Showing papers in "Soil Science in 1993"

Wood-ash composition and soil pH following intense burning

Abstract: Thousands of hectares of wildlands are burned annually in the western United States The composition and mineralogy of wood-ash produced by severe burning, and the changes in pH of soils underlying the ash, were examined at five sites in Califor-nia Soil pH increased by as much as 3 pH units (to pH

Chemistry of the Solid-Water Interface Processes at the Mineral-Water and Particle-Water Interface in Natural Systems

Abstract: This book presents an introduction to the chemistry of the solid-water Other CABI sites 

Field wind erosion: vertical distribution

Abstract: The quantity of soil material transported by wind will decrease with height above the surface. Airborne samples were obtained at five levels above four soils. Mass distribution with height differs for materials in saltation or in suspension. A technique was developed to mathematically describe the two modes of transport so the total quantity being transported could be determined by integrating the two equations. Transition height, where the transport mode changes from saltation to suspension, is termed TSS. TSS decreases as surface soil texture changes from a fine sandy loam to a loam, indicating a higher percentage of the eroded material is moving at a greater distance above the soil surface. TSS increases as roughness of the soil surface increases, indicating a decrease in the suspension component and that the majority of eroded material is moving close to the soil surface.

Differential adsorption of trace metals by soils as influenced by exchangeable cations and ionic strength

Abstract: The objective of this study was to evaluate the relative effects of Ca, Mg, and K on the adsorption of Zn and Cu by several Florida soils under citrus production and to differentiate the specific cation effects vs. effects of ionic strength on adsorption of Zn and Cu. A batch-equilibration technique was employed to evaluate the adsorption of Cu and Zn (added at 10−4 M) in the presence of varying concentrations of Ca or Mg (2.5–15 mmol) or K (5.0–30 mmol). Adsorption of both Cu and Zn decreased with an increase in concentrations of either Ca or Mg. The inhibitory effects of added cations on the metal adsorption was much greater for Zn than for Cu. Addition of K slightly decreased the adsorption of Zn but had little effect on Cu. The inhibitory effects of Ca and Mg on the adsorption of Cu or Zn appear mainly due to competition for the exchange sites on soil colloids.

Influence of Rainfall Intensity and Crop Residue on Leaching of Atrazine Through Intact No-Till Soil Cores

Abstract: Pesticide leaching may be affected by rainfall parameters and the amount and type of vegetation on the soil surface. This study was conducted to determine the effect of rainfall intensity and crop residue on the movement of [ring-14C]atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) and b

A soil classification system for describing water and chemical transport

Abstract: The authors present an initial version of a soil classification system based on selected soil properties believed to be useful in describing water and chemical transport through soils. The system is based primarily on surface texture, clay mineralogy, and nature of soil structure. We now have developed this system for the more extensive soil series in South Carolina, and these soils have been grouped into eight different classes. While variability of some soil properties within a given class certainly exists, a class is distinct from each of the other seven classes in water and chemical transport characteristics. A classification system such as this can help to identify those soil properties that most affect transport processes and will help to provide the framework for development of mathematical transport models that incorporate these same soil properties.

Dimension and Volume of Cracks in a Vertisol Under Different Crop Covers

Abstract: Depth, width, and length per unit area of cracks were measured in a Udic Haplustert from India during the summer season after the harvest of different crops (chickpea, wheat, sorghum, sunflower, and safflower) and compared with that of a fallow plot. The width, depth and length of cracks exhibited a wide size range. Crack width was significantly less (1.3 cm) in the fallow plot compared with those plots planted to crops. Crack depth in a majority of the plots was not significantly different from fallow except for plots planted to safflower and sorghum. Crack length was the highest in the fallow plot compared with cropped plots and, as a result, the surface cracking pattern was more intricate in the fallow plot. No single crack dimension adequately characterized the cracking intensity [...]

Comparison of three methods for assessing soil hydraulic properties

Abstract: Three methods for assessing soil hydraulic properties were conducted and their results compared for two soils in Western Massachusetts. The methods compared are: the Instantaneous Profile Method, the Guelph Permeameter, and laboratory determination using intact soil cores. The saturated hydraulic co

Sewage sludge effects on chemical properties of acid soils

Abstract: Field experiments were established at two locations (on an Oxisol and an Ultisol) to evaluate the effects of 0, 8, 16, and 24 metric tons ha−1 of aged municipal sewage sludge on soil properties and growth of four crop species. Soil samples taken from each plot, before sludge application and at harve

Spectral differentiation of surface soils and soil properties: is it possible from space platforms?

Abstract: Spectral radiance data from Landsat's Thematic Mapper (TM) sensor were used to evaluate its effectiveness in differentiating among surface soils of similar properties and to identify the TM spectral band combination useful in estimating selected soil properties. Correlation, regression, and discrimi

Influence of surface and subsoil properties on herbigide sorption by atlantic coastal plain soils

Abstract: Information on soil properties that influence herbicide sorption throughout the soil profile is needed to identify soil-herbicide combinations with varying degrees of risk for groundwater contamination. In this study we investigated the effects of soil properties on the sorption of five herbicides commonly used in grain production in the Atlantic Coastal Plain (atrazine, cyanazine, dicamba, 2,4-D, and metolachlor), using subsoil and surface horizons from six Delaware soils. Our objective was to develop simple screening models, based on soil properties available from routine soil tests or regional soil databases, to identify soils that may have an increased risk of groundwater pollution. Each soil was sampled by horizon to a depth of approximately 2 m to include major variations present in the soil profile above the surface water table. Herbicide distribution coefficients (Kdm) were determined for each horizon and herbicide by sorption studies using a batch equilibrium technique and 14C-labeled herbicides. The ranking of herbicide sorption, over all soil horizons, was metolachlor > cyanazine > atrazine > 2,4-D > dicamba (Kdm = 1.03, 0.94, 0.85, 0.65, and 0.25 L kg-1, respectively). Multiple regression analysis between Kdm and soil properties identified two rapid soil tests (KCl exchangeable acidity and organic matter content) as important predictive variables for atrazine, cyanazine, dicamba, and 2,4-D sorption (R2 = 0.81***, 0.56***, 0.26*, 0.68***); metolachlor retention was best described by oganic matter content and effective cation exchange capacity (R2 = 0.78***), another easily measured or estimated soil property.

Evolution Of Nitrous Oxide From Soil: I. Model Development

Abstract: Gaseous N emissions arising from biological denitrification in soils is of economic and environmental consequence. However, the biological and physical processes controlling emissions are complex, and, therefore, mathematical simulation is useful in understanding them. A mathematical model was constructed from a hypothesis based on preferential reduction of O2, followed by NO3− and then N2O during microbial oxidation of carbon substrates. The hypothesis allowed the model to reproduce the time course of N2O and N2 production and consumption during anaerobic incubations of soil amended with 37.5 to 300 μg NO3− -N g−1 soil. Biologically based models of denitrification, coupled to physically based models of the soil environment, may allow greater insight into the dynamics of denitrification and N2O emission in the field.

Methane emissions from louisiana first and ratoon crop rice

Abstract: Field experiments were conducted to measure CH4 fluxes over the first and ratoon cropping seasons from a flooded Louisiana rice field. Treatment plots contained the semidwarf, early, long-grain rice cultivar Texmont, drill-seeded into a Crowley silt loam soil (Typic Albaqualfs). Main crop treatments

The effects of redox on Mo, U, B, V, and As solubility in evaporation pond soils

Abstract: Soils and irrigation drainwaters from the west side of the San Joaquin Valley, California have elevated levels of Mo, U, B, V, As, and Se. Much of the drainwater is disposed of in evaporation ponds that may be periodically dried, resulting in cyclic changes in the redox status of the pond sediments. A laboratory incubation study was conducted to evaluate the effects of redox status on the solubility of trace elements in saline sediments and soils from the San Joaquin valley. The elements U and Mo were mobilized under oxidizing conditions, while Fe, Mn, Ni, V, and As were more soluble under reducing conditions. Reduction and precipitation of Mo, apparently as MoS[sub 2], was observed from 1 to 10 days after flooding, but when reaerated the Mo resolubilized in less than 1 day. The reductive dissolution of Fe- and Mn-oxyhydroxides released adsorbed B, which resulted in an increased solution concentration of B. Low redox conditions in drainwater ponds may reduce the solution concentrations of U, Mo, and Se, thereby reducing their chances of entering the food chain through algae uptake. However, low redox conditions favor the solubilization of As and V, which may pose an alternative threat to wildlife visitingmore » the ponds. 16 refs., 7 figs., 1 tab.« less

Plotsize and sample number for neutron probe measurements in small field trials

Abstract: Soil water storage over a 2.85-m soil depth was measured from 200 aluminum access pipes, separated by 0.3 m in both directions, in a 1.2 × 15.0-m plot in dry and wet periods during 1988 and 1989. The objective was to determine the minimum plot size and number of soil water content measurements if me

Soluble organics and extractable nitrogen in paired prairie and cultivated soils of central iowa

Abstract: The internal N cycle in soils of native and established prairies is highly conservative of N, whereas that of cultivated soils has a greater potential for loss of N to denitrification and leaching. In addition to rapid plant uptake of inorganic N, the efficiency of the N cycle in prairie soils has b

Changes in the Ketone Portion of Lipidic Components during the Decomposition of Plant Debris in a Hydromorphic Forest-Podzol

Abstract: The ketonic part of soil lipids was studied in a hydromorphic forest-podzol. The undecomposed forest litter layer (L) and the fragmented mycelium-invaded litter layer (F), and the soil A1 horizon were sampled and analyzed for total lipid and total ketone contents. Total ketones were separated into methylketones and triterpenic ketones. Extractable ketones were not observed in the L layer, but were determined in the F layer of the soil litter. From the F litter layer to the soil A1 horizon, the portions of the two types of ketones, mainly the methylketones, decreased sharply. These last components, which are not primarily plant substances, originated essentially from the β-oxidation of n-alkanes, and the amount of transformation of n-alkanes into methylketones was in inverse ratio to their carbon number. Triterpenic ketones were the dominant part of soil ketones, and all their identified components were of plant origin. An important decrease of the amount of triterpenic ketones was observed from litter to soil, but their decomposition processes were not clearly determined.

Soil volumetric shrinkage measurements: a simple method

Abstract: Moisture changes in swelling clays are associated with corresponding volume changes, causing these soils to swell upon wetting and shrink upon drying. These volume changes cause subsidence, heave, and crack formation. It is becoming increasingly clear that the engineering and agronomic use of such soils requires special care. Present methods of determining soil volume changes have many constraints. They require the use of hazardous chemicals, take a long time to complete, are not useful near the wet end of the moisture range, and have limited accuracy. A new method of soil volumetric shrinkage measurements using a balloon apparatus is presented. In this method, the soil bulk volume is determined by measuring the displacement of the soil specimen in water with the soil specimen wrapped in a flexible rubber membrane, an ordinary rubber balloon. The method is very simple and doesn't require use of any chemicals. Therefore, it is environmentally safer than other methods. The volumetric shrinkage measurements can be completed for the full moisture range in a short time. The proposed method compares very favorably with the results of the resin coating method.

Periodic temperature variations in an inhomogeneous soil: a comparison of approximate and exact analytical expressions

Abstract: Comparisons (of the first harmonic) between exact and two approximate analytical solutions to the one-dimensional heat conduction equation for an inhomogeneous soil show that the approximate analytical solutions are potentially more useful for profiles of soil thermal properties that exhibit positive or zero concavity than for those that exhibit negative concavity. Comparisons between the two approximate analytical solutions also suggest that one solution provides a much easier method for estimating profiles of soil thermal properties from soil temperature profiles than does the other. A brief summary of three analytical solutions to the one-dimensional heat conduction equation is also given. Furthermore, some of these extent analytical solutions are unique to the present study and employ relatively simple and easily implemented algorithms for their evaluation. For many applications involving periodic variations in soil temperature, these algorithms are likely to provide more realistic results than can be obtained by assuming homogeneous soil properties with their associated “exponentially decaying” solution for soil temperatures. It is further suggested that the solutions presented in this work could be used to verify more complex numerical models of soil heat flow.

Clay dispersion as related to soil properties and water permeability

Abstract: Seal formation is affected by clay dispersion, and both parameters depend on the same soil and soil solution properties. Since clay dispersion can be determined easily in the laboratory, its use for predicting soil susceptibility to seal formation was evaluated. Laboratory clay dispersion tests were conducted on soil samples from semi-arid (northern Cameroon and Israel) and humid (Georgia, USA) regions. Clay dispersion (presented as percent of total clay) in distilled water (to simulate rain-water) was significantly correlated with silt and clay content. Clay dispersion was severe (>40%) in soils with silt and clay content >15%, which were the kaolinitic soils from the humid region and the predominantly smectitic soils from semi-arid regions. Kaolinitic and illitic soils from the semi-arid regions, whose silt and clay content was

Partitioning and Distribution of Cadmium and Zinc in Selected Cultivated Soils in Norway

Abstract: Eleven samples, collected from three Norwegian cultivated soils under different management practices, were analyzed by sequential extraction to isolate five operationally defined fractions of Cd and Zn. On average, 47, 4, 33, and 5% of the sum of the Cd fractions (ΣCd) were found as weakly adsorbed (F1), adsorbed (F2), strongly adsorbed (F3), and very strongly adsorbed (F4) forms of the element, respectively. Eleven percent was regarded as incorporated in resistant minerals (F5). The relatively high proportion of the F1 fraction indicates that much of the Cd under these conditions, may be easily available to plants. In contrast to Cd, the highest percentages of ΣZn (31 and 47%), on average, were associated with strongly (F3) and incorporated with resistant minerals (F5), respectively. The F2 and F4 fractions contributed little to the sum of the fractions for both elements, and the low percentage of the weakly adsorbed (F1) for Zn is indicative of low mobility and availability of the element in these soils. For Cd, F1-F3 were directly correlated with OC and TFe. OC also seemed to be important in retaining F4, whereas F5 correlated best with clay. Positive correlations were also found between F1 and F3 of Zn with OC. The direct relation between F3 and TMn may indicate a stronger association of Zn with the oxides of Mn than of Fe in these soils. F5 of Zn correlated best with OC, TFe, and silt.

Evolution of nitrous oxide from soil: ii. experimental results and model testing

Abstract: The dynamic processes controlling N2O evolution in the field are complex; therefore, estimates of long-term evolution from periodic measurements are likely to be unreliable. Greater reliability in such estimations may be possible by reproducing these processes mathematically within a dynamic simulation model. A mathematical hypothesis for denitrification and N2O production was used within a larger ecosystem simulation model to study N2O evolution under laboratory and field conditions. Hourly N2O fluxes estimated by the model were compared with fluxes recorded over an inundated soil core during a 10-day laboratory incubation after a 100-g N Mg−1 amendment with 15N-KNO3. Estimated values were within 20% of those recorded for fluxes, ranging from 0 to 4 mg N m−2 h−1. Recovery of both mineral and labeled N from the amendment after 10 days was estimated within 2 g Mg−1 of recorded values. Hourly N2O fluxes estimated by the model were also compared with fluxes recorded during spring thaws during 2 years at a field site in central Alberta. Fluxes ranging from 0.1 to 10.0 mg N m−2 h−1 were reproduced by the model after different fertilizer treatments. Increased rates of N2O evolution followed periods of saturation in the upper profile caused by snowmelt. These increased rates continued for about 1 week in both years before declining as soil drying progressed. In the model, evolution arose from the volatilization, during drainage, of aqueous N2O generated from biological NO3- reduction that occurred during periods of low aqueous O2 concentrations caused by water accumulations in the thawing soil profile. The simulated evolution supports the hypothesis that denitrification accompanies soil thawing after snowmelt at this site.

Dictionary of Soil Science

Abstract: Translation of the second French edition published in 1990 (first, 1986). Briefly defines some 2,800 words relating to general soil science, mineralogy, petrology, micromorphology, geomorphology, and the major systems of classification.