bluuebunny/crossref_metadata_2025 huggingface dataset:
Large‐scale Zonal Rotors in Soil Science
Authors: Francis C. W. , Brinkley F. S. , Bondietti E. A.
Published: July 2010

A large‐scale zonal rotor was developed to band isopycnically soils and sediments in nonaqueous density gradients. The major advantage of such a rotor over conventional swinging bucket rotors is that relatively large quantities may be segregated; 15 g in large‐scale zonal rotors vs. 0.25 g per centrifugal tube with swinging bucket rotors. The rotor was used to isolate and identify soil‐sediment reaction sites of 137Cs, 60Co, and 106Ru. The 137Cs was found to be associated with micaceous minerals, the 60Co with Fe‐sesquioxides, and the 106Ru with organic rich soil components. An edge‐unloading rotor containing sucrose gradients (max. density 1.3 g/cm3) was used in a rate‐zonal mode to isolate Cd and Ni enriched fractions of sediment taken near the wastewater discharge of a Cd‐Ni battery plant. In sediments enriched in carbonates, Cd was found to be largely associated with the carbonates while Ni was concentrated in the organic rich soil components. Biological availability of Cd was evaluated by growing bush bean seedlings (Phaseolus vulgaris L.) in nutrient solutions containing density fractions of a soil clay. Density gradient separations using large‐scale rotors were shown to be a valuable adjunct to chemical extraction techniques for characterizing trace element interactions with soils and sediments.
Adsorption of Alkaline Earth, Transition, and Heavy Metal Cations by Hydrous Oxide Gels of Iron and Aluminum
Authors: Kinniburgh D. G. , Jackson M. L. , Syers J. K.
Published: July 2010

Freshly precipitated Fe and Al gels (points of zero change at pH 8.1 and 9.4, respectively) strongly specifically adsorb divalent cations from 1M NaNO3 solution. Adsorption from a mixed solution of eight divalent cations (each 0.125 × 10‐3M) in suspensions of freshly precipitated Fe and Al gels (0.093M with respect to Fe or Al) was measured as a function of pH in 1M NaNO3. The selectivity sequence (lower pH = greater selectivity) for the retention of the alkaline earth cations by Fe gel was Ba > Ca > Sr > Mg, but for the Al gel was Mg > Ca > Sr > Ba. The selectivity sequence (Figures in parentheses indicate pH ± 0.2 for 50% retention) for the Fe gel was: Pb (3.1) > Cu(4.4) > Zn(5.4) > Ni(5.6) > Cd(5.8) > Co(6.0) > Sr(7.4) > Mg(7.8), whereas the sequence for the Al gel was: Cu(4.8) > Pb(5.2) > Zn(5.6) > Ni(6.3) > Co(6.5) > Cd(6.6) > Mg(8.1) > Sr(9.2). Significant adsorption occurred even when the extent of cation hydrolysis was much < 1%, and invariably occurred at a pH lower than that for hydroxide precipitation. Although the adsorption‐pH sequences are related to cation hydrolysis and hydroxide precipitation pH values, the relationship is far from perfect, as is evidenced by the different sequences for the two gels. On aging of the Al gel in the presence of alkaline earth cations, the retention of Mg increased, while that of Ca, Sr, and Ba decreased. This result was thought to result from the structural incorporation of some Mg and the exclusion of the other cations.
Experimental Study of Wetting Front Instability Induced by Sudden Change of Pressure Gradient
Authors: White I. , Colombera P. M. , Philip J. R.
Published: July 2010

Twenty‐two experiments were performed on stability of infiltration flows in Hele‐Shaw cells. Flows were perturbed by suddenly changing G, the pressure gradient behind the wetting front, from a definite negative to a definite positive value. Three methods were used: (i) increasing air‐pressure ahead of the front, (ii) employing a nonwetting stratum, and, (iii) suddenly stopping liquid supply and preventing air‐entry. Glycerol and silicone, with contrasting properties, were used as the infiltrating liquids. The experiments confirmed the theory of Philip (1975a): immediately G was made positive, all flows became unstable, and the observed wavelengths of fingering agreed closely with those predicted by the theory.

A modification of the theory to take account of the geometry of the microscopic air‐liquid interface predicts wavelengths in soil about twice as large as does the original theory. A preliminary experiment on infiltration of water in a coarse sand confirmed the theory qualitatively, but the observed wavelength was twice that predicted theoretically. In a preliminary experiment on infiltration in a fine sand, perturbation failed to produce instability. This divergence from theory is attributed to deviations from the delta‐function model on which the theory is based. Further experimental and theoretical work is needed.
Error Propagation in Determining Hydraulic Conductivities from Successive Water Content and Pressure Head Profiles
Authors: Flühler H. , Ardakani M. S. , Stolzy L. H.
Published: July 2010

The flux of water in unsaturated soils can be determined indirectly by using Darcy's Law. The critical part of this approach is the determination of the hydraulic conductivity at a given depth and time. In this paper we analyze the relative errors of hydraulic conductivities determined from a transient drainage field experiment. Knowing the errors of this method would be useful in planning future experiments. It allows putting limitations on the conclusions to be drawn from such experiments and it further allows re‐examination of already published field data.

In the wet range of the conductivity function errors are 20–30% of the k‐value. In the range where k‐values are small, the relative errors may be > 100%. Errors stemming from tensiometer readings are significant when the hydraulic gradient is < 0.3 mbar · cm‐1. During the early stage of the transient drainage experiment these errors are always considerable and are more important than other errors. On the other hand, the errors in the measured water content changes are dominant when drainage is slowed down due to desaturation of the soil.

The errors contained in the conductivity, k, are calculated by means of error propagation equations. These errors are also simulated using the Monte Carlo technique. The simulation shows that the conductivity errors predicted by explicit error propagation equations are optimistic minimum estimates.
Heterovalent Cation Exchange Equilibria in Soils with Variable and Heterogeneous Charge
Authors: Munns D. N.
Published: July 2010

Divalent cations were incrementally displaced, from limed and unlimed samples of three soils, by suspending the soils in increasing volumes of 2mM KCl. Mass action coefficients for exchange between Ca and Mg were constant. But for the exchange of divalent cations by K, the exchange coefficients of Kerr, Vanselow, Gapon, Krishnamoorthy and Overstreet, and Gaines and Thomas increased markedly as potassium saturation or pH increased.

For each cation species, separate fractions which were relatively tightly or relatively loosely adsorbed could be estimated by a simple regression analysis. The loosely adsorbed Ca, which may control Ca availability to plants, could be independently estimated by a leaching procedure. Mass action exchange coefficients for the loosely adsorbed cations were approximately constant under all conditions tested.

The variable charge mobilized by liming differed from the fixed charge in having a slightly higher proportion of sites with high divalent affinity, in an Oxisol, and a much lower proportion in a Vertisol and a Mollisol.
An Improved Technique for Measuring Soil pH
Authors: Mubarak A. , Olsen R. A.
Published: July 2010

Soil solution is obtained by immiscible displacement using centrifugation in the presence of an excess of carbon tetrachloride. A combination glass electrode is then introduced into the soil solution which is floating on top of the carbon tetrachloride. By keeping the system closed, changes in pH induced by loss or gain of carbon dioxide are avoided. No water need be added to a naturally occurring soil so changes in pH induced by the dilution effect and/or the salt effect are obviated. There is no contact between reference electrode and soil particles so there is considered to be no junction error involved in the measurement. The technique is simple and reasonably convenient; the readings are stable and apparently reliable.
The Red Latosols of Sri Lanka: I. Macromorphological, Physical and Chemical Properties, Genesis, and Classification
Authors: de Alwis K. A. , Pluth D. J.
Published: July 2010

The Red Latosols of Sri Lanka have developed on the Quaternary Red Earth Formation into very deep, excessively drained soils with weak horizon differentiation. The three major soil series of this subgroup, the Gambura, Mullaitivu and Wilpattu series, were studied from the point of view of their morphological properties, particle size distribution, bulk density, 1/3 and 15 bar moisture, pH, organic carbon, total nitrogen, CEC, exchangeable cations and free Fe and Al oxides by means of representative pedons for purposes of characterization and determination of the genetic processes.

The Red Latosols all show some clay illuviation with the vertical distribution of the illuviated clay inversely related to the clay content. Free iron oxides are present largely as discrete particles and have themselves migrated downward, though to a lesser extent than the clay. The CEC values are low and consistent with clay fractions dominated by the kaolinite group. The CEC's also indicate a high proportion of pH‐dependent exchange sites. The exchange acidity appears to result largely from the presence of Al‐hydroxy compounds in the exchange complex. The dominant basic cation is Ca. The free iron oxides are almost entirely crystalline and seem to have moved principally by physical translocation of the particles, although another mechanism has also been postulated. Differences in the properties of the three series of the Red Latosols mainly reflect differences in clay and iron oxide contents.

According to the USDA Soil Taxonomy the Gambura series is a fineclayey kaolinitic isohyperthermic Rhodic Oxic Paleustalf, whereas the other two series are fine‐loamy siliceous isohyperthermic Rhodic Oxic Paleustalfs.
Evaporation Reduction from Soil with Wheat, Sorghum, and Cotton Residues
Authors: Unger Paul W. , Parker Jessie J.
Published: July 2010

Wheat (Triticum aestivum L.), grain sorghum [Sorghum bicolor (L.) Moench], and cotton (Gossypium hirsutum L.) are major irrigated crops on the Southern Great Plains. While irrigated wheat residue mulches increase soil water storage and decrease evaporation, very limited data are available regarding the effectiveness of grain sorghum and cotton (stalk) residues for this purpose. Therefore, this study was conducted to compare the effectiveness of wheat, grain sorghum, and cotton residues for decreasing evaporation under three potential evaporation conditions and to determine which residue characteristics are most effective for decreasing evaporation.

The laboratory tests were conducted on Pullman elay loam soil columns at potential evaporation rates of 0.66, 0.92, and 1.29 cm/day. Besides a bare soil (check) treatment, residue treatments were 4, 8, 16, and 32 metric tons/ha for sorghum and cotton, and 8 metric tons/ha for wheat. About 16 metric tons/ha of sorghum and more than 32 metric tons/ha of cotton residues were needed to decrease evaporation to levels obtained with 8 tons/ha of wheat residue. Multiple regression analyses indicated that residue thickness most strongly affected cuniulative evaporation and evaporation rates at selected days of the study. Other independent variables considered were potential evaporation, relative humidity, and residue specific gravity, application rate, and surface coverage.
Contribution of Subsurface Flow from the Upper Slopes of Forested Watersheds to Channel Flow
Authors: Beasley R. S.
Published: July 2010

Overland flow and subsurface flow from 0.054‐ and 0.089‐ha plots on the upper slopes of forested watersheds were intercepted and measured in trenches located at the bases of the plots. Channel flow was measured in flumes at the watershed outlets and intensity, duration, and amount of rainfall were measured by gages on the watersheds. Over a 3‐year period, 115 storms produced little overland and subsurface flow above the B‐horizon. Subsurface flow over an impermeable clay layer was as much as 90% of rainfall during a calendar quarter. Thirty‐six of the storms produced subsurface flow on one or both plots. For these storms, subsurface flow from the upper third of the watersheds was equivalent to 26% of the channel flow on one watershed and to 27% on the other. For 27 of the 36 storms, subsurface flow from the plots peaked sooner than channel flow. Twelve storms produced subsurface flow within 20 min of the onset of rainfall, and 15 storms produced channel flow within the same time. Subsurface flow often began shortly after rainfall began even when there was neither saturation at the point of outflow nor high antecedent soil moisture. Interconnected channels through the soil formed by decayed roots and animal burrows are the best explanation for the quick subsurface flow responses. The similarity in timing of subsurface and channel flows indicates that subsurface flow from upper slopes can contribute significantly to storm hydrographs in forested areas where permeable surface soils overlie an impermeable stratum.
Hexafluorosilicic Acid Reagent Modification for Quartz Isolation
Authors: Jackson M. L. , Sayin Mahmut , Clayton R. N.
Published: July 2010

Up to three sequential 3‐day treatments with commercial H2SiF6 were required to remove feldspar XRD peaks from many samples of loess and glacial till. Two such repeated treatments lowered the yield of isolated quartz by about 10%. For example, with Memphis C horizon loess from Yalobusha Co., Miss., the yield dropped from 29 to 19% of the 1–10 µm size fraction. Pretreatment of the H2SiF6 with finely ground quartz (1–100 µm size fraction) raised the quartz yield after one or two 3‐day treatments about 10%, for example from 29 to 39% of the initial 1–10 µm fraction of Yalobusha loess. After a third 3‐day treatment the yield was 32%. The quartz of this loess was of 100% purity after one 3‐day H2SiF6 treatment, as established by XRD and XRS. The oxygen isotope delta value was affected a little, the δ18O declining from 17 to 16‰ for the 1–10 µm quartz isolates treated one to three times with H2 SiF6, and fine quartz particles were released (SEM) from clusters in fine chert contained in the loess.
Fitting Solute Breakthrough Equations to Data Using Two Adjustable Parameters
Authors: Elprince A. M. , Day P. R.
Published: July 2010

Negative adsorption of anions reduces the volume of liquid available for the transport of electrolytes in the soil, and hence affects the nature of the breakthrough curve. A similar problem arises when there are appreciable volumes of soil solution which are essentially stagnant, and thus do not contribute significantly to the convective flux. These effects can be taken into account by introducing a second adjustable parameter (the effective solution volume) into the transport equation, in addition to the dispersion coefficient. The calculations demonstrate in a given example that a least squares procedure, applied simultaneously to the two parameters during the curve‐fitting process, resolves the apparent discrepancy between the theoretical breakthrough curve and the experimental data.
Effect of pH on Adsorption of Arsenic and Selenium from Landfill Leachate by Clay Minerals
Authors: Frost R. R. , Griffin R. A.
Published: July 2010

Adsorption of As(V), As(III), and Se(IV) anions from municipal landfill leachate solutions by the clay minerals kaolinite and montmorillonite is strongly dependent upon solution pH.

The H2AsO4‐ and HSeO‐3 ions are the apparent primary As(V) and Se(IV) species being adsorbed by the clay minerals. Activation of the anion adsorption sites on the clay minerals by H+ ions is important in determining the amount of HSeO3‐ ions adsorbed by the clay minerals, but it is apparently not important in determining the amount of H2AsO4‐ ions adsorbed.

Montmorillonite adsorbed more As(V), As(III), and Se(IV) anions than kaolinite. Although no definite proof is given, the higher adsorption by montmorillonite is attributed to a higher edge surface area.

The results of the study suggest that disposal of As and Se wastes in municipal landfills, especially under alkaline conditions, could produce ground water contamination by As and Se.
Influence of pH on the Sorption of Co2+, Zn2+ and Ca2+ by a Hydrous Manganese Oxide
Authors: Loganathan P. , Burau R. G. , Fuerstenau D. W.
Published: July 2010

The uptake of Co2+, Zn2+, and Ca2+ by δ‐MnO2 at 24.0 ± 0.5°C as a function of pH and salt concentration was investigated. At pH values < 5, δ‐MnO2 released structural Mn to solution phase during the sorption of Co2+ and to a lesser extent during Zn2+ sorption. Calcium sorption did not release any Mn to solution phase. In addition Co2+, Zn2+, and Ca2+ were shown to adsorb specifically at the δ‐MnO2 surface by exchange with bound H. The pH values had very little influence on the sorption of these cations.

At pH values above 6, abrupt increases in the sorption of Co2+ and Zn2+ in narrow pH ranges were observed whereas no such marked increase of Ca2+ sorption was found up to pH 9.2. This type of sharp increase in sorption is due to specific adsorption and is related to hydroxylation of the metal ions. Measurements of microelectrophoretic mobility of δ‐MnO2 in the presence of Co2+, Zn2+ and Na+ suggested that Co(OH)2 or Zn(OH)2 may be nucleated at the δ‐MnO2 surface at pH values lower than those thermodynamically calculated (no supersaturation) which would result in precipitation of the pure hydroxides in bulk solution.

At pH values between 5 and 6 any of the above mechanisms may be operative.
Changes in the Rhizosphere Due to NH4+ and NO3‐ Fertilization and Phosphorus Uptake by Corn Seedlings (Zea mays L.)
Authors: Soon Y. K. , Miller M. H.
Published: July 2010

Corn (Zea mays L.) seedlings were grown for 11 days on 3 soils of pH 7.1, 5.5, and 4.3, and fertilized with monocalcium phosphate, and either (NH4)2SO4, Ca(NO3)2, or CaCl2.

Rhizocylinder (roots plus adhering soil) and bulk soil solutions were isolated by centrifugal filtration and analyzed for pH and phosphate.

The pH of the rhizocylinder solution was lowered by the absorption of NH4+ and increased slightly by NO3‐ absorption. Reduced rhizocylinder pH was associated with increased rhizocylinder solution phosphate concentration and P uptake by corn seedlings. The difference in P absorption between NH4+‐fertilized and NO3‐‐fertilized corn can be explained by induced changes in the H2PO4‐concentration associated with rhizocylinder pH. But, in addition, NH4+ and NO3‐ enhanced P absorption probably as a result of increased physiological capacity to absorb P and/or increased root growth.
Measurement of Isotopic Exchangeable Soil Phosphorus and Interrelationship among Parameters of Quantity, Intensity, and Capacity Factors
Authors: Dalal R. C. , Hallsworth E. G.
Published: July 2010

The applicability of various techniques to measure isotopically exchangeable phosphorus for widely different soils was investigated. The E‐values obtained in the laboratory by carrier‐free (E‐value) and carrier‐methods (Ec value) were comparable to L‐values obtained in the greenhouse in low‐phosphorus fixing soils but were very much higher in high phosphorus fixing soils. In the latter group E‐values obtained by inverse‐dilution technique (EI.D. value) were more comparable to L‐values.

The parameters for available phosphorus in terms of quantity, intensity and capacity factors were discussed in relation to soil properties. The E, Ec, and Q0 values were influenced primarily by total phosphorus content of soils whereas L value was significantly correlated with exchangeable Ca and Mg, soil pH, organic C and oxalate, and dithionite extractable Fe (Feo and Fed) of soils. EI.D. value was correlated with oxalate extractable Al and organic C of soils. Thus both L and EI.D. values were affected by soil characteristics that influence the availability of phosphate in soil. The intensity factor was mainly influenced by soil reaction. The parameters of capacity factor, both phosphate buffering capacity (PBC) and maximum buffering capacity (Mb) were significantly correlated with dithionate extractable Al (Ald) of soils. It is suggested that since parameters of quantity, intensity, and capacity factors were generally influenced by different soil characteristics, plant available phosphorus can be described better by consideration of more than one factor.
Fertilization of Trifolium Subterraneum L. Growing on Serpentine Soils
Authors: Jones M. B. , Williams W. A. , Ruckman J. E.
Published: July 2010

Serpentine‐derived Henneke soil from 23 sites was tested in greenhouse studies to determine nutrient deficiencies for subclover (Trifolium subterraneum L.), and to evaluate for soil Ca status.

The soils (pH 6.3–6.9) were generally very deficient in P and S. When P and S were supplied, Ca increased subclover yields on 17 of the 23 soils, K on 10 soils, and Mo on 14 soils.

Applications of P and S increased these two elements in clover tops from below critical levels to adequate.

Yields were correlated with Ca and Mg in the plant and soil by the equation: Y = a[1−b exp (−cX)], where Y = relative yield, X = the variable under study, and a, b, and c are coefficients which determine the characteristics of the curve. The R2 values which are a measure of goodness of fit, occurred in descending order as follows: Percentage of Ca in clover tops > exchangeable Ca expressed as a percentage of the cation exchange capacity > exchangeable soil Ca > ratio of Ca/Mg in clover tops = ratio of exchangeable Ca/Mg in the soil > exchangeable Ca expressed as a percentage of the sum of the exchangeable cations. The R2 values were significant at the 1% level.
Soil Formation on Loess in Southwestern Indiana: I. Loess Stratigraphy and Soil Morphology
Authors: Harlan P. W. , Franzmeier D. P.
Published: July 2010

Thin loess deposits and underlying Sangamon paleosols were studied and related to modern soil development. Ninety‐one sites were sampled along four traverses extending 60–80 km eastward from the lower Wabash River, the main loess source. The ground soils, located mostly on primary divides, have a parent material sequence of silty loess (Peoria), sandy loess, upper part of Sangamon paleosol, and lower part of Sangamon paleosol. The paleosols developed in till or outwash of Illinoian age or in residuum of Pennsylvanian or Mississippian age.

Soil development increases with increasing distance from the loess source. Thick loess (> 2m) soils have an A‐B2t‐C horizon sequence, whereas the thinner loess (1–2 m) soils have an A‐B2t‐(A′2)‐Bx horizon sequence. Soils with < 0.75 to 1 m of loess have B2t horizons in both loess and residuum and usually do not have fragipans. Fragipans tend to be associated with sandy loess, but usually do not coincide with it. They may be just above the sandy loess, coincident with it, or in some combination of sandy loess and adjacent parent materials. It is believed that soil moisture relations influenced by the sandy loess, or the underlying paleosols, or both promote fragipan development.
Soil‐landscape Relationships in the Occidental Plateau of São Paulo State, Brazil: I. Geomorphic Surfaces and Soil Mapping Units
Authors: Lepsch I. F. , Buol S. W. , Daniels R. B.
Published: July 2010

This study was conducted in a 70.8 km2 area that includes most of the soils and landscapes present in the Occidental Plateau region of São Paulo State, Brazil. Surficial deposits of unknown derivation and age and Cretaceous age carbonate cemented sandstone are the soil parent materials. Both geomorphic surfaces and soils were mapped. Surface and subsurface soil chemical and physical characteristics of 103 sites were summarized to evaluate the soil variation of geomorphic surfaces and soil mapping units.

Soil properties that are expressions of weathering indices are related to geomorphic surface, but clay illuviation, base saturation, and carbon content do not regularly increase or decrease from the oldest to the youngest surface.

More than one soil mapping unit can be found on one geomorphic surface. Most soil physical and chemical properties have smaller coefficients of variation when grouped by soil mapping unit than when grouped by geomorphic surface.
Time as a Factor in the Genesis of Four Soils Developed in Recent Alluvium in Pennsylvania
Authors: Bilzi A. F. , Ciolkosz E. J.
Published: July 2010

Four soils developed in recent alluvium in the Ridge and Valley physiographic region of central Pennsylvania were studied in an attempt to relate chronologic age to pedologic age. Wood or charcoal found at the boundary between a recent and a buried soil profile at each site was radiocarbon dated. These dates were as follows: (i) < 205, (ii) 320 ± 80, (iii) 470 ± 80 and (iv) 1955 ± 80 years B. P., and indicate the maximum age of the alluvium in which the recent soil profiles developed. The relative distinctness of horizons evaluated by a field morphology rating scale, the volume (in cross section) of oriented illuvial clay films and the in situ weathering of clay minerals in these soil profiles indicate that morphological properties are effective in distinguishing chronologic age differences in alluvial soils which differ by approximately 1,500 years in age, but are not effective when the age differences are only a few hundred years. The data also indicate that cambic horizons can develop in <200 years and are still present after 2,000 years of soil formation.
Profile Modification of a Fragiudalf to Increase Crop Production
Authors: Bradford J. M. , Blanchar R. W.
Published: July 2010

Root development and crop yields are greatly reduced in soils having fragipan layers because of restricted air and water movement, high bulk densities and soil strength, and high acidity. In the first year after soil profile modification by trenching of a Missouri Typic Fragiudalf, available water storage and yields of grain sorghum (Sorghum bicolor (L.) Moench) were increased. Within unmodified areas, sorghum yields averaged 1,841 kg/ha. Deep trenching without chemical or physical additives increased yields to 4,322 kg/ha. Mixing lime, fertilizer, and sawdust with the soil material within the trenches increased grain sorghum yields to 5,987 kg/ha. The sawdust significantly increased water storage and water extraction, resulting in the grain yield increase.

Reexcavation of a pit used by the Soil Conservation Service for soil series identification of the Hobson soil showed no signs of soil density or strength reformation during the 16‐year period since the pit was refilled.
Chemical Detoxication of Atrazine by Dexon
Authors: Brown C. B. , Rahman S. F.
Published: July 2010

The nonphytotoxic analogs of atrazine (2‐chloro‐4‐ethylamino, 6 isopropylamino‐s triazine) are hydroxyatrazine and protonated hydroxyatrazine. Distinctive infrared bands of these compounds appear at 1620, 1680, and 1740 cm‐1, respectively. By monitoring these distinctive bands of the compounds, it has been demonstrated that in a combination of atrazine and dexon (p‐[dimethylamino] benzenediazo sodium sulphonate) there is a time‐dependent chemical change of some atrazine to protonated hydroxyatrazine indicating a reduction in phytotoxicity of the s‐triazine. A part of dexon‐atrazine antagonism—the reduction of atrazine toxicity to certain plants in the presence of dexon—is due to chemical reaction.
Soil Moisture Conservation and Yield of Crops No‐Till Planted in Rye
Authors: Gallaher Raymond N.
Published: July 2010

This experiment was conducted to evaluate soil water use by no‐till planted corn (Zea mays L.) and soybeans (Glycine max (L) Merrill) in rye (Secale cereale (L)) mulch (RM) vs. rye stubble (RS) where rye was removed. Soil water was measured throughout the summer months at 15 and 46 cm depths using electrical resistance gypsum blocks. Soil water curves showed that corn and soybeans went through three periods of severe moisture stress, which at times lasted as long as 2 weeks. Crops planted into killed RM, conserved soil water, were more drought tolerant, and showed evidence of greater use and earlier depletion of water by roots deep in the soil profile as compared to RS treatments. Corn grain and soybean yields were 45.6 and 30.3% greater, respectively from the RM as compared to the RS treatment. These data show the tremendous potential for increasing corn and soybean yields under no‐till mulch planting management.
Determination of Inorganic Phosphorus in Oxalate Extracts of Soils
Authors: Owens L. B. , Nelson D. W. , Sommers L. E.
Published: July 2010

A simple and rapid procedure for the determination of inorganic phosphorus in acid ammonium oxalate extracts of soils was developed by modifying the ascorbic acid‐molybdenum blue colorimetric method. The oxalate interference in the determination of P was overcome by addition of excess ammonium molybdate. A molar ratio of molybdate to oxalate, in the final solution, of 2.51:1 was required in order to eliminate the oxalate interference.
Phosphorus Sorption Characteristics of Flooded Soils
Authors: Khalid R. A. , Patrick W. H. , DeLaune R. D.
Published: July 2010

Surface soils representing Alfisols and Inceptisols were collected from various parts of Louisiana under rice (Oryza sativa L.) cultivation and incubated under oxidized (aerobic) and reduced (anaerobic) conditions for 2 weeks in a soil to 0.01M CaCl2 solution ratio of 1:5. The release of native soil P and the sorption of added inorganic P was investigated under these conditions. The soils selected for study were characterized for clay content, total carbon, extractable P, pH, and oxalate‐extractable Fe, soil properties associated with P sorption. The results show that generally more soil P was released under reduced than oxidized conditions, and this increase in soluble P under reduced conditions was significantly related to Bray no. 2 extractable P, clay content, and oxalate Fe. At high levels of added P, more P was sorbed under reduced conditions than under oxidized conditions in 14 out of 20 soils under study. However, in Midland fine sandy loam essentially all of added P was recovered in the equilibrium solution under both oxidized and reduced conditions, suggesting this soil had no capacity to sorb P. The relationship between P sorbed at 500 µg/g added P and oxalate‐extractable Fe was described by fitting two linear curves with different slopes. In the reduced soil samples the slope of Region I (≤ 3,000 µg Fe/g) suggests that 5.4 Fe sorbed 1 P and that this ratio did not change until all of the added P was sorbed. In the oxidized samples this ratio was about 16 Fe/1 P for Region I (≤4,500 µg Fe/g). The slopes for Region II of the linear curves for both reduced and oxidized samples were essentially zero. A closer relationship between P sorbed and oxalate extractable Fe under reduced conditions indicates that poorly crystalline and amorphous oxides and hydroxides of Fe play a primary role in P retention by flooded soils and sediments. A probable greater surface area generated by the transformation of oxyferric hydroxide to more reactive ferrous compounds may be responsible for greater P sorption under reduced conditions.
Charge Characteristics of Spodic Horizons
Authors: Laverdière M. R. , Weaver R. M.
Published: July 2010

Surface charge properties of six Spodosol Bir horizons, enriched in sesquioxides and organic matter, were investigated by acid‐base potentiometric titrations and ion adsorption measurements. The results indicate that the horizons have electrochemical properties similar to constant surface potential colloids as the sign and magnitude of the net charge were dependent upon the pH and indifferent electrolyte concentration of the ambient solution. The pH values (pHzpc) at which the net surface charge underwent reversal ranged from 4.2 to 4.9, and the values obtained by acid‐base potentiometric titrations agreed fairly well with those obtained by ion adsorption measurements. Although sesquioxidic components in combination with organic matter apparently dominate the charge properties of these Bir horizons, there was evidence from the titration curves of small amounts of clay minerals with a permanent negative charge. The latter was confirmed by potentiometric titrations of two Bir horizons to which various quantities of montmorillonite had been added. While the electrochemical behavior of these Spodosol Bir horizons was qualitatively identical to that of reversible interface colloids, theoretical mathematical models applicable for a quantitative description of the latter, such as the Stern double layer model, were found to give an inadequate representation of the observed values of surface charge and potential.
Adsorption of Parathion, Fenitrothion, Methyl Parathion, Aminoparathion and Paraoxon by Na+, Ca2+, and Fe3+ Montmorillonite Suspensions
Authors: Bowman B. T. , Sans W. W.
Published: July 2010

This study was conducted to investigate the influence of the saturating cation on the adsorption of parathion, methyl parathion, fenitrothion, aminoparathion, and paraoxon by montmorillonite suspensions. In all cases the saturating cation distinctly influenced the Freundlich‐type adsorption, with adsorption decreasing in the following sequence: Fe3+ − >Ca2+‐ > Na+‐montmorillonite. Adsorption of parathion, methyl parathion, fenitrothion and aminoparathion at low concentrations varied inversely with their water solubilities in Na+ − and Ca2+‐montmorillonite suspensions, i.e. parathion > fenitrothion > methyl parathion > aminoparathion > fenitrothion > methyl parathion > aminoparathion adsorption. Paraoxon adsorption was slightly greater than the compound with the next lower solubility, aminoparathion. The water solubility of parathion at 20°C was 12.9 µg/ml. Aminoparathion was more than 99.9% adsorbed from solution by Fe3+‐montmorillonite, suggesting the possibility of protonation of the ‐NH2 group by the acidic clay surfaces. In Na+ − and Ca2+‐montmorillonite suspensions, there was some conversion of paraoxon to p‐nitrophenol. Parathion adsorption‐desorption exhibited greater hysteresis effects in Fe3+‐montmorillonite than in Ca2+‐montmorillonite. The desorption pathway was dependent only on the initial concentration. The volume of solution removed in each cycle did not alter the desorption pathway, but only the rate at which the desorption proceeded down the desorption isotherm.
Behavior of Vapam and Methylisothiocyanate in Soils
Authors: Gerstl Z. , Mingelgrin U. , Yaron B.
Published: July 2010

An investigation was undertaken to study the behavior of the fungicide Vapam (sodium‐N‐methyldithiocarbamate) and its toxic degradation product MIT (methylisothiocyanate) in soils to obtain the necessary parameters for predicting the distribution of these compounds when applied in irrigation water. These parameters include absorption by the soil components, the degradation of Vapam to MIT and the subsequent breakdown of MIT to nontoxic substances, and the distribution of MIT between the liquid, gaseous, and adsorbed phases in the soil. Adsorption was determined by both batch and flow methods. The results indicated that degradation of both Vapam and MIT followed first‐order kinetics. The breakdown of Vapam to MIT was rapid, half‐life generally < 30 min at moisture contents below saturation, while MIT was found to persist for 2 weeks or more. The rapid breakdown of Vapam will result in a soil solution containing mainly MIT. MIT adsorption was relatively low (Kads = 0.41 and 0.57 ml/g for the soils higher in clay and organic matter content). The soils with the lower adsorption coefficients (Kads < 0.05) will give a practically uniform MIT distribution with depth when Vapam is applied at a constant concentration in the irrigation water. The behavior of Vapam in heavy textured soils needs further investigation.
Differences in Exchangeable Aluminum and Soil Acidity in Loess Soils of Iowa
Authors: Richardson J. L. , Riecken F. F.
Published: July 2010

The relationship of soil natural drainage, native vegetation, and textural development to exchangeable aluminum, exchange acidity, pH (CaCl2), total carbon and clay was studied in selected loess soils in Iowa. Greatest differences in measured properties in the laboratory were observed along biosequences. Prairie soils had only trace amounts of exchangeable aluminum, but usually had the most A‐horizon exchange acidity. Forest soils had both maximum exchangeable aluminum and exchange acidity in the B‐horizon, corresponding to maximum clay accumulation. “Transition” soils, presumably an encroachment of forest on a former prairie, were similar to forest soils. Only minor differences in measured properties were observed in natural drainage sequences. Acidity correlates with organic matter in prairie soils and with clay content in forest soils. The organic matter appears to act as a buffer in prairie soils and in the A‐horizon of transition and forest soils. Aluminum acts to buffer the forest and transition soil B‐horizons.
Numerical Evaluation of Granule Size Effect on Dissolution Rate of Potassium Silicates and Potassium Polyphosphate in Aqueous Solution
Authors: Miwa Eitaro , Kurihara Kiyoshi
Published: July 2010

The rate of potassium dissolution from spherical granules of K2O · 4SiO2, K2O · 5SiO2, and (KPO3)n was measured in water, NH4Cl and acetic acid solutions. Experimental results were analyzed using first‐order kinetics, involving a rate constant (k) and the concentration at saturation (Cs). The kCs values in H2O were 3.65 × 10−2, 1.17 × 10−2, and 7.08 × 10−3 mg K/mm2 per day for K2O · 4SiO2, K2O · 5SiO2, and (KPO3)n, respectively. Extremely high kCs values were obtained for the dissolution of (KPO3)n in solvents rich in H+ or NH4+. Based on these experimental data and assumed values for Cs, the whole process of K dissolution from each material at various granule sizes in aqueous solutions was calculated by the equations given by Hixson and Crowell (1931). As much as 83 mg of K from granules up to 3.22 mm in diameter will dissolve within 4 days in 100 ml of 0.001M NH4Cl solution. Only small differences in kCs values were obtained for K2O · 4SiO2 and K2O · 5SiO2 in the solvents used. Potassium dissolution from K2O · 5SiO2 in aqueous solutions will be extended beyond 2‐3 days by increasing granule size to 0.34 mm or greater.
Clay Formation from Basic Volcanic Rocks in a Humid Mediterranean Climate
Authors: Singer A. , Navrot J.
Published: July 2010

Clay minerals from soils formed on a variety of basic volcanic rocks in the northern Golan Heights, under humid Mediterranean conditions, have been examined mineralogically. The clay from basalt derived soils, mainly Rhodoxeralfs and Haploxeralfs (Red and Brown Mediterranean Soils) contains kaolinite and dioctahedral vermiculite partially interlayered with Al and Fe hydroxy layers. The presence of some illite and quartz in the upper soil horizons is explained by aeolian accretion. A scoria‐derived Rhodoxeralf contains, in addition, some hematite.

The clay fraction from Rhodoxeralfs and Haploxeralfs formed on partly palagonitised tuff‐lapilli is composed primarily of b‐axis disordered kaolinite and a poorly crystalline, partly expanding, 2:1 clay mineral, presumed to represent a smectite randomly interlayered with chloritic layers. In the lower horizons of these soils the kaolinite is replaced by a hydrated, spheroidal halloysite. No distinctly amorphous clay minerals were identified. A scheme of an alteration sequence of basic pyroclastics under humid Mediterranean conditions is suggested.
A Note on the Use of Infiltration Equations
Authors: Parlange J.‐Y.
Published: July 2010

It is shown, with the help of an exact example, that the cumulative infiltration, i, may be represented as a function of time t by a relation of the form, st1/2 + at, which can be accurate over a finite time interval. Contrary to a recent suggestion, this expression cannot be identified in general with a time expansion of i. In addition the values of s and a depend on the time interval considered and have no a priori relationship to the soil properties. Consequently such an expression has at most some empirical value. A better suggestion is that data from infiltration experiments should be fitted with analytical expressions which approach the proper limits as t → 0 and t → ∞, whenever possible.
A Method for the Simultaneous Control of the Water Regime and Gaseous Atmosphere in Soil Columns
Authors: Wagenet R. J. , Starr J. L.
Published: July 2010

A technique useful in laboratory soil columns which allows control of soil water content, regulation of the average composition of the soil atmosphere, and collection of leachate in variable increments is described. The design and construction of the system, as well as its advantages and disadvantages, are explained in detail and references are made to the adaptability of the technique to studies involving N transport and transformation, microbial populations, salinity, reduction‐oxidation reactions, or soil gas sampling.
Water Intake by a Water‐Filled Plexiglas Permeameter Cell
Authors: Tsuji G. Y. , Swartzendruber D.
Published: July 2010

Water entry into a Plexiglas (acrylic plastic) permeameter cell was measured by the recession of water in capillary standpipes connected to the water‐filled cell. Submergence of the permeameter in water demonstrated that the water entry was not caused primarily by a slight leak in the permeameter or by water‐vapor diffusion through its walls. Also, the rate was essentially unaffected when the permeameter contained a water‐saturated mixture of sand, silt, and bentonite. Calculations for the permeameter in air indicated the observed intake rate to be 20 times that attributable to water‐vapor diffusion through the Plexiglas walls, and 1/8 that attributable to direct water absorption as obtained from a maximal handbook value. Hence, it appears that direct absorption by the Plexiglas is the likely cause of water entry into the permeameter.
Influence of Citric Acid on the Hydrolytic Reactions of Aluminum
Authors: Ng Kee Kwong K. F. , Huang P. M.
Published: July 2010

Hydrolytic reactions of Al were studied at the initial Al concentrations of 1.10 × 10−4M and 1.10 × 10−3M and at varying degrees of hydrolysis as influenced by the presence of 1.0 × 10−6M and 1.0 × 10−4M citric acid. The effect of citric acid on the formation of the readily extractable Al and moderately extractable Al by the 8‐quinolinolate method varied with the initial concentrations of Al and citric acid and OH/Al molar ratios of the system. Hindrance to the hydrolytic reaction of Al by the acidity of citric acid and its complexation with Al ions were two counteracting reactions governing its effect. Citric acid substantially promoted the formation of the nonextractable Al fraction. The precipitation of the solid phase products was invariably hindered by citric acid.

Electron diffraction analysis showed that citric acid, at the concentrations used, hampered the formation of even microcrystalline bayerite and gibbsite. The data obtained from X‐ray diffraction and thermal analyses indicate that on aging, the degree of order in the solid phase improved upon the replacement of the citrate in the structure by the hydroxyl. Citric acid evidently hampered the hydroxyl bridging mechanism in the hydrolytic reaction of Al and thus imparted a rough fluffy surface to the solid phase as opposed to well‐formed crystals in its absence.

The present study clearly illustrated the important role of citric acid in influencing the hydrolytic reaction of Al and the nature of the resulting solid phase reaction products which should be of concern in the study of pedogenesis and other soil physico‐chemical reactions.
Effect of Mixed Na‐Ca Solutions on the Hydraulic Properties of Unsaturated Soils
Authors: Russo David , Bresler Eshel
Published: July 2010

The effects of mixed Na‐Ca solutions on soil water diffusivity and unsaturated hydraulic conductivity were tested for a loamy soil from Gilat, Israel. Soil water diffusivity functions, D(θ), were determined by the horizontal infiltration method. Unsaturated hydraulic conductivity functions, K(θ), were determined both directly (by vertical infiltration for suction heads of 0–50 cm H2O) and indirectly (from diffusivity functions and soil water retention curves). Prior to determinations, soil samples were equilibrated with solutions containing a given concentration and composition of Ca and Na. The results show that D(θ) and K(θ) are independent of solution concentrations in a Ca‐saturated system. In mixed Na‐Ca systems, hydraulic conductivity and soil water diffusivity functions are highly dependent on the composition and concentration of the soil solution, in addition to their dependence on soil water content, θ. For any given θ, both K(θ) and D(θ) decrease as either soil solution concentration decreases or the sodium fraction in the soil solution increases. The negative effect of a combination of high Na‐to‐Ca ratio and low soil solution concentration on K(θ) is directly related to the degree of water saturation of the soil. Low values of θ can compensate for the negative effects of high Na‐to‐Ca ratio and low solution concentration.
Influence of Exchangeable Cation on the Sorption of Trace Amounts of Cadmium by Montmorillonite
Authors: García‐Miragaya J. , Page A. L.
Published: July 2010

The effect of different exchangeable cations on the sorption of trace amounts of Cd by montmorillonite (clay fraction, Upton, Wyoming) was studied by equilibrating samples of homoionic clay suspensions with CdCl2 solutions ranging from 15 to 120 µg Cd/liter. These Cd concentrations are similar to those found in natural and contaminated soil‐water systems. The amount of Cd sorbed on the montmorillonite surfaces depended on the kind of exchangeable cation, decreasing in the order Na‐montmorillonite > K‐montmorillonite > Ca‐montmorillonite > Al‐montmorillonite. Exchangeable Al was found to be particularly effective in reducing Cd sorption by high energy sites on montmorillonite.
Oxidation of Elemental Sulfur in Soils
Authors: Nor Y. M. , Tabatabai M. A.
Published: July 2010

Studies of oxidation of elemental S in soils showed that thiosulfate and tetrathionate are produced during S oxidation in soils. In this work, unamended and elemental S‐amended soils were incubated (30°C) under aerobic conditions for various times. The amounts of S2O3‐, S4O6‐, and SO4‐S produced during incubation were determined. Results showed that S2O32‐ was produced within the first few days of incubation and that S4O62‐ accumulated in some soils. The rate of S oxidation increased with increasing incubation temperature (5, 15, and 30°C) and with increasing the rate of S application (50, 100, and 200 µg S/g soil). For 100 µg S/g soil, the rates of oxidation of elemental S in 10 Iowa surface soils ranged from 39 to 75 µg S/g soil after incubation at 30°C for 70 days; rates were more rapid in alkaline soils than in acid soils. There was little change in pH of soils even when the S application rate was increased from 50 to 200 µg S/g soil. The rate of S oxidation was lower in air‐dried soils than in field‐moist soils.
Manure Effects on Water Intake and Runoff Quality from Irrigated Grain Sorghum Plots
Authors: Mathers A. C. , Stewart B. A. , Thomas J. D.
Published: July 2010

Feedlot manure was incorporated into Pullman clay loam at rates of 0, 22, and 67 metric tons per ha annually (tons/ha/per year). Additional treatments were 67 tons/ha manure the first year only and 224‐kg N/ha/per year as anhydrous ammonia. The time required for irrigation water to advance down graded furrows was increased by the manure treatment. Also water intake and grain yields were higher on manure‐ than on ammonia‐treated plots. Runoff quality was not markedly reduced by manure treatments as indicated by NO3, P, and Cl concentrations in the runoff water.