bluuebunny/crossref_metadata_2025 huggingface dataset:
New and Conventional Evaporative Systems in Concentrating Nitrogen Samples Prior to Isotope‐ratio Analysis
Authors: Lober R. W. , Reeder J. D. , Porter L. K.
Published: July 2010

Studies were conducted to quantify and compare the efficiencies of various evaporative systems used in evaporating 15N samples prior to mass spectrometric analysis. Two new forced‐air systems were designed and compared with a conventional forced‐air system and with an open‐air drybath technique for effectiveness in preventing atmospheric contamination of evaporating samples. One of the new system designs was compared with the conventional forced‐air evaporative system and with the open‐air drybath technique for levels of 15N cross‐contamination among evaporating samples. The forced‐air evaporative systems significantly reduced the time needed to evaporate samples as compared to the open‐air drybath technique; samples were evaporated to dryness in 2.5 h with the forced‐air systems as compared to 8 to 10 h on the open‐air drybath. The effectiveness of a given forced‐air system to prevent atmospheric contamination of evaporating samples was significantly affected by the flow rate of the airstream flowing over the samples; the optimum flow rate was different for each of three forced‐air systems tested. When operated at optimum air flow rate, the forced‐air evaporative systems reduced atmospheric contaminants to <0.2µg N per sample, even when a contaminant of ∼77 µg NH3‐N per sample vial was added upstream of the scrubbing systems. The average atmospheric contaminant N found in samples evaporated on the open‐air drybath was 0.3 µ N, indicating very low concentrations of atmospheric NH3 during this study. Both these contaminant levels are sufficiently low to be of little or no significance in most tracer N studies. However, in previous studies we have experienced significant contamination of 15N samples evaporated on an open‐air drybath because the level of contaminant N in the laboratory atmosphere varied and could not be adequately controlled, even when NH3‐containing chemicals, cleansers, and paints were not stored or used in or around the working area. Average cross‐contaminant levels of 0.28, 0.20, and 1.01 µ of N were measured between samples evaporated on the open‐air dry‐bath, the newly‐designed forced‐air system, and the conventional forced‐air system, respectively. The cross‐contamination level is significantly higher on the conventional forced‐air system than on the other two systems, and could significantly alter the atom % 15N of high‐enriched, low [N] evaporating samples. The data from this study demonstrate that effectiveness in preventing atmospheric contamination and potential for cross‐contamination vary from system to system; thus, a given evaporative system should be carefully tested before being used in routine 15N sample processing.
Titratable Acidity to Estimate Ammonia Retention
Authors: Izaurralde R. C. , Kissel D. E. , Cabrera M. L.
Published: July 2010

Simulation models of fertilizer behavior in soils are potentially useful tools to improve fertilizer use efficiency. Presently, there are no satisfactory models that describe NH3 retention in soils. In order to develop such a model, a better understanding of how soils retain NH3 and a quantitative measure of soils' NH3 retention capacity are needed. We compared soil cation exchange capacity (CEC) and several measures of soil titratable acidity for predicting the amount of NH3 retained in the center of a band resulting from anhydrous NH3 application to soil. The titratable acidity to pH 9 estimated with NH4OH was a much better predictor than CEC of the NH3 retained. In some soils, the pH in the center of an NH3 retention zone differed slightly from pH 9, resulting in some error in estimating the NH3 retained. This error was greatest on a salty soil because of the small slope of the buffer curve near pH 9. We found soil titratable acidity to be stoichiometrically related on a 1:1 basis to the amount of NH3 retained. Apparently, CEC is a poor predictor of the amount of NH3 retained by soil because many of the cation exchange sites do not participate in a soil's capacity to adsorb NH3. Since a soil's titratable acidity to pH 9 is a stoichiometric predictor of NH3 retention capacity in soils, it may be used to more easily model the properties of an NH3 retention zone as affected by factors such as N fertilizer rate applied, spacing between application points, and soil bulk density.
Phosphorus Fertilizer Carriers and Their Placement for Minimum Till Corn Under Sprinkler Irrigation
Authors: Raun W. R. , Sander D. H. , Olson R. A.
Published: July 2010

Several methods of placement and sources of P were evaluated for sprinkler irrigated corn (Zea mays L.) grown under minimum tillage on a Sharpsburg silty clay loam (Typic Argiudoll) and a Coly silt loam (Typic Ustorthent). Nitrogen and P, dual placed in a localized band (anhydrous ammonia applied with liquid P sources), accomplished greater P uptake and higher corn grain yields on a P deficient calcareous soil than P banded to the side of the seed or banded below the seed, although both methods increased early plant growth compared to either broadcast or P dual placed with NH3. Broadcast preplant applications of P were equally as effective as dual placed P in this study. Explanation of yield and P uptake enhancement by dual placement may lie in the synergistic effect of ammoniacal N and P placed together. The superior performance of the broadcast method of P application was apparently due to root activity near the surface of the soil or in the soil residue interface. In contrast, starter band applications gave higher yields than broadcast or dual placed methods of P application on a slightly acid medium P soil. While it is not known why differences were obtained between the performance of methods of P application on these two soils, low subsoil P levels in the calcareous soil compared to the acid soil was believed to be a contributive factor. Enhanced early P uptake with such row applications may increase yields where high subsurface P levels exist. Urea phosphate (UP) provided greater yields, grain P uptake, and total P uptake than ammonium polyphosphate (APP) and diammonium phosphate (DAP) at the calcareous site—especially when band (side), broadcast, and dual placement methods of P application were used. Total P concentration from plant tissue taken at the eight‐leaf stage was greater for UP than APP and DAP on the slightly acid soil, but no yield differences could be attributed to sources at this site.
Inexpensive Equipment for Evaluation of Tillage Power Requirements
Authors: Jones A. J. , Bruce S. , Krall J. L. , Ferguson A. H.
Published: July 2010

Portable inexpensive equipment is described for measurement of tillage power requirements. Equipment consisted of (i) a modified chisel plow; (ii) a four‐wheel drive pickup; (iii) a hydraulic system including pressure transducer; and (iv) a voltage integrator‐timing device. A calibration curve related the voltage output from the pressure transducer to force required to pull the chisel plow. Coefficients of variation among test fields ranged from 4.3 to 5.9% for voltage output, 3.7 to 5.0% for velocity, and 7.2 to 11.0% for calculated tillage power requirements. Construction cost was approximately $1000 plus labor. The chisel plow was transported in the pickup or on a small trailer.
Ammonia Volatilization from Liquid Digested Sewage Sludge as Affected by Placement in Soil
Authors: Adamsen F. J. , Sabey B. R.
Published: July 2010

In a laboratory study, liquid sewage sludge was added to an Olney sandy loam (fine‐loamy, mixed, mesic, Ustollic Haplargids) at a rate equivalent to 7.6 Mg ha−1 either on the surface or 25 mm below the surface. The sludge contained 11.2 g kg−1 NH4‐N and 21.6 g kg−1 organic‐N on a dry weight basis and 27 g L−1 solids. Surface applied sludge lost 40.3% of its NH4‐N as NH3 in the first 2 weeks (95% of the total loss) while subsurface applied sludge lost 0.35% of added NH4‐N as NH3 in the same period. Total NH3‐N loss from surface applied liquid sludge was 36.0 kg ha−1, which was 42.4% of added NH4‐N. Soil analyses at the end of the study showed that 96% of the inorganic‐N was in the form of NO3 in sludge amended treatments. Fertilizer value of liquid sludge will be greater with subsurface injection than surface application. Where available N limits sludge loading rates surface application would reduce land requirements.
Effect of Fertilizer Amendments, Bulk Density, and Moisture on Calcium and Magnesium Diffusion
Authors: Mullins G. L. , Edwards J. H.
Published: July 2010

The fertility of acid subsoils may be improved by the injection of fertilizer materials into narrow slits that can be cut in subsoils during tillage operations. Little information is available to describe the effects that soil properties and added fertilizers have on the diffusion of Ca2+ and Mg2+ in acid subsoils. Laboratory studies were conducted with an acid subsoil of a Marvyn sandy loam soil (fine loamy, siliceous, thermic, Typic Hapludult) to determine the effects of fertilizers, bulk density, and volumetric moisture (Θ) on the diffusion of Ca2+ and Mg2+. The soil was treated with either dolomitic limestone, NH4NO3, NH4H2PO4, Ca(H2PO4)2, or Ca(NO3)2. Limestone was applied at a ratio of 79 g kg−1, whereas the remaining treatments were applied to provide 2.64 g kg−1 of either NO‐3 or H2PO‐4. The rates were used to simulate the concentrations that would occur in the zone of injection if the amendments were injected into the subsoil under field conditions. Calcium diffusion coefficients (De) measured with a cation exchange resin paper method ranged from 2.4 × 10−9 cm2 s−1 in the check to 3.9 × 10−6 cm2 s−1 in the Ca(NO3)2 treatment, and counter De for Mg2+ ranged from 3.6 × 10−9 cm2 s−1 in the check to 5.1 × 10−6 cm2 s−1 in the Ca(NO3)2 treatment. All treatments increased De for Ca2+ and Mg2+ relative to the check. In general, De increased as the concentration of Ca2+ and Mg2+ in the soil solution increased, and as the proportion of the extractable cation associated with the solid phase decreased. Diffusion coefficients for Ca2+ and Mg2+ increased as Θ increased from 0.12 to 0.30. Calcium and Mg2+ De reached a maximum at a bulk density of 1.6 to 1.7 Mg m−3 and then decreased slightly as bulk density increased to 1.9 Mg m−3. Bulk density effects were more pronounced at soil‐water pressure head values <0.033 MPa.
Temporal and Spatial Soil Variability on Three Forested Landtypes on the Mid‐Cumberland Plateau
Authors: Hammer R. David , O'Brien Ralph G. , Lewis Russell J.
Published: July 2010

Temporal and spatial variability of selected soil chemical properties were determined within and among three forested mid‐Cumberland Plateau landtypes at two locations. Major soils included Typic Fraguidults on uplands, Humic Hapludults on slopes, and Aquic Dystrochrepts in first‐order bottoms. Temporal soil variability was measured at monthly intervals for 25 consecutive months from samples taken from 0.5‐ by 0.5‐m subplots within two 2.5‐ by 2.5‐m plots on each landtype. Spatial variability samples were collected from similar, adjacent plots during a 1‐week period. A total of 300 spatial and 300 temporal observations were taken for each soil property in each of three soil horizons. Extractable Ca, Mg, and K, and pH in H2O and KCl were measured for A, AB, and Bt horizons, and total C was determined for A horizons. Magnitudes of variability were statistically compared using a procedure robust for nonnormally distributed data. Magnitudes of soil variability were significantly related to landtypes at the Bonferroni significance level. Only three of 16 soil variables differed in magnitudes of spatial vs. temporal variability. Variability on sites was of the order slopes > bottoms > uplands. Soil morphological features and parent materials appeared to strongly influence magnitudes of temporal and spatial variability.
Floodwater Properties, Nitrogen Utilization, and Nitrogen‐15 Balance in a Calcareous Lowland Rice Soil
Authors: De Datta S. K. , Fillery I. R. P. , Obcemea W. N. , Evangelista R. C.
Published: July 2010

Large areas of lowland rice (Oryza sativa L.) soils in South and Southeast Asia are calcareous. Field studies in the 1983 dry and wet seasons evaluated the effects of N source and application method on N loss and N utilization in a calcareous clay loam soil using the 15N‐balance technique. In the 1983 wet season and the 1984 dry season, crop recovery of the residual 15N remaining after the first crop was determined. When urea supergranules (USG) were deep point‐placed, the partial pressure of ammonia (pNH3) in the floodwater was negligible. High floodwater pNH3 was calculated with split application of fertilizer. Farmers' split of prilled urea (PU) gave the highest pNH3 (0.44 Pa in the wet season). pNH3 in the floodwater peaked on the third day and dropped to negligible thereafter. Deep placement (10 cm) of USG had the highest grain yield in the dry season. Ammonium sulfate produced a yield similar to that of urea. The highest 15N recovery by the crop (straw + grain) was 78% in the dry season and 64% in the wet season with deep point placement of USG. Nitrogen‐15‐balance data showed that with point placement of USG, 3% N was not accounted for after harvest in the dry season and 10% in the wet season. In contrast, when urea or ammonium sulfate was split‐applied using improved timing and water management (researchers' split), 26 to 28% of applied N was not recovered at harvest in the dry season and 36 to 41% in the wet season. Soil N fractionation showed that 14 to 26% of 15N‐labeled fertilizer was immobilized into the acid‐hydrolyzable organic N fraction in the dry season and 9 to 18% in the wet season. With point placement of USG and band placement of urea, the decrease in the value of hydrolyzable organic N fraction at harvest indicated N release for plant use during the cropping season. Applied N immobilized into the nonhydrolyzable organic N and fixed in the nonexchangeable N was not significant.
Fine Clay Mineralogy of Soil Matrices and Clay Films in Two Michigan Hydrosequences
Authors: Cremeens D. L. , Mokma D. L.
Published: July 2010

Fine clays (<0.2 µm) from the matrices and clay films of soils from two Michigan hydrosequences were analyzed by x‐ray diffraction to determine depth distributions and relationships to weathering and translocation processes associated with position in the hydrosequence. Illite contents of matrices generally increased, whereas vermiculite decreased with depth. This depth function was most prominent in the well and moderately well drained soils and diminished with decreasing natural drainage. Vermiculite content was negligible in both, and smectite was found in only one of the two poorly drained soils. Clay films from the well and moderately well drained soils had a mixed mineralogy of illite, kaolinite, and vermiculite, whereas those from the somewhat‐poorly drained soils were primarily illitic. Where present, clay films from the poorly drained soils contained smectite in addition to illite and kaolinite. Depth distributions of matrix clay minerals in the better drained soils suggested that illite had weathered to vermiculite and hydroxy‐interlayered vermiculite. Prolonged saturation and associated higher pH values may have favored illite‐smectite transformations in the poorly drained positions. We suggest that hydrosequence differences in moisture content of the eluvial zones resulted in a differential dispersion of clay minerals upon wetting. This may have led to selective translocation and the observed differences in clay film mineralogy.
Forest Floor Dynamics in Even‐Aged Northern Hardwood Stands
Authors: Snyder K. E. , Harter R. D.
Published: July 2010

Forest floor beneath three even‐aged pin cherry (Prunus pensylvanica L.)‐birch (Betula alleghaniensis Britton and B. papyrifera Marsh.) stands were analyzed for concentrations of Ca, Mg, K, N, P, C, and total forest floor mass. A 93‐yr‐old even‐aged northern hardwood stand served as the preharvest comparison. A trend of net forest floor material loss continued beyond canopy closure, with the Oa horizon being responsible for the change. Nutrient concentrations did not change in the Oi horizon over time. The Oe showed a peak Ca concentration at 30 yr of more than two and one‐half times that of the younger and preharvest stands. Nitrogen concentration decreased in the Oe horizon and the C/N ratio widened at 10 yr. The Oa horizon had no change in Ca or Mg, but K and N increased significantly in the 10‐ and 30‐yr stands.
Simple Kinetic Fractionation of Reactive Aluminum in Soil “Solutions”
Authors: Bartlett Richmond J. , Ross Donald S. , Magdoff Fred R.
Published: July 2010

A method is described that measure empirically the highly reactive portion of Al in 50 to 1000‐uL soil “solution” samples such as those removed from field moist soil by pressure, centrifuging, immiscible displacement, or lysimetry. Three categories of Al reactivity are identified in a single sample: rapidly reacting (RR Al), moderately rapid (MR Al), and total reactive Al (TR Al). Compared with other operational kinetic methods for labile Al, this method is applicable to small samples and is quick, simple, and precise because measurement is integrated over a period of minutes rather than confined to a single time point observation. Correcting for Fe interference does not require reduction and complexation procedures that alter Al speciation. Because of its sensitivity to very small changes in reactivity of Al, this method should be useful for the experimental evaluation of possible increases in mobility of biologically active soil Al, such as those hypothesized to be induced by acid precipitation.
Enhanced Phosphorus Status of Maize Resulting from Nitrogen Fertilization of High Phosphorus Soils
Authors: Kamprath E. J.
Published: July 2010

Short‐term greenhouse and culture solution studies have shown that P uptake and translocation is regulated by N. The objective of this study was to determine the effect of N rate on P status of corn (Zea mays L.) grown on soils with varying levels of available P in the range adequate for growth. Field experiments were conducted on Dothan (Plinthic Paleudults), Goldsboro (Aquic Paleudults), and Portsmouth (Typic Umbraquults) soils. Nitrogen rates used were 0, 56, 112, 168, and 224 kg N ha−1 supplied as NH4NO3 and urea. Phosphorus was applied at a rate of 22 kg P ha−1. Leaf P concentration at silking was increased by N fertilization and was highly correlated with leaf N concentration. Total Paccumulation was highly correlated with total N accumulation. Available soil P levels had little effect on leaf P concentration and total P accumulation. Nitrogen supply was the main factor affecting the P content of corn on soils with adequate levels of available P.
Relative Availabilities of Native, Residual, and Fertilizer Phosphorus to Winter Wheat
Authors: Sharpley A. N.
Published: July 2010

The uptake of fertilizer P by winter wheat (Triticum aestivum L.) was investigated for four Southern Plains soils in 900‐cm2 field plots over 4 yr, to quantify the relative availability and uptake of native, fertilizer, and residual fertilizer P. Statistically significant differences between duplicated treatments were determined by analysis of variance. Winter wheat was harvested 70 d after the September planting. At this time the proportion of soil Bray P from native and residual P increased (3.7‐ to 4.6‐fold) with successive annual fertilizer P applications (30 kg P ha−1 yr−1), while that from fertilizer P remained fairly constant. The uptake of winter wheat P from native and residual P increased and from fertilizer P decreased with successive fertilizer applications, due to an increasing amount of residual P uptake. Residual fertilizer P uptake by winter wheat was distinguished from native soil P and quantified as the difference in uptake determined by nonisotopic and isotopic methods. The nonisotopic method represents the difference in uptake between check and fertilizer P treatments, which will include fertilizer and residual P uptake, whereas the isotopic method represents only fertilizer P uptake. It was thus calculated that uptake of residual fertilizer P increased annually, representing from 4 to 40% of P uptake by winter wheat at harvest. By comparing the amount of wheat P from soil and fertilizer, it was found that the relative availability of native and fertilizer P did not change with continued fertilizer application to the four soils.
Application of a Modified Langmuir Isotherm to Phosphate Sorption by some Acid Soils
Authors: Kuo S.
Published: July 2010

Phosphate sorption by 11 acid soils was conducted at 298 K and at a pH of about 6.0 to determine how well the sorption can be described by a modified Langmuir isotherm. The modified Langmuir isotherm, which takes into consideration the electrostatic interaction among the phosphate surface species, described the sorption data reasonably well. The average affinity constant for the soils was 1.82 × 104 L mol−1, and the energy derived from the interaction component averaged 1.42 RT, where R is a gas constant and T is absolute temperature. The affinity constant was significantly affected by the amorphous Al and Fe contents of the soils, but no significant relationship between the interaction energy and the clay, organic matter, and amorphous Al and Fe contents of the soils was observed. Although the classical Langmuir isotherm slightly overestimated or underestimated the affinity constant, depending on which linearized form was used, it considerably underestimated the capacity of the soils to sorb phosphate particularly at higher phosphate concentrations. A simplified equation was developed based on the modified Langmuir isotherm, assuming a constant 1 RT contribution from the interaction component. The equation was as simple as that for the classical Langmuir isotherm but provided a better estimate of the sorption capacity of phosphate by soils than did the latter one.
A Unifying Quantitative Analysis of Soil Texture: Improvement of Precision and Extension of Scale
Authors: Shirazi Mostafa A. , Boersma Larry , Hart J. Warren
Published: July 2010

This paper extends a procedure for transforming the standard textural triangle into a new diagram based on mean particle size, dg, and standard deviations of particle size, σg. Values of dg and σg, obtained from the mechanical analysis on percents of clay, silt, and sand, provide a unified basis for comparing soils and physical and chemical properties of the soils. It is shown that the procedure proposed earlier is valid for samples that do not have a lognormal distribution for the whole sample. Using this approach, samples with very different distributions of each fraction can be accurately described. Information from different classification systems (e.g., USDA, ISSS, and engineering) can be used to calculate dg and σg, thus making it possible to unify the systems. The procedure further makes it possible to extend the scale to include particles with diameters > 2 mm. Mean particle size and standard deviates are correlated with soil properties. An application is shown in the from of a relationship between water retention and dg and σg.
Evaluation of Relationships Between Oak Site Indices and Properties of Selected Dystrochrepts
Authors: Edmonds W. J. , Rector D. D. , Wilson N. O. , Arnold T. L.
Published: July 2010

Soils derived from argillaceous rocks in the Blue Ridge and Valley and Ridge in Virginia have been mapped and correlated as members of Typic (Berks) and Lithic (Weikert) Dystrochrepts. SCS‐SOI‐5 interpretation records show soils of the Berks series to have higher estimated upland oak site indices than soils of the Weikert series. To explain observed differences in distributions of upland oak site indices, distributions of 34 soil and site properties were evaluated. According to the Shapiro‐Wilk test, the majority of these properties had nonnormal distributions. Therefore, α levels associated with the parametric, two‐sample t‐test would be unreliable. The nonparametric Wilcoxon rank sum test is distribution free and provides reliable α levels for small samples with nonnormal distributions if the samples have similar dispersions. According to the Moses ranklike test, only available water capacity (AH2O) had significantly different (p = 0.05) dispersions for Typic and Lithic Dystrochrepts. Typic Dystrochrepts had significantly larger (p = 0.05) median values for depths to C and R horizons, AH2O, and AL3+ saturation of the cation exchange capacity (CEC). Lithic Dystrochrepts had significantly larger median values for exchangeable Ca2+, total exchangeable bases, CEC, pH‐dependent charge, exchange acidity, ratio of the CEC to clay, and feldspar. Observed median values for upland oak site indices of 56 and 52 for Lithic and Typic Dystrochrepts, respectively, were not significantly different. Significantly larger amounts of feldspar and exchangeable bases, especially Ca2+, and significantly lesser amounts of exchangeable Al3+ saturation of the CEC of Lithic Dystrochrepts are hypothesized as reasons for their slightly higher upland oak site indices. Significantly larger amounts of exchange acidity in Lithic Dystrochrepts are the result of larger amounts of pH‐dependent charge and probably do not adversely influence tree growth. The simultaneous consideration of selected combinations of these properties using discriminant analysis does not produce mutually‐exclusive groups or groups that correspond to limits defined for Lithic and Typic Dystrochrepts. Only the limit of 50 cm depth to bedrock produces classes that correspond to these subgroups.
Polymer Type and Water Quality Effects on Soil Dispersion
Authors: Helalia Awad M. , Letey J.
Published: July 2010

Ten polyacrylamide (PAM) and derivatized guar compounds, with different charges were tested at 0, 10, and 50 mg L−1 concentration with low electrolyte solution (1 molc m−3) at 0, 5, and 20 sodium absorption ratio values for their ability to reduce dispersion of three soils. Dispersion was determined by measuring the soil settling rate in solution. All compounds were effective in promoting clay flocculation at a concentration of 10 mg L−1. When compared at comparable charge, the PAM compounds were more effective than the guar compounds. This result is consistent with their higher molecular weight. The order of effectiveness of the compounds was cationic > nonionic > anionic. No cationic PAM compounds were available and the cationic guar compound (CP‐14) was comparable to the nonionic PAM. Flocculation decreased very slightly as the SAR increased, suggesting that the effect of low electrolyte concentration was the prominent factor in dispersion. The cationic guar “CP‐14” was tested separately with low (0.05 dS m−1) and moderate (0.7 dS m−1) electrolyte concentrations simulating canal and well waters from California. Its effect on flocculation was very high at 5 mg L−1 concentration in both waters after only 10‐min settling. Increasing the concentration >10 mg L−1 did not improve the flocculation results.
Effects of Low Ionic Strength Solutions on pH of Acid Forested Soils
Authors: Richter D. D. , Comer P. J. , King K. S. , Sawin H. S. , Wright D. S.
Published: July 2010

“Salt effects” on soil pH are not well‐documented with highly acidic soils in contact with solutions of very low ionic strength (< 1 mMc/L). These dilute, acidic conditions are typical of soil solutions in many forest ecosystems. A wide range of acid forested soils were contacted with very dilute salt solutions to determine effects of low electrolyte concentrations on soil and solution pH under a variety of experimental conditions. In many soils, pH was lowered markedly following addition of dilute salt solutions. In fact, salt effects on pH (i.e., dpH) were greatest at low concentrations of added salts (e.g., between 0 and 0.6 mMc/L of added salt solutions). At least 40% of the variation in dpH among the 19 mineral soils was attributable to soil differences in low‐level concentrations of water soluble electrolytes. Leaching experiments that manipulated electrolytes in soil solution demonstrated that pH could be depressed up to 1 pH‐unit by increasing salt concentrations by as little as 0.3 mMc/L. Significant correlations between low ionic strength and dpH indicated that water‐soluble electrolytes influence pHw, even of unfertilized, acid soils that are very low in concentrations of soluble ions. Measuring pH of forest soils with 0.01 M CaCl2 is thus preferable to such measurements with water, to mask variations in soil pH that are caused by variations in relatively low concentrations of water‐soluble electrolytes. Results support the contention that variations in electrolyte concentrations in soil solutions on the order of 0.1 to 0.5 mMc/L (due to natural causes or “acid rain”) affect soil‐solution pH, although probably by relatively minor amounts in many or most soils.
Phosphate Adsorption by Two Highly‐weathered Soils
Authors: Mehadi Ahmed A. , Taylor Robert W.
Published: July 2010

Phosphorus adsorption by two highly‐weathered soils, Decatur clay loam (clayey, kaolinitic, thermic, Rhodic Paleudult) and Hartsells sandy loam [fine‐loamy, siliceous, thermic, Typic Hapludult] from northern Alabama was studied. Virgin and cultivated soils were used and adsorption curves developed at 15 and 25 °C. From these data the isosteric heat of adsorption (), the Langmuir adsorption maximum (b), and binding constant (K) were calculated. The virgin soils which had lower pHs and higher exchangeable Al and free Fe oxide, adsorbed more P than the cultivated soils. At the higher temperature, P adsorption (x/m) and K increased, indicating that P adsorption was an endothermic process and suggesting that P was held more tightly to the surface. Generally virgin soils had higher than the corresponding cultivated soils in agreement with the calculated K for the soils. decreased with an increase in surface coverage, finally levelling‐off for all soils which gave curvilinear (two slope) Langmuir plots. For the Hartsells cultivated soil, however, was almost constant and a near perfect fit of the linear form of the Langmuir equation was obtained. This suggested that, in this soil, P was adsorbed basically with one energy of adsorption and may explain the good fit to the linear Langmuir equation. The curvilinear lines gave straight lines when plotted according to the Brunauer‐Emmett‐Teller (BET) equation. We speculate that P adsorpation by the soils may be described by at least two previously hypothesized mechanisms of adsorption.
Enzymatic Coupling of 2,4‐Dichlorophenol to Stream Fulvic Acid in the Presence of Oxidoreductases
Authors: Sarkar Jawed M. , Bollag Jean‐Marc , Malcolm Ronald L.
Published: July 2010

The coupling of 14C‐ring‐labelled 2,4‐dichlorophenol (2,4‐DCP) to stream fulvic acid was investigated in the presence of several oxidoreductases including tyrosinase, peroxidase, and laccases of Rhizoctonia praticola and Trametes versicolor. During 12‐h incubation of each of the oxidoreductases with 14C‐2, 4‐DCP and stream fulvic acid, a substantial amount of the radioactivity was incorporated into fulvic acid. Chromatographic analyses indicated that although a large portion of the radioactivity remained in solution, no unbound 14C‐2,4‐DCP was present in the supernatant. The effects of pH, temperature, concentration of fulvic acid, and concentration of enzyme on the coupling processes were studied. The results of this research provide evidence that the enzymatic coupling of certain xenobiotic pollutants to humic substances is an important natural process which must be considered in studies of the fate, reactivity, and persistence of these organic compounds in soils and stream waters.
Micromorphological and Physico‐chemical Characteristics of Soil Crust Types in Northwestern Alberta, Canada
Authors: Arshad M. A. , Mermut A. R.
Published: July 2010

The micromorphology and submicroscopy of naturally‐formed surface crusts in several soils from the Peace River region, alberta were studied in order to understand the types and mechanisms of crust formation. Although the soils studied contained stable aggregates in the dry state, these aggregates almost completely broke down when wet, leading to the crusting tendency of the soils. Other soil characteristics that likely induced the structural deterioration were high silt contents, exchangeable Na and Mg, and low organic matter contents. Three morphological types of surface crusts were identified, including (i) lamellar, (ii) sedimentational, and (iii) disruptional. Lamellar crusts were typical of soils high in clay and exchangeable Na and Mg. Sedimentational crusts were found in areas which were subject to large amounts of surface runoff and subsequent sedimentation of suspended materials. Disruptional crusts were formed by direct raindrop detachment of soil aggregates, subsequent disruption of aggregates, and a reduction of volume within the crust. Disruptional crust was the most common crust formed in the silty soils of the Peace River region. One characteristic, very common to all crust types, was the presence of 2 to 5 µm thick layers within the immediate surface that caused the complete sealing of the soil surface. The moisture content of the immediate surface layer determines the strength of the crust. Hence, water management and mulching is crucial for crust prone soils.
Using Ground‐Penetrating Radar to Update Soil Survey Information
Authors: Schellentrager G. W. , Doolittle J. A. , Calhoun T. E. , Wettstein C. A.
Published: July 2010

Rapid changes in land use in many areas of the USA, and evolving concepts of soils and soil mapping have resulted in the need to update information gathered as part of the National Cooperative Soil Survey Program. In Florida, because of optimum soil conditions, large amounts of soils information can be gathered at a rapid rate by using ground‐penetrating radar (GPR). The information is being used to update soil surveys. Soil maps of the older soil survey report were evaluated first in order to determine if the map unit delineations consistently separate mappable landform and vegetative features. Using GPR, transects were made within randomly selected map unit delineations. Soils were identified and classified using conventional methods and their respective proportion and distribution along the transects were determined using the GPR imagery. These data were statistically analyzed to estimate the variability and composition of closely similar soils within each map unit and to justify correlation decisions. These data are presented in descriptive as well as tabular form in the published soil surveys. When compared to costs for traditional methods, the costs for updating soil survey information with GPR were dramatically reduced.
Analysis of Erodibility of Two Tropical Soils Using a Process Model
Authors: Lo A. , El‐Swaify S. A. , Rose C. W.
Published: July 2010

Field‐scale runoff and sediment data obtained by rainfall simulation are conventionally analyzed to derive empirical erodibility such as the K‐factor in the universal soil loss equation (USLE). In this study such data were obtained under standardized rainstorms on two highly weathered tropical soils from Hawaii (Typic Torrox and Hydric Dystrandept). In addition, a simplified version of a physicallybased model which embodies the processes of rainfall detachment, runoff detachment (entrainment) and deposition (sedimentation) was used to analyze the same data set. Higher USLE erodibility values corresponded well with higher values for the entrainment efficiency of overland flow. It was concluded that this process‐based model can complement the empirical USLE to provide a transferable quantitative understanding of soil susceptibility to erosion.
Etch‐Pit Measurements on Scanning Electron Micrographs of Weathered Grain Surfaces
Authors: Cremeens D. L. , Darmody R. G. , Jansen I. J. , Norton L. D.
Published: July 2010

Digital image analysis (DIA) was successfully used to evaluate the size and shape distribution of etch pits on the surfaces of weathered hornblende and microcline grains. An interpretative tracing of the image of etch pits and grain perimeter from projected SEM micrographs was used. Histograms of size‐frequency distributions of etch pits proved useful for comparisons between grains, while plots of shape factors of etch pits allowed an evaluation for individual grains. Manual calculation of etch‐pit density with a dot grid overlay gave results similar to those with DIA, although with less variation on replication. Precision with both methods was associated with operator interpretation of the grain surface, and consistency in interpretation.
Reduction of Organic Sulfur in Soils with Tin and Phosphoric Acid
Authors: Pirela H. J. , Tabatabai M. A.
Published: July 2010

The chemical nature of organic S in soils is not well understood. In this study, a Sn‐H3PO4 reagent was used for reduction of organic S in soils to H2S for subsequent determination as methylene blue. The reduction of soil organic S was compared with that of model S compounds, and with the fractions reduced with HI and with Raney Ni. Results showed that, in general, most of the reduction of organic S in 13 Iowa and 7 Chilean surface soils occurred after distillation for 1 to 3 h, but some soils continued to release H2S for up to 10 h of distillation with this reagent. Expressed as a percentage of total organic S in Iowa surface soils, the amounts of Sn‐H3PO4‐reducible S ranged from 15 to 64% (avg = 35%) and from 42 to 91% (avg = 60%) for 1 and 10 h of distillation, respectively. The corresponding percentages of the Chilean surface soils were from 8 to 73% (avg = 25%) and from 29 to 100% (avg = 55%). The Sn‐H3PO4‐reducible S values were significantly correlated with organic S [r = 0.71*** (P < 0.001) and 0.88*** for 1 and 10 h of distillation, respectively]. The amounts of organic S potentially reducible (Sr) with this reagent ranged from 35 to 86% (avg = 61%) of organic S in Iowa surface soils. The corresponding values for the Chilean soils ranged from 33 to 100% (avg = 66%). The times required to distill 50% of Sr ranged from 0.3 to 1.7 h (avg = 0.8 h) for the Iowa soils, and from 0.4 to 9.2 h (avg = 3 h) for the Chilean soils. Studies with five Iowa soil profiles showed that the percentages of organic S reduced with Sn and H3PO4 in 1 and 10 h of distillation varied with depth of sampling and that these values were similar, lower, or greater than those obtained with the HI‐reducing mixture.
Comparison of Aluminon and 8‐Hydroxyquinoline Methods in the Presence of Fluoride for Assaying Phytotoxic Aluminum
Authors: Noble A. D. , Sumner M. E. , Alva A. K.
Published: July 2010

A nutrient solution study was conducted to evaluate the effects of varying pH (4.2, 4.5, and 4.8), Al (0, 20, 40, and 80 µM Al) and F‐ (0, 10, 20, and 40 µM F‐) on soybean [Glycine max (L.) Merr. cv. Lee] root growth. The ability of Al fractions measured by the modified aluminon and 8‐hydroxyquinoline methods in predicting the phytotoxic component of Al was also investigated. In the presence of Al up to 40 µM, increasing levels of F‐ resulted in an increase in root length. Aluminum speciation in solutions predicted by GEOCHEM program showed an increase in concentration of F‐ complexed Al species with an increase in concentration of F‐. A very poor relationship was observed between tap root length and the sum of predicted concentrations of F‐ complexed Al species. Thus, F‐ complexed Al species would appear to be less phytotoxic than the other Al monomers. A highly significant correlation was found between tap root length and predicted concentration of Al3+ (R2 = 0.971). The relationship was further improved when sum of predicted concentrations of Al3+ and hydroxy‐Al species was considered (R2 = 0.986). Tap root length was poorly correlated with the concentration of monomeric Al determined by the modified aluminon method, which included a larger portion of less phytotoxic F‐ complexed Al species. In contrast, a highly significant correlation (R2 = 0.984) was found between tap root length and the concentration of labile Al determined by the 8‐hydroxyquinoline (15‐s reaction) method. The labile Al may include only a very small fraction of F‐ complexed Al species. Therefore, in solutions containing varying concentrations of F‐, Al measured by the 8‐hydroxyquinoline (15‐s reaction) method is a better predictor of Al phytotoxicity than that measured by the modified aluminon method.
Thematic Mapper and Digital Elevation Modeling of Soil Characteristics in Hilly Terrain
Authors: Lee Kyoo‐seock , Lee G. B. , Tyler E. J.
Published: July 2010

Transformed thematic mapper (TM) data and topographic information from a digital elevation model (DEM) were combined to determine soil characteristics of hilly terrain in southwestern Wisconsin. Map units from a rasterized soil map were compared with a combination of spectral classification obtained from TM, and DEM derived elevation and slope data. Five soil classes were differentiated. Three were silt loams, varying in landscape position and drainage characteristics. The fourth was comprised mainly of well‐drained loamy soils, while the fifth was a Histosol. These results suggest that a general identification of soils is possible by this method. There was 72% agreement between the soil map and the classification used in the study. Simple addition was found to be accurate and efficient when combining TM and DEM data. The importance of topographic data in the differentiation of hilly soils was demonstrated.
Measurement of Exchange Properties of Andisols by the Compulsive Exchange Method
Authors: Gillman G. P. , Hallman M. J.
Published: July 2010

Following recent criticism that the compulsive exchange method for the determination of cation exchange capacity (CEC) and anion exchange capacity (AEC) is not appropriate for Andisols, the method has now been applied to 22 samples from eight Andisol profiles from Papua New Guinea. Results obtained for CEC and AEC compared favorably with those obtained by a Schofied‐type method, and amounts of soil exchangeable cations could be explained by the CEC values measured. Specific adsorption of sulphate, if it occurs, following addition of MgSO4 in the procedure, does not affect the CEC value obtained.
Modeling the Transport of Inorganic Ions Through Undisturbed Soil Columns from Two Contrasting Watersheds
Authors: Jardine P. M. , Wilson G. V. , Luxmoore R. J.
Published: July 2010

The transport of several inorganic cations and anions (i.e., Mg2+ NH+4, Br−, NO−3), via saturated flow, through large undisturbed soil columns from two contrasting watersheds was investigated. The mobility of nonreactive tracers was described well with the convection‐dispersion (CD) equation using flux‐averaged solute detection in the effluent. Reactive tracers were also modeled well using various linear and nonlinear, equilibrium and nonequilibrium, transport codes based on the CD equation. Appropriate independent estimates of model predicted chemical retardation were possible only through experimental development of “dynamic isotherms” using a steady flow method on small undisturbed soil columns. The latter condition can accurately predict solute retardation on large soil columns, since tracer movement is largely controlled by the physical aspects of the soil (e.g., preferential flow zones). Adsorption isotherms generated on disturbed soils using a batch equilibration method, overestimated the amount of solute retardation from displacement experiments on the large undisturbed soil columns. The use of batch adsorption measurements in curve‐fitting transport models to describe data from saturated column displacement experiments on undisturbed soils, may result in erroneous transport parameter estimates.
Analysis of Chemical Kinetics Data from Dilute, Dispersed, Well‐mixed Flow‐through Systems
Authors: Schnabel R. R. , Fitting D. J.
Published: July 2010

Flow‐through techniques for studying chemical kinetics in soils are gaining acceptance. Of these techniques, those resulting in dilute, dispersed, well‐mixed suspensions minimize the hydrologic control on effluent concentration. The increased understanding of chemical kinetics gained by minimizing hydrologic control can be lost by improper data analysis. The following research was performed to develop a procedure for analyzing the kinetics of chemical retention by soil in a dilute, dispersed well‐mixed flow‐through system. The results of the research demonstrate that data analysis must account for the mass of unreacted chemical in the reactor. Failure to do so results in systematic underestimation of rate coefficients. Data analysis based on measured effluent concentration, rather than on secondarily calculated chemical retained, is more versatile and minimizes propagation of errors.
Effect of Land Clearing Method on Chemical Properties of an Ultisol In the Amazon
Authors: Alegre J. C. , Cassel D. K. , Bandy D. E.
Published: July 2010

This study quantified soil chemical properties as affected by land clearing method and subsequent soil management. It was conducted on a Yurimaguas soil (fine‐loamy, siliceous, isohyperthermic Typic Paleudults) covered by a 20‐yr‐old evergreen forest in the Amazon Basin of Peru. The experimental design, a split plot replicated three times, included six main plot treatments: (i) slash and burn clearing; (ii) bulldozer clearing with a straight blade; (iii) straight blade clearing followed by chisel plowing 25 cm deep; (iv) bulldozer clearing with shear blade, vegetation burned, followed by disking 30 cm deep; (v) shear blade clearing and rototilling with a 10‐KW tractor; and (vi) shear blade clearing, 30‐cm‐deep disking, followed by rototilling. Three post clearing soil management practices (subplots) were: (1) flat planted with no fertilizer or lime; (2) flat planted with fertilizer and lime applications incorporated, based on soil test recommendations; and (3) soil bedded at 1.1‐m spacings, and fertilizer and lime applied as in Subplot 2. Five successive crops, rice (Oryza sativa L.)‐soybean [Glycine max (L.) Merr.]‐corn (Zea mays L.)‐rice‐corn were grown from July 1980 to July 1982. Soil samples collected before or just after harvest of the first, second, and third crops were analyzed for chemical properties. Burning dried vegetation resulted in higher concentrations of Ca, Mg, P, and K in the 0‐ to 45‐cm soil layer. No significant differences due to main treatments were found for the other chemical properties. The pH of the surface soil increased from 4.0 to 5.2 for all limed subplots. Percent aluminum saturation decreased from 82 to 7%, and P, Ca, Mg, and effective cation capacity increased. The decrease in topsoil organic carbon at 14 wk for all mechanically cleared treatments was probably due to increased oxidation rates due to tillage and higher soil temperatures. Concentrations of Cu, Fe, and Mn in the soil were unaffected by treatment.