Function Of Soil Properties Research Articles

Manganese Distribution and Patterns of Soil Wetting and Depletion in a Piedmont Hillslope

The distribution of Mn in soils across the landscape is a function of mineralogy, topography, vegetation, and soil properties that control soil water movement and solute transport. We hypothesized (i) that current landscape properties and processes would explain the observed distribution of acid-extractable soil Mn in a cropped hillslope in the Carolina Slate Belt of the southern Piedmont, and (ii) that the current spatial patterns of soil water movement would be related to the observed Mn distribution. Soil samples were collected in 10-cm increments to the 1-m depth at 5-m intervals along 110-m-long Transect AB and at 10-m intervals along 80-m-long Transect CD. The air-dried samples were analyzed for acid-extractable (1 M HCl) Mn. Soil water content (θ) along the transects was periodically monitored by neutron attenuation to the 120-cm depth. Duplicate banks of tensiometers were installed at depths of 30, 45, and 60 cm at these locations. The concentration of acid-extractable soil Mn was greatest in the footslope (FS), exceeding values >500 and 600 mg kg−1 soil for Transects AB and CD, respectively. For a wet period in July 1989, θ along Transect AB varied from 0.40 m3 m−3 for the FS to 0.50 m3 m−3 at the summit and was significantly correlated with clay content. Increases in water content of a dry soil after rainfall of 80 mm in July 1989 were similar at all landscape positions, but further increases following additional rainfall were less for the FS, indicating that soil at the FS was already near saturation. The slightly coarser-textured FS consistently had the lowest water contents. Tensiometric and lateral Br transport data for this site, coupled with the water content measurements, indicate that subsurface flow of water and dissolved Mn from higher to lower elevations on the hillslopes is occurring.

The 1999 R.M. Hardy Lecture: The implementation of unsaturated soil mechanics into geotechnical engineering

The implementation of unsaturated soil mechanics into geotechnical engineering practice requires that there be a paradigm shift from classical soil mechanics methodology. The primary drawback to implementation has been the excessive costs required to experimentally measure unsaturated soil properties. The use of the soil-water characteristic curve has been shown to be the key to the implementation of unsaturated soil mechanics. Numerous techniques have been proposed and studied for the assessment of the soil-water characteristic curves. These techniques range from direct laboratory measurement to indirect estimation from grain-size curves and knowledge-based database systems. The soil-water characteristic curve can then be used for the estimation of unsaturated soil property functions. Theoretically based techniques have been proposed for the estimation of soil property functions such as (i) coefficient of permeability, (ii) water storage modulus, and (iii) shear strength. Gradually these estimations are producing acceptable procedures for geotechnical engineering practices for unsaturated soils. The moisture flux ground surface boundary condition is likewise becoming a part of the solution of most problems involving unsaturated soils. The implementation process for unsaturated soils will still require years of collaboration between researchers and practicing geotechnical engineers.Key words: unsaturated soil mechanics, soil suction, unsaturated soil property functions, negative pore-water pressure, matric suction, soil-water characteristic curve.

Inverse modeling to estimate LNAPL plume release timing

Methodologies are presented for dating releases of light nonaqueous phase liquids (LNAPLs) using an inverse modeling approach with simple analytical models. Models for LNAPL plume migration are presented to predict LNAPL plume velocity in the unsaturated and saturated zones as a function of basic soil and fluid properties. A relative mobility factor is introduced for LNAPL movement at the water table that depends primarily on the van Genuchten n parameter (related to the breadth of the soil pore size distribution) and the magnitude of water table fluctuations. Estimated LNAPL plume velocities compare reasonably with more rigorous numerical models, which may be used in cases where data availability warrant the greater effort entailed. Two methods of estimating release timing and its uncertainty are investigated. A direct estimation method is described that determines travel time for a single observed travel distance based on estimated soil and fluid properties. Release date uncertainty may be determined using the first order (FO) or Monte Carlo (MC) methods. The second method for estimating release date involves nonlinear parameter estimation utilizing distance vs. time measurements and other data. A case study is presented for a field site where independent estimates of release timing were obtained from a numerical modeling analysis. Release timing estimates based on direct inversion of the analytical timing model agree well with the numerical analysis. Results for a second field site indicate that release date confidence limits estimated by the FO method, assuming log-normally distributed travel times, are close to values determined by the MC method, which makes no assumption regarding the form of the travel time probability distribution. Results for a hypothetical problem indicate that LNAPL velocity and travel time may be accurately estimated if sufficient data on travel distance vs. time are available. Incorporating prior information on relevant soil and fluid properties into the objective function reduces the uncertainty in release date if prior estimates are accurate. However, biased prior estimates may lead to over- or underestimation of release date uncertainty. Simultaneous estimation of soil and fluid properties and release date is possible if prior information is available to condition the parameter estimates.

Hydrologic Responses of Shortgrass Prairie Ecosystems

Runoff hydrographs from 3 separate rainfall simulation runs at 11 different shortgrass prairie sites were evaluated to determine the hydrologic similarity within a single ecosystem at widely separated sites. There were no consistent patterns in the equilibrium runoff among sites and simulator runs. When the sites were stratified by soil type, there were differences in time-to-peak of the runoff event and the regression slope of the rising limb of the runoff ratios. Spearman's rank correlation showed no relation of the rising limb slope regression coefficient to measured vegetative characteristics across all sites. There was minimal correlation between the runoff regression coefficient and the percent cover and bare soil. Differences in the biotic components of the sites were not useful in predicting runoff characteristics. If equilibrium runoff was the measured hydrologic response, the sites were dissimilar. Using the time-to-peak and slope of the rising limb components of the runoff hydrograph, the sites were similar on the same soil type. The technique of comparing components of the runoff hydrograph, other than equilibrium runoff has promise to allow one to quickly compare responses among ecosystems to determine if they have similar hydrological functions. Our study on shortgrass prairie sites indicated that easily estimated factors such as biomass, cover and litter were not good indicators of hydrologic function. Also, it is necessary to identify which portion of the runoff event is most important in the assessment. Future hydrologic and erosion models need to develop nonlinear prediction equations to estimate infiltration rates as a function of cover, biomass, and soil properties and also to stratify soils into functional units to accurately estimate runoff rates. DOI:10.2458/azu_jrm_v53i4_weltz

Soil pH Affects Copper Fractionation and Phytotoxicity

Phytotoxicity of copper (Cu) depends on the relative distribution of different chemical forms, which is a function of soil properties, such as soil pH and organic matter content. Sequential fractionation was conducted to partition the total Cu into exchangeable, sorbed, organically bound, precipitate, and residual forms. Three soils were sampled from existing citrus groves and 0 to 400 mg Cu kg−1 were added. The soils used were: Myakka fine sand (sandy, siliceous, hyperthermic Aeric Haplaquods; pH = 5.7), Candler fine sand (hyperthermic, uncoated, Typic Quartzipsamments; pH = 6.5), and Oldsmar fine sand (sandy, siliceous, hyperthermic Alfic Arenic Haplaquods; pH = 8.2). Phytotoxicity of added Cu was evaluated using citrus rootstock (Swingle citrumelo) seedlings grown for 330 d. In Cu‐unamended soils, the major portion of the total Cu was in the organically bound form in the low pH soils. However, in the high pH soil, the precipitate form was the dominant form. As the rate of Cu increased, the concentration of the readily soluble Cu forms (exchangeable + sorbed forms) increased in the low pH soils, that is, from 0.8 to 89.5 mg kg−1 (8.4–25.3% of total Cu) in the Myakka soil, and from 2.2 to 70.3 mg kg−1 (3.1–20.3% of total Cu) in the Candler soil. In the high pH Oldsmar soil, however, the concentration of readily soluble Cu forms increased only from 1.1 to 5.3 mg kg−1 In relation to the total Cu content this was equivalent to a decrease from 5.2 to 1.5%. The citrus seedling growth was negatively correlated with Cu concentrations in the readily soluble forms and positively correlated with those of the precipitate form. A 20% decrease in the top and root weights occurred at 2.5 mg kg−1 of readily soluble Cu in the Candler soil (pH = 6.5). The critical concentration was lower (1.7 mg kg−1) for root growth on the Myakka soil (pH = 5.7). The critical Cu concentration in the leaves varied from 60 to 68 mg kg−1, while that in the roots was 62 mg kg−1 in the Myakka soil, but increased to 270 mg kg−1 in the Candler soil. This study demonstrated that the readily soluble form of Cu is the most phytotoxic, and an increase in the precipitate form is, thus, responsible for a reduction in Cu phytotoxicity.

Hydrologic responses of shortgrass prairie ecosystems

Runoff hydrographs from 3 separate rainfall simulation runs at 11 different shortgrass prairie sites were evaluated to determine the hydrologic similarity within a single ecosystem at widely separated sites. There were no consistent patterns in the equilibrium runoff among sites and simulator runs. When the sites were stratified by soil type, there were differences in time-to-peak of the runoff event and the regression slope of the rising limb of the runoff ratios. Spearman's rank correlation showed no relation of the rising limb slope regression coefficient to measured vegetative characteristics across all sites. There was minimal correlation between the runoff regression coefficient and the percent cover and bare soil. Differences in the biotic components of the sites were not useful in predicting runoff characteristics. If equilibrium runoff was the measured hydrologic response, the sites were dissimilar. Using the time-to-peak and slope of the rising limb components of the runoff hydrograph, the sites were similar on the same soil type. The technique of comparing components of the runoff hydrograph, other than equilibrium runoff has promise to allow one to quickly compare responses among ecosystems to determine if they have similar hydrological functions. Our study on shortgrass prairie sites indicated that easily estimated factors such as biomass, cover and litter were not good indicators of hydrologic function. Also, it is necessary to identify which portion of the runoff event is most important in the assessment. Future hydrologic and erosion models need to develop nonlinear prediction equations to estimate infiltration rates as a function of cover, biomass, and soil properties and also to stratify soils into functional units to accurately estimate runoff rates.

Changes in 15 N abundance and amounts of biologically active soil nitrogen

Estimation of the capacity of soils to supply N for crop growth requires estimates of the complex interactions among organic and inorganic N components as a function of soil properties. Identification and measurement of active soil N forms could help to quantify estimates of N supply to crops. Isotopic dilution during incubation of soils with added 15NH4 + compounds could identify active N components. Dilution of 15N in KCl extracts of mineral and total N, non-exchangeable NH44 +, and N in K2SO4 extracts of fumigated and non-fumigated soil was measured during 7-week incubation. Samples from four soils varying in clay content from 60 to 710 g kg–1 were used. A constant level of 15N enrichment within KCl and K2SO4 extracted components was found at the end of the incubation period. Total N, microbial biomass C and non-exchangeable NH4 + contents of the soils were positively related to the clay contents. The mineralized N was positively related to the silt plus clay contents. The active soil N (ASN) contained 28–36% mineral N, 29–44% microbial biomass N, 0.3–5% non-exchangeable NH4 + with approximately one third of the ASN unidentified. Assuming that absolute amounts of active N are related to N availability, increasing clay content was related to increased N reserve for crop production but a slower turnover.

Release of soil phosphate by sequential extractions as a function of soil properties and added phosphorus

Abstract A study of sequential phosphate (P) extraction by water and iron oxide‐impregnated paper strip procedures was carried out on three Italian soils ranging widely in soil characteristics and enriched with three rates of fertilizer P. The degree of change was dependant on P addition, soil P properties, and type of extraction. For the Fe‐oxide strip procedure, a greater release of P than for water extraction was observed for soils with and without added P. At a given level of added P, more P was released from the soil with the lowest P sorption index (SI). However, at a given level of NaHCO3‐extractable P, less P was released from the soil with lower SI than from soil with a higher SI, indicating that a greater available P content was necessary for low P sorbing soils to maintain a given rate of P release. The variation of SI accounted for 96% and 92% of the variation in amount of water‐extractable and Fe‐oxide strip P at a given P addition. Furthermore, SI accounted for 97% and 98% of the variation i...

Engineering Behavior of Lime-Treated Louisiana Subgrade Soil

Lime stabilization is often used to treat subgrade soils when they are soft and cohesive in nature. A study was conducted to investigate the engineering behavior, including the resilient and strength behaviors, of a lime-treated subgrade soil. The lime treatment procedure was adapted from the specifications of the Louisiana Department of Transportation and Development. Silty clay, a soil often found in Louisiana subgrades, is used as a base soil. A summary of various engineering properties of a lime-treated soil from resilient modulus, unconfined compression strength, and California bearing ratio (CBR) tests conducted at five moisture content and dry density levels is provided. Tests were also performed on the raw soil without lime treatment, and these results were compared with those of tests with the lime-treated soil. The comparisons indicate that the present lime treatment method results in an increase in strength and resilient modulus properties and a decrease in plasticity characteristics and plastic strains. A regression model with three constants was used to analyze the resilient modulus test results. The model constants are presented as functions of soil properties. Resilient modulus correlations that use either CBR or unconfined compression strength, moisture content, dry density, degree of compaction, and stresses as dependent attributes are developed.

Predicting Multicomponent Adsorption and Transport of Fluoride at Variable pH in a Goethite−Silica Sand System

Environmental impacts of soil pollution are greatly affected by the mobility and migration contaminants in soil. Multicomponent transport processes can play an important role in this migration. Therefore, modeling of transport processes and prediction of contaminant mobility as a function of soil properties can be a useful tool in risk evaluation. This work shows how a mechanistic model of ion adsorption on variable charged surfaces combined with a convective dispersive solute transport model was used to predict multicomponent transport of fluoride at variable pH in a goethite−silica sand column. In order to show the potential of this type of modeling, the chemical properties of the column material used in the transport calculations were not derived from measurements on the material itself, but predicted from independent data on synthetic goethite and silica. In this way the only parameters needed to predict the transport of fluoride and acidity were the chemical composition of the infiltrating solution, ...

Engineering Behavior of Lime-Treated Louisiana Subgrade Soil

Lime stabilization is often used to treat subgrade soils when they are soft and cohesive in nature. A study was conducted to investigate the engineering behavior, including the resilient and strength behaviors, of a lime-treated subgrade soil. The lime treatment procedure was adapted from the specifications of the Louisiana Department of Transportation and Development. Silty clay, a soil often found in Louisiana subgrades, is used as a base soil. A summary of various engineering properties of a lime-treated soil from resilient modulus, unconfined compression strength, and California bearing ratio (CBR) tests conducted at five moisture content and dry density levels is provided. Tests were also performed on the raw soil without lime treatment, and these results were compared with those of tests with the lime-treated soil. The comparisons indicate that the present lime treatment method results in an increase in strength and resilient modulus properties and a decrease in plasticity characteristics and plastic strains. A regression model with three constants was used to analyze the resilient modulus test results. The model constants are presented as functions of soil properties. Resilient modulus correlations that use either CBR or unconfined compression strength, moisture content, dry density, degree of compaction, and stresses as dependent attributes are developed.

Tire footprint characteristics as a function of soil properties and tire operations

The main objective of the following presentation is to examine the possibility of predicting agricultural tire footprint parameters under different operational conditions. The experimental part of the research involved the operation of two agricultural transport tires on two soils, under variations of tire load, inflation pressures and soil moisture contents. Results obtained show that tire footprint parameters, such as contact area, length, width and sinkage, can be reliably predicted using multifactorial linear and total regressions, within the range of recommended tire loads, inflation pressures and soil moisture contents around the plastic limit.

Laboratory Determination of Interrill Soil Erodibility

AbstractLaboratory soil pans and rainfall simulators have been used to study fundamental erosion processes affecting interrill soil loss. Problems exist when laboratory results are extended to those determined under field conditions. Experimental methodology influences a soil's interrill erodibility and interrill erodibility ranking among soils. We compared interrill soil loss and erodibility data from two erosion pans with field data from identical soils. Three plot size‐rainfall simulator methodologies were used: (1) 0.14‐m2 lab pan under a constant drop size (4.6 mm) rainfall simulator, (2) 0.32‐m2 lab pan with soil border areas under an oscillating nozzle (2.3 mm median drop diameter) rainfall simulator, and (3) 1‐m2 field plots under the same rainfall simulator as used in Method 2. Soil loss was measured at 5‐min intervals. Interrill erodibility (Ki) was calculated from two equations (E = KiiI2 and E = KiqIq) using measured soil loss (E), rainfall intensity (I), and flow discharge (q) values. The interrill erosion equation, methodology, time, and initial water content influenced calculated Ki values. Soil loss and Ki values from Method 1 did not correlate with and were greater than corresponding values from Methods 2 and 3. Soil loss and Ki values from Method 2 were correlated (r = 0.56 to 0.79) with corresponding values from Method 3. The Kiq values decreased with time and were a function of soil properties related to soil detachment and sediment transport. The Kii values (i) increased with time, (ii) were primarily a function of soil properties related to soil detachment only, and (iii) did not account for infiltration and runoff differences among soils.

Adsorption and Desorption of the Herbicide Thiazafluron as A Function of Soil Properties

Abstract The effect of soil composition on the adsorption and desorption of the herbicide thiazafluron [1.3-dimethyl-1-(5-trifluoromethyl-1,2,3-thiadiazol-2-yl) urea] by 20 soil samples of 13 selected soil profiles of southern Spain has been studied. The adsorption curves conformed the Freundlich equation and the values of the constants, Kf and nf, ranged from 0.13 to 4.64 and from 0.14 to 1.30, respectively. The simple and multiple regression analysis between Kf and soil properties revealed soil clay content, illite content and CEC as fundamental factors determining thiazafluron adsorption by soils. Unlike other substituted ureas, non significant correlation was found with soil organic matter. Desorption of thiazafluron was hysteretic in all cases, showing and values much lower than those for adsorption. Desorption kinetic indicated that this hysteresis is essentially due to irreversible adsorption, although some degradation seems also to occur. The Freundlich desorption Kfd values were closely related to the same factors as Kf: clay and illite contents and also montmorillonite content, suggesting that most of the hysteresis was due to thiazafluron irreversibly bound to soil clay mineral components.

Solute fluxes and sulfur cycling in forested catchments in SW Germany as influenced by experimental (NH4)2SO4 treatments

Results are presented from the research project ARINUS which investigates biogeochemical cycling in Norway spruce (Picea abies KARST.) ecosystems in the Black Forest (SW Germany) and effects of experimental (NH4)2SO4 additions. The interaction of the terrestrial and aquatic system is assessed using an integrated approach which combines flux measurements in representative plots on the stand level with input-output budgets of small catchments. The approach, field installations and experimental manipulations are described. Results from element flux measurements in the untreated systems are presented and processes controlling N and S transformations are discussed for two catchments representing contrasting site conditions. Even though the S budget is negative for both systems there is a distinct difference in the relation between organic vs. inorganic S fractions in the soil. Sulfate mineralization and desorption, respectively are discussed as controlling processes. Sulfate retention is not only a function of soil properties, but also of water fluxes and pathways. The uptake of added SO 4 2- was highly controlled by the counter-cation. Microbial N retention in the soil was highly influenced by the site management history. The extent of streamwater acidification was highly dependent on the transformations and mobility of N and S in the soils which in turn controlled cation leaching and alkalinity.

Visualizing soil behavior

Soil behavior is a function of intrinsic soil properties, interacting environmental processes, and cultural practices. Observation, prediction, and visualization of soil behavior at variable spatial and temporal scales are required to enhance our understanding of complex soil processes and to develop optimal environmental management strategies. Recent advances in information technology, simulation modeling, and computer graphics provide opportunities to convey our knowledge and perception of soil behavior under variable environmental conditions and soil management regimes. Soil information is commonly presented in textual, map, and graphical forms which often fail to convey the dynamic nature of soil behavior under field conditions. Historical and contemporary developments in the presentation of soil information and behavior are reviewed, and a framework for soil visualization is proposed.

The formulation effect of propoxur on leaching as a function of soil properties

This work investigates the kinetics of propoxur washing out and its residues in five arable soils with a clay content from 4–28% and an organic matter content from 1.3–1.8%. It has been noted that the fastest washing out occured with the emulsion form, the slowest washing out with the pure active substance, whereas an intermediate velocity was observed for the suspension form. The amount of propoxur in the reflux was also highest for the emulsion form, intermediate for the suspension form and lowest for the pure active substance. The highest residue level in the investigated soils was observed for the pure active substance. The kinetics of propoxur washing out in all the investigated forms was inversely proportional to the content of clay particles in the soils. Adsorption increased with the increase of clay particle content.

INTERRILL ERODIBILITY: COLLECTION AND ANALYSIS OF DATA FROM CROPLAND SOILS

ABSTRACT Interrill erodibility was measured on eighteen cropland soils in the western half of the United States, using a rotating boom rainfall simulator. There were significant differences in infiltration rates, runoff rates, and erosion rates among the soils. A slope factor, based on plot slope, to account for differences observed in interrill erosion rates, is proposed. The data show that this slope factor may also be a function of soil properties. An interrill erodibility coefficient is proposed for each soil.

SOIL PROPERTIES EFFECT ON RANDOM ROUGHNESS DECAY BY RAINFALL

ABSTRACT Rainfall modifies random roughness (RR) at varying rates for different soils. Methods to estimate RR decay are needed for computer models which simulate physical processes occurring at or near the soil surface. The objective of this study was to estimate RR decay curves as a function of soil properties. Surface roughness has been reported for selected soils before and after simulated rainfall (5 to 80 mm on five soils, 35 to 300 mm on one soil) and before and after natural rainfall (7 to 350 mm on two soils). The soils represent a wide range of textural and physical properties. A modified exponential function was fit to normalized RR values (RR after rainfall/initial RR) using rainfall amount as an independent variable. The coefficients of this function were tiien approximated as a function of two soil properties: percentage organic carbon and percentage clay. Surface stability increased with greater amounts of organic carbon. Surface stability increased with clay content to about 31% and then decreased with greater amounts of clay. Random roughness decay curves may be estimated for specific soils by using the exponential function.

Soil Properties Influencing Corrosion of Steel in Texas Soils

AbstractCorrosion of steel specimens was monitored in 15 Texas soils in order to test the current system for assessing soil corrosivity. Corrosion, measured in situ at two depths using electrical resistance probes, was a function of many soil properties and could not be adequately described using any single property. The current system, developed by the USDA‐SCS, which places soils into corrosion potential classes based on soil characterization data and descriptions, was found to overestimate corrosivity of many soils. A revised system was developed that more accurately predicted corrosion rates of buried steel under field conditions. Soil properties used in the revised system include electrical conductivity, texture, exchangeable acidity, and wetness class. When the two systems were tested using an independent set of data collected by the National Bureau of Standards, soil corrosion potential classes of the revised system correlated with actual corrosion better than the current SCS system.