system or MgCl2 and CaCl2 for the Mg‐Ca system. For the K‐Ca system, the selectivity coefficients were high indicating a greater affinity of the clay for K than for Ca. The high equilibrium constant and the negative values of standard free energy and enthalpy changes for the exchange of Ca for K also revealed a preference of the clay for K relative to Ca ions.

In the Mg‐Ca system, the exchange isotherms and the low selectivity coefficients indicated a preference of Ca ions for the clay phase. This exchange of Ca for Mg was accompanied by an increase in the free energy and enthalpy changes also pointing to a more stable Ca‐clay than Mg‐clay.
Surface Charge Manipulation of Constant Surface Potential Soil Colloids: I. Relation to Sorbed Phosphorus
Authors: Wann S. S. , Uehara G.
Published: July 2010

A significant correlation was found between the zero point of charge and the quantity of phosphorus applied to soil material from an Oxisol. Sorbed phosphorus lowered the zero point of charge and increased surface charge density at any pH above the zero point of charge. The soil was treated with 0, 100, 500, and 1,500 ppm P as (NH4)2HPO4. For the soil with no added phosphorus, low concentration of monovalent electrolyte and within two pH units of the zero point of charge, diffuse layer theory adequately predicted surface charge. For high electrolyte concentration and high pH, the Stern theory with specific adsorption energy predicted the experimental results. The calculated results indicated charge reversal in the high‐phosphorus samples.
Transient Changes in the Soil‐water System from Irrigation with Saline Water: II. Analysis of Experimental Data
Authors: Jury W. A. , Frenkel H. , Devitt D. , Stolzy L. H.
Published: July 2010

Twenty‐three lysimeters containing four soil types with alternate wheat (Triticum aestivum L.) and sorghum (Sorghum vulgare Pers.) crops were irrigated with three synthesized levels (2.2, 3.9, 7.1 mmho/cm) of irrigation water. Salt balance was calculated from soil salinity sensor electrical conductivity EC measurements by determining a relationship between solution EC and solution concentration using a chemical equilibrium model. Solution samples and saturation extracts were taken to determine ion balances, and exchangeable cations were measured after the third crop.

All methods of determining salt balance showed the order of 50% salt precipitation over the first 500 days of the experiment, approximately two times the expected amount when root zone salt concentrations have reached steady state. Release of Ca2+ ions from exchange sites and subsequent enhanced gypsum and CaCO3 precipitation was assumed to be responsible for the difference between transient and steady‐state behavior.

The drainage composition of a lysimeter which had moved one pore volume through the root zone showed that only Cl‐ was approaching a steady‐state value. Exchange effects and enhanced precipitation were assumed to be buffering the concentration of the other ions.

Water uptake in all lysimeters is occurring primarily in the top 20 cm, a consequence of high irrigation water salinity and daily irrigation.
Calcium Ion Complexation by Fulvic Acid Extracted from Sewage Sludge‐soil Mixtures
Authors: Sposito Garrison , Holtzclaw Kenneth M. , LeVesque‐Madore C. S.
Published: July 2010

The complexes formed between Ca2+ and fulvic acid extracted from sewage sludge were investigated by potentiometric titration of K/H‐fulvate with Ca(NO3)2 at pH 7 and 25°C, in an ionic medium of 0.1N KNO3. Formation functions, giving the number of moles of Ca bound per mole of K/H‐fulvate, were calculated from the titration data and plotted against the concentration of Ca2+, with the concentration of K/H‐fulvate being a fixed parameter for each plot. The molarity of K/H‐fulvate, which was held rigorously constant during each titration, was determined with the help of separate experiments in which the number‐average molecular weight of the K/H‐fulvate sample employed was measured by vapor pressure osmometry. The formation functions were interpreted as evidence of: (i) a relatively strong ion pair that is formed between Ca2+ and the most acidic functional groups in fulvic acid, and (ii) a weaker ion pair that is formed between Ca2+ and the more weakly acidic functional groups. The properties of the latter complex depend both on pH and on the concentration of fulvic acid, since these variables in part determine the number of ionized, weakly acidic functional groups that can react with Ca2+. The Ca2+ ion was shown to have a modest ability to displace protons from undissociated acidic functional groups in sludge‐derived fulvic acid.
The Acetylene Inhibition Method for Short‐term Measurement of Soil Denitrification and its Evaluation Using Nitrogen‐13
Authors: Smith M. Scott , Firestone Mary K. , Tiedje James M.
Published: July 2010

Acetylene was found to effectively inhibit the reduction of N2O by anaerobic soils. With concentrations of C2H2 above 0.1 atm, added NO3‐ was quantitatively converted to N2O, and added N2O was reduced at an insignificant rate. Experiments with 13N demonstrated that at low soil nitrate concentrations at least 0.1 atm C2H2 was required for effective inhibition. Denitrification rates determined by 13N and by C2H2 inhibition methods correlated well, as did determinations of N2O/(N2 + N2O). The methods also revealed that an acceleration in denitrification rate occurred within a few hours after soil was exposed to anaerobic conditions. The acetylene method was generally used to measure denitrification rates in soils incubated as anaerobic slurries, but was also used to determine rates for field moist aggregrates incubated anaerobically and aerobically. When assayed as anaerobic slurries, initial denitrification rates ranged from 0.1 to 0.7 nmoles N gas · soil−1 · min−1 for the mineral soils examined. The denitrification rate in aerobic aggregrates was approximately 1,000 times less, showing the strong inhibitory effect of O2 on the indigenous denitrifying enzymes.
Toposequences of Loess‐derived Soils in Southwestern Indiana
Authors: Norton L. D. , Franzmeier D. P.
Published: July 2010

Soil properties are related to stratigraphy of parent materials and to hillslope position in southwestern Indiana where the landscape consists of gently rolling hillslopes and nearly level plains. Loess was uniform thickness downslope. Two distinct units were recognized. The upper (Peoria) loess contained about 15% less sand and had greater calcium carbonate equivalent, greater field water content, and lesser bulk density than the lower (sandy) loess. The Sangamon paleosol below the loess consisted of an upper slightly developed horizon and lower well developed horizons. The percentages of some heavy minerals were similar in the two loess units and similar in the two paleosol units, but differed between the loess and the paleosols. The lower loess showed slight soil formation. A fragipan was present only on summit and shoulder positions where the paleosol formed in weathered sandstone and shale, but not where it formed in outwash. Apparently there was slight soil formation in the lower loess before its surface was covered by the upper loess. Our data support the hypothesis that fragipans form in loess underlain by less permeable materials at certain depths and that silica (or silicate) acts as a bonding agent in fragipans. We believe that the fragipan forms by processes associated with the modern landscape, but its formation is influenced by pre‐Peoria soils or weathering zones.
Ammonia Volatilization Losses from Flooded Rice Soils
Authors: Mikkelsen D. S. , De Datta S. K. , Obcemea W. N.
Published: July 2010

The pH of the flood water in rice fields is largely determined by the chemical equilibria that exist between the CO2 balance achieved by the aquatic biota and the various solutes, solids, and gases in the water. Water pH values undergo diurnal changes, increasing by midday to values as high as pH 9.5–10 and decreasing as much as 2–3 pH units during the night. The pH of shallow flood water is greatly affected by the total respiration activity of all the heterotrophic organisms and the gross photosynthesis of the species present.

Ammonium form fertilizers broadcast into a high pH water are highly susceptible to direct NH3 volatilization losses. Nitrogen losses from fertilizer broadcast into flood water on a fertile, neutral‐pH Maahas clay were as high as 20% of the amount applied, but losses varied depending upon water pH, the nitrogen source, and rate, time, and method of application. Losses from an acid Luisiana clay, where the flood water was not conducive to algal growth and did not exceed pH 6.8, produced NH3 volatilization losses consistently less than 1% of the total N applied. Placement of N fertilizer in the soil at depths of 10–12 cm reduced NH3 volatilization losses to less than 1% of the total N applied.
A Rapid Method for Estimating the Nitrogen‐Supplying Capability of a Soil
Authors: Fox R. H. , Piekielek W. P.
Published: July 2010

Nitrogen fertilizer recommendations in humid regions have been primarily based on crop N requirements without regard for the variability in the N‐supplying capability of the soil. We found (reported in a separate article) that two previously proposed N availability indexes, 0.01M NaHCO3 and boiling 0.01M CaCl2 extractable N, were well correlated (r = 0.77 and 0.86, respectively; P < 0.01 for both) with the capability of eight Pennsylvania soils to supply N to field grown corn, (Zea mays L.). However, the time and expense required for these analyses may preclude their routine use by soil testing laboratories. In seeking ways to shorten and simplify the analyses, we found that the ultraviolet (UV) absorption by the 0.01M NaHCO3 soil extract at 260 nm was as well correlated with the N‐supplying capability of the test soils (r = 0.865 P < 0.01) as the best of the previously evaluated extractable N indexes. This new method is as rapid, simple, and inexpensive as the methods currently used to measure availability of other essential nutrients in the soil. We also demonstrate how this method can be used to predict more accurately the fertilizer N needs for corn.
Absorption Rates of Ammonium and Nitrate by Red Kidney Beans under Salt and Water Stress
Authors: Frota J. N. E. , Tucker T. C.
Published: July 2010

The purpose of this study was to gain additional knowledge regarding the influence of salinity and water deficit on plant uptake of NH4+ and NO3‐. The absorption patterns of NH4+ and NO3‐ by red kidney beans (Phaseolus vulgaris L.) were determined under normal conditions (control), NaCl treatment (salt stress), and carbowax treatment (water stress) using an inverse isotope dilution technique with 15N. Salt and water stress inhibited the absorption of both NH4+ and NO3‐. There was no difference between these two stress treatments in NH4+ uptake, but carbowax restricted NO3‐ uptake more than did NaCl. Under NaCl salinity the plants absorbed the same amount of N independent of N source; under water stress more NH4+ than NO3‐ was absorbed. Water absorption was reduced by both stress treatments; N and water uptake were highly correlated. Root permeability decreased in plants subjected to stress. Dry matter production and total N per plant decreased, but the N percentage increased in the stressed plants.
Map Unit Composition Assessment Using Drainage Classes Defined by Landsat Data
Authors: Kirschner F. R. , Kaminsky S. A. , Weismiller R. A. , Sinclair H. R. , Hinzel E. J.
Published: July 2010

Soil survey map units are designed such that the dominant soil represents the major proportion of the unit. At times, soil mapping delineations do not adequately represent conditions as stated in the map unit descriptions. Digital analysis of Landsat multispectral scanner (MSS) data provides a means of accurately delineating and quantifying soil map unit composition.

Digital analysis of Landsat MSS data collected on 9 June 1973 was used to prepare a spectral map for a 430‐ha area in Clinton County, Indiana. Sixteen spectral classes were defined, representing 12 soil and 4 vegetation classes. The 12 spectral soil classes correlated with soil drainage characteristics and were grouped into four drainage classes. The four spectral vegetation classes were grouped for convenience into one vegetation class.

The soil delineations produced using these groupings were compared to a conventionally prepared soil map. Three map units were investigated in detail: (i) Mahalasville silty clay loam, poorly drained; (ii) Reesville silt loam, 0 to 2% slopes, somewhat poorly drained; and (iii) Xenia silt loam, 2 to 6% slopes, eroded, moderately well drained.

Results indicate that soil drainage characteristics can be identified. Correlation of drainage characteristics with soil series allows for the composition of soil map units to be accurately ascertained.
Efficient Amendment Use in Sodic Soil Reclamation
Authors: Prather R. J. , Goertzen J. O. , Rhoades J. D. , Frenkel H.
Published: July 2010

A laboratory column study of sodic soil reclamation was carried out using two soils high in exchangeable sodium percentage (ESP) and cation exchange capacity (CEC). Three amendments (CaSO4·2H2O, CaCl2·2H2O, and H2SO4) were used singly and in combination to test their effectiveness and efficiencies with respect to amount of amendment, time, and leaching needed.

As a single amendment, H2SO4 is more effective than CaSO4 and results in a more desirable ESP profile than CaCl2. Combining either CaCl2 or H2SO4 with CaSO4 (proportions of ¼ and ¾, respectively) appreciably reduced the time and leaching needed to achieve reclamation as compared with CaSO4 alone. Certain soil conditions preclude or make undesirable the use of CaSO4 alone. Combining amendments results in effective reclamation and a potential savings in amendment costs.
The Effect of Stabilized, Hydrophobic Aggregate Layer Properties on Soil Water Regime and Seedling Emergence
Authors: Rawitz E. , Hazan A.
Published: July 2010

Soil crusts affect both the profile water regime and the fate of crop seedlings. The former is affected via modification of infiltration, evaporation, and redistribution, while mechanical crust impedance prevents or retards seedling emergence. Growers alleviate this problem by frequent, small irrigations which are costly in water, equipment, and labor. This study was conducted to determine whether surface soil properties could be modified by layers of stabilized, hydrophobic aggregates so as to render these irrigations unnecessary.

Unstable aggregates of a clay‐loam soil were treated with 7% potassium siliconate and 1% polyvinyl acetate based on dry‐weight of soil and sprayed in water to wet the soil to 15% gravimetric water content. Layers of soil mixes with different aggregate‐size distribution were placed in transparent columns and given a simulated rainfall; then the progress of infiltration, redistribution, and drying was followed. The most promising mix was used in large outdoor tanks as a mulch for carrots (Daucus carotta L.), using 1‐ and 4‐cm mulch layers with 0, 25, 50, and 100% cover of the soil surface. The soil was given one post‐sowing sprinkler irrigation, and the soil moisture regime was monitored by microtensiometers and a two‐probe gamma gauge.

A 100% cover of 4‐cm deep mulch of treated aggregates was the most effective for water conservation. It decreased water loss by 20% over a 14‐day period. Seedling emergence was close to 90% under a 1‐cm mulch and 50% under a 4‐cm layer, both of which were superior to the unmulched control treatment.
Juglone Inhibits Pine Growth Under Certain Moisture Regimes
Authors: Fisher R. F.
Published: July 2010

Black walnut (Juglans nigra L.) produces juglone (5‐OH‐1, 4‐napthoquinone), a phytotoxin that has allelopathic effects on certain plant species. Field studies were conducted in southwestern Ontario, Canada, in mixed plantations of red pine (Pinus resinosa Ait.), white pine (P. strobus L.) and walnut growing on the Brant‐Tuscola‐Colwood catena of fine sandy loam soils. On excessively drained Brant sites pine often suppressed the walnut while on imperfectly drained Tuscola and poorly drained Colwood sites, walnut suppressed or even killed the pine. In laboratory studies juglone and its inhibitory activity readily disappeared from Brant soil under a “dry moisture regime” but remained in Brant soil under a “wet moisture regime”. The field and laboratory studies suggest that edaphic conditions play an important role in the interactions between walnut and other species.
The Behavior of Nutrient Elements Added to a Forest Soil with Sewage Sludge
Authors: Riekerk H.
Published: July 2010

Sludge applications were made at a rate of 247 metric tons/ha dry weight to a cleared gravelly Douglas fir forest soil to test limits of nutrient conservation mechanisms. First year losses due to treatments were 8% of added N, 15% of Ca, 1% of K, and none of P. Predictably, NO3‐N was the dominant mobile anion significantly increasing the calcium nitrate level in the ground water. Differences between sludge treatments, including plowing, reflected the degree of aeration and decomposition of NO3‐N production and P‐fixation. These differences were more pronounced deeper in the soil, except for K which was more controlled by the stage of weathering. A very heavy sludge application rate (618 metric tons/ha) had less impact on soil nutrient behavior due to a high water absorption capability. Alternate ways of reducing NO3‐N leakage from the forest soil are being investigated.
Measurement of Furrow Infiltration Rates Made Easy
Authors: Miller D. E. , Rasmussen W. W.
Published: July 2010

An irrigation system was developed for infiltration studies that utilized overflow controls to maintain nearly constant inflow into irrigation furrows. Furrow outflow was measured with HS flumes equipped with water‐level recorders. Data were easily and rapidly converted to infiltration rates and cumulative infiltration by a computer.
A Universal Dimensionless Phosphate Adsorption Isotherm for Soil
Authors: Shayan A. , Davey B. G.
Published: July 2010

A unique dimensionless phosphate adsorption isotherm, covering the solution concentration range 10−6 to 10−1M P, which has been found to fit 17 materials including 15 soils, pure kaolinite and amorphous Al(OH)3, is derived. The soils shown to fit the isotherm include chromic luvisols, pellic vertisols, calcic luvisols, a tropeptic eutrorthox, a volcanic ash soil from New Zealand, and a number of English soils.

The necessary parameters to derive, a complete adsorption isotherm for a particular soil, from the universal isotherm, requires three adsorption experiments in the high concentration range (10−4 to 10−1M P) to define the linear portion of the isotherm and the critical concentration. Three other determinations in the range 10−6 to 10−4M P are needed to obtain the Freundlich isotherm from the data after correction for the effect of the linear region of the isotherm at high concentration. The Freundlich constant a was shown to be a capacity factor, and the constant b to be related to the chemical potential of the phosphate in solution. For the soils studied the variation in the magnitude of b was found to be smaller (0.11 to 0.37) than in a (1.60 to 9.66).

The advantage of this universal isotherm over conventional isotherms, is that it requires less experimental work to define and is applicable over a wide range of P concentrations such as might be found surrounding a fertilizer granule.
Exchange Adsorption of Trace Quantities of Cadmium in Soils Treated with Calcium and Sodium: A Reappraisal
Authors: Milberg R. P. , Brower D. L. , Lagerwerff J. V.
Published: July 2010

Cadmium was selectively adsorbed over Ca in Cecil, Winsum, and Yolo soils with up to 1.7% of the total cation exchange capacity occupied by Cd. Selectivity was greatest in Yolo and least in Cecil. Effects of undissociated Cd in solution were minor. Separation factors (Ks) decreased with increasing exchangeable Cd. Reexamination of Cd‐Na exchange revealed that anomalous earlier results were due to the dispersion of organic matter during treatment with Na2CO3 in the preparation of Na‐saturated soils. Na‐Cd exchange was normal where organic matter loss was prevented.
Predicting Site Productivity of Mixed Conifer Stands in Northern Idaho from Soil and Topographic Variables
Authors: Brown H. G. , Loewenstein H.
Published: July 2010

Characteristics of 32 soils, consisting of an upper sequum influenced by volcanic ash over a buried sequum, and topographic variables were used to develop prediction equations for site index, height, and total volume of mixed coniferous stands in northern Idaho. Soil and topographic variables explained 70% of the variation in site index. Ninety‐four percent of the variation in height of the site trees, and 86% of the variation in total volume of the stand were explained by soil and topographic properties and age. Depth of volcanic ash influence, bulk density, P content, and elevation were important soil and topographic variables.

Site index was negatively correlated with elevation, and positively correlated with extractable Ca, exchange acidity, cation exchange capacity, organic matter, total N, soil to rock ratio of the buried soils, and clay of the ash derived soils.
Effect of pH and Redox on Predicted Heavy Metal‐Chelate Equilibria in Soils
Authors: Sommers L. E. , Lindsay W. L.
Published: July 2010

Metal‐chelate stability diagrams were developed as a function of pH and redox to predict the behavior of DTPA, EDTA, CDTA, EGTA, and HEDTA in soils. The metals evaluated include H+, Fe3+, Fe2+, Al3+, Mn2+, Ca2+, Mg2+, Zn3+, Cu2+, Cd2+, Pb2+, and Ni2+. In acid systems, Ni2+ at 10−5 to 10−7M was the predominant ligand species for all chelating agents. Similar results were obtained in alkaline systems when NiCO3 controlled Ni2+ solubility. In the absence of Ni2+, either Cd2+ or Pb2+ ligand species dominated at alkaline pH for all chelating agents. In acid systems, Cu, Pb, Fe, and Zn are the major chelated species.

In acid soils, the chelating agents EDTA, EGTA, and HEDTA deserve further study as extractants for metals and as reagents for determining metal ion activities through competitive equilibria. The results identify ligands which may be useful in determining various metal ion activities in soils. The DTPA soil test appears to have a sound theoretical basis for evaluating plant available Pb, Cd, and Ni in soils.
Copper(II) Complexation by Fulvic Acid Extracted From Sewage Sludge as Influenced by Nitrate Versus Perchlorate Background Ionic Media
Authors: Sposito Garrison , Holtzclaw Kenneth M.
Published: July 2010

The possible adverse effect of CuNO3+ ion pairs on studies of the complexes formed between Cu(II) and fulvic acid extracted from sewage sludge was investigated by potentiometric titration of 2 × 10−3M K/H fulvate with Cu(NO3)2 and Cu(C104)2, at pH 5 and 25°C, in ionic media of 0.1M KNO3 or KC104, respectively. It was shown that the degree of complexation of Cu2+ in the NO3 medium was always significantly greater than that in the C104 medium for total Cu concentrations in the range 10−4M to 10−2M. This result was interpreted as evidence for significant concentrations of CuNO3+ ion pairs and mixed CuNO3‐fulvate complexes in the NO3 medium. Further support for the existence of CuNO3+ in the NO3 medium was obtained through a successful calculation of the thermodynamic stability constant for this ion pair that employed data from blank titrations with Cu(NO3)2 and Cu(ClO4)2. It was concluded that ClO4 ionic media should be used instead of NO3 ionic media in studies of Cu(II) complexation with the functional groups of fulvic acid.
Exchangeable Cation Hydrolysis and Soil Weathering as Affected by Exchangeable Sodium
Authors: Oster J. D. , Shainberg I.
Published: July 2010

The specific conductance and chemical composition of aqueous soil suspensions were measured as a function of time on suspensions prepared from three arid soils pretreated with acidified salt solutions to remove lime. The release of Ca2+, Mg2+, and K+ from silicate minerals and the hydrolysis of exchangeable Na+ occurred rapidly and prevented the preparation of homoionic Na soils. Crystalline ion release and hydrolysis of exchangeable Na+ and Ca2+ continued after the soils were suspended in distilled water. The rate was enhanced by increasing exchangeable NA+. The combination of Ca2+ hydrolysis and its release from silicate minerals was sufficient, when coupled with Na+ hydrolysis, to cause the solution phase of the suspension to be supersaturated with lime for one soil.

Separate experiments with untreated soil and its silt fraction indicated that silt weathers rapidly and contributes significantly to the increase in soil conductance. Silt weathering was enhanced by increasing exchangeable Na+.
Dissolution of Selected Rocks and Minerals in a Dilute Salt Solution as Influenced by Temperature Regime
Authors: Lanyon L. E. , Hall G. F.
Published: July 2010

Soil environments are generally characterized by temperatures that vary diurnally and/or seasonally, but mean temperatures are often reported to describe these environments. This study was designed to monitor the dissolution of ground samples of olivine (OL), microcline (M), a sandstone (SD) and a shale (SH) in 0.01N AlCl3 when subjected to an alternating temperature regime (mean 25°C with range 3 to 47°C) and constant temperature regimes of 3, 25, and 47°C for periods of up to 90 days. The concentration of a structural cation (Mg for OL and K for M, SD and SH) in the suspending medium was employed as an indicator of the extent of dissolution. Dissolution increased approximately linearly with increasing constant temperature in the order OL > M > SD > SH. The effect of the alternating temperature regime was to increase dissolution relative to a constant temperature of 25°C; the magnitude of the increased varied with the material. An “effective temperature” was calculated to quantify the relative effect of the alternating temperature to the constant temperature regimes. The ranking of the effective temperatures was OL > SH > SD > M. The concepts developed from this laboratory study may be related to reported observations of soil development/aspect relationships in the field where it appears that variables that describe factors such as the interaction of the nature of the parent material and the magnitude of environmental differences may need to be included.
Volatility of Mercury from Soils Amended with Various Mercury Compounds
Authors: Rogers Robert D.
Published: July 2010

A study was conducted to determine the rate of mercury volatilization from soils freshly amended with mercury compounds. Mercuric nitrate, mercuric chloride, mercuric acetate, mercuric oxide, and mercuric sulfide were used in conjunction with three soils; a loamy sand, a sandy loam, and a clay loam. Mercury was evolved from all combinations and was shown to be dependent upon the solubility of the mercury compound and possibly the texture of the soil.
Adsorption of Magnesium and Calcium by a Soil with Variable Charge
Authors: Chan K. Y. , Davey B. G. , Geering H. R.
Published: July 2010

The subsoil of a xanthic ferralsol was used to determine the effect of varying ionic strength and pH on the cation exchange capacity and the amounts of Na, K, Ca, and Mg in exchangeable form.

The cation exchange capacity increased with both pH and ionic strength from 2.6 meq/100 g at pH 2.5 and 0.01M ionic strength to 6.9 meq/100 g at pH 9.5 and 1.0M ionic strength.

Sodium and K remained completely exchangeable over all the ionic strengths (0.01 to 1.0M) and pH range 2.5 to 9.5. By contrast Mg became fixed in nonexchangeable forms as the pH increased so that 62% of Mg originally exchangeable at pH 4.0 was fixed at pH 9.5 and 1.0M ionic strength. Calcium also appeared to become fixed in nonexchangeable form as the pH increased, but to a much lesser extent than Mg.
Carbohydrate Content of Fungal Humic Acid‐type Polymers (Melanins)
Authors: Linhares L. F. , Martin J. P.
Published: July 2010

The carbohydrate contents of a variety of fungal humic acid‐type melanins ranged from 1.1 to 5.9%. Values were 1.7 to 2.6% for soil humic acids and 0.4% for Leonardite peat humic acid. Fungal culture medium polymers not precipitated by acid and fungal cells contained from 12 to 55% carbohydrates. The uronic acid content of all products was very low, ranging from essentially zero (not detected) to 1.1%. Stachybotrys atra was the only fungus where uronic acids were detected in all samples. Uronic acids were, however, present in all soils, the values ranging from 0.3 to 0.4%. Recovery of uronic acids after acid hydrolysis using galacturonic acid as a check gave low values. The necessity of eliminating interferring substances before the colorimetric determination of sugars and uronic acids in soil and fungal polysaccharide hydrolysates was demonstrated. Thin‐layer chromatography of concentrated hydrolysates from the humic acid‐type fungal melanins and soil humic acids showed the presence of glucose, galactose, mannose, and xylose in most of the samples. A mass spectrum of the pyrolysis fragments of Aspergillus glaucus sp. humic acid‐type polymer showed definite series peaks related to polysaccharides, the most prominent, however, were related to proteins and phenolic substances.
Variation in Surface Charge Characteristics in a Soil Chronosequence
Authors: Hendershot W. H. , Singleton G. A. , Lavkulich L. M.
Published: July 2010

The surface charge characteristics of the B horizons of seven soils in a chronosequence developed on sandy beach material were studied. The soils range in age from 127 to 550 years and exhibit morphological and chemical characteristics ranging from Typic Udipsamment to Aquic Haplorthod. The difference between the zero point of charge (ZPC) and the pH of the soil decreased as the age of the soils increased, from a maximum value at the youngest site of 0.72 to a minimum value at the oldest site of 0.11. The decrease in this ΔpHzpc value is interpreted as indicating that the soils are approaching a steady‐state with time. The ΔpHzpc value is presented as a measure of pedogenic development.
Thermal Conductivity of Soils as a Function of Temperature and Water Content
Authors: Sepaskhah A. R. , Boersma L.
Published: July 2010

Apparent thermal conductivities of loamy sand, loam, and silty clay loam soils were measured with a cylindrical heat probe at several water contents and temperatures. Values of λ were also calculated with the de Vries model. Results show that the model may be used satisfactorily to calculate λ. However, improvements may be needed to account for the enhancement of vapor transfer at high temperatures (45° C) in medium to fine textured soils. The heat probe method of measuring the thermal conductivity requires a correction factor to allow for errors due to the entrapment of air at the surface of the heat probe, when used at water contents ranging from 0 to about 30% of saturation.

The contribution of vapor distillation to thermal conductivity was analyzed by comparing λ at 25 and 45° C. The ratios λ45/λ25 were nearly equal to unity when < 5% of total pore space was filled with water. The ratios increased, due to vapor distillation, as water filled the pores and reached maximum values of 2.17, 2.71, and 2.96 when 22, 27, and 35% of total pore space was filled with water, corresponding to soil water potentials of −0.8, −9.0, and −8.0 bars for loamy sand, loam, and silty clay loam, respectively. As the water content increased further, the ratios decreased and approached unity when > 50% of total space was filled with water.

The apparent thermal conductivity was independent of water content at very low water contents. The water molecules are in layers only a few molecules thick. The water content below which the apparent thermal conductivity is not affected by water content is a function of the soil temperature and the clay content. In our experiments these water contents were 0.03 and 0.05 cm3/cm3 at 45° C and 0.13 and 0.18 cm3/cm3 at 25° C for the loam and silty clay loam respectively.
Infiltration as Influenced by Irrigation Water Quality
Authors: Oster J. D. , Schroer Fred W.
Published: July 2010

After 19 months of irrigation with waters of different quality, columns of Heimdal loam cropped to alfalfa had infiltration rates that were correlated better with irrigation water sodicity and salinity than with soil surface (0–76 mm) or column average (0–530 mm) exchangeable sodium and soil salinity. Two sets of irrigation water parameters were tested: (i) total cation concentration (Cc) in molc m‐a (meq liter−1) and sodium adsorption ratio (SARc) of the irrigation water in equilibrium with solid phase CaCO3 at a PCO2 of 0.07% based on ion activities corrected for ion pairing; and, (ii) total cation concentration of the irrigation water as prepared and the adjusted sodium adsorption ratio based on the calculated pH of the water in equilibrium with CaCO3. On the basis of multiple linear regression analyses, the best correlation was obtained with the lime‐equilibrated water parameters (R2 = 0.87). The corresponding relationship between infiltration rate (I) in mm hour−1 and the chemical parameters was I = 6.80 − 1.10 SARc + 0.79 Cc. Cation concentration greatly affected infiltration rates even at low SAR levels (2<SAR<5). Apparently, the mechanical action of the applied water greatly enhances the effects of exchangeable sodium and soil solution concentration on swelling and dispersion at the soil surface which, in turn, has a large effect on infiltration rates.
Aluminum Organic Matter in Acid Soils: Buffering and Solution Aluminum Activity
Authors: Bloom P. R. , McBride M. B. , Weaver R. M.
Published: July 2010

The variation of solution Al3+ activity with pH, the effect of suspending salt solution cation on Al3+ activity, and the buffering intensity were determined for salt solution suspensions of three soil samples and an Al substituted peat that contained one equivalent of Al3+ for each equivalent of carboxyl groups. The soil samples used were a surface and a subsurface horizon of an Inceptisol from New York and a surface horizon of an Oxisol from Brazil. The soils were equilibrated for periods of up to 35 days in 0.02N solutions of the chlorides of K+, Na+, Ca2+, Mg2+, Cu2+ and La3+ with the addition of acid or base. In the pH range 3.9 to 4.9, plots of pH vs. pAl were linear with ΔpAl/ΔpH<2.5, significantly different from the value of 3 predicted by Al(OH)3 solubility. At a given pH, Al3+ activity was a function of the solution cation. The Al substituted peat in 0.02N CaCl2 gave a pH vs. pAl plot very similar to that of the surface horizon of the Inceptisol. Also, the addition of partially rotted leaf humus to the Inceptisol subsoil caused a reduction of Al3+ activity at any given pH even after 35 days of equilibration.

It was concluded that hydrolysis of organically bound Al is a major source of buffering in the pH range of 4 to 5 for dilute salt suspensions of acid soils and that exchange of Al ions from organic matter exchange sites controls the relationship between pH and Al3+ activity in acid soils that have a low amount of permanent charge CEC relative to the quantity of organic matter.
Effects of Burning on Chaparral Soils: I. Soil Nitrogen
Authors: DeBano Leonard F. , Eberlein Gary E. , Dunn Paul H.
Published: July 2010

Undisturbed moist or dry soil slabs collected from beneath chaparral plants were burned at different intensities in the laboratory. Inorganic and organic nitrogen levels were measured before and after burning. An intense burn over dry soil slabs decreased KCl‐extractable NH4+‐N in the litter but increased it in the underlying soil. In contrast, NO3‐‐N was decreased in both soil and litter during an intense burn over dry soil. Little change in NO3‐‐ and NH4+‐N occurred when litter and soil were moist. About 67% of the total N in the litter and soil was lost during the intense burn over dry soil, but less than 25% was lost when the soil and litter were moist. Amino acids were particularly sensitive to heating and were almost destroyed in dry litter during the intense burn. Almost 75% of the hexosamines in the litter and soil were also destroyed by the intense burn over dry soil.
Efficiency of Phosphorus Utilization by Alfalfa from Manure and Superphosphate
Authors: Goss D. W. , Stewart B. A.
Published: July 2010

Efficiencies of phosphorus utilization by alfalfa (Medicago sativa L.) from feedlot manure and superphosphate were examined in greenhouse and field studies. Alfalfa grown in soil treated with superphosphate removed a higher percentage of the added P than alfalfa grown in soil treated with manure. However, alfalfa grown in manured soil had the higher P utilization efficiency, as measured as yield increase per unit increase in P removed. This was due in part to more luxury consumption of P by the early cuttings on the superphosphate treatment. The P in feedlot manure was released more slowly for plant uptake and the P level remained adequate for a longer period. Apparently, microbial activity is important in the slow release of manure P. This was thought to be due to the increase in microbial activity as a result of the added energy source. Field studies indicated that P from feedlot manure carries over from year to year and becomes available with time.
Uptake, Translocation and Utilization of 15N‐Depleted Fertilizer in Irrigated Corn
Authors: Bigeriego Manuel , Hauck R. D. , Olson Robert A.
Published: July 2010

The objective of this study was to derive a better understanding of the manner in which N serves the nutritional needs of corn (Zea mays L.) and thereby afford a basis for improved fertilization practices. Measurements of uptake, translocation and utilization of tagged nitrogen (N) fertilizer in irrigated corn as influenced by time and rate of N application were made in a field experiment at the University of Nebraska Field Laboratory. Plant parts of root, crown, foliage, and eventually ear and grain were taken and analyzed for total N, NO3‐‐N and isotope ratio at eight growth stages.

Application of N at planting resulted in greater vegetative production, but summer sidedressed N effected slightly larger grain production with a higher grain/stover ratio. Isotope ratio analyses revealed significantly greater utilization of fertilizer N in grain production with delayed application due to more active root uptake and translocation of the fertilizer source during the grain filling period.

Following harvest, residual mineral N in soil from applied fertilizer was greater with summer sidedressing such that 24% more of the N applied could be accounted for in the crop and soil than with planting time application.
Characterization of the Thickness and Uniformity of the Coatings of Sulfur‐coated Urea
Authors: Jarrell W. M. , Pettygrove G. S. , Boersma L.
Published: July 2010

The objective of this study was to develop a test which can accurately predict the contribution of coating characteristics to the control of rates of release of urea from SCU granules. It was assumed that product quality is a function of average coating thickness and uniformity of coating thickness.

To achieve the stated objective, concentric layers of coating were removed in successive increments by dipping granules in benzene and determining at each step the percentage of granules rendered available to water penetration due to exposure of cracks or pinholes. Five SCU materials were used with a range of coating characteristics. For materials which were coated with both sulfur and sealant, the results could be explained by postulating the existence of three classes of granules: Class I granules, which have unobstructed holes through the coating, Class II granules, with holes through the sulfur coating which are plugged with sealant, and Class III granules, which have sulfur coatings with no holes through them. Class I granules begin to release urea as soon as they are wetted, Class II granules begin to release urea as soon as the sealant is broken down or removed, and Class III granules begin to release urea as soon as the sulfur coating is penetrated by removal of parts of it.
Effect of H‐SPAN on Water Retained by Soils After Irrigation
Authors: Miller D. E.
Published: July 2010

The effect of hydrolyzed starch‐polyacrylonitrile graft polymers (H‐SPAN or super slurper) on the water retention proper ties of three soils to which it had been added was evaluated in soil columns. Its effect on water retention was negligible in medium‐textured soils but it markedly increased water retained by sand. H‐SPAN added at 0.5% by weight to the upper 60 cm of sand increased the available water retained to nearly the same levels as that of a loam and a silt loam soil. The H‐SPAN treatment was more effective after the second and subsequent irrigation than after the first one. H‐SPAN reduced infiltration rates in all soils.
Absorption of Water by Soil: The Constant Flux Boundary Condition
Authors: White I. , Smiles D. E. , Perroux K. M.
Published: July 2010

Absorption of water into soil as the result of a constant flux condition at the soil surface is examined.

Experiments for a fine sand show that the surface water content, movement of the wetting front, and the water content profiles may be predicted from the soil water diffusivity function using the notion of the flux‐concentration relation of Philip (1973).

Reduced space and time variables X = Vox and T = Vost are introduced. Use of these variables greatly simplifies treatment of the system and reveals that the surface water content and the reduced position of the wetting front are uniquely defined by T while the water content profiles at any value of T are unique in terms of X.
Nitrous Oxide Emission During Denitrification in a Flooded Field
Authors: Denmead O. T. , Freney J. R. , Simpson J. R.
Published: July 2010

Little field information is available on the amounts of nitrous oxide (N2O) released from soils during denitrification, or the proportion of the denitrification loss attributable to N2O production. The paper reports studies of N2O evolution and the simultaneous disappearance of nitrate (NO3) in a flooded rice field which initially contained 4 g NO3‐N m−2 in the top 0.08 m of soil.

Measurements were made continuously for 18 days after the field was flooded. Nitrous oxide emission was calculated from the rate of increase of N2O in air circulating in a closed loop between a chamber installed in the field and an infrared gas analyzer. Emission rates as small as 1.8 ng N m−2 sec−1 could be measured. Nitrate disappearance was measured by chemical analysis of water samples.

Nitrous oxide emission showed a diurnal cycle in phase with water temperature. Between the second and nineteenth day of flooding, 2.7 g NO3‐N m−2 disappeared from the water and 0.038 g N2O‐N m−2 were produced, only 1.4% of the apparent N loss. In a supplementary, small‐bay experiment in which sodium nitrate and glycerol were added to the water, N2O production accounted for only 0.8% of the NO3 disappearance. Even allowing for NO3 removal through other mechanisms, the production of N2O in both experiments was very much less than the 7% commonly assumed for denitrification in current models of the global N2O budget.
Characterization of Hysteresis in the Desorption of 2,4,5‐T from Soils
Authors: Koskinen W. C. , O'Connor G. A. , Cheng H. H.
Published: July 2010

Methods for characterizing adsorption‐desorption of 2,4,5‐T (2,4,5‐trichlorophenoxyacetic acid) in the soil were investigated. Using the conventional method, the adsorption isotherms conformed to the linearized Freundlich equation for initial 2,4,5‐T concentrations of 2 to 176 µmol/liter. Desorption of 2,4,5‐T from soils exhibited significant hysteresis at all concentrations, with lower concentrations showing greater hysteresis. The longer the equilibration time for desorption, the greater was the observed hysteresis. Therefore, nonattainment of equilibrium was not evident as a major cause of the hysteresis effect. Using a modified method, biochemical degradation of 2,4,5‐T during the desorption process accounted for a significant amount of the hysteresis observed. In the Palouse soil, approximately 63% of the observed hysteresis was eliminated by taking into account the biochemical degradation. In the Glendale soil, approximately 35% of the hysteresis was attributed to biochemical degradation.
Transport of Inorganic Phosphorus in an Alfisol
Authors: de Camargo O. A. , Biggar J. W. , Nielsen D. R.
Published: July 2010

Adsorption, desorption, and movement of phosphorus in an Alfisol soil were characterized by miscible‐displacement and batch‐type experiments. The influence of pore‐water velocity, aggregate size, and pretreatment of the soil with P was evaluated. A model which considers the interaction of P with soil as an equilibrium kinetic process was utilized to differentiate between instantaneous and time‐dependent reactions which appear to govern the adsorption‐desorption process during displacement.

Pore‐water velocity has a greater influence on the adsorption rather than the desorption process which appeared to be more chemically controlled. Aggregate size affected the time‐dependent more than the instantaneous processes of soil‐P interaction. Instantaneous reactions between P and soil were shown to be mitigated by pretreatment of the soil with P in contrast to time‐dependent reactions. A pore model was hypothesized to explain the differential uptake and release of P during displacement.