bluuebunny/crossref_metadata_2025 huggingface dataset:
Calcium Phosphate Precipitation: Effects of Common and Foreign Ions on Hydroxyapatite Crystal Growth
Authors: Brown J. L.
Published: July 2010

Calcium phosphate precipitation from slightly supersaturated solutions was induced by addition of hydroxyapatite (HAP) seed crystals. The rate of seed crystal growth was measured during the first 60 min by disappearance of P from solution. Effects of solution Ca2+, F‐, initial P, Mg2+, HCO3‐, and HAP seed concentrations on crystal growth were measured by evaluating the empirical reaction order (n) and the rate constant (K) for P‐removal by fitting the data to the equation for interface‐controlled crystal growth. Phosphate disappearance had second‐order dependence on the P concentration when initial F was > 0.05 mM. An increase of either 1 mM Ca or 0.1 mM F caused an increased‐P removal rate of about 10 times. Both Mg and HCO3 interfered with crystal growth. The P‐removal rate was aproximately seven times more rapid at the 1‐mM HCO3 level than at the 6‐mM level. Apatite crystal growth was strongly reduced in the presence of Mg. An increase of 1 mM Mg decreased the P‐removal rate by greater than two orders of magnitude. Reactions exhibited second‐order dependence on the P concentration when interfering ion concentrations were minimal and F was present. Values of (n) increased regularly when increasing concentrations of either Mg or HCO3 were present. Surprisingly, relatively high initial P concentrations caused temporary crystal growth interference although this could also have been due to Mg. Apatite crystal growth was strongly influenced by seed concentrations. An increase of 100 mg/liter HAP resulted in a rate constant increase for P‐removal of more than three orders of magnitude.
Effect of Lime on Exchangeable Magnesium in Variable Surface Charge Soils
Authors: Grove J. H. , Sumner M. E. , Syers J. K.
Published: July 2010

Early work with commercial‐grade limestones containing small quantities of MgCO3 (2–10%) demonstrated that exchangeable Mg was reduced as the soil pH was increased in several soils. An incubation experiment was conducted to more precisely determine the extent of the Mg “fixation” and to evaluate several hypotheses regarding the mechanism behind this pH‐dependent phenomenon.

Five acid topsoils were used in this study. The clay fractions of four of these were dominated by constant‐surface potential colloids. Five levels of lime (CaO) and three levels of Mg from two sources (MgCO3 and MgSO4) were applied in complete factorial combination. Exhaustive extraction with 0.2N NH4Cl was used to determine exchangeable Mg and K. Cation exchange capacities were obtained by extracting the NH4+ saturated samples with 0.2N KNO3.

The Mg‐fixation reaction was essentially complete in 24 hours. Lime application reduced NH4Cl‐extractable Mg in all soils, although not until the soil pH was raised to 5.1 (1N KCl). Effective CEC increased with lime addition but was unaffected by Mg treatment. It appears that the Mg was lost to a surface‐solid phase involving Al. For the soils with clay fractions dominated by constant‐surface potential colloids, Mg recovery by NH4Cl was inversely related to the quantity of exchangeable Al per unit mass of clay found in the acid‐end member of each soil. The lack of change in effective CEC and exchangeable K with Mg addition at higher soil‐pH values indicated that a charge blocking brucite‐like interlayer was not formed.
Release Rate of Potassium and Structural Cations from Micas to Ion Exchangers in Dilute Solutions
Authors: Feigenbaum S. , Edelstein R. , Shainberg I.
Published: July 2010

The rate of release of K and structural cations from three micas (biotite, phlogopite, and muscovite) was measured in two‐particle size ranges (5 – 20µm and 20 – 50µm), in dilute electrolyte solutions (0.001N), and at pH 3.0 and 7.0. The rate of K release from phlogopite and biotite was similar to the rate of release of structural cations under acidic conditions and significantly higher under neutral conditions. These findings indicate that structural decomposition of phlogopite and biotite is dominant in acidic conditions, and that the role of interdiffusion increases in neutral conditions. Decomposition was more sensitive than interdiffusion to particle size.

The rate of K‐release from muscovite was about 5 and 15% that from biotite and phlogopite, respectively. The rate of K release from muscovite was higher than the rate of Al release. This indicates that muscovite is the most stable of the three micas and that the decomposition mechanism for K‐release in muscovite was less important.
Application of Phosphorus, Potassium, and Zinc to Corn Grown for Grain or Silage: Early Growth and Yield
Authors: Rehm G. W. , Sorensen R. C. , Wiese R. A.
Published: July 2010

Considerable effort has been devoted to the study of the application of N and S for corn (Zea mays L.) production on irrigated sandy soils in the western Corn Belt. Requirements for P, K, and Zn have not been extensively researched. This study, initiated in 1974 and continued through 1978, was designed to measure the effect of repeated applications of P, K, and Zn to irrigated sandy soil under systems of continuous grain and silage production.

Two adjacent series of plots were used. In one series, corn was harvested for grain and the residue was incorporated with a disk. Corn from the adjacent series was harvested for silage each year, thus eliminating the return of any residue to the soil. Twenty‐three treatments were selected from a 53 complete factorial to fit a central composite design with identical treatments used in both series. To measure early growth, whole plant samples were collected when plants were 40–60 cm tall. Silage yields were measured prior to or at physiological maturity. Grain yields were measured in mid‐October.

Fertilizer P had the most consistent effect on early plant growth, yield, and crop maturity. The application of fertilizer P had a curvilinear effect on early growth and yield with maximum yield produced by the application of 22–33 kg P/ha. The rate of fertilizer P required to achieve maximum production in any one year was not related to yield level. The effect of P on crop maturity was not consistent with the effect being linear in some years and curvilinear in others. The effect of fertilizer K was inconsistent throughout the study. Application of fertilizer Zn had no effect on corn growth, yield, and crop maturity. There was no significant P × Zn interaction throughout the study.
Ammonia Loss and Associated Reactions of Urea in Calcareous Soils
Authors: Fenn L. B. , Miyamoto S.
Published: July 2010

Urea in soil is a mobile compound which can be lost by leaching or ammonia (NH3) volatilization. This research examined the contributions of water additions and chemical reactions in explaining the behavior of applied urea.

Urea [CO(NH2)2] initially moves undissociated into the soil with added water. Ammonia losses from surface‐applied urea thus decreased with increasing amounts of applied water. Ammonia losses from urea were minimal if injected into the soil 2.5 cm or more, whereas NH3 losses from (NH4)2SO4 (AS) were still high when placed 7.5‐cm deep. Application of AS produced chemically equivalent amounts of Ca and Mg whereas urea and NH4OH precipitated Ca and Mg. The amount of Ca and Mg precipitated increased with decreasing NH3 losses. Precipitation of divalent cations enhanced adsorption of NH4 on soil cation exchange sites, thereby reducing upward movement of NH4 and subsequent NH3 losses. The presence of Ca from reaction of AS with CaCO3 enhanced upward movement of NH4 and increased NH3 losses.
The Basic Cation Saturation Ratio Concept and Lime and Potassium Recommendations on Delaware's Coastal Plain Soils
Authors: Liebhardt William C.
Published: July 2010

A lime‐potassium factorial experiment (four K and seven lime treatments) was established on a Coastal Plain soil in 1970. Wide ranges in soil pH and percent Ca, Mg, and K saturation were obtained. Results indicate that the use of the Basic Cation Saturation Ratio Concept for making fertilizer recommendations should be modified for Delaware's sandy Coastal Plain soils. This concept, used by commercial labs, recommends that the exchange complex contain 75% Ca, 15% Mg, and 2–5% K. Research shows that use of these saturation percentages and the resulting Ca/Mg, Ca/K, and Mg/K ratios is not warranted and may result in reduced yields or increased costs, or both. A liming program which maintains the soil pH between 5.5 and 6.0 is suggested. Soil pH > 6.0 tends to result in Mn deficiency. To maintain a soil pH between 5.5 and 6.0 requires a Ca plus Mg saturation of 65–75% rather than that presently suggested by commercial labs (85–90%). Calcium plus magnesium saturation of this magnitude results in a soil pH of 6.5–6.8 on these sandy soils and a resulting Mn deficiency. Wide ranges or ratios of Ca and Mg have not influenced yield as long as soil pH is in the correct range.

A K saturation of 2–5% is suggested by the use of this concept, data indicates that this saturation percentage is sufficient for corn and soybeans on Delaware's sandy Coastal Plain soils.
Soil Variability on Surface‐Mined and Undisturbed Land in Southern Illinois
Authors: Indorante S. J. , Jansen I. J.
Published: July 2010

Five different soil units were defined on surface‐mined land to group soils that were constructed by similar mining and reclamation methods and from similar materials. Three soil units were defined on undisturbed landscape using the traditional soil series concepts of soil classification and mapping. The goal in defining and mapping soil units on both surface‐mined land and undisturbed land was to minimize variation of soil properties within soil units.

A nested sampling design allowed for testing the lateral variation of selected properties within and among the five units on surface‐mined land and within and among the three units on undisturbed land. The analysis of variance conducted separately for the constructed soil units and the undisturbed units indicate that there are more significant differences among the five constructed soil units than among the three undisturbed soil units.

Variability, as measured by the coefficient of variation, within the constructed soil units was similar to that within the soil units on undisturbed land. Pre‐mine overburden characteristics and method of soil construction are useful guides for mapping soils on surface‐mined land.
Backfill Alteration Effects on Pipe Drainage of a Clay Soil
Authors: Taylor G. S. , Hundal S. S. , Fausey N. R. , Schwab G. O.
Published: July 2010

A permeable backfill may improve pipe drainage for soils that have a slowly permeable subsoil. Permeable backfills were created directly over drains installed 8 years earlier by replacing soil with gravel and by trenching and refilling. The permeable zone extended from the bottom of the plow layer to the drain. The research was conducted on a poorly drained, cultivated, lakebed clay soil in Ohio. The addition of gravel increased drain flow rates by a factor of 2 to 3 during periods of ponding but had no effect on flow rates under nonponded conditions nor on water table drawdown rates. The ponded flow rates for drains with gravel have not changed after 3 years. During the first year, trenching and refilling had the same effect on drain flow rates as gravel. During the second year, the ponded flow rates declined to only 50 or 60% of those with gravel. The permeable backfill functioned as a hydraulic connector and permitted ponded water to bypass the relatively impermeable subsoil in flowing to the drain. Sediment concentrations in the drain water were unaffected by backfill alterations.
Nitrous Oxide Emissions from a Native Shortgrass Prairie
Authors: Mosier A. R. , Stillwell M. , Parton W. J. , Woodmansee R. G.
Published: July 2010

Nitrous oxide (N2O) emissions from a native shortgrass prairie averade 2.3‐g N ha−1 day−1 during a summer sampling period. Although N2O emissions from the native grassland were small, they were substantially larger than earlier estimates from uncultivated soils. The losses accounted for about 10% of N inputs from atmospheric deposition and N2‐fixation, which represented a significant N‐loss mechanism that had not been recognized. Nitrous oxide losses from similar sites treated with urea to simulate ungulate urine deposition were about three times greater than from untreated soils, but still amounted to only 0.6% of the added N.
Representative Sampling for Bulk Density in a Vertisol
Authors: Chan K. Y.
Published: July 2010

Undisturbed bulk density samples (7.5 cm internal diam and 7.5 cm long) were collected using a Tanner Sampler at different depths down to 50 cm from a Vertisol in Australia. Representative samples were obtained only for the top 20 cm layer. For the deeper layers, the bulk density results followed the one‐dimensional shrinkage relationship, instead of the three‐dimensional one, and therefore suggested nonrepresentative sampling. This was explained in terms of the increasing size of the soil structural units with depth, and hence the core samples from below 20 cm were too small to represent the field soil structures.
Inorganic Phosphorus in Calcareous Rockland Soils of the Bahamas
Authors: Taylor Robert W. , Woods Jonathan
Published: July 2010

The phosphorus (P) status of cultivated and forest calcareous “rockland” soils of the Bahamas was investigated to acquire information on available P, forms of inorganic P, and P adsorption maxima. Available P was extracted by four methods: Bray P‐1, 0.5M NaHCO3, 0.01M CaCl2, and distilled‐deionized H2O. Soil P was fractionated according to the Chang and Jackson procedure, and Langmuir P adsorption maximum was determined by the method of Olsen and Watanabe for soils.

For cultivated soils the order for amount of P removed by the extractants was generally NaHCO3 > Bray > H2O > CaCl2. The pattern for forest soils, having less available P, was NaHCO3 > H2O > CaCl2 > Bray. Phosphorus fractionation data of selected soils indicated that 55.7 to 99.9% of the inorganic P was in the Ca‐P fraction. Correlation analysis between P fractions and available P revealed that all four extraction methods were positively correlated only with the Ca‐P fraction. Most of the adsorption maxima (computed from region I of the isotherms) for cultivated and forest soils were in the upper medium range. The Langmuir P adsorption constant, K1, related to the energy of adsorption, was generally smaller for cultivated soils, suggesting that P, being more loosely bound to these soil surfaces, would be more available to plants. Some fine‐textured forest soils had very high K1 values, ranging from 52 × 104 to 222 × 104 liters/mole. The implication is that these soils will require heavy fertilizer P applications to adequately supply crops with P when cultivated initially.
Particle Size Fractions and Their Use in Studies of Soil Organic Matter: I. The Nature and Distribution of Forms of Carbon, Nitrogen, and Sulfur
Authors: Anderson D. W. , Saggar S. , Bettany J. R. , Stewart J. W. B.
Published: July 2010

Organo‐mineral complexes in various size fractions from the surface horizons of two Chernozemic soils (Typic Argiboroll and Udic Haploboroll) were separated without chemical pretreatment by ultrasonic dispersion in water, followed by sieving and centrifugation. The organic carbon (C), nitrogen (N), and sulfur (S) composition in the size fractions and the degree of polycondensation of humic materials extracted by an alkaline pyrophosphate technique were compared. Fifty‐five to 58% of the organic C was in the clay fraction, with greatest absolute amounts in the coarse clay (2–0.2 µm). Carbon/nitrogen ratios narrowed as particle size decreased. The organic matter separated from the coarse‐clay and fine‐silt fractions (5–2 µm) was dominated by conventional humic acids (HA‐A), which based on their strong adsorption at 280 nm and resistance to acid hydrolysis, were considered strongly aromatic and recalcitrant in soil. In contrast, the organic matter associated with the fine clay (<0.2 µm) was largely fulvic acids (FA‐A, FA‐B) and humic acids (HA‐B) that were less aromatic than conventional humic acids and contained considerable amounts of hydrolyzable N. The fine‐ and coarse‐clay fractions (<2 µm) contained >70% of the total soil S, >80% of the HI‐reducible S, and >64% of the carbohydrate C. In relation to C and N, S was preferentially associated with the fine‐clay fractions. The C/S and N/S ratios decreased substantially from maximum values in the fine‐silt fraction (approximately 120:1 and 10:1, respectively) to minimum values in fine clay (approximately 33:1 and 4.5:1, respectively). The distinct differences between the humus of the coarse clay‐fine silt and the fine‐clay fractions indicate that size fractionation following ultrasonic dispersion in water is a promising method of isolating stable and labile forms of soil organic matter. The data also support earlier hypotheses on the nature of soil S that were based on studies of chemical separation of organic matter from complete soils.
Ammonia Losses from Surface‐Applied Nitrogen Fertilizer as Controlled by Soluble Calcium and Magnesium: General Theory
Authors: Fenn L. B. , Taylor R. M. , Matocha J. E.
Published: July 2010

Ammonia volatilization from soils after surface application of urea or inorganic N was reduced by Ca and Mg nitrates or chlorides. Sulfates were only slightly effective. Suppression of NH3 loss was a result of two chemical reactions: (i) precipitation of CO3 by Ca, thus preventing permanent (NH4)2CO3·H2O (AC) formation, and (ii) Ca depression of soil pH by depression of the dissociation of the CaCO3‐Ca(OH)2 buffer system. Soil pH values as low as 6.5 were recorded in calcareous soil and 3.9 and 4.5 in the acid soils after addition of Ca. Soil pH values in the presence of Ca reached approximate neutrality in 24 hours even in acid soils. Soil pH without Ca but with AC increased to > 9.0 in every soil. Addition of AC plus Ca reduced the pH of calcareous soil to 5.3 and raised it to 5.7 in acid soils. Calcium carbonate precipitation eventually occurred in acid soils, preventing high NH3 losses. Evidently, CaCO3 precipitated on the surface of acid soils after the pH reached a certain critical value and, as expected, the pH was maintained near that of the pure CaCO3 system.
Leaf‐Cutter Ant (Atta cephalotes) Influence on the Morphology of Andepts in Costa Rica
Authors: Alvarado Alfredo , Berish Cory W. , Peralta Francisco
Published: July 2010

Twenty‐seven soil profiles distributed within a 2.5‐ha site were described as Typic Dystrandepts of the Colorado soil series. Leaf‐cutter ant influence was noted in 85% of the pedons. The influence on each profile was estimated, and out of all profiles, 37% had low, 26% medium, and 22% high disturbance. The surface area covered by leaf‐cutter mounds was 38.9% of the study area; only 1% of the aboveground disturbed area was active, however. Leaf‐cutter ants transport material from the AB and B horizons to the soil surface, producing a new A1 horizon and, in addition, some subsoil chambers are filled with plant material. It is proposed to use a subindex (i) to denote insect influence as an agent on the formation of a subsoil horizon (ABi, B2i) and also, for the overburden (Ai).
Subsurface Horizon Blending: An Alternative Strategy to B Horizon Replacement for the Construction of Post‐Mine Soils
Authors: McSweeney K. , Jansen I. J. , Dancer W. S.
Published: July 2010

This study was initiated to evaluate various combinations of substratum and B horizon materials, as subsurface rooting media. Materials were collected from each solum and substratum horizon to a depth of about 6 m at two surface mine sites. One of the sites was in southern Illinois and had an infertile Darmstadt (Albic Natraqualf) surface soil with a strongly acid (pH 5.2) and natric subsoil. The other was in west central Illinois and had a Sable (Typic Haplaquoll) surface soil which supports high yielding grain crops with proper management.

The experiment was conducted in a greenhouse using large plant containers. The test crop, soybean, was germinated in A horizon material, or in a blend of materials containing A horizon, placed over the given surface rooting medium. This procedure was employed in order to simulate field conditions where seeds germinate in topsoil and root into the underlying material. Performance of the test crop was best where A horizon was segregated and replaced over a blend of the next 3 m of material for treatments made from the Darmstadt materials from southern Illinois. It was poorest where A horizon material was replaced over material from the Darmstadt B2 horizon. The other treatments were intermediate in performance between the A/Top 3 m and the A/B2 (subsoil). A similar trend was found with the Sable materials from west central Illinois, but the difference between the best performing treatment, A/Top 3 m, and the poorest, A/B2 (subsoil), was not as marked.
Granule Size and Composition of Superphosphate Containing Added Copper and Zinc
Authors: Gilkes R. J. , Sadleir S. B.
Published: July 2010

This study determined the distribution and forms of P, S, Ca, Cu, and Zn in Cu‐Zn superphosphate in order to determine whether uniform application of nutrients to soils is promoted by use of such fertilizers. Concentrations of insoluble and water‐soluble Cu, Zn, Ca, P, S, and citrate‐soluble P in various sized fractions of commercial Cu‐Zn superphosphates were almost uniform, apart from a relative concentration of insoluble Cu in the finest‐sized fraction. Most of each constituent was present in 1‐ to 4‐mm granules as a consequence of the preponderance of this size granule in the fertilizers. Individual granules were chemically analyzed and showed little variation in S, Ca, and P concentrations, whereas much wider variations occurred in Cu and Zn concentrations. These variations probably are not of agronomic significance.
X‐Ray Diffraction Line Profile Analysis Vs. Phosphorus Sorption by 11 Puerto Rican Soils
Authors: Jones R. C.
Published: July 2010

The increase in the areas under goethite (110), gibbsite (002), and hematite (104) x‐ray diffraction lines, due solely to small crystallite effects, was plotted against phosphorus sorption for 11 Puerto Rican soils. This increase is shown to be proportional to the total surface area of each phase measured and is therefore referred to as the surface area index. The data showed a very high correlation (R2 = 0.95 for a straight line and R2 = 0.96 for a second‐order polynomial) between the surface area index of goethite and phosphorus sorption. In comparison, the correlation between the surface area index of gibbsite and phosphorus sorption was poor (perhaps because gibbsite was present in low concentrations relative to goethite) but judged to be significant (R2 = 0.56). The correlation between the surface area index of hematite and phosphorus sorption was not significant (R2 = 0.26) as compared to goethite and gibbsite. The sum of the surface area indices of goethite and gibbsite showed a near‐perfect correlation with phosphorus sorption (R2 = 0.98 for a second‐order polynomial). The study demonstrated that, in the case of goethite and to a lesser extent gibbsite, the mean crystallite size is more important than the abundances of the phases for explaining observed phosphorus sorption characteristics of soils.
Variation in Natural N‐15 Abundance of Central Saskatchewan Soils
Authors: Karamanos R. E. , Voroney R. P. , Rennie D. A.
Published: July 2010

Natural 15N abundance data from 38 well‐drained cultivated, 11 native pasture, and 9 saline seep soil profiles from Saskatchewan were compiled. The mean δa15N value (per mill 15N excess) for all surface soil samples was 9.4 with a standard deviation of 3.0. Land use was not a factor determining δa 15N values as there was no differences in the δa15N values of surface soil samples from cultivated and native pasture areas; the mean δa15N value for both these types of profiles was 8.6 with a standard deviation of 1.9. However, the mean δa15N value for saline seeps (13.8 ± 3.8) was significantly higher than that of either well‐drained cultivated or pasture soils.

Spatial variability does not appear to unduly limit use of natural variations in 15N abundance to study important agronomic processes in Chernozemic soils.
Nitrous Oxide Production by Nondenitrifying Soil Nitrate Reducers
Authors: Smith M. Scott , Zimmerman Karen
Published: July 2010

Of 214 soil bacterial isolates able to reduce NO3‐, 209 produced nitrous oxide (N2O), even though only 46 were respiratory denitrifiers (competent to carry out complete reduction of NO3‐ to N gases). Nitrite or NH4+ was the major product of NO3‐ reduction by the nondenitrifying organisms, but typically about 5 to 10% and up to 34% of the NO3‐ reduced by them was released as N2O during a 2‐week incubation. Bacillus and Enterobacter were the most commonly observed genera of nondenitrifying N2O producers. Fermentative NO2‐ reduction and N2O production by a Bacillus sp. and a Citrobacter sp. were characterized in pure culture studies. Dinitrogen (N2) was not produced in detectable quantities by these organisms. When added to autoclaved soil, they accumulated more N2O than two denitrifying pseudomonads, since the latter consume and produce N2O. In tryptic soy broth (TSB), which allows active fermentative growth, NH4+ was apparently the major product of NO3‐ reduction. In nutrient broth (NB), NO2‐ accumulated. Added NH4+ did not inhibit N2O production or apparent reduction to NH4+, indicating that these processes are not assimilatory. The effect of added glucose on N2O production varied with the organism and media composition. Nitrous oxide production from NO2‐ by these organisms was shown to be at least partially a biochemical reaction. The N2O evolved slowly in batch cultures and mostly after apparent growth ceased. This is apparently a novel mechanism of N2O generation which differs significantly from respiratory denitrification.
Measurement of Mycorrhizal Infection in Soybeans
Authors: Bethlenfalvay G. J. , Pacovsky R. S. , Brown M. S.
Published: July 2010

Infection of soybean [Glycine max (L.) Merr.] roots by the vesicular‐arbuscular mycorrhizal fungus Glomus fasciculatus (Thaxt. sensu Gerd.) Gerd. and Trappe was assessed throughout the ontogeny of the symbiotic association. Degree of infection was evaluated by a histological method as percent infection and colorimetrically as mg chitin/g mycorrhiza. Correlation of data by the two methods was highly significant (r = 0.99) below 60% infection and not significant (r = 0.62) at higher levels. Assessment of infection by the histological method did not yield significantly different data above 60% infection. Data by the colorimetric method were statistically distinct at all levels of infection. The effects of biological and chemical contaminants on the colorimetric assay were determined. The fungal component of mycorrhizae was compared to purified chitin standards. Use of chitin for standard curves in the absence of degradation products from uninfected root materials significantly (p < 0.05) overstated the degree of infection. Colorimetric determination of fungal infection in mycorrhizae is recommended when high levels of infection are expected.
Pyrite and Marcasite Surface Area as Influenced by Morphology and Particle Diameter
Authors: Pugh C. E. , Hossner L. R. , Dixon J. B.
Published: July 2010

The morphology of massive and framboidal pyrites and marcasite extracted from lignitic cores was examined with light and scanning electron microscopes. The primary objective was to determine the surface area for these sulfide minerals. Framboidal pyrite spheres consisted of micron‐sized crystals and suggested a high surface area compared to other iron (Fe) sulfides. Specific surface space was determined using the linear form of the B.E.T. equation and N2 gas as the adsorbate.

Framboidal pyrite was composed of individual microcrystals that ranged from 1 to 5 µm in diameter. Surface area of framboidal pyrite remained near 2.0 m2/g for mean diameters ranging from 150 to 60 µm but increased to as high as 4.0 m2/g for diameters between 5 and 2 µm. Marcasite spheres were 4 to 5 times larger in diameter than single framboids. Surface area of all fractions of marcasite and massive pyrite ranged from 0.2 to 0.5 m2/g. Specific surface decreased as particle size increased.
Simulated Weathering of Lignite Overburden Shales from Northeast Texas
Authors: Senkayi A.L. , Dixon J.B. , Hossner L.R.
Published: July 2010

Unweathered overburden shale was continuously leached with water and sulfuric acid solutions (10−3 and 10−2N) for periods of up to 3 months. Clay samples from the shale were also subjected to artificial weathering by incubation in sulfuric acid solutions. Acidity resulted in increased leaching of the basic cations from the exchange complex, particularly Ca and Mg, and a decrease in percent base saturation from 100 to < 20. The more concentrated acid solutions appreciably increased release of structural cations, especially Al, Fe, and Mg. Release of Fe and Mg was mostly associated with weathering of ferromagnesian chlorite. Progressive disappearance of chlorite from clay suspensions aged in solutions of increasing acidity was observed. Differential dissolution of chlorite and smectite resulted in concentration of kaolinite and mica. The relative stability of the layer silicate minerals to acidic conditions decreased in the following order: kaolinite > mica > smectite > chlorite. Weathering of chlorite in the overburden materials is a potential source of Fe oxides in reclaimed strip‐mined lands.
Mineralogy and Chemistry of Arctic Desert Soils on Ellef Ringnes Island, Arctic Canada
Authors: Foscolos A. E. , Kodama H.
Published: July 2010

Morphological, mineralogical, and chemical characteristics of five soil profiles derived from different parent materials have been studied on the Ellef Ringnes Island, Canadian Arctic Archipelago. The aim was to investigate weathering and pedogenesis of Arctic desert soils.

Morphological, mineralogical, and chemical data of the soil horizons indicate that there is very little soil differentiation between the parent material and the top horizons. However, since the Wisconsin retreat, some 11,000 years ago, bioxidation of pyrite Thiobacillus ferroxidans has converted most of the studied soil to acid sulfate soils containing sulfate‐bearing minerals such as natrojarosite and gypsum.
On the Estimation of N‐Mineralization Parameters from Incubation Experiments
Authors: Talpaz H. , Fine P. , Bar‐Yosef B.
Published: July 2010

Accurate prediction of nitrogen mineralization in soils requires reliable parameters which are determined in incubation experiments. The estimated values of the potentially mineralizable organic nitrogen (No) and the mineralization rate constant (k) also depend on the mathematical analysis of the incubation results. Analysis of data by other researchers (Stanford and Smith, 1972) by a nonlinear regression procedure gave estimates of No and k which differed from those obtained by a linear regression technique. Theoretical considerations show that the difference between the two techniques results mainly from the specified behavior of the error term in the mineralization rate equation. The nonlinear regression procedure is shown to be preferable to the linear regression technique.
The Thermodynamics of Ternary Cation Exchange Systems and the Subregular Model
Authors: Chu Shu‐Yuan , Sposito Garrison
Published: July 2010

The thermodynamic theory of ternary exchange equilibria is developed. It is shown that the analogs of well‐known thermodynamic expressions for binary exchange systems can be derived for ternary systems as well. The subregular model of ternary cation exchange systems, which was applied recently to NH4‐Ba‐La exchange on montmorillonite, is examined critically within the thermodynamic context. It is found that the subregular model for a ternary system cannot be expressed solely in terms of parameters that depend only on data obtained for binary systems, in contradiction with claims made recently in the literature. The subregular model is shown to contain one parameter that requires ternary exchange data for its evaluation. A calculation of this ternary constant for NH4‐Ba‐La exchange on montmorillonite indicated that its value was zero within experimental precision. Nonetheless, in general it must be concluded that the behavior of ternary exchange systems cannot be predicted from data on binary exchange systems alone.
Nutrient Diagnosis in Corn Grown on Hydric Dystrandepts: II. Comparison of Two Systems of Tissue Diagnosis
Authors: Escano C. R. , Jones C. A. , Uehara G.
Published: July 2010

Recent studies suggest that the Diagnosis and Recommendation Integrated System (DRIS), which utilizes ratios of tissue nutrient concentrations rather than the concentrations themselves, consistently produces more accurate diagnoses of nutrient deficiencies and imbalances than critical concentration approaches. However, preliminary results indicated that the DRIS based on published optimum ratios of maize earleaf nutrient concentrations gave inaccurate diagnoses of N and P fertilizer responses on Hydric Dystrandepts. The objectives of this study were to evaluate several locally calibrated modifications of the DRIS and to compare their diagnostic accuracies with those of a locally calibrated critical concentration approach. The percentage of correct diagnoses [method (D) in the first paper in this series] was used to determine the diagnostic accuracy of the two approaches. Both approaches were more accurate when the critical values of nutrient concentrations or the critical values of ratios of nutrient concentrations were derived from experimental data rather than from published values. The accuracy of the DRIS approach was improved by (i) judicious selection of the high‐yielding subpopulation, (ii) selecting the critical values of DRIS indexes based on their effects on diagnostic accuracy, and (iii) using 10 rather than either 3 or 36 ratios of nutrient concentrations to calculate DRIS indexes. After calibration of both approaches, the DRIS approach was 8% more accurate than the conventional approach for diagnosis of N deficiency. The two approaches were almost equally accurate for diagnosis of P deficiency.
Estimation of Saturated Hydraulic Conductivity from Soil Morphological and Genetic Information
Authors: King J. J. , Franzmeier D. P.
Published: July 2010

Saturated hydraulic conductivity, Ksat, was measured below the water table by the piezometer method for subsurface horizons of several Indiana soils. Lowest Ksat rates were in compact glacial till, paleosols formed in till and fragipan horizons formed in loess. Camblc and argillic horizons had intermediate rates. Highest rates were in B3 horizons formed in water‐reworked glacial till materials. For prediction purposes, data were grouped by soil texture and standard soil structure classes in one classification and by texture, origin of parent material, and kind of genetic horizon in another classification. The second grouping resulted in more homogeneous classes, but some of these classes spanned more than one order of magnitude. The proposed method for determining Ksat and using the results to estimate it for other horizons can be used by field soil scientists to obtain better estimates for many soils.
Substrate Characterization of an Experimental Marsh and Three Natural Marshes
Authors: Lindau C. W. , Hossner L. R.
Published: July 2010

Dredge material from the Gulf Intracoastal Waterway near Galveston, Tex., was used as a substrate material in the construction of an experimental intertidal salt marsh. Chemical and physical properties of dredge substrate samples at 270 sites were monitored over a 16‐month period. Cation exchange capacity (CEC), extractable phosphorus (P), total Kjeldahl nitrogen (TKN), NH4‐N, and organic matter increased from 3.0 to 7.4 meq/100 g, 24 to 96 µg P/g, 85 to 296 µg N/g, 3.0 to 9.9 µg N/g, and 0.2 to 0.5%, respectively. No significant increases in N and P were observed in the substrate due to fertilization.

A separate study comparing substrate properties of the experimental marsh to three natural marshes demonstrated that organic matter, TKN, and NH4‐N concentrations in the experimental marsh were lower. Organic matter, TKN, and NH4‐N in the experimental marsh substrate averaged 0.6%, 260 µg N/g, and 5.4 µg N/g compared to 2.3%, 650 µg N/g, and 12.1 µg N/g, respectively, for the three natural marshes. Within each of the four marsh sites extreme spatial heterogeneity of chemical and physical properties was apparent.
Ammonium Orthophosphate and Ammonium Polyphosphate as Sources of Phosphorus for Potatoes
Authors: Rhue R. D. , Hensel D. R. , Yuan T. L. , Robertson W. K.
Published: July 2010

A field experiment was initiated in 1978 to compare the effects of granular diammonium phosphate (DAP) and liquid ammonium polyphosphate (APP) on growth, nutrient content, and yield of potatoes (Solanum tuberosum L.). Two sites on a coarse‐textured Inceptisol with markedly different cropping histories were selected, one with 5 ppm P, the other with > 200 ppm P extractable with 0.05N HCl + 0.025N H2SO4. Fertilizers were banded at P rates of 0, 56, 112, and 168 kg/ha at the low P site, and 0, 24, and 48 kg/ha at the high P site. At the low P site tuber yields and tissue P concentrations were lower with APP than with DAP, while tissue concentrations of Ca, Mg, Mn, and Zn were higher with APP. At the high P site, tuber yield and top dry weight were not affected by P source, but tissue Ca and Mg were higher and tissue P lower with APP.

In 1979 and 1980, DAP and APP were applied at a rate of 56 kg P/ha at the low P site. Tissue levels of P again were lower while those of Ca, Mg, Mn, and Zn were higher with APP both years. Tuber yields were lower with APP in 1980.

In 1980, DAP and APP were applied at the high P site at the same rates used in 1978. Yields were unaffected by P source but tissue P was lower and tissue Zn was higher with APP.

Extractable P levels in soil samples taken after harvest were higher in 1978 with APP. With time, extractable P declined for both sources, and by the following crop season, there were no differences in extractable P due to P source. Extractable P again was higher in 1980 where APP had been applied.

The results showed that availability of fertilizer P for winter‐planted potatoes was less with APP than with DAP. Less P was found in tops of potatoes with APP regardless of the level of available soil P. Tuber yields, however, were less affected by P source, and the data suggest that most years' tuber yields will not be different with these two sources except on soil with very low levels of available P. Application of APP also resulted in increased uptake of Ca, Mg, Mn, and Zn by potatoes.
Soil Water Content by Microwave Drying: A Routing Procedure
Authors: Gee G. W. , Dodson M. E.
Published: July 2010

A routine procedure was established for determining soil water content by microwave drying. The procedure requires small, 20‐gram soil samples heated for a 20‐min period at full power (600 to 650 W) in a household‐type microwave oven. Using this procedure, consistent agreement (within 0.5 wt%) was obtained between microwave and electric oven drying for soil materials ranging from quartz sands to fine silts and clays, with water contents ranging from air‐dry to saturation and with organic matter ranging from 0 to > 20 wt%.
Copper(II) and Iron(III) Complexation by the Carboxylate Group of Humic Acid
Authors: Boyd Stephen A. , Sommers Lee E. , Nelson Darrell W.
Published: July 2010

Infrared (IR) spectroscopy, between 2,000 and 1,000 cm−1, was used to identify the mode by which carboxylates of a soil humic acid (HA) complexed Cu2+ and Fe3+. Carboxylic acid groups of HA (R‐COOH) were converted to carboxylates (R‐COO‐) by forming coordinate bonds with Cu2+ and Fe3+. The separation Δ of the antisymmetrical and symmetrical stretching vibrations of R‐COO‐ was obtained from the IR spectra of the metal‐HA complexes. The Δ values for the metal‐HA complexes were significantly larger than the corresponding reference value of Δ for uncomplexed ‐COO‐, demonstrating that R‐COO‐ formed a unidentate complex (i.e., a single M‐O bond) with Cu2+ and Fe3+. The formation of bidentate or bridging complexes between R‐COO‐ of HA and Cu2+ or Fe3+ was not observed.
Spatial Variability of Soil Hydraulics and Remotely Sensed Soil Parameters
Authors: Lascano R. J. , Van Bavel C. H. M.
Published: July 2010

The development of methods to correctly interpret remotely sensed information about soil moisture and soil temperature requires an understanding of water and energy flow in soil, because the signals originate from the surface, or from a shallow surface layer, but reflect processes in the entire profile. One formidable difficulty in this application of soil physics is the spatial heterogeneity of natural soils. Earlier work has suggested that the heterogeneity of soil hydraulic properties may be described by the frequency distribution of a single scale factor. The sensitivity of hydraulic and energetic processes to the variation of this scale factor is explored with a suitable numerical model. We believe that such an analysis can help in deciding how accurately and extensively basic physical properties of field soils need to be known in order to interpret thermal or radar waveband signals. It appears that the saturated hydraulic conductivity needs to be known only to its order of magnitude, and that the required accuracy of the soil water retention function is about 0.02 volume fraction. Furthermore, the results may be helpful in deciding how the total scene or view field, as perceived through a sensor, is composed from the actual mosaic of transient soil properties, such as surface temperature or surface soil moisture. However, the latter proposition presupposes a random distribution of permanent properties, a condition that may not be met in many instances, and no solution of the problem is apparent.
Interflow of Water through a Sloping Soil with Seepage Face
Authors: Ahuja L. R. , Ross J. D.
Published: July 2010

A theoretical analysis of interflow pathways, source areas, and rates is presented for saturated, steady, and homogeneous conditions. Investigated were the effects of slope length to soil depth ratio, soil slope, slope‐of the seepage face, boundary condition at the upper end of the slope, leakiness of the base, and of ditch water covering the seepage face. Two regions of interflow could be distinguished: (i) flow through the main body of the soil (region 1), and (ii) flow from infiltration near the seepage face (region 2). For soil on an impermeable base, all the interflow water in region 1 entered the soil through a small area near the upslope end and flowed parallel to the slope before seeping out of the face near the base. For a slope length to soil depth ratio of 10 or larger, this part of interflow could be approximated as one‐dimensional flow with hydraulic gradient equal to the sine of the soil slope angle. Presence of a seepage face at the lower end of the slope caused considerable additional infiltration to contribute to interflow, entering from a distance near the face of about 2.5 times the depth of soil (region 2). This flow increased as the face slope (with respect to the base) increased, but was not influenced by slope length and was influenced in a minor way by soil slope. When the ditch water covered the seepage face completely, the infiltration in region 2 was prevented. For soil on a leaky base with leakage rate as low as 1/100th the hydraulic conductivity of the soil, all the water entering upslope of a short distance from the seepage face flowed downward into the leaky base. The slope length and soil volume traversed by interflow were reduced drastically. The boundary between the interflow and leakage flow regions could be approximated by a straight line of slope v/K tan ω passing through the origin, where v is the leakage rate, K is the hydraulic conductivity of soil, and ω is the soil slope angle.
Trace Metal Chemistry in Arid‐zone Field Soils Amended with Sewage Sludge: I. Fractionation of Ni, Cu, Zn, Cd, and Pb in Solid Phases
Authors: Sposito Garrison , Lund L. J. , Chang A. C.
Published: July 2010

The surface horizons of two arid‐zone field soils that had received amendments of either liquid or dried, anaerobically digested sewage sludge for 4 years were sampled to determine the forms of selected trace metals in the solid phase. The soils had been amended with sludge twice annually at rates of 0, 22.5, 45.0, or 90.0 tons · ha−1 · year−1. Barley and sorghum had been grown on the soils in randomized experimental plots. The soil samples were analyzed for total Ni, Cu, Zn, Cd, and Pb and were fractionated by sequential extraction to estimate the quantities of these metals in “exchangeable,” “sorbed,” “organic,” “carbonate,” and “sulfide” forms.

The total contents of the five metals in the two field soils were governed by the total content of the metals in the sludges applied and by the rate of sludge application. The accumulation of metals in the surface horizons of field plots receiving liquid sludge was less than that in the plots receiving composted sludge, possibly because of a lesser reduction in soil bulk density resulting from sludge applications. The percentage of the total metal content in exchangeable and sorbed forms was very low, averaging between 1.1 and 3.7% for all of the metals regardless of the type of soil, the form of sludge applied, or the sludge application rate. The application of sludge tended to reduce the sulfide fraction and to increase the organic and carbonate fractions of all five trace metals. At the highest rate of sludge application, the predominant forms of the metals were: Ni, sulfide; Cu, organic; and Zn, Cd, and Pb, carbonate.
Field Measurement of Denitrification: III. Rates During Irrigation Cycles
Authors: Rolston D. E. , Sharpley A. N. , Toy D. W. , Broadbent F. E.
Published: July 2010

Absolute amounts and rates of denitrification from a Yolo loam field profile at Davis, Calif., were studied in relation to the influence of irrigation frequency and soil incorporation of crop residue. Two different carbon (C) treatments were established by using plots to which no crop residues had been incorporated within 1 year prior to the experiment and plots to which 10 metric tons ha−1 of chopped barley straw were incorporated into the top 10 cm of soil 2 months prior to fertilization. The same total amount of water was applied at frequencies of three irrigations per week, one irrigation per week, and one irrigation every 2 weeks to areas cropped with perennial ryegrass. Fertilizer was applied as KNO3 (≅ 285 kg N ha−1) enriched with 56 to 60% 15N to 1‐m2 plots. The surface flux of denitrification gases was measured from the accumulation of nitrous oxide (N2O) and 15N2 beneath airtight covers placed over the soil and from measurements of N2O using the acetylene (C2H2) inhibition method. Small fluxes of denitrification gases were measured in this well‐drained alluvial soil under normal cyclic applications of irrigation water. Total denitrification ranged from 0.7 to 5% for the least frequently irrigated (no straw) and most frequently irrigated (straw) plots, respectively. Surface denitrification gas fluxes were largest after the first irrigation, decreased to near zero values within 1 or 2 days after each irrigation, and generally decreased for subsequent irrigations. The amount of N2 produced was much greater than N2O. The nitrous oxide flux at the soil surface varied between 5 and 27% of the total denitrification over a 40‐ to 50‐day period. Nitrous oxide mole fractions tended to be smallest immediately after irrigation and increased as the soil water redistributed and the soil profile became less anoxic. The irrigation frequency of three irrigations per week gave higher soil NO3‐ concentrations within the root zone of the crop than those of the other two frequencies. Thus, frequent, small irrigations may result in less leaching losses than infrequent, large irrigations.