Showing papers in "Soil Science in 1985"

Fractionation method for soil microelements

Abstract: To evaluate a sequential extraction procedure to separate chemical forms of soil microelements, I fractionated 16 soils, both surface and subsoils. The purpose of the sequential extractions was to solubilize the Mn, Cu, Fe, and Zn in the exchangeable, organic matter, Mn oxide, amorphous Fe oxide, and crystalline Fe oxide fractions. The solid portion remaining was separated into sand, silt, and clay sizes, and each was dissolved and analyzed for the above elements. Soil properties were determined, and whole soils were analyzed for total microelement content.

IN SITU MEASUREMENT OF FIELD-SATURATED HYDRAULIC CONDUCTIVITY, SORPTIVITY, AND THE α-PARAMETER USING THE GUELPH PERMEAMETER

Abstract: The Guelph permeameter method is used in 0.02-m- and 0.03-m-radius wells to measure in situ the field-saturated hydraulic conductivity (K10) and matric flux potential (φm) of a heterogeneous, anisotropic, structured loam soil. The K10, estimates, obtained using both Richards (GP-R) and Laplace (GP-L

Elements of Soil Physics

Abstract: Elements of soil physics , Elements of soil physics , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Properties of goethite and hematite in kaolinitic soils of southern and central Brazil

Abstract: Iron oxides in clay fractions of Inceptisols, Ultisols, and Oxisols from Rio Grande do Sul and Goias State in southern and central Brazil, respectively, were essentially goethite and hematite. Their Al substitution was around 10 mole % for hematites and between 15 to 25 mole % for goethites in southern Brazil and around 15 and 33 mole %, respectively, for those in central Brazil. The ratio of the Al substitution of hematite and goethite in the same sample is concentrating around 0.5:1. The size of the hematite crystals as measured by XRD-line broadening was between 10 to 15 nm thick (along the z axis) and 20 to 30 nm wide (along the x axis). The goethite crystals generally appeared to be smaller, as judged from the speClfic surface area obtained from a correlation between line broadening and surface area of 42 synthetic goethites. Under the electron microscope goethite and hematite crystals look very much alike: they appear mainly as subrounded, isodimensional particles. Hexagonal (hematite) and aClcular (goethite) particles are rare. The Fe-oxide crystals appeared not to be closely assoClated with kaolinite crystals, but were aggregated among themselves.

The constant head well permeameter: effect of unsaturated flow

Abstract: In this paper, the constant head well per-meameter (CHWP) theory is extended analytically to account for the effects of unsaturated flow. This results in a more accurate estimate of the field-saturated hydraulic conductivity and in new methods for in situ estimation of the soil sorptivity and the α parameter of the exponential hydraulic conductivity-pressure head function. Calculations using the extended CHWP theory and “average”sand, loam, and clay soils indicate that the original CHWP theory is only slightly in error for soils exhibiting weak capillarity, but can be substantially in error for soils exhibiting strong capillarity. The extended theory successfully predicts results of previous numerical investigations of the CHWP method.

Infiltration under ponded conditions

Abstract: Under ponded infiltration the cumulative infiltration is a function of soil properties, initial conditions, and water layer thickness above the soil surface. For arbitrary soil properties and arbitrary dependence of water layer thickness on time but uniform initial water content, an optimization tec

Static and dynamic three-dimensional studies of water in soil using computed tomographic scanning1

Abstract: Previous work of Petrovic et al. (1982) demonstrated the possibility of using x-ray transmission, computed tomography (CT) scanning for soil bulk density analysis in soil. The authors show that CT can also be used for measuring the water content of soil. They also show that CT can be applied to measure and follow dynamically the motion of water in soil in three dimensions. Furthermore inhomogeneities of water content and motion in soil can be observed with this technique. Using a third-generation CT scanner, several different techniques can be applied, such as differential, real-time, and spatial distribution scanning modes. A linear dependence was demonstrated for the Hounsfield units (HU) used in Ct and water content. The use of CT for water content and motion in soil in three dimensions opens new possibilities in this area of investigation.

Thermal conductivity, thermal diffusivity, and thermal capacity of some Nigerian soils

Abstract: Thermal conductivity increased with increasing soil water content. Clayey soils had lower thermal conductivity than sandy soils at all water levels studied. Thermal conductivity ranged from 0.37 to 1.42 for sandy loam, from 0.37 to 1.90 for loam, from 0.38 to 1.71 for sandy clay loam, and fr

Properties of nonallophanic andosols from Japan

Abstract: We studied various properties of nonallophanic Andosols in Japan. Our results showed that, despite many similarities between nonallophanic and allophanic Andosols, significant dissimilarities also exist between the two groups of soils. The nonallophanic Andosols used for our study formed from rhyolitic, dacitic, or andesitic volcanic ash in a humid temperature climate. They had distinctive morphological properties common to allophanic Andosols in Japan: (1) very dark, thick humus horizons, (2) granular structure in the humus horizons, (3) friable to very friable consistence, and (4) abrupt or clear smooth boundaries between humus and nonhumus horizons. The clay mineralogy of the nonallophanic Andosols was very different from that of the allophanic Andosols. In nonallophanic Andosols the clay fractions are mostly dominated by chloritized 2:1 minerals and the active Al (acid-oxalate-ex-tractable Al) consists largely or wholly of Al complexed with humus (pyrophosphate-extractable Al). The nonallophanic Andosols had mostly medium to fine textures and considerable high water retention at 15 bars. We noted that these soils have characteristically low bulk density, which is closely correlated with the organic carbon content. A remarkable accumulation of humus took place in the nonallophanic Andosols and was closely correlated with the formation of Al-humus complex. The high CEC of these soils was ascribed to the high humus content. We noted that nonallophanic Andosols are strongly acid to very strongly acid, reflecting the abundance of chloritized 2:1 minerals and the very low base saturation. Therefore, they had high Al saturation and large amounts of KCl-exchangeable Al, which is a major deterrent to plant growth in the soils. The average values of Al saturation and KC1-ex-changeable Al were 74.4% and 5.51 meq/ 100 g for humus horizon soils and 59.8% and 3.50 meq/100 g for nonhumus horizon soils, respectively. Almost all the nonallophanic Andosol samples had pH (NaF) >10 and phosphate retention > 85%. These values were significantly correlated with the acid-oxalate-extractable Al (Alo). Soils containing > 1% Alo have pH (NaF) > 9.4 and phosphate retention >85%. Therefore, we noted that Al complexed with humus has a significant amount of OH groups and is highly reactive. The analysis of pyro-phosphate-soluble components indicated that the humus associating with Al and Fe consists largely or wholly of humic acid with the highest degree of humification.

Caldep: A Regional Model For Soil Caco3 (caliche) Deposition In Southwestern Deserts

Abstract: Our objective was to develop and validate a regional model for CaCO3 deposition in desert soils of the southwestern United States. There were five major components in the simulation model: a stochastic precipitation model, an evapotranspiration model, chemical thermodynamic relationships, soil parameterization, and a soil water and CaCO3 flux model. For the present climate, a cold-dry Pleistocene climate, and a cool-wet (summer) Pleistocene climate, the model predicted a shallower depth for the calcic horizon than was found in field soils. However, the model was compatible with field soils if one assumed that most pedogenic carbonate formed during a cool-wet (winter) Pleistocene climate. The model was highly sensitive to the frequency of extreme precipitation events and to soil water-holding capacity. The biotic factor played an important role in CaCO3 deposition through its control of soil CO2 concentrations and evapotranspiration rates. The range in predicted CaCO3 deposition rates agreed with the rates for most field studies (1 to 5 g/m2/yr); also, the model predicted an increasing rate of CaCO3 deposition with increasing precipitation, which agreed with field studies. The model is a valuable research tool for evaluating the role of state factors on soil CaCO3 deposition.

Soil Nitrogen Transformations as Affected by Salinity

Abstract: The results presented in this paper reveal that salinity has a major influence on soil N transformations. Studies were conducted to test the effects of Na2SO4, NaCl, and CaCl2, applied at rates that produced electrical conductivities of saturation extracts (ECe) of 5, 10, 15, and 20 dS m−1, on ammon

Effects of Soil Type, Liming, and Sludge Application on Zinc and Cadmium Availability to Swiss CHARD1

Abstract: An investigation was made of the effects of sludge application, liming, and soil type of Zn and Cd availability to Swiss chard (Beta vulgaris L.) in pot culture under field environmental conditions. Increasing sludge application reduced soil pH, increased the amounts of Zn and Cd extractable by MgCl/sub 2/ and DTPA, and increased metal accumulation in the plants. Total metal levels in soil did not predict the accumulation in plants as well as did levels of extractable metals, even though the coefficient of determination (R/sup 2/) between extractable and total levels was high. Soils containing high amorphous Fe oxide levels generally had lower metal extractability at a constant rate of sludge application than those with low amorphous Fe oxide levels. Although pH was important in influencing metal availability for any particular soil, its influence was often less than that of amorphous Fe oxide content when availability was compared among soils. Inclusions of both pH and amorphous Fe oxide content, along with total metal content, gave the best prediction of metal availability. Soil organic matter had little relation to metal availability. Results suggest that soils high in Fe oxide content, in conjunction with soil liming, may give the best control of more » metal availability for accumulator species, such as Swiss chard. « less

Soil water evaporation suppression by sand mulches

Abstract: This paper reports experiments performed to study sand as a soil mulch. The objective was to determine the comparative effectiveness of 0-, 2-, and 6-cm-thick covering sand layers in suppressing evaporation from columns of soil. Measurements were made by using potential evaporation rates of 1.1 and

CARBON-13 Cpmas NMR and FTIR Spectroscopic-Studies of Humic Acids

Abstract: Carbon-13 NMR spectra, acquired with cross-polarization and magic angle sample spinning (CPMAS), and Fourier-transform infrared (FTIR) spectra were obtained on solid humic acids (HAs) extracted from material sampled at four selected stages in a large municipal waste treatment process. The complexity of the spectra manifests the compositional diversity of these substances. 13C-′H solid-state NMR interrupted-decoupling spectroscopy aided in the examination of aromatic groups and of organic functional groups with no C-H bonds, which are typically only poorly resolved in normal 13C solid state NMR spectra of such systems. Data measured with this pulse sequence also indicate that certain moieties, such as methyl groups, are quite mobile even in the solid state. NMR and FTIR spectra combined with quantitative elemental analyses allow a comparison of both differences and similarities among the HAs considered here.

Carbon-13 nuclear magnetic resonance for a humic and a fulvic acid: signal to-noise optimization, quantitation, and spin-echo techniques1

Abstract: We carried out a 13C NMR solution study on a humic and a fulvic acid from a mineral soil. T1 values were 0.2 to 2.O s, with maximum values for carboxyl and methoxyl carbons, and nOes were up to 1 (theoretical maximu 2). Qualitative spectra were effectively obtained with short acquisition tim

Estimating available water-holding capacity of western Nigerian soils from soil texture and bulk density, using core and sieved samples

Abstract: Using core and sieved soil at −1/3 and −15 bar matric potentials, we determined water retention on a number of western Nigerian soils and related it by predictive equations to soil textural separates and bulk density (BD). We obtained the soils from forested and cultivated croplands over 12 sites se

Characteristics, genesis, and classification of pennsylvania minesoils

Abstract: This paper reports on 24 nontopsoiled, noncultivated minesoils described and sampled in Pennsylvania. The minesoils varied in age from 1 to 29 years. They all have high rock fragment contents (40 to 60% in the surface and >70% in the subsoil). The lower content of rock fragments in the surface plus

Availability of Applied Heavy Metals as a Function of Type of Soil Material and Metal Source

Abstract: The authors applied the heavy metals Cd, Cu, Ni, and Zn, as sulfate salts and as lime-stabilized, digested Washington, D.C., sewage sludge, to surface and subsurface horizon materials of six Maryland soils in the greenhouse. Rates of metal addition were equivalent to field rates of 224 metric tons (t)/ha of the sludge. Corn (Zea mays L.) was grown for 30 d, 13 mo after treatment application, and the tissue was analyzed for metals. Yields of plant material were generally enhanced by sludge and suppressed by metal salts. Tissue levels of both Cd and Zn were considerably elevated. In general the sludge did not elevate tissue Cu and Ni, whereas metal salts slightly elevated tissue Cu and Ni with some soil materials. An interaction between type of soil material and source of metal on plant tissue metal levels was observed. Essentially inert soil materials tended to produce tissue with the highest metal levels when metal-salt-treated, but with the lowest metal levels when sludged. Conversely, reactive soil materials, tended to produce tissue with relatively lower levels of metals than other materials when metal-salt-treated, but with relatively high levels when sludged.

Leaching from a tropical Andept during big storms: a comparison of three methods

Abstract: Over the last few decades, soil scientists, hydrologists, foresters, and ecologists have become increasingly interested in monitoring downward water and nutrient fluxes in soils. There have been problems with various methods for measuring these fluxes, especially in the field studies on small plots. This paper compares three methods for measuring water and nutrient leaching in the field. These methods provide estimated flux using the Darcy flow equation, a water balance, and zero-tension lysimeters. The methods were compared in an Andept near Turrialba, Costa Rica, during two large storms (33 cm and 22 cm/wk), at two soil depths (25 and 110 cm), and in four kinds of 1- to 2.5-yr-old vegetation. The water balance was the most accurate method, because the other two techniques sample only parts of the flow. Zero-tension lysimeters were evaluated for use in measuring channeled flow under certain conditions.

Kinetics of Cu2+ and Cd2+ Adsorption by AN Italian Soil

Abstract: We investigated the kinetics of adsorption of Cu2+ and Cd2+ on an organic soil. The process investigated was of the first order with respect to both heavy metal and substrate concentration. The rate of the process, at constant temperature, was supposed to depend on internal diffusion, which produced a decrease of the specific rate of adsorption as a function of time or better as a function of the amounts of Cu2+ or Cd2+ adsorbed.

Comparative prediction of yield response and phosphorus uptake from soil using anion- and cation-anion-exchange resins

Abstract: Phosphorus desorbed from 18 South Australian soils by anion-exchange resin (AER-P) and cation-anion-exchange resin (AER-P) at different periods was core-lated with yield response and P uptake by wheat (Triticum aestivum cv. Gabo). The relationship between the quantity of P desorbed by both resin systems and P uptake and grain yield was found to improve significantly as the period of desorption increased up to about 10 h; after that it improved only slightly (up to 21 d). The CAER-P was better correlated with P uptake and grain yield and predicted yield response more closely than AER-P. The quantity of the latter was less than the former at all desorption periods. The two-constant rate equation (C= Kt, where C, is CAER-P or AER-P (mg/kg soil), K is the initial desorption rate constant, t is the desorption period (s), and b is the rate coefficient) described P desorption from soils by AER and CAER at different periods (from 10h to 21 d) satisfactorily. The ratio of K (CAER-P)/K (AER-P) was primarily affected by exchangeable calcium and magnesium and clay content of the soil (R= 0.91). Thus, the capacity of AER to desorb P compared with CAER was decreased, possibly by the buildup of calcium and magnesium in soil solution and the reduced diffusion of P through soil. The CAER-P may be a better measure of available P than AER-P by its capacity to take up cations as well as P from the soil solution, thus better simulating cations and P uptake by plants.

Pore gas composition in waste rock dumps undergoing pyritic oxidation

Abstract: We measured oxygen and carbon dioxide concentrations in the pore space of two waste rock dumps that are significant sources of acid and trace metal pollutants to a local river system. The release of these pollutants is a consequence of the oxidation of pyritic material within the dumps, which are at the abandoned Rum Jungle mine in the Northern Territory, Australia. Comparison of oxygen concentration distributions with heat source distributions indicates that oxygen supply is the oxidation-rate-limiting mechanism in most regions of the dumps. Gas transport into the dumps is by diffusion and advection due to both thermal effects and atmospheric pressure changes. The extent to which one transport mechanism dominates reflects the proximity of the edge of the dump and differences in the properties of the material in different regions. In some areas, at least two transport mechanisms determine the pore gas composition. Carbon dioxide levels, which are generally one to three orders of magnitude higher than atmospheric levels, indicate that the bacteria that catalyze pyritic oxidation have a plentiful supply of carbon dioxide, which is essential for their metabolism.

Allophane and humus-aluminum in spodosols and andepts formed from the same volcanic ash beds in New Zealand

Abstract: We examined the colloid materials in two Spodosols (Tihoi and Mangorewa) and two Andepts (Taupo and Oturoa) formed from the same volanic ash beds, using a combination of chemical and instrumental techniques. The dominant colloid material in all horizons of the Vitrandepts was allophane, except for the A horizon of the Taupo soil, which contained humus-Al complexes and opaline silica and had low pH (H2O) and high amounts of organic matter. Humus-Al, kaolin, and 2:1 layer silicates were the main colloidal materials in the two Haplo-humods, except in the C horizon of the Tihoi soil and the 2Bsh and 3Bsh horizons of the Mangorewa soil, which contained allophane. In these exceptions the release of Al from primary minerals is considered to exceed the accumulation of organic matter, thus allowing the formation of allophane. Allophane formation in the soils studied tends to be related to both the (Al + Fe)/C atomic ratio and soil pH (H2O). The presence of significant amounts of opaline silica, even in the A horizon of the Spodosol where intensive leaching occurs, suggests that the limiting factor in allophane formation, both in the Spodosols and the Andepts, is the concentration of Al, rather than Si, in soil solution.