bluuebunny/crossref_metadata_2025 huggingface dataset:
Micromorphology of some Chernozemic Soils with Grumic Properties in Saskatchewan, Canada
Authors: Mermut A. R. , St.Arnaud R. J.
Published: July 2010

Two clayey soils (Indian Head and Balcarres Associations) and two fine loamy soils (Swinton and Weyburn Associations), all currently classified under the Chernozemic order (Borolls), were used in this study to establish the micromorphology of soils with grumic properties. Micromorphometric analyses consisted of fabric classification and estimation of void types, skeleton grains, and plasmic fabric by a point counting method. Basic plasmic fabric, plasma separations, and pedological features separate the clay soils from the two other Chernozemic profiles. The clayey soils have produced entirely different void patterns with a majority of planar voids, suggesting stress phenomena in these soils. The presence of soil nodules partly incorporated into the f‐matrix which is considered to be strong evidence of a churning process and especially the fraction of masepic plasmic fabric in the total plasma are in good agreement with void and related distribution pattern characteristics indicating a dynamic layer of up to 1 m in thickness within the two clayey profiles. Aside from the climatic parameters, these soils are very similar to Vertisols. The study signifies the necessity to reconsider the classification of such soils.
Amides as Sources of Nitrogen for Plants
Authors: Cantarella H. , Tabatabai M. A.
Published: July 2010

Amidase activity was detected recently in soils. This enzyme catalyzes the hydrolysis of aliphatic amides to NH3 plus their corresponding carboxylic acids. The activity of this enzyme in soil deserves special attention because its substrates are potential N fertilizers. In this study, six amide compounds (formamide, acetamide, 2‐cyanoacetamide, glycinamide, oxamide, and azodicarbonamide) were tested in a greenhouse experiment for their N‐supplying potentials to plants, compared with those of two conventional N fertilizers (ammonium nitrate and urea). Annual ryegrass (Lolium multiflorum Lam.) was used as the indicator plant. Ryegrass was grown on three soils (Storden, Fayctte, and Clarion), treated at the rates of 0, 240, 480, and 720 mg N/pot (3 kg of soil) and harvested four times at 1‐month intervals. With all the N sources tested, the dry matter yield increased with increasing the rate of N application on Fayette and Clarion soils. The results were inconsistent with the sandy Storden soil. Statistical analysis (Duncan's Multiple Range Test, P = 0.05), showed that the total dry matter yields obtained with formamide, glycinamide, 2‐cyanoacetamide, and oxamide were not significantly different from those obtained with urea and ammonium nitrate at the three rates of N application on Fayette and Clarion soils and at the 480 mg N/pot rate on Storden soil. The total dry matter yields obtained with acetamide tended to be lower than those obtained with the other N sources at the three N rates on Fayette soil and at the highest N rate on Clarion soil. The results with azodicarbonamide always were significantly lower than those obtained with the other N sources tested. Expressed as a percentage of the N applied, the total N uptake from azodicarbonamide was significantly lower than those obtained with the other N sources studied. Considering all the N sources and rates of N application, dry matter yield was significantly correlated with N uptake from all three soils, indicating that the effectiveness of a unit quantity of N taken up by ryegrass in increasing the dry matter yield was similar among the amides and conventional fertilizers in this study.
Biological Cycling of 15N‐Labeled Fertilizer Nitrogen in Lignite Minesoil Materials
Authors: Chichester F. W. , Smith S. J.
Published: July 2010

Soil profile and overburden core materials from a lignite minesite in east central Texas were amended with 15N‐labeled Ca(NO3)2 fertilizer and cropped to forage grasses in the greenhouse to determine their relative potential for supporting an active biological N cycle. Soils and overburden materials were sampled before and after cropping and analyzed for distribution of total N and fertilizer 15N in various chemical compartments. Several soil properties which affect N cycling were also measured. Plant tops from several harvests plus roots and crowns from the final harvest were analyzed for total N and 15N content. Results were compared among soil and grass treatment combinations, for uncropped and cropped samples, to determine any differences in N behavior, particularly between surface (A horizon) soils and subsurface strata materials. Nitrogen fertilizer recovery by plants averaged 65% of that applied. Approximately 21% of 15N was unaccounted for and assumed lost through denitrification by the end of the cropping period. There were no significant differences in either measurement due to soils or grasses. There were significant differences (p = 0.05) in amounts of 15N remaining in soils after cropping. Total indigenous soil N was composed of chemically more stable organic forms in the subsurface materials, with generally higher C:N ratios than in the surface soils. Distribution of the more recently‐incorporated fertilizer 15N among soil N forms was similar in surface and most subsurface materials, with a greater proportion found in chemically less stable forms. The acid lignitic clay was the one exception in that 15N distribution within the acid‐soluble fractions was different from that of other soils.

The amount of indigenous soil N mineralized during aerobic incubation was significantly greater in surface than subsurface samples, measured either before or after cropping. Percent mineralization of immobilized fertilizer 15N was greater on the average than that of total soil N residual. The relative amounts of 15N mineralization among soils was no different, however, than that for indigenous soil N, even though the 15N was similarly incorporated into less stable forms in each. Apparently differences in the C:N ratio were strongly determinant of differences in 15N disposition observed among soils. The measured tendancy for the C:N ratio to decrease with cropping demonstrated the potential to increase N incorporation and cycling through proper fertilizer management on minesoils constructed from materials evaluated in this study.
Soil Solution Composition as Affected by Liming and Incubation
Authors: Curtin D. , Smillie G. W.
Published: July 2010

Samples of three acid soils were limed with CaCO3 and incubated at approximately field capacity moisture content. Soil solution samples were obtained by miscible displacement at intervals of 1, 5, 27, and 52 weeks after liming. The rapid influence of added CaCO3 was shown by the large increases in soil solution pH, Ca, and HCO3 found 1 week after liming. Other effects of liming included increases in soil solution NO3 and organic matter, and reductions in K and Si. The activities of the major cations (Ca, Mg, K, and Na) and NO3 increased substantially, whereas pH decreased during incubation. The decline in pH was accompanied by increases in Al, Mn, and Zn in solutions obtained from unlimed soils. The changes with time were apparently due to liberation of protons along with NO3 into soil solution as a result of organic matter mineralization. Basic cations were displaced from exchange sites by protons, while Al, Mn, and Zn were released into solution as the acidity of the system increased. Logarithims of activities of Al3+, Mn2+, and Zn2+ were linearly related to solution pH. These relationships were such as to suggest that the mechanisms controlling the solubilities of these ions were similar in each soil. The solubilities, however, were not consistent with published solubilities of any common minerals. A tendency for solubilities to be comparatively high at higher pH may be an indication that soluble organic complexes were underestimated.
Soils on Terraces Along the Cauca River, Colombia: I. Chronosequence Characteristics
Authors: Alexander E. B. , Holowaychuk N.
Published: July 2010

Soils on two floodplain and six terrace levels, developing under lowland tropical evergreen or semideciduous forest before recent deforestation, were studied to determine the properties found to vary most with relative age. They are in a sequence from a Typic Tropaquent and an Aeric Tropaquept on the two floodplain levels through Haplustults and Paleustults to a Tropeptic Haplustox on the highest terrace. The soil properties may be placed into three categories based on their variations with relative soil age. (i) Soil properties which are similar in all of the terrace soils are bulk density, clay content in the B horizons, 15 bar water retention, organic C content, and dithionite‐citrate‐extractable Fe. Differences in soil morphology are small, other than the relative thinness of the solum in the soil on the lowest terrace, an anomalous (with respect to age) hardpan in the soil on the next terrace, and slightly higher chroma in the soils on the two highest terraces. (ii) The proportions of different exchangeable cations exhibit age trends in the younger (lower) terrace soils but are either similar in the older (higher) terrace soils or so erratic that an age trend is not apparent. (iii) Except for properties of the clay fractions, only the extractable Fe ratio (Feo/Fed) was found to vary systematically through the entire sequence of terrace soils. It decreases from slightly > 0.4 in the lower floodplain soil to < 0.01 in the lower solum of the oldest soil.
A Numerical Study of Raindrop Impact Phenomena: The Elastic Deformation Case
Authors: Huang C. , Bradford J. M. , Cushman J. H.
Published: July 2010

Understanding the deformation processes of soil material under raindrop impact is a basic step in studying soil resistance against particle detachment by raindrop splash. To simulate the deformation pattern of a solid material under impact, we used the finite difference technique to solve the dynamic equation of linear elasticity. The selected material properties resembled soil media of wide ranges of elasticity. Two types of impact loading were imposed: a steady, uniform load and a simulated raindrop impact load. Materials responded differently under these loading conditions and showed dissimilar deformation patterns. For a material with low modulus of elasticity, a uniform depression was found under steady, uniform load, while a cone‐shaped depression was shown under simulated raindrop impact. The shape of the surface deformation gave us insight into the mechanism of material detachment. The interaction of the lateral jet stream and the obstacles in its course are believed to be the major factor in determining the material detachment. The obstacles can be the sides of the cavity or the irregularities on the granular material itself.
Zinc and Copper Sorption and Interaction in Soils
Authors: Kurdi Fuad , Doner H. E.
Published: July 2010

Zinc or Cu ion sorption by different soil types conformed to a Freundlich equation but not to a Langmuir equation. Sorption differences among the soils were more related to equilibrium pH than to cation exchange capacity (CEC). Zinc or Cu sorption resulted in release of H and Mn. The release increased with increasing metal ion sorption and was higher with Cu than with Zn. Sorbed Cu was not significantly affected by Zn addition up to 250 µg/mL, though the presence of Cu even at a concentration of 15 µg/mL completely prevented Zn sorption in one soil low in CEC.
Adsorption and Availability of Phosphorous Following the Application of Limestone to an Acid, Aluminous Soil
Authors: Sims J.T. , Ellis B. G.
Published: July 2010

Changes in the adsorption and availability of P in an acid, aluminous soil (surface and subsoil) were evaluated following liming to neutralize 1N KCl‐exchangeable Al (minimal liming) or to pH 6.8 as determined by the SMP (Shoemaker‐McLean‐Pratt) buffer method. Langmuir adsorption isotherms were utilized to ascertain changes in P adsorption. A greenhouse bioassay was conducted to evaluate differences in P availability to plants (Oats, Avena sativa L. cv. Korwood) due to liming and incubation treatments. Results from these studies confirm that minimal liming is the most effective approach, from both agronomic and economic standpoints. Minimal liming optimized P uptake and minimized the P adsorption maxima (Langmuir b values). Liming by the SMP recommendation did not improve P uptake despite the application of three times as much lime, and also markedly reduced exchangeable Mg. Aging of adsorbate surfaces in the soil reduced their bonding intensity for P (Langmuir K), as did increasing soil pH. Development of ordered, less soluble Al‐OH polymers with fewer nonstructural OH groups capable of ligand exchange with P is postulated as the mechanism underlying these observations. Increases in pH‐dependent negative surface charge and P adsorption by free CaCO3 may be involved.
An 8‐Hydroxyquinoline Method for Labile and Total Aluminum in Soil Extracts
Authors: James Bruce R. , Clark Christopher J. , Riha Susan J.
Published: July 2010

The 8‐hydroxyquinoline method was modified to measure kinetically labile Al in aqueous soil extracts containing Al‐complexing ligands and to measure total soluble Al after removal of fluoride and organic C. Nonlabile Al complexed by F, C, Si, and OH in the original samples is calculated as the difference between total and labile forms. The method measures as little as 100 ng of Al in soil extracts and natural water samples.
Potassium Rates and Sources for Coastal Bermudagrass
Authors: Nelson L. R. , Keisling T. C. , Rouquette F. M.
Published: July 2010

During the past few years stands of ‘Coastal’ Bermudagrass (Cynodon dactylon L. Pers) have been reduced even though recommended rates of fertilizer have been applied. Many of the soils tested have been low in potassium. The objectives of this study were to determine (i) if the recommended fertilization rates of K were sufficient for optimum yield, (ii) the effect of single and split applications of K on forage yield, and (iii) the advantages of sulfur‐coated KCl or K2SO4 on forage yield production of Coastal Bermudagrass. Coastal bermudagrass was fertilized with nine potassium treatments on Cuthbert fine sandy loam (Typic Hapludult; clayey, mixed, thermic) and Darco fine sand (Grossarenic Paleudult; loamy, siliceous, thermic) soils for 3 years at Overton, Tex. Potassium treatments included rates of 0, 139, and 278 kg K/ha as KCl in single and split (four) applications. In addition, sulfur‐coated muriate of potash (S‐KCl) and sulfur‐coated potassium sulfate (S‐K2SO4) were applied at both 139 and 278 kg K/ha. On the Cuthbert soil a slight forage yield increase due to the K treatments was measured in the 1st year. Highly significant forage yield responses were noted on this soil in both the 2nd and 3rd years. On the Darco soil, small but insignificant increases in forage yield were measured in the 1st and 2nd years. Forage yield was not significantly higher at 278 than at the 0 kg K rate until the 3rd year. Forage yield responses tended to occur late in the growing season usually at harvest three or four, indicating a depletion of available K reserves. Improved yields were not observed for split applications of K. Sulfur‐coated KCl tended to produce highest forage yields annually and at several of the harvest dates. The S‐coated treatments generally resulted in lowest soil pH values. Available K was reduced significantly in the surface 15 cm after 3 years on both the 0 and 139 kg K/ha rates. The 278 kg K/ha treatment resulted in exchangeable‐K levels of 146 and 104 kg K/ha at the 0‐ to 15‐cm depth for the Cuthbert and Darco soils, respectively, at the termination of the study. These K levels were below the original soil K levels for both soils. Results indicate that in the long term, soil K would be depleted by high yields of Coastal bermudagrass with the K rates used in this study.
On the Measurement of Permanent Charge in Oxisols
Authors: Sposito Garrison
Published: July 2010

It is shown that the method used recently by Tessens and Zauyah to measure net permanent charge in Oxisols, based on a recommendation by Gillman and Uehara, can be justified theoretically without an appeal to diffuse double‐layer theory, or to any other detailed, molecular model of the interfacial region. The mathematical relationship between permanent charge and the net adsorbed ion charge at the point of zero salt effect, which forms the basis of the Gillman‐Uehara method, can be derived solely from the law of surface charge balance under the assumption that the point of zero salt effect is equal to the point of zero net proton charge.
Tracing Subsurface Flow on Roadcuts on Steep, Forested Slopes
Authors: Megahan Walter F. , Clayton James L.
Published: July 2010

In situ hydraulic conductivity was determined in a forested soil in the Idaho batholith by a tracer technique, and values were compared to hydraulic conductivity determined in the laboratory on cored samples. We injected NaCl solutions into piezometers placed in soil above a roadcut, and determined time for Na+ or Cl‐ to appear in outflow at the roadcut during saturated subsurface flow generated from spring snowmelt. Hydraulic conductivity values determined with the NaCl tracer averaged an order of magnitude greater than laboratory derived values. This is likely due to rapid flow in macropores formed from root channels or other biological activity that cannot be sampled by conventional coring and laboratory conductivity tests. Although the field tests indicated flow was clearly non homogeneous and anisotropic, an evaluation of the Reynold's number for the test conditions indicated Darcy flow was occurring. Sodium analysis provided a more distinct peak than Cl‐ when both concentrations were plotted vs. time.
Multifactor Kinetics of Phosphate Reactions with Minerals in Acidic Soils: I. Modeling and Simulation
Authors: Lin Chenfang , Busscher W. J. , Douglas L. A.
Published: July 2010

A mathematical model was developed to simulate phosphate reactions with minerals in acidic soils. Phosphate in solution was assumed to react with kaolinite, gibbsite, and goethite simultaneously. Each reaction had a two‐step sorption mechanism, i.e., mineral + solution P ⇄ labile P ⇄ nonlabile P, where labile and nonlabile forms are defined as isotopically exchangeable and nonexchangeable, respectively. The first step of the sorption mechanism followed the kinetic version of the Langmuir adsorption isotherm and was a second‐order reaction in nature. The second step of the sorption mechanism was a linear reversible kinetic equation. Seven ordinary differential equations describing the system were solved by numerical methods. The model effectively simulated the trend of phosphate reactions with soil minerals. Using the model to study the adsorption isotherm, we found that the Langmuir plot, i.e., concentration/adsorption vs. concentration, was linear when minerals had relatively homogeneous adsorption rates (or adsorption energies) and was nonlinear for widely differing rates, implying that a homogeneous surface provides a sufficient condition but not a necessary condition for a linear Langmuir plot. Simulation and analysis of a two‐surface Langmuir equation supported this finding.
Determination of Total Sulfur and Chlorine in Plant Materials by Ion Chromatography
Authors: Busman L. M. , Dick R. P. , Tabatabai M. A.
Published: July 2010

A simple and precise ion chromatographic (IC) method for simultaneous determination of total S and Cl in plant materials has been developed. It involves combustion of a plant sample (20–100 mg) in a Schoniger‐type oxygen flask containing 25 mL of deionized water. The SO2‐4 and Cl‐ formed in the aqueous solution (the S and Cl gases produced are absorbed by water) are determined by using a Dionex Model 10 IC. The IC method is based on separation of the anions by a separator column containing Dionex low‐capacity anion exchange resin in the HCO‐3 form and on converting the various anions to their corresponding acids by a suppressor column containing a strong acid cation exchange resin in the H+ form. A solution 3.0 mM NaHCO3 + 1.8 mM Na2CO3 is used as the eluent, and electrical conductivity is used as the mode of detection. Results obtained for total S in a variety of plant materials by the IC method agreed closely with those obtained by the methylene blue method after digestion with NaOBr. The average total S values of 15 plant samples by the two methods were 0.255 and 0.259%, respectively. Comparison of the results obtained for Cl by the IC method and by a colorimetric method involving the use of mercuric thiocyanate and ferric ammonium sulfate showed that the averge Cl values for the plant samples were 0.380 and 0.377%, respectively. The recovery of total N and P was not quantitative. A single operator can perform about 40 analyses in a normal working day.
Nitrogen Fertilization Practices for Sequential Cropping of Wheat, Turnips, and Sweet Corn
Authors: Sanmaneechai M. , Koehler F. E. , Roberts S.
Published: July 2010

The fertilizer requirement for multiple or sequential cropping needs to be better defined. Therefore, a three‐crop field experiment was conducted on a Warden silt loam (coarse‐silty, mixed mesic, Xerollic Camborthids) to study the effects of preplant soil mineral N and rates of applied N on yield and N uptake by spring wheat (Triticum aestivum L.), turnips (Brassica rapa L.), and sweet corn (Zea mays L.). Spring wheat and turnips were grown sequentially in 1979 followed by sweet corn in 1980. Wheat yield was not significantly increased with over 135 kg N/ha, but near maximum yield of 7.5 Mg/ha on the yield curve was at 180 kg N/ha. The concentration of N in the straw and grain continued to increase with N rates of 180 and 270 kg/ha. Yield of turnips (roots plus tops) which reached 5.8 Mg/ha and N uptake increased with increasing N rates up to the maximum use of 270 kg/ha. Only the highest rate of N applied for wheat significantly increased yield and N uptake of the following turnip crop. Sweet corn yields increased to 23 Mg/ha with increasing N rates up to 135 kg/ha, and then leveled off, whereas N uptake increased up to 180 kg N/ha. Residual effects from N applied for previous crops increased yield and N uptake of sweet corn. Responses by corn to residual N were greatest where N was applied for both wheat and turnips and least where N was applied for spring wheat only. It was concluded that turnips benefited less than sweet corn from residual and mineralizable N. The total N uptake by three crops exceeded the amount of N applied showing that N mineralization during crop growth was an important factor in the N uptake by the crops.
Importance of Phosphate Buffer Power for Phosphate Uptake by Rye
Authors: Prabhakaran Nair K. P. , Mengel K.
Published: July 2010

As soil test data for available P are often unsatisfactory, it was investigated whether the integration of the P buffer power of soils would improve the information from soil tests. The P buffer power of eight soils differing widely in their characteristics was assessed by plotting the calcium‐lactate exchangeable P (P quantity) vs. the electro‐ultrafiltration extractable P (P intensity). After dressing these soils with increasing amounts of soluble phosphate, they were analyzed for available P after an incubation period of 1 week by extracting P using electro‐ultrafiltration (EUF‐P) and calcium‐lactate (CAL‐P). The P concentration in the tops and the P uptake of young rye (Secale cereale L.) plants grown on these soils in pots supplied with five increasing P rates were correlated with the EUF‐P and CAL‐P soil test data. Significant and highly significant correlations between soil test and the P uptake and soil test and P concentration in rye seedlings, respectively, were obtained. These correlations were further much improved when the P buffer power of soils was integrated into the computation in the form of a multiple regression analysis. The R2 thus obtained was about 0.8, showing that about 80% of the variance in P uptake and P concentration in plant tops can be related to the variance in the P soil test data (CAL or EUF technique) and to the variance of the P buffer power of soils. It is concluded that soil tests for available soil P can be substantially improved by taking into consideration the P buffer power of soils.
Rapid Method to Obtain Carbonate‐free Residues from Limestone and Petrocalcic Materials
Authors: Rabenhorst M. C. , Wilding L. P.
Published: July 2010

A relatively rapid procedure for carbonate removal was desired for the study of noncarbonate residues from indurated calcareous materials. Carbonates were therefore removed from two calcareous smectite containing samples using various acid treatments. The degree of clay mineral alteration was assessed by x‐ray diffraction (XRD) and cation exchange capacity (CEC) of residue clay (< 2‐µm) fractions. Minor reductions in CEC were observed as a consequence of carbonate removal using pH 5.0 sodium acetate (NaOAc) buffer. Mineralogical changes were not detected by XRD. Further lowering of the NaOAc buffer pH to 2.5 had little or no additional effect. Use of pH 4.5 NaOAc buffer for dissolution of gravel size (< 8‐mm) limestone and petrocalcic materials greatly reduced the time necessary for carbonate removal compared with traditional pH 5.0 NaOAc procedures.
The Release of Nonexchangeable Ammonium (15N Labelled) in Wetland Rice Soils
Authors: Keerthisinghe G. , Mengel K. , De Datta S.K.
Published: July 2010

The release of nonexchangeable (fixed) NH+4 was studied for three representative rice soils of the Philippines. Soil samples from these soils were treated with 15NH+4 in the laboratory so that they contained appreciable amounts of nonexchangeable NH+4 in 15N form. Special soil holders were filled with the labelled soil and incubated in the wetland rice soils from July to October at a depth of 0.2 m. During this period of incubation, highly significant amounts of labelled nonexchangeable NH+4 were released from all three soils. For the Maligaya silty clay loam and Guadalupe clay, both containing vermiculite, the total release of nonexchangeable NH+4 was higher than the release of labelled nonexchangeable NH+4 showing that non‐labelled NH+4 was released as well. 15N analysis of the rice plants showed that the nonexchangeable labelled NH+4 was subsequently available to the crop. Assuming a soil bulk density of 1 and a rooting depth of 0.2 m release of nonexchangeable NH+4 from the Maligaya silty clay loam ranged from 80 to 100 kg N ha−1, while for the Guadalupe clay and Santa Rita clay the net release of nonexchangeable NH+4 amounted to about 20 to 40 kg N ha−1, respectively. It is concluded that nonexchangeable NH+4 may play a major role in N nutrition of rice crops grown in wetland rice soils rich in vermiculite.
Reduction of Natural Ferric Iron Chelators in Disturbed Forest Soils
Authors: Perry D. A. , Rose S. L. , Pilz D. , Schoenberger M. M.
Published: July 2010

Hydroxymate siderophores (HS) are high affinity FE3+ chelators which are produced and secreted into the soil by various soil microflora, including mycorrhizal fungi. HS are important in the iron nutrition of both the microorganisms which produce them and higher plants, and they may also protect higher plants from soil‐borne pathogens. We used a standard bioassay technique to compare HS concentrations in soils from 10 pairs of logged and adjacent unlogged sites in various areas of Oregon. In 8 of the 10 sites HS concentrations were significantly lower in soils from logged areas than in those from adjacent undisturbed forests. HS reductions were greater where slash was burned than where it was unburned or windrowed. Pot tests of soils from one site indicated that Douglas‐fir seedlings (Pseudotsuga menziesii [Mirb.] Franco) were iron limited in logged and burned but not in undisturbed forest soils. Soil pasteurization induced iron limitation in undisturbed soils, which suggests that iron limitation in soils from the logged and burned area may have been due to reduction of HS‐producing organisms.
Soil Manganese: E Values, Distribution of Manganese‐54 among Soil Fractions, and Effects of Drying
Authors: Goldberg S. P. , Smith K. A.
Published: July 2010

The Mn labile pool was determined in a wide range of United Kingdom soils, using 54Mn tracer and two different extractants, CaCl2 and DTPA. Good agreement was obtained between E values obtained by two different equilibration procedures in CaCl2, but for most soils the concentrations of CaCl2‐extractable Mn were considerably lower than the E‐values. Higher E‐values were obtained in DTPA than in CaCl2, indicating that the former dissolved some nonisotopically exchangeable Mn. The rate of disappearance of 54Mn from the soil solution, and its distribution in various fractions, differed greatly between the soils. Generally, the radioisotope labeled all the soil fractions determined, with the majority of 54Mn associated with the water‐soluble + exchangeable, organically bound and easily reducible oxide fractions. When the labeled soils were subjected to air and oven‐drying, net gains of 54Mn were observed in the water‐soluble + exchangeable, resistant and residual Mn fractions, with corresponding reductions in the easily reducible oxide fractions. Upon drying, native Mn increased in the water‐soluble + exchangeable and EDTA‐extractable fractions. Possible mechanisms for these changes are discussed.
Estimation of Water Potential Components of Saline Soils of Great Basin Rangelands
Authors: Roundy Bruce A.
Published: July 2010

A rapid method is described to assess the solute and matric components of the total soil water potential at field water contents of a saline soil in central Nevada. The solute potential is estimated from saturated paste conductivity (ECp) measurements easily made on the conductivity cell of an instant salinity meter and assumes that the salt concentration varies inversely with water content. The method requires determination of the relationship between ECp and the electrical conductivity of the saturated paste extract, ECe. The total water potential is measured with a Peltier psychrometer. Subtraction of the solute potential from the total water potential results in an estimate of matric potential. Matric potentials estimated in this way were similar to those determined by a pressure plate at volumetric water contents greater than 0.09 m3 m−3 soil and soil ECe's < 15 dSm−1. The method tends to underestimate solute potentials and overestimate matric potentials of soil with lower soil water contents and higher salinity. These measurements are useful in determining plant adaptability on saline, semiarid rangeland soils.
Leaching Losses and Plant Recovery from Various Sulfur Fertilizers
Authors: Korentajer Leonid , Byrnes Bernard H. , Hellums Deborah T.
Published: July 2010

Two greenhouse experiments were conducted with soils fertilized with various S fertilizers. The soils were subjected to percolation during early growth of a corn (Zea mays, L. var. Funks G5757) crop to determine the effects of leaching rate, sulfur rate, and S source on SO2‐4 leaching losses and plant growth. In the first experiment, the effects of percolation rate (0–6.1 mm d−1) and rate of gypsum application (0–40 µg S g−1) on SO2‐4 leaching losses and S recovery by two successive crops were studied. Increasing the percolation rate greatly increased SO2‐4 leaching losses and decreased the apparent fertilizer recovery by the first crop. Apparent S recovery was also greatly reduced with increasing amounts of applied gypsum. In the second experiment, S leaching losses from gypsum and anhydrite of various particle sizes and from powdered elemental S were evaluated at one percolation rate (3.9 mm d−1). The rate of SO2‐4 leaching loss from powdered gypsum and anhydrite gradually decreased with time, indicating a decrease in the dissolution rate of the source as the amount of solid phase material decreased. Increasing the particle size of the materials decreased the leaching losses but had no effect on apparent S recovery by the plants. At a given particle size other than powdered materials, there were no differences in leaching losses between gypsum and anhydrite. The amount of powdered gypsum leached, however, was three times greater than the amount of powdered anhydrite leached. Leaching losses from powdered elemental S were similar to the losses from the larger‐sized particles of gypsum and anhydrite. Moderate to high percolation rates led to SO2‐4 losses and decreased fertilizer efficiency. Increasing the size of gypsum particles and the use of anhydrite are promising methods of reducing such losses.
Relating Rainfall Erosivity Factors to Soil Loss in Kenya
Authors: Ulsaker L. G. , Onstad C. A.
Published: July 2010

Runoff plots were established on a representative soil site in Kenya in 1980 to evaluate soil and water losses as influenced by climate, soil, and management practices. Fifteen erosivity factors were regressed to ascertain best fit on the soil loss from 3 fallowed plots for each of 35 storms between March 1982 and April 1983. Two of the best rainfall erosivity factors with their respective coefficients of determination are: total kinetic energy times maximum 30‐min intensity (EI30), r2 = 0.69, and rainfall amount times the maximum 30‐min intensity (AI30), r2 = 0.72. A regression equation was developed relating EI30 to rainfall amount, A. The coefficient of determination was 0.902. Soil erodibility for this Alfisol was found to be 0.0314 tonne hectare hour per hectare megajoule millimeter or 0.24 in customary English units. Erodibility factor values ranged from 0.07 for storms producing soil losses less than 1 t/ha to 0.55 for storms producing soil losses greater than 10 t/ha.
Scale Factors in Soil Science
Authors: Tillotson Patricia M. , Nielsen Donald R.
Published: July 2010

Methods used in soil science to derive scale factors for soil properties include the dimensional method called similitude analysis which is based on physical characteristics of a soil system and an empirical method called functional normalization which is based on regression analysis. In the past, researchers have assigned physical significance to empirically determined scale factors on the basis of corresponding scale factors derived from similitude analysis. This paper demonstrates that scale factors determined through functional normalization are not always physically equivalent to those determined from similitude analysis. This paper also describes two additional dimensional methods that can be used to derive scale factors for soil properties, namely dimensional and inspectional analysis. Examples of dimensional analysis, inspectional analysis, and functional normalization are presented for a variety of soil science disciplines.
Absorption of Gaseous Ammonia by Douglas‐Fir
Authors: Pang Patrick C.K.
Published: July 2010

Absorption of labelled ammonia (15NH3) by excised shoots of Douglas‐fir [Pseudotsuga menziesii (Mirb.) Franco] was determined under laboratory conditions to increase as the ammonia concentration increased from 0 to 1.09 volume %. Photosynthesis was unaffected by the presence of ammonia except at the highest concentration studied. Although Douglas‐fir is demonstrated to have the potential to absorb ammonia, the amount of ammonia absorbed under field conditions is suggested to be influenced by factors affecting rates of diffusion and mass flow of NH3 out of the canopy.
Weighing Lysimeters for Long‐Term Water Balance Investigations at Remote Sites
Authors: Kirkham R. R. , Gee G. W. , Jones T. L.
Published: July 2010

Two weighing lysimeters were installed at a remote location on the Dep. of Energy's Hanford Site in Washington State in 1978 and 1979. Platform‐type electronic scales were placed below the soil surface to measure the weight changes of a large (∼7 Mg) container of soil. The load cells of the scales have been exposed to high humidity and to periodic contact with drainage water, but have operated without failure since installation (over 5 years). Weight changes are continuously recorded, with hourly averages transmitted by phone line directly to the laboratory. The sensitivity of the scale is 50 g, equivalent to 0.02 mm of H2O.
A Field Comparison of Null‐Aligned and Mechanistic Soil Heat Flux
Authors: Pikul J. L. , Allmaras R. R.
Published: July 2010

Soil heat fluxes using the mechanistic soil heat flux model of Philip and de Vries were compared with those experimentally determined in the field using a null‐alignment method. Comparisons at 20 depths in the top 60 cm of soil during midsummer showed better agreement of theory and measurement for the wet than for the dry Walla Walla silt loam. Average water content in the top 11 cm was 0.22 and 0.12 m3/m3 for the wet and dry plots, respectively, during the 24‐h measurement period. Measured daily soil heat energy at 0.25 cm was 935 and 910 kJ/m2 for the wet and dry plots, respectively. Computed energy totals at this same depth overestimated measured totals 10‐fold. At 11 cm, the approximate seeding depth of wheat, measured daily soil heat energy was 562 and 863 kJ/m2 for the wet and dry treatments, respectively; respective computed energy totals were 616 and 1345 kJ/m2. The greatest disparity between measured and computed heat flux density occurred at shallow depths (<2 cm) during midday. Computed heat flux density in the top 35 cm generally was overestimated by 20 and 35%, as compared to measured fluxes for the wet and dry plots, respectively. Water content changes at depths equivalent to the seedzone (5–11 cm) in the dry plot were predicted within a factor of two by the vapor flux components of the heat flux model. Computed conductive heat fluxes were more seriously overestimated than were the vapor flux components.
An Automated Manometric Method for Quantitative Determination of Calcite and Dolomite
Authors: Evangelou V. P. , Whittig L. D. , Tanji K. K.
Published: July 2010

A rapid automated method is described for differentiation and quantitative determination of calcite and dolomite in earth materials. The method is based on differential pseudo‐first‐order kinetic rates of dissolution of the two carbonate species when reacted with excess of 5M HCl. The method employs manometric measurement of acid‐liberated CO2 with a differential pressure transducer coupled to a strip chart recorder. Tested on calcite and dolomite singly and together in geologic materials, the method is highly discriminatory, highly sensitive, and extremely rapid. Theoretical treatments of pseudo‐first‐order kinetic reactions and of manometric measurements associated with the method are reviewed.
Residual Copper(II) Complexes in Purified Soil and Sewage Sludge Fulvic Acids: Electron Spin Resonance Study
Authors: Senesi Nicola , Sposito Garrison
Published: July 2010

Electron spin resonance (ESR) spectra were obtained for both frozen (77 K) aqueous solutions and solid samples of purified fulvic acid (FA) extracted from sewage sludge and from soil organic matter. Large scan range (5000 G) ESR spectra indicated the presence of organic free radical species of semiquinone nature and of iron(III) in sites of highly rhombic character. Narrower scan range (2000 G) ESR spectra were characterized by absorptions of the axiaI type near g = 2, which indicated the presence of residual copper(II) in a dx2−y2 groundstate complexed with ligands arranged in a tetragonal environment. The coordination of the copper(Cu) was shown to be of the equatorial type, involving both oxygen‐(O) and nitrogen‐(N) ligand atoms of FA. The main resonances in the spectrum obtained for the frozen solution of the soil FA were consistent with a principal binding site of 4 O atoms, whereas the minor ESR component in the same spectrum was assigned to a binding site involving 3 O‐and 1 N‐ligand atoms. The reverse order of importance was found in the ESR spectrum of the solid sample, indicating that more N‐containing functional groups of the FA were involved in the binding of residual copper when the FA was not dissolved in water. The ESR parameters for the sludge FA samples indicated that the main resonances were consistent with a 3 O‐1 N‐binding site and the minor ones with 4 O‐or 2 O‐and 2 N‐coordinating environments. ESR spectra of the sludge FA run over a very narrow scan range (1000 G) suggested that an intensely structured pattern at g⊥ could be assigned to a superhyperfine coupling of the unpaired Cu electron to two equivalent N ligand nuclei.
Soil Moisture Regimes on Some Rangelands of Southeastern Idaho
Authors: Jensen Mark E.
Published: July 2010

Soil temperature and moisture were measured in 1981 and 1982 on 24 rangeland sites of the Caribou National Forest in southeastern Idaho. Those sites have aridic moisture regimes within cryic soil temperature regimes. Soil Taxonomy does not recognize this combination of soil climatic parameters, although they are probably extensive throughout the higher elevation areas of the Intermountain Region. The sagebrush‐grass and mountain brush vegetative types studied have a mean of 44 d in which moisture is held in the soil moisture control section at < 1.5 MPa (15 bars) suction when the soil temperature at the 0.5‐m depth exceeds 5°C, i.e., growing period. A knowledge of the mean growing period on a site provides the range manager an alternative tool for determinations of range readiness. Soil temperature and moisture monitoring facilitates prediction of range readiness dates and may be used to approximate range readiness over a potentially broader area than site‐specific visual assessment of plant phenology allows.
Perceiving and Defining Soils on Disturbed Land
Authors: Indorante S. J. , Jansen I. J.
Published: July 2010

This study outlines and applies a procedure for mapping and classifying soils on surface‐mined land. Soils are mapped by defining soil units and then delineating corresponding bodies as they exist on the landscape. For a given landscape, soil unit concepts are most useful if they facilitate grouping soils that are alike and separating soils that are different. Soil units on the surface‐mined land were defined by considering premine soil and overburden characteristics, method of mining, and method of soil construction. Considering these historical factors provides clues to soil characteristics and geographic patterns of the soils much as applying geomorphic and conventional soil genesis concepts do for natural soils. Four series were mapped on surface‐mined land. The Morristown, Lenzburg, Schuline, and Swanwick series are Typic Udorthents. Particle size class, which included rock fragments, and reaction class of the control section are the main differences among the series. The approach to defining soil units used in this study is an effective method for perceiving order on surface‐mined land so that the soils can be mapped and classified.
Field Estimation of Amorphous Aluminum with 4M Potassium Hydroxide
Authors: Holmgren G. G. S. , Kimble J. M.
Published: July 2010

A procedure is described that provides the field scientist with a rapid, quantitative measure of a form of amorphous Al characteristic of Spodosols and Andepts. The proposed procedure is as follows: React 0.2 g of soil for 10 min with 2 mL of 4M KOH. Dilute to 20 mL and neutralize with HCl to a phenolphthalein end point. Add 2 mL of 1M KF and re‐titrate the suspension to the same end point with drop count additions of 0.1M HCl. Studies of the procedures' sensitivity to reagent concentration, soil/solution ratio and time are presented. Evidence is also presented to demonstrate that this method does not extract Al from crystalline clay minerals. KOH extractable Al values compare well with acid ammonium oxalate extractable Al for amounts 20 g kg−1(2%). Above this, ammonium oxalate Al generally exceeds KOH aluminum by an amount equivalent to the silica extracted by ammonium oxalate.
Computerized Scheme for Chemical Classification of Natural Waters and Soil Extracts
Authors: Held P. , Maianu A.
Published: July 2010

A classification triangle (similar to the USDA textural one) is often used to define the chemical classes of water based on anionic and/or cationic composition. The method is laborious. A SAS3 program was developed to do the work rapidly and with high precision. The program was designed for anionic composition, and may be used for cations by changing certain variables.
Application of the Potential Concept to Soil Water Equilibrium and Transport
Authors: Corey A. T. , Klute A.
Published: July 2010

This study examines the view that a “total soil water potential” can be defined such that (i) the water component will always move from regions of higher to regions of lower potential, and (ii) that if the total potential is constant at all points, the water component is in equilibrium. Soil science literature is reviewed to discover why such a concept is widely accepted. It is found that many analyses leading to the total potential concept contain shortcomings which have resulted in invalid conclusions. The key shortcoming is a failure to distinguish between components of a potential that apply only to elements of the soil solution and those that apply only to the water component. Concepts from texts dealing with transport processes and thermodynamics are used to show that there is no single potential that is a function of the state of the soil solution only, whose gradient will always indicate the direction of net transport of the water component, or which if constant in all parts of the system will ensure that equilibrium exists.
Simulated Solute Movement in Wastewater‐Ponded Soil
Authors: Mansell R. S. , McKenna P. J. , Hall M. E.
Published: July 2010

A finite‐difference numerical model was used to predict sorption and transport of P in a rapid infiltration land system for renovating urban wastewater. The soil was assumed to be water‐saturated and two‐dimensional steady flow was assumed to occur from a 2‐m wide ponded recharge zone toward a subsurface collection drain located at a lateral distance of 3 m. The rectangular area of interest was bounded underneath by an impermeable layer at the 1‐m depth and was limited to a lateral length of 5 m. Phosphorus sorption in the soil was assumed to occur as two consecutive kinetic reactions—rapid physical adsorption followed by slower chemisorption. Transient movement and sorption of P in the soil was predicted with the model for a step‐function increase in P concentration in the applied waste‐water. Results predicted by the model were used to construct plots of concentration isopleths of P in solution and sorbed phases in the soil. Sorption reactions removed P from the flowing solutions in the soil directly beneath the recharge area, resulting in a retardation of the concentration of P appearing in the drainage water. Simulated breakthrough curves for the concentration of a nonreactive solute in the drainage effluent compared well to those obtained with an approximate analytical model from published literature.
Solute Dispersion During Axisymmetric Three‐Dimensional Unsaturated Water Flow
Authors: Clothier B. E. , Elrick D. E.
Published: July 2010

An approximate, analytic solution is presented for the smearing of solute by both convection and dispersion during axisymmetric three‐dimensional constant flux infiltration from a surface point source in unsaturated soil. The steady‐state pattern of axisymmetric streamlines is used to track individual parcels of water as they move away from the surface emitter. A simple analytic expression is developed to describe the time course of the hydrodynamic dispersion of solute about the convected front as it moves along any given streamline. The location of the convected front at any time is predicted from the profile of wetting along that streamline. The plane‐of‐separation concept is used to find the distance travelled by the convected front along the streamline. The invading solution is considered to act as if to effectively piston‐displace the antecedent soil water. Profiles of bromide concentration along three streamline paths were measured during constant‐flux point‐source infiltration experiments in the laboratory with fine sand. These measurements compared favorably with the theoretical predictions.