bluuebunny/crossref_metadata_2025 huggingface dataset:
A Thermodynamic Model for Predicting the Formation, Stability, and Weathering of Common Soil Minerals
Authors: Rai Dhanpat , Lindsay W. L.
Published: July 2010

Numerous workers have examined the weathering products of soil minerals and have proposed empirical weathering sequences. The present paper outlines the development of a thermodynamic model that predicts in a systematic way several mineral transformations that can occur in soils.

According to this model, the stability of primary minerals increases in the order: Na‐glass, K‐glass, pyroxene, analcime, anorthite, low albite, muscovite, microcline, and quartz. The stability of secondary clay minerals depends on soluble silica. At pH 6 with high silica (≃ 10‐3M) the order of increasing stability is: chlorite, halloysite, gibbsite, illite, dickite, beidellite, kaolinite, and montmorillonite; at low silica (≃ 10‐5M) the order is: chlorite, halloysite, illite, beidellite, montmorillonite, dickite, kaolinite, and gibbsite. The stability of both primary and secondary minerals increases with pH.

The observed weathering of volcanic ash agrees well with the predictions of this model. The model makes use of important thermodynamic data accumulated for soil minerals and helps to pinpoint deficiencies in these data. The need to examine the kinetics of mineral transformations in soils in greater detail also becomes obvious from this model.
Hydrothermal Soils of the Crater of Mt. Baker, Washington
Authors: Bockheim J. G. , Ballard T. M.
Published: July 2010

Soils and rocks were sampled near active steam vents in the crater of Mt. Baker, in order to determine the soil chemical and mineralogical properties associated with hydrothermal and solfataric alteration. X‐ray diffraction analysis indicated the formation of kaolinite, montmorillonite, analcime, gibbsite, and some other minerals in these materials. The soils range from very gravelly sand to gravelly loamy sand in texture, and are extremely acid (pH 1.2–2.8). These soils have low cation exchange capacity (2.7–5.8 meq/100 g), high to very high electrical conductivity (1.3 to 11.2 mmho/cm), and small amounts of free Fe, Al, and Si. Dominant water soluble ions are HSO4‐ and SO42‐, Fe2+, Al3+, H+, Mg2+, and Ca2+. Altered andesite rock and soil are depleted in Al2O3, CaO, and MgO, and locally enriched in Fe2O3.
Solute Travel‐Time Estimates for Tile‐Drained Fields: I. Theory
Authors: Jury W. A.
Published: July 2010

A model based on papers by D. Kirkham (1949; 1958) is proposed for calculating solute travel times and effluent water quality for tile‐drained soil profiles for cases of ponded and unsaturated surface water input. Variables required for utilization of the model are drain spacing, depth of tile, depth to impermeable zone, soil porosity, and mean discharge rate over the time of study. By using dimensionless variables a characteristic travel‐time parameter is introduced which will represent a system and allow the model calculations to be summarized on a single graph. Simulations are run for cases of miscible displacement, step‐function surface solute input, and periodic surface solute input; differences between ponded and unsaturated leaching are discussed for tile systems.
Transport of Water and Heat in a Frozen Permeameter
Authors: Miller R. D. , Loch J. P. G. , Bresler E.
Published: July 2010

Transport of water in frozen soils is probably not restricted to fluid phases. In a frozen permeameter a series‐parallel mode of transport should exist in which the ice phase may move with uniform translational velocity in a stationary pore system formed by particles having adsorbed films of unfrozen water. A microscopic model for coupled mass and heat transport would be complex, but foundations for such a model are laid in an exercise which derives direct and cross coefficients for coupled transport equations applicable to a permeameter containing a simplified (nontortuous) “soil” with uniform cylindrical channels, ice‐filled except for films adsorbed at channel walls. Temperature dependence of coefficients, assuming Newtonian shear in the film, can be modeled using standard double‐layer theory. It is shown that the resultant coefficients are relatively insensitive to temperature (film thickness) but are highly dependent on thermal conductivities of components. Identity of cross‐coefficients in this mechanical model is demonstrated. Expressions for computing phenomenological soil coefficients from coefficients measured in a practical permeameter are given, and a workable permeameter for such studies is postulated.
Stability Analysis of Infiltration
Authors: Philip J. R.
Published: July 2010

A rigorous hydrodynamic stability analysis of the delta‐function model of infiltration is developed. Raats recently proposed as the criterion for instability that wetting front velocity should increase with front penetration. This detailed analysis, on the other hand, shows that the fundamental criterion is that the water pressure gradient immediately behind the front should oppose the flow. The two criteria agree only in the special case where five significant parameters of the system are all constant and independent of depth, or of depth to the front. The Raats criterion fails in the various more general cases with one or more of these quantities variable.

Quantitative criteria are developed for various specific circumstances in which the flow may become unstable: penetration to a non‐wetting stratum; compression of air ahead of the front; redistribution following infiltration; increase of conductivity with depth.

The analysis indicates a definite maximum wave number for unstable disturbances, Mcrit, and a wave number for disturbances which are amplified most rapidly, 3‐½ Mcrit. Flows in a laboratory soil column may therefore remain stable because the cross‐sectional dimensions are too small. Observed dimensions of fingers in unstable infiltration flows are consistent with the predicted wave number for maximum amplification.

The study is readily extended to time‐dependent flows of two immiscible fluids in heterogeneous media. It applies also to time‐dependent flows in heterogeneous Hele‐Shaw cells.

Care should be exercised in applying results for the deltafunction model to flows with gradual wetting fronts, especially when nonwetting strata are involved.
Acidification and Deacidification of Coastal Plain Soils as a Result of Periodic Flooding
Authors: van Breemen N.
Published: July 2010

Periodic flooding of recent coastal plain soils causes either acidification or deacidification of the surface horizons. Acidification of sulfate‐bearing “nonacid” soils (pH > 5) involves formation of FeS and partial loss of alkalinity (HCO3‐) in the flood water during the wet season, followed by oxidation of FeS to ferric oxide and sulfuric acid in the dry season. Deacidification of acid soils (pH < 4.5) takes place during flooding. This involves reduction of ferric oxides to Fe2+, the simultaneous release of adsorbed SO42‐ or hydrolysis of basic sulfates (that function as proton donor during iron reduction at low pH), followed by oxidation of dissolved FeSO4 to ferric oxide and sulfuric acid at the soil‐water interface, and removal of H2SO4 by lateral surface drainage. During soil reduction the actual pH increases and a shift from one process to the other takes place if the pH becomes high enough (4.5 to 5) for the weak acids CO2 and H2S to function as proton donors. Therefore, deacidification beyond pH 4.5 to 5 automatically invokes the release of alkalinity. Conversely, acidification to a pH below 4.5 to 5 during a dry season will be undone by deacidification in the following wet season. This explains why the surface horizons of periodically flooded acid sulfate soils and nonacid marine soils eventually attain the same pH under dry conditions. This pH is fundamentally related to the dissociation constant, the solubility and the partial pressure of CO2.
In situ Measurement of Gas Diffusion Coefficient in Soils
Authors: Lai Sung‐Ho , Tiedje James M. , Erickson A. Earl
Published: July 2010

A method for determination of the gas diffusion coefficient of soils without disturbing the natural state of the soil was developed. The method was based on the theory of radial diffusion of a finite quantity of gas into a semi‐infinite porous medium. Needles were inserted into the soil through which O2 was injected. The change of concentration of the injected O2 was determined by gas chromatography through the same needle after increasing periods of time. A least square fit between the measured O2 concentrations and that of the theoretical values was conducted to find the best fit value of the diffusion coefficient. The diffusion coefficient determined by the proposed method was used to calculate the flux of CO2 in field soils. The flux so calculated was compared to that measured from the field with good agreement. The method was used in several different field soils and conditions to determine the diffusion coefficients.
Comparisons of Calculated and Measured Capillary Potentials from Line Sources
Authors: Thomas Adrian W. , Duke Harold R. , Zachmann David W. , Kruse E. Gordon
Published: July 2010

This paper is a sequel to D. W. Zachmann and A. W. Thomas' (1973) development of equations describing steady infiltration from line sources. Calculated distributions of capillary potentials are compared with those measured in a soil bin designed to model the water distribution from a subsurface irrigation system. Limitations of the steady‐state equations for predicting capillary potentials are given. A procedure for selecting lateral depth and spacing to attain a given matric flux potentials is also given.
Comparison of Field‐measured and Calculated Soil‐heat Fluxes
Authors: Kimball B. A. , Jackson R. D. , Reginato R. J. , Nakayama F. S. , Idso S. B.
Published: July 2010

Soil‐heat fluxes calculated using DeVries' theory (1958, 1963) were compared with those experimentally determined in a field of Avondale loam at Phoenix, Ariz., on 6 days representing different seasons of the year. A fair agreement between measured and computed fluxes was obtained only after modifying the air shape factor curve and ignoring heat transfer due to water vapor movement. The omission of the latter implied that heat transfer by pure conduction was most important and that thermal and isothermal vapor fluxes exactly cancelled during the day and were insignificant at night.

“Measured” thermal conductivities were also determined from the ratio of the measured heat fluxes to the corresponding temperature gradient for those times when it was unlikely that isothermal vapor movement was significant. The lack of a temperature dependence in these data, as well as the flux comparisons, strongly indicate that the theory overestimated thermal vapor movement. These data plus others in the literature indicate that an individual “calibration” of the theory for a particular soil is required before reliable predications of soil‐heat flux can be obtained.
Soil‐heat Flux Determination: Temperature Gradient Method with Computed Thermal Conductivities
Authors: Kimball B. A. , Jackson R. D. , Nakayama F. S. , Idso S. B. , Reginato R. J.
Published: July 2010

Surface soil‐heat fluxes were determined for 6 days in a field of Avondale loam using the null‐alignment method, the combination method, and four variations of the temperature gradient method with thermal conductivities computed from the DeVries' theory for particular reference depths. For all methods, calorimetry was used to obtain the surface flux from the flux determined for the reference depth.

There was 10% or less difference between the null‐alignment, combination, and temperature gradient methods for a 20‐cm reference depth. However, the difference with respect to the null‐alignment method increased to 35% for a 5‐cm reference depth when DeVries' theory was closely followed. This difference was reduced to 3% when a modified air shape factor was used in the computations and all vapor movement was ignored. We concluded that the temperature gradient method with conductivities computed from DeVries' theory could be reliably used with a 20‐cm reference depth, but that a “calibration” of the theory for a particular soil should be obtained before the method is used with a 5‐cm reference depth.

When properly used, the temperature gradient method with computed conductivities has the advantage that reliable estimates of surface soil‐heat flux can be obtained without requiring heat flux plates like the usual combination method nor many computations like the null‐alignment method.
Phosphorus Fertilization with Drip Irrigation
Authors: Rauschkolb R. S. , Rolston D. E. , Miller R. J. , Carlton A. B. , Burau R. G.
Published: July 2010

Application of plant nutrients with drip irrigation systems is desirable for labor and energy savings and flexibility in timing nutrient applications. Evaluations of P movement in the soil and uptake by tomatoes (Lycopersicum esculentum) were made when orthophosphate and glycerophosphate were applied through a drip irrigation system and in comparison with 26 kg of P/ha banded below the seed at planting. A significantly higher P content was measured in seedling leaves when 26 kg of P/ha was applied by drip irrigation than when the same rate was banded. No differences in P content of whole tops of seedlings were measured at equal rates of inorganic or organic P applied through the drip system. There was a significant linear response of P uptake to P rate.

With drip irrigation, orthophosphate moved a much greater distance into the soil than had been previously observed for comparable application rates per hectare. Glycerophosphate moved 5 to 10 cm farther through the soil at application rates of 6.5 and 13 kg of P/ha than did orthophosphate. At the relatively high rate of 39 kg of P/ha, orthophosphate moved 25 cm horizontally and 30 cm vertically in the soil profile. Movement of orthophosphate resulted from saturation of the soil reaction sites near the point of application with phosphorus and subsequent mass flow with the soil water. The distance of P movement was proportional to the application rate. Glycerophosphate must undergo enzymatic hydrolysis before releasing orthophosphate ions into the soil solution where orthophosphate can be removed from solution by soil reactions. Consequently, glycerophosphate moved farther than orthophosphate at low application rates.
Properties of Some Tidal Marsh Soils of Florida
Authors: Coultas C. L. , Calhoun F. G.
Published: July 2010

Psammaquents, Sulfihemists, and Sulfaquents were found in the tidal marshes of Hernando (Gulf Coast) and Duval (Atlantic Coast) counties, in Florida. They were saline and near neutral in pH and, with the exception of the Psammaquents, contained higher levels of S (2.66–5.19%). Hernando County soils were shallow over limestone and much sandier than those in east Florida. Duval County soil clays were primarily montmorillonite, mica, and kaolinite but Hernando County soil clays were mostly vermiculite‐chlorite intergrade and kaolinite‐metahalloysite. Except for one of the Psammaquents, the soils contained relatively high levels of organic matter (7.8–28.9% organic C) and extractable bases. Juncus roemerianus Scheele is the principal plant in these marshes. The bulk density of the organic soil layers ranged from 0.13 to 0.36 g/cm3, whereas that of the clayey layers was 0.16 to 0.25 g/cm3.
Soil‐Site Productivity for Natural Stands of White Pine in Massachusetts
Authors: Mader Donald L.
Published: July 2010

Soil and site characteristics for prediction of white pine (Pinus strobus L.) growth were studied in over 80 stands throughout Massachusetts. Soil descriptions, site characteristics, and stand growth were noted in the field. Samples from the soil horizons were analyzed in the laboratory for physical and chemical properties. Step‐wise multiple regression computer analyses provided growth prediction equations for several levels of complexity of the soil and site data input. Prediction from topographic variables was poor. Addition of soil physical and chemical variables improved the prediction. Of the growth measures, height was predicted most accurately, age plus soil variables accounting for 80–90% of the variation. Soil and site variables accounted for up to about 60% of the variation in site index, and for periodic cubic volume increment up to about 70%. Total board and cubic volume are predicted quite well by age and soil‐site factors (R2 ca 0.6–0.8). Basal area is not predicted well. Textural components, coarse materials, drainage class, organic matter, pH of lower horizons, and moisture characteristics were common significant factors. The equations for site index, total height and cubic volume growth should be useful for prediction of white pine site productivity in Massachusetts.
The Separation Factor Applied to Some Soil Ion Exchange Equilibria
Authors: Kittrick J. A.
Published: July 2010

A variety of exchange equations are available to investigators, who may select the one that best fits their purposes or experimental data. Although equations based upon the separation factor (which does not contain ionic valences as exponents) have not been frequently used in ion exchange equilibria in soils, this investigation indicates that the approach may deserve more attention. Some monovalent‐divalent ion exchange equilibria with montmorillonite are closely predicted by the separation factor. Further, variations in the separation factor with soil mineralogy and total solution concentration appear to be small enough to permit useful prediction of the ratio of exchangeable Na+ and Ca2+ in the soil from the ratio of Na+ to Ca2+ in the saturation extract.
Tripolyphosphate and Pyrophosphate Hydrolysis in Sediments
Authors: Blanchar R. W. , Riego D. C.
Published: July 2010

The rate of hydrolysis of tripolyphosphate (TPP) and pyrophosphate (PP) in river, creek, and lake sediments was determined. Half‐lives for the hydrolysis of TPP and PP ranged from 1.6 to 2.6 and 6.7 to 27.4 days, respectively. The influence of temperature, biological activity, and pH on the rate of TPP and PP hydrolysis was investigated using Flat Branch Creek sediment. The rate of TPP and PP hydrolysis increased with increasing temperature. The activation energy was 5,415 cal/mole for TPP and 10,412 cal/mole for PP. TPP and PP hydrolyzed slower in sediment which had been autoclaved than in non‐sterilized sediment. The half‐life for TPP hydrolysis was 1.76 day at pH 5, 1.61 day at pH 7, and 2.16 day at pH 9. The rate of PP hydrolysis was increased as pH increased from 5 to 7 to 9 as indicated by half‐lives of 13.7, 10.0, and 7.3 days, respectively. When TPP was added to the sediment as a Ca5(P3O10)2 precipitate, the rate of hydrolysis was slower than when TPP was added as a solution.
Particle Shape and Sodium Self‐diffusion Coefficient in Mixed Sodium‐calcium Montmorillonite
Authors: Dufey Joseph E. , Banin Amos , Laudelout Henri G. , Chen Yona
Published: July 2010

Various parameters related to the shape of clay particles and self‐diffusion coefficients of sodium were measured in Camp‐Berteau montmorillonite suspensions equilibrated with NaCl‐CaCl2 solutions of 0.01 total normality, and variable ratios of Na to Ca. As the equivalent ionic fraction of exchangeable sodium decreased from 1.0 to 0.0, the anion exclusion volume decreased from 2.9 to 0.5 ml g‐1, the hydration of clay sediment decreased from 8.6 to 4.4 ml g‐1, the average number of plates per tactoid increased from 1.4 to 3.9, and the axial ratio of the clay particles decreased from 190 to 90. At clay content of about 27 g/liter, the self‐diffusion coefficient of Na increased from about 0.40 × 10‐5 to 0.76 × 10‐5 cm2 sec‐1 at 16°C and from 0.55 × 10‐5 to 1.16 × 10‐5 cm2 sec‐1 at 33°C, as the ionic fraction of exchangeable Na decreased from 1.0 to 0.15.

The calculated surface diffusion coefficient of sodium was found to be about 30% of its value in the free solution for a pure sodium clay and thereafter increased up to about 50% of that value for a clay loaded by 15% Na. The activation energy involved in the surface diffusion process was calculated to be in the range of 3 to 6 kcal/mole, and a minimum was found for the clay containing about 70% Na. As evaluated from the data on the number of platelets per tactoid the internal surfaces of which were assumed to be preferentially occupied by Ca, this minimum could perhaps correspond to a completely demixed system. A less refined but nevertheless rather satisfactory approach was also attempted for interpreting the variation of the observed self‐diffusion coefficient of Na as a simple result of the change in the distribution of that ion between the surface phase and the free solution.
Control of Zn2+ in the Soil Solution by Sphalerite
Authors: Kittrick J. A.
Published: July 2010

Zinc (Zn2+) levels in the soil solution are in the parts per billion range. Most known Zn compounds are too soluble to control Zn2+ at such levels. However, ZnS (sphalerite) is a highly insoluble compound in the presence of even traces of H2S. Although H2S is thermodynamically unstable under aerobic conditions, concentrations of H2S actually found in the atmosphere are high enough to engender control of Zn2+ in the soil solution by ZnS in aerated soil samples. In soils, especially under anaerobic conditions, even higher levels of H2S prevail which could depress Zn2+ concentrations to very low levels. Some of the deleterious effects of H2S on plants under anerobic conditions actually may be due to Zn deficiency.
Potassium Sources and Availability in a Deep, Sandy Soil of East Texas
Authors: Hons F. M. , Dixon J. B. , Matocha J. E.
Published: July 2010

Soil properties were assessed that may have contributed to the failure of Coastal bermudagrass [Cynodon dactylon (L. Pers.)] to respond to application of K on Darco fine sand for 5 consecutive years. The depth to which plant roots absorbed K was assessed by field observation and by determination of K levels in control and treatment plots. Potassium minerals were determined by chemical methods to assess potential nutrient sources.

Potassium removal was indicated to at least 160 cm by soil solution content and to 235 cm by exchangeable K concentration and Gapon selectivity values. Depth of bermudagrass rooting was in agreement with chemical indicators of K removal.

Mica and interstratified mica in the fine silt and clay fractions correlated best with exchangeable K (r2 = 0.97) suggesting a direct influence of the finer micaceous materials in Darco soils upon K retained in an exchangeable form and possibly upon K release. Inclusion of feldspar‐K with mica‐K reduced the r2 value from 0.97 to 0.83 suggesting that K‐feldspar does not contribute appreciable K to exchangeable form. Feldspar was present mostly in the sand and two coarser silt fractions which expose little surface area to weathering forces.

The large rooting volume of Coastal bermudagrass in Darco soil in conjunction with the mica and appreciable interstratified mica present may explain why no plant response was obtained to K application.
A Technique to Determine Iron Efficiency in Plants
Authors: Brown J. C. , Jones W. E.
Published: July 2010

Soil tests should predict crop response to fertilization. In the case of Fe, plant factors seem to affect the use of Fe by the plant; thus, soil tests may not be reliable. Use of soil Fe by plants is genetically controlled by an adaptive mechanism which is activated in Fe‐efficient plants in response to Fe‐stress, but remains inactive if Fe is sufficient. Fe‐inefficient plants develop less Fe‐stress response than Fe‐efficient plants. Using this range of Fe‐stress response in plants as a basis, we developed a technique to screen plants for Fe efficiency.

A limited supply of Fe and some control of pH in the growth medium were required in this technique. The pH was controlled by using nutrient solutions, N only as No3, and N as NH4 and NO3, and by varying the CaCO3 and P concentrations in the solutions. The optimum supply of Fe (0.2 mg Fe/liter) was determined by growing the plants at different Fe concentrations.

Four Fe‐inefficient and four Fe‐efficient plant varieties, representing four plant species, were used as test plants. The plants were screened in mixed cultures and were rated in order of greatest Fe efficiency as follows:

T3238FER tomato (Lycopersicon esculentum Mill.) ≥ Hawkeye soybean (Glycine max (L.) Merr.) > W59 Corn (Zea mays L.) > Pioneer 846 sorghum (Sorghum bicolor (L.) Moench) > PI‐54619‐5‐1 soybean > Wheatland sorghum > ys1/ys1 corn > T3238fer tomato.

Green plants contained more and chlorotic plants contained < 43 µg Fe/g, but the degree of Fe‐chlorosis was the best index of Fe‐efficiency. A suggested sequence for screening plants for Fe‐efficiency is presented.
High‐altitude Photography in the Development of a Generalized Soil Map
Authors: Rust R. H. , Finney H. R. , Hanson L. D. , Wright H. E.
Published: July 2010

State‐wide panchromatic photography of Minnesota was obtained at a contact scale of 1:90,000 and used for compiling a series of generalized soil maps. The taxonomic legend used was developed from selected concepts in Soil Taxonomy, generally at the subgroup level. The mapping rate is about one township per day with maximum use of stereo‐interpretation. Maps are compiled on composites of the U.S. Geological Survey 1:250,000 quadrangles. A concept of geomorphic regions is used to identify and isolate distinctive parent materials and topography. About 75 such regions are delineated. A concept of soil landscape units (SLU) was developed for mineral soils. These are viewed as collections of soil bodies having broad similarity in particlesize class of the control section and of material below the control section; in position and duration of the water table; and in the presence or absence of a mollic epipedon. For areas of organic soils, a taxonomic legend using suborder concepts was developed.
Particle‐Size Distribution Characterization for the Coarse Fraction of a Granite Soil. I. A model.
Authors: Russell D. A.
Published: July 2010

Many central African soils are sandy single‐grain‐structure materials developing under semiarid conditions, and derived from the underlying granite. To obtain a useful size distribution function for the nonclay fraction required a quantitative model for granite disintegration.

Methods of characterizing particulate distributions are briefly reviewed with reference to the mechanisms giving rise to them. J. G. Bennett's (1936) description of brittle solid disintegration has been extended to yield the incomplete gamma function as a descriptor of the product of granite disintegration. This is discussed and compared with the log‐normal and Weibull functions in terms of postulated mechanisms.

It is concluded that the mechanism presented here more closely approximates the disintegration process than those yielding the above two functions, and that the resulting incomplete gamma function should be a reasonable basic descriptor of the particle‐size distribution of disintegrating granite.
Influence of Row Spacing and Straw Mulch on First Stage Drying
Authors: Adams J. E. , Arkin G. F. , Ritchie J. T.
Published: July 2010

Evaporation during first stage drying was measured with evaporation plates on the soil surface in grain sorghum plots with 25‐, 50‐, and 100‐cm row spacings, during several stages of grain sorghum [Sorghum bicolor (L.) Moench] development in 1972 and 1973. Evaporation during first stage drying was affected by row spacing, leaf area index (LAI), and soil shading. Both LAI and soil shading were related to row spacing and plant population. The more complete plant canopy of grain sorghum with narrow‐row spacing decreased penetration of radiant energy to the soil surface and reduced the evaporation rate of soil water during first stage drying. Evaporation was greatest during the early part of the season when shading was least and lowest during boot stage and pollination, when all leaves were fully expanded and provided maximum plant canopy and soil shading. Narrow‐row spacing established an earlier, and more complete plant canopy than conventional 100‐cm row spacing and shaded more of the soil surface from early vegetative growth to maturity. Soil surface shaded near solar noon was a better indicator of first stage evaporation beneath a canopy than LAI.

The combined effect of a mulched surface and a plant canopy on reducing evaporation was the product of the fractional reduction in potential evaporation resulting from the plant canopy and the evaporation resulting from the mulched surface with no canopy cover. An empirical equation was developed from the evaporation data for use in calculating first stage evaporation as related to potential evaporation, fraction of the soil surface shaded, and mulch rate.
Sequel to “Residual Availability of Fertilizer Zinc”
Authors: Boawn Louis C.
Published: July 2010

A previously reported experiment which evaluated residual availability of fertilizer Zn for 5 years after application was sampled for two additional years. These additional data confirm that fixation of Zn against extraction with DTPA solution reaches an equilibrium and that a new extractable‐Zn level is established for each rate of Zn added.
Percolation of Surface‐applied Water in the Field
Authors: Quisenberry V. L. , Phillips R. E.
Published: July 2010

Percolation of surface‐applied water tagged with chloride was studied in Maury silt loam and Huntington silty clay loam under field conditions. Soil samples were taken in small increments to the 90‐cm depth several times following application of water. Analyses of chloride content with depth indicated the position of the applied water relative to the initial soil water in the profile.

Three percolation studies were conducted on Maury silt loam soil. In study 1 an application of 4.2 cm of water increased the water content to the 60‐cm depth within 1 hour following irrigation even though the volumetric water profile averaged 5% below the upper limit of the water holding capacity through this depth. A second study conducted at a slightly higher initial water content showed that 20% of a 4.2‐cm application had penetrated below the 90‐cm depth immediately after application and 40% penetrated below this depth within 1 hour.

Similar results were measured in Huntington silty clay loam. Simulated rainfall increased the water content significantly to approximately the 15 cm depth in each of three studies. A large percentage of the water passing this depth apparently percolated past the 90‐cm depth with very little adsorption of water and chloride between these depths.

Location of chloride in the profile and movement of chloride past the 90‐cm depth indicated that a large percentage of the applied water percolated past the water initially present with little displacement of the initial water.
Influence of Physical and Mineralogical Properties on Swelling of Soils in Yolo County, California
Authors: Schafer William M. , Singer Michael J.
Published: July 2010

Surface samples from 16 California soils with a wide range of swelling characteristics were studied. The coefficient of linear extensibility (COLE) of each soil was correlated with other properties. Total clay content was highly correlated with COLE (r2 = 0.868) while the ratio of expandable clay/total clay (partial r2 = 0.454) also significantly affects swelling. The percent of expandable clay is the single variable best correlated with COLE (r2 = 0.907). Models established to predict COLE from other soil properties were selected from the literature and applied to these soils. Results are compared with measured COLE values, and a new model calculating COLE from interlayer expansion of the smectite fraction of soil is proposed.
Laboratory Testing of Water‐repellent Soil Treatments for Water Harvesting
Authors: Fink D. H.
Published: July 2010

Field testing of repellents for water harvesting is both slow and costly, often hindering the orderly, rapid progression of the technique. Laboratory tests were developed for rapidly evaluating the effectiveness of water‐repellent treatments on soils. The effect of accelerated weathering from ultraviolet radiation, ozone, and freeze‐thaw cycling on the retention of water repellency and on soil stability were studied. The effect on soil stability of prolonged hydration and water erosion was also considered. Using these laboratory tests, numerous soils, organic materials, and treatment techniques can be quickly evaluated so that field testing can be reserved for only the most promising. A small representative laboratory study, reported here to illustrate the technique, showed that two repellents (a petroleum resin dust‐suppressant oil and paraffin wax) when combined made soil generally more resistant to total weathering effects than did either repellent alone. The dust suppressant helped to stabilize the soil against damage by freeze‐thaw cycling, while the was protected it from degradation by ultraviolet radiation. These laboratory results compare favorably with observations from field plots treated with these two repellents.
Surface and Charge Characteristics of Selected Soils in the Tropics
Authors: Gallez A. , Juo A.S.R. , Herbillon A.J.
Published: July 2010

Specific surface area and surface charge characteristics of some Alfisols and Ultisols from Nigeria were studied. Specific surface are measured by ethylene glycole retention was generally 2 to 3 times greater than the specific surface area measured by N2 adsorption for both surface and subsoil samples. Soils derived from basalt had the greatest surface area per gram of clay as measured by both methods.

The surface charge‐pH curves of the soils bear the characteristic features of metallic oxides, indicating that surface charge behaviour of the soils studied follows the constant potential model. Values of PZC for Alfisol and Ultisol samples ranged from pH 3.0 to 3.9. Subsoils generally have higher PZC than corresponding surface horizons. Specific adsorption of sulfate resulted in a shift of the PZC to a higher value and an increase in the magnitude of positive charge.

Cation and anion retention measurements showed that soils derived from basement complex rocks and sandstones contain negligible amount of positive charge while soils from basalts bear moderate amount of positive charge at their natural pH condition. Evidence also indicated that the Alfisols and Ultisols bear a small amount of permanent negative charge ranging from 1 to 4 meq/100 g.

The limitation of using CEC value determined by conventional procedures as a criteria for soil taxonomy is discussed.
Evaluation of the Mass Spectral Analysis of Soil Inositol, Inositol Phosphates, and Related Compounds
Authors: L'Annunziata Michael F. , Fuller Wallace H.
Published: July 2010

The potential of mass spectrometry in the structure analysis of soil inositol, inositol phosphate carbon, and soil microbial metabolites was evaluated. Mass spectra of myo‐inositol (I) isolated from the organic phosphate fraction of a forest soil, quebrachitol (II), myo‐Inositol hexaacetate (III), d,l‐epi‐inosose (IV), and of compounds I and II labeled with deuterium in the hydroxyl groups were determined. Intense fragment ion spectral peaks at mass/charge (m/e) 60, 73, and 102 were common to each of the natural occurring cyclitol structures studied. Structural variations of inositol were found to be identifiable by peak shifts from m/e 60, 73, and 102 to other m/e values as due to attached groups or to other carbon oxidation states. An exchange of the hydroxyl protons with deuterium permitted the determination of the number of hydroxyl groups on a given mass spectral ion fragment and supplied evidence for the presence of attached groups. Studies dealing with phosphated compounds in soils required a hydrolysis of the phosphate esters prior to the mass spectral analysis. The mass spectral analysis was found most useful for the identification of cyclitol structures in soil, microbial, and plant metabolism studies when the sample size is limited to microgram quantities.
Fate of Fertilizer Nitrogen in a Flooded Rice Soil
Authors: Patrick W. H. , Reddy K. R.
Published: July 2010

In order to improve the efficiency of fertilizer N utilization by rice (Oryza sativa L.), it is important to know what happens to N applied to the soil. Field experiments utilizing 15N‐enriched ammonium sulfate were carried out to determine the fate of fertilizer N (100 kg N/ha) applied to Crowley silt loam soil. The distribution of fertilizer N in the plant‐soil system at harvest time was determined using 2.32 m2 plots. The distribution of fertilizer N in the plant‐soil‐floodwater system at six times during the growing season was measured in smaller plots (0.28 m2).

The results from the larger plots showed that fertilizer N recovered in the grain ranged from 30.9 to 37.3 kg N/ha depending on the method of application. Recovery of fertilizer N in the straw ranged from 18.2 to 24.2 kg N/ha. A considerable portion of fertilizer N (24.2 to 27.1 kg N/ha) remained in the soil (including roots) after cropping. Total recovery of the 100 kg/ha addition of labelled fertilizer N in the soil‐plant system was 75.0 to 85.6 kg N/ha for the different methods of N application examined. Experiments using the smaller 0.28 m2 plots showed rapid uptake of fertilizer N immediately after application, with no apparent further uptake after about 3 weeks. Soil N was the major and perhaps sole source of N for the plant during the last part of the growing season.
Analytical Properties of the Soluble, Metal‐complexing Fractions in Sludge‐soil Mixtures: II. Comparative Structural Chemistry of Fulvic Acid
Authors: Sposito Garrison , Holtzclaw Kenneth M. , Baham John
Published: July 2010

The fulvic acid fractions of three representative sludge‐soil mixtures were extracted, purified, and then studied for their analytical properties. The fulvic acids extracted from sewage sludge (SS fulvic acids) were found to contain from 20 to 40 times as much S as a typical fulvic acid extracted from natural soil organic matter (SOM fulvic acid). Two of the SS fulvic acids also had somewhat less O than a typical SOM fulvic acid. Ultraviolet and visible spectra of the SS fulvic acids suggested that they may be highly aromatic materials and that they may have condensed structures, comparable even with those in SOM humic acids, in those cases where the O content is relatively low. The aromatic nature of the SS fulvic acids could be inferred indirectly from their X‐ray diffraction patterns, which yielded a γ‐band centered more nearly at 4Å than 5Å, thus implying a relatively small content of aliphatic components.

The infrared spectra of the SS fulvic acids were generally similar to the Type III spectrum of SOM fulvic acid: The absorption due to C = O in carboxyl groups is not pronounced and the presence of polysaccharides and protein decomposition products is indicated. The spectra differed importantly from the Type III spectrum in showing bands due to the sulfone group and to functional groups substituted on aromatic rings.

Metal‐SS fulvic acid solutions were extracted directly from the three sludge‐soil mixtures and were fractionated on Sephadex G‐10 gel. It was found that Cu, Fe, and Zn were complexed by SS fulvic acid, but that Cd and Ni were not. The relative order of complex stability for Ni and Zn implied by these results is different from what has been reported for SOM sulvic acids.
Cadmium Availability to Rice in Sludge‐amended Soil under “Flood” and “Nonflood” Culture
Authors: Bingham F. T. , Page A. L. , Mahler R. J. , Ganje T. J.
Published: July 2010

Rice plants (Oryza sativa var. ‘Colusa’) were grown to maturity in pots containing a soil (Domino silt loam, pH 7.5, Xerollic calciorthid) amended with 1% sewage sludge enriched with variable amounts of CdSO4 ranging up to 640 µg Cd/g. Two sets of soil cultures were used, one for rice under continuous flood and the other under nonflood conditions. Grain production for rice under flood management was relatively unaffected by the Cd treatment; 25% yield decrement was associated with a treatment of 320 µg Cd/g. Under nonflood management, however, a comparable decrement in grain production was observed with a treatment of only 17 µg Cd/g. The Cd content of mature leaves at early flowering varied from approximately 0.3 µg Cd/g for the controls to 2.8 µg Cd/g for plants receiving the highest Cd treatments. Leaf Cd values were slightly higher under the nonflood culture. The Cd content of the grain under nonflood management was approximately 55% greater than that of grain under flood management. The Cd content of mature leaves correlated with grain production (r = 0.872***) for rice produced under either flood or nonflood culture. Chemical analysis of saturation extracts revealed greatly reduced Cd concentrations in soil solutions under flood management which may account for the greater tolerance of the cultivar to soil Cd under flood culture. This reduced availability of Cd in flooded soils is attributed to precipitation of CdS.
Genesis of Argillic Horizons in Soils Derived from Coarse‐textured Calcareous Gravels
Authors: Rostad H. P. W. , Smeck N. E. , Wilding L. P.
Published: July 2010

Soils with fine‐textured argillic horizons overlying calcareous gravel are of widespread occurrence on terraces, kames, and eskers in Ohio. The objective of this study was to determine if the argillic horizon in these soils, generally containing 25–50% clay, could develop from a calcareous gravelly deposit containing < 10% clay. Two pairs of sites were chosen, one pair developed on gravel material containing 60% carbonates, the other pair on gravel containing 40% carbonates. One member of each pair occurred on a terrace whereas the other occurred on a kame.

A reconstruction technique utilizing Ti and Zr contents of the soil fraction >2 µm was used to calculate the gains and losses of various constituents in the solum relative to the parent material. The residue remaining after acid dissolution of carbonates was determined for gravel, sand, and silt fractions. The carbonate content of the C horizons ranged from as high as 90% in the 16–32 mm fraction to < 5% in the clay fraction. Dissolution of carbonates and addition of clay residue from the carbonate rocks decreased the gravel content from 75 to 52% and increased the clay content from 1.4 to 10.3%. A calculation of gains and losses for weathered solum shows substantial gains of clay, silt, and sand which is balanced by a loss of gravel. It has been proposed that the gain in sand, silt, and clay is a result of disintegration of shale, siltstone, sandstone, and crystalline lithics in the sand and gravel fractions. It is therefore concluded that fine‐textured B horizons could develop from coarse‐textured calcareous gravelly outwash.
Loess Identification in Soils of Southeastern Pennsylvania
Authors: Carey J. B. , Cunningham R. L. , Williams E. G.
Published: July 2010

A silty mantle generally 1 m thick in southeastern Pennsylvania was thought to be loess. Sorting coefficients determined from particle size analysis of horizons from 20 profiles indicate the silty materials are well sorted. Bartlett's (X2) test for homogeneity of variances of the percent clay‐free silt among 21 profiles of Duncannon soils shows a homogeneous population having a mean variance of 3.9. A mean variance of 2.3 was determined for Fayette, a known Midwest loess soil. Transects through the area of thickest loess show percent very fine sand decreasing from south to north. The mean percent very fine sand of the profiles in each transect shows a decrease from east to west. The physical properties, sorting coefficients, and homogeneity indicate the silty mantle is loess. The mantle's geographic location, gradation in thickness, and very fine sand content indicate that the Coastal Plain and the adjacent rivers are probable source areas for the loess.
Erosion of Selected Hawaii Soils By Simulated Rainfall
Authors: Dangler E. W. , El‐Swaify S. A.
Published: July 2010

Erodibilities, or K values of the universal soil loss equation, were determined for ten soils representing five soil orders on the islands of Oahu and Hawaii. Two successive simulated rainstorms were used, each with an approximate intensity of 6.35 cm/hour and duration of 2 hours. Values obtained covered the wide range from 0 to 0.60 metric tons/ha per metric erosion index × 0.00774 (tons acre‐1 erosion index‐2)3 and, in most cases, were higher for the second (wet) than for the first (dry) storm. Erodibility values for cropped Oahu soils, belonging to four soil orders, ranged from 0 to 0.26 for dry storms and from 0.001 to 0.41 for wet storms. Values for volcanic ash soils on Hawaii, belonging to only two orders, had the considerably wider range of 0.08 to 0.60 for dry storms and 0.07 to 0.51 for wet storms. Three of these soils exhibited essentially the same erodibility for dry and wet conditions.

Dry and wet values were combined to calculate a weighted mean erodibility for each soil based on the distributions of natural rainfall throughout the year at the test sites. The weighted erodibility of a soil at a given location was in general, inversely related to the amount of natural precipitation at that location.
Predicting Runoff Initiation Times Under Field Conditions in Tropical (Hawaii) Soils
Authors: Ahuja L. R. , Dangler E. W. , El‐Swaify S. A.
Published: July 2010

Runoff initiation times measured during field rain‐simulation studies on 10 important Hawaii soils are examined in relation to antecedent soil‐water status. The experimental data show considerable scatter due mainly to natural soil variability within a soil series. However, the data exhibited a fairly proportional relationship between runoff initiation time and antecedent soil saturation deficit (final minus initial soil‐water content), in accordance with a simple Green‐Ampt type equation. The results indicate a potential method for estimating erosive portions of rainstorms and subsequent soil loss hazards in relation to varying antecedent soil‐water contents during different seasons of the year.
The Transfer of Heat and Hydrophobic Substances During Burning
Authors: Debano L. F. , Savage S. M. , Hamilton D. A.
Published: July 2010

Wet and dry sand was tested for water repellency, after burning pine litter (Pinus coulteri D. Don). Four conditions were studied: a burn of 25 min over dry or wet sand and a burn at 5 min over dry or wet sand. The thickest and most intense water‐repellent layer was produced by a 5‐min burn over dry sand. Although organic materials were translocated deeper in the dry sand during the 25‐min burn (down to 4 cm), some of the water repellency was destroyed in the upper 1‐cm layer. In wet sand, water repellency was concentrated in the upper 0‐ to 1.5‐cm layer. The translocation of hydrophobic substances and resulting water repellency depends on changes in their polarity and oxidation state. Relationships developed for fire over a dry soil may not adequately account for movement of organic substances in a moist soil. These results suggest prescribed burning should be done when the soil is moist on areas where water repellency is a problem.
The Necessity of Independent Testing of Soil‐Site Equations
Authors: McQuilkin Robert A.
Published: July 2010

A black oak (Quercus velutina) soil‐site study in Missouri has shown that the standard regression statistics (R2, standard error, etc.) of soil‐site equations are not reliable indicators of the accuracy of these equations. Data from 54 plots were used to derive a soil‐site equation that had an R2 of 0.66 and a standard error of 1.00 m. These statistics plus a graphed comparison of observed vs. predicted site indexes indicated that the equation satisfactorily predicted site index. When the equation was tested with data from 27 additional plots, however, the correlation between the observed and predicted site indexes had an R2 of only 0.01 and a standard error of 1.81 m. These statistics plus a graphed comparison of observed vs. predicted site indexes showed that the equation was completely unreliable as a site index predictor.

Inadequate sampling, incomplete data analysis, or chance correlations may have caused the errors in the equation, but the errors were undetectable until the equation was tested with the independent data.