bluuebunny/crossref_metadata_2025_split huggingface dataset:
Infiltration into Sealed Soils as Influenced by Gravel Cover
Authors: Valentin C. , Casenave A. 
Published: July 2010

AbstractThe influence of stone gravel on water infiltration is not thoroughly understood, in that previous studies led to contradictory results. This field work was conducted to determine the effect of gravel on infiltration into sealed soils and to develop a regression model for infiltration based on the areas of the exposed and covered surfaces. Data were collected on 11 soils from three great groups from the fringe of the Sahara to the wet savanna zone of West Africa. A portable rainfall simulator was used to simulate rainfall on 28 undisturbed 1 by 1 m plots. Surface slope (P), portions of surface areas covered by grass vegetation (V), coarse fragments partly embedded in a surface seal (E), free coarse fragments (F), and sealed patches (S) were assessed as well as mean diameters (MD) of coarse fragments. The surface coverage by free surface gravel alone accounted for 68% of the variance of the cumulative infiltration/rainfall ratio, denoted as the infiltration ratio (IO). A simple nonlinear model taking into account S, F, and MD resulted in a high coefficient of determination of IO (R2 = 0.95). This model tested with three other sets of data was regarded as satisfactory to predict IO (r2 = 0.87). The results suggest that infiltration rate (IR) could be better related to the effective infiltrating annulus (AN) along the perimeter of free gravel than to the whole area under the free gravel (F). Moreover, simulated results indicated that IR increased with increasing F for MD < 0.029 m. For higher values of MD, IR decreased with increasing F. Thus, in the regions where large gravel‐size coarse fragments prevail, infiltration decreases with increasing stone cover, especially if the stones are embedded in a surface seal, as in desert pavements. Conversely, infiltration is enhanced by stone cover where small free coarse fragments are dominant, like those originating from a dismantled Fe pan.
Water Transport in an Unsaturated Medium to Roots with Differing Local Geometries
Authors: Petrie C. L. , Hall A. E. , Kabala Z. J. , Simunek J. 
Published: July 2010

AbstractPearl millet [Pennisetum glaucum (L.) R. Br.: syn. P. americanum (L.) Leeke] develops substantially lower predawn leaf water potentials than cowpea [Vigna unguiculata (L.) Walp.] under conditions of soil dehydration, but overall root length densities are greater in millet than in cowpea. The hypothesis was tested that, due to differences in root geometry and root length density, root systems of millet become less efficient in water uptake than those of cowpea as soil dries. Plants were grown in an artificial medium in pots or 1.15‐m tubes in a greenhouse and subjected to soil drying. Root geometries, root length densities, and water potentials of cowpea and millet were measured as the rooting medium dried. Distribution of roots was quantified by calculating a clumping ratio (total root length density divided by the root length density in the region surrounding individual root segment axes) at several depths within the profile. Overall root length densities were higher in millet than in cowpea, and root distributions differed. Millet roots were clumped locally along the root axis and globally within the profile, with the highest root length densities at the surface. Cowpea root lengths were one‐half as dense as millet along the root axis and distributed fairly uniformly throughout the profile. These data were used in two‐dimensional modeling of horizontal water transport from soil to branched segments of root axes of cowpea and millet to test the hypothesis. Simulations in which millet water potential became substantially lower than cowpea, and millet root length was twice as great as cowpea, predicted little difference in cumulative water flow to the roots of millet or cowpea during soil dehydration. This prediction is consistent with observations. Simulated water velocity vector fields indicated that millet's dense and clumped local root geometry became less efficient in water uptake under soil water deficits than cowpea's less dense and more evenly distributed root geometry because water uptake by millet was mainly at the root tips; in contrast, most of the root length of cowpea contributed to water uptake. Simulations conducted with millet root axes having different root length densities indicated that the low efficiency of millet in water uptake was due to the combined effects of local clumping and high root length density. When input parameters for roots and soil were varied, conclusions from the simulations remained the same.
Modeling the Hydraulic Properties of a Multiregion Soil
Authors: Wilson G. V. , Jardine P. M. , Gwo J. P. 
Published: July 2010

AbstractNumerical techniques for modeling transport of solutes in multiple porosity systems have recently been developed to better represent the physical attributes of structured soils. Multiregion flow modeling requires characterization of the water content (θ) and hydraulic conductivity (K) as a function of pressure head (h) for each region of the system. A technique is presented for determining the θ(h) and K(h) relationships for a three‐region soil system based on a typical water retention data base. The demarcation between Region 1 (macropore) and Region 2 (mesopore) was assumed to occur at h = −10 cm. The effect of this assumption was evaluated against criteria of h = −2 and −25 cm, with h = −10 cm giving the best results. The θ(h) function was described as a Fermi function for Region 1 and combined with the van Genuchten model for describing Regions 2 and 3 (micropore). Continuity in θ(h) and K(θ) between regions was achieved and an excellent agreement between predicted and measured values was obtained for each region. However, the derivative of the θ(h) and K(θ) functions were occasionally not continuous through the junction points. The Fermi function based on measured and assumed parameters gave erroneous predictions of K(θ) when a large (25‐cm) range in h was used for Region 1. A modified Fermi function was developed that gave an excellent prediction of K(θ) based on assumed parameters.
Interpretation of Solute Transport Data Obtained with Fiberglass Wick Soil Solution Samplers
Authors: Poletika N. N. , Roth K. , Jury W. A. 
Published: July 2010

AbstractThe fiberglass wick soil solution sampler has shown potential for use in unsaturated soil, but its effect on determination of transport properties is not fully characterized. This study investigated transport behavior in the sampler of Br‐, simazine [2‐chloro‐4,6‐bis(ethylamino)‐s‐triazine], and MS‐2 coliphage. Travel‐time moment analysis for several steady flow experiments involving narrow pulse inputs of these components showed rapid breakthrough with well‐defined peaks and negligible adsorption. Assuming a convection‐dispersion process in a two‐layer system consisting of homogeneous soil overlying a sampler, moment analysis suggests that, for the flow rates tested, both expected travel time and its variance are little influenced by transport through the porous wick for layer thicknesses commonly used in solute transport studies.
Plant and Soil Composition as Affected by an Alternative Lime Source Containing Sulfate
Authors: Marsh Brian H. , Grove J. H. 
Published: July 2010

AbstractThe reduced crude oil conversion system uses a fluidized bed combustion system for in situ SO2 removal. The reduced crude conversion spent lime (RCCSL) that results contains mostly CaO, CaSO4, and MgO. This material was evaluated as an alternative lime source in greenhouse studies with tobacco (Nicotiana tabacum L.) and corn (Zea mays L.). Equivalent amounts (CaCO3 basis) of RCCSL, reagentgrade Ca(OH)2, and agricultural‐grade (ag) dolomitic limestone were applied at rates of 0, 0.33, 0.67, 1.0, and 1.33 times the 50 mmol CaCO3 kg−1 soil lime requirement (LR) to an acid Maury silt loam (fine, mixed, mesic Typic Paleudalf). The RCCSL and Ca(OH)2 were equivalent in raising the soil pH and reducing active Al3+, H+, and Mn2+. Ag lime was less effective. Soil solution electrical conductance increased with increasing rate for Ca(OH)2 and RCCSL, but not for ag lime. After 5 wk, plant dry matter was highest at 0.33 and 0.67 LR. Dry matter was reduced for both crops by the highest application rate of all lime sources. Leaf tissue N, K, S, B, and Zn generally declined with increasing lime rates. Chloride accumulation increased with rate and was higher with RCCSL. No deleterious or unusually high amounts of Cd, Pb, Ni, or V were detected. The overliming response could not be ascribed to impaired P, Mg, or Zn nutrition in either species and was speculatively attributed to Al toxicity at near‐neutral pH. The results indicate that field evaluations of the RCCSL material are warranted.
Erosion Effects on Soil Water Storage, Plant Water Uptake, and Corn Growth
Authors: Andraski B. J. , Lowery B. 
Published: July 2010

AbstractMany investigators have suggested that the greatest negative effect of erosion on soil productivity is the decrease in available water‐holding capacity, but few have attempted to evaluate this relation directly. In this 4‐yr study, we evaluated the effects of past erosion on soil water storage, plant water uptake, and corn (Zea mays L.) growth on a linear slope of Dubuque silt loam soil (fine‐silty, mixed, mesic Typic Hapludalf) in southwestern Wisconsin. Levels of past erosion were based on depth to red clay (2Bt horizon): slight, 0.95 m; moderate, 0.74 m; and severe, 0.45 m. The total quantity of plant‐extractable water that could be stored in the upper 1 m of slightly eroded soil (181 mm) was 7% more than that for moderately eroded soil (169 mm) and 14% more than that for severely eroded soil (159 mm). For all erosion levels, water retained in the 0.5‐ to 1.0‐m soil depth was utilized by corn. Erosion level had no negative effect on early‐season plant growth. As plant‐extractable water decreased to <55 to 60% of total, evapotranspiration (ET) and vegetative‐growth rates decreased as erosion level increased. The greatest differences in ET rates among erosion levels were observed during a 35‐d period in the drought year of 1988 when rates averaged 3.7 mm d−1 for slight erosion, 2.6 mm d−1 for moderate erosion, and 2.2 mm d−1 for severe erosion. For the 3 yr in which plant water stress was observed, maximum plant heights for the slight erosion level averaged 7% more than those for moderate erosion and 13% more than those for severe erosion. Although the soil's capacity to store and supply water decreased as erosion increased, the observed effects of erosion level on grain and stover yields, grain‐yield components, and harvest populations typically were not significant.
Hydraulic Compaction Device for Making Soil Cores
Authors: Torbert H. A. , Prior S. A. , Elkins C. B. 
Published: July 2010

AbstractIt is now well established that soil compaction of agricultural land used for crop production is a major problem. For basic laboratory investigations of soil compaction, it is important that multiple soil cores of varying bulk densities be reproduced within statistically acceptable ranges. A device was designed, constructed, and tested to consistently compact soil cores of varying dimensions and bulk densities. The device uses two opposing hydraulic cylinders to evenly compress soil samples. The compactor is designed to generate compacted cylinders varying from 50 to 100 mm in diameter and 25 to 150 mm in length. Bulk density values for 10 replications of a 150‐mm soil cylinder with a 50‐mm diameter did not vary significantly when compacted under a single pressure. Pressures of 0.35, 1.04, and 2.07 MPa produced cores having bulk densities of 1.66, 1.76, and 1.86 g cm−3, respectively. Approximately 10 cylinders per hour can be prepared with this device.
Fertilizer Placement for Conventional and No‐Tillage Barley in the Subarctic
Authors: Cochran V. L. , Schlentner S. F. 
Published: July 2010

AbstractBanding all fertilizer near the seed at planting saves time and often increases nutrient uptake and yields of small grains, but adds to the cost of the drill. Some growers have successfully banded all of the fertilizer with barley (Hordeum vulgare L.) in cold soils. This study compares banding 100, 66, 34, and 0% of the fertilizer with the seed and placing the remainder in a deep band between rows and broadcasting all fertilizer. Fertilizer rates were 90, 20, 37, and 18 kg ha−1 of N, P, K, and S, respectively; urea was the N source. Both tilled and no‐till treatments were included on a Volkmar silt loam (coarsesilty over sandy or sandy‐skeletal, mixed Aquic Cryochrept) at Delta Junction, AK. Banding 100% of the fertilizer with the seed in field studies reduced emergence 2 of 3 yr for both tillage treatments, but did not affect nutrient uptake or yields. Nitrogen uptake and grain yields were reduced by broadcasting the fertilizer in no‐till but was not affected in the tilled treatments. Seedling injury from urea applied with barley seed at soil temperatures of 5, 15, and 25 °C was evaluated in root‐zone temperature chambers using Tanana silt loam (loamy, mixed, nonacid Pergelic Cryaquept). These studies confirmed that percentage of emergence increased with reduced soil temperature when urea was placed with the seed, but that emergence rate was delayed at all temperatures. This indicates that the risk of injury from banding urea with the seed is less in cold soil than in warm soil, but there is still danger of injury to the crop.
New Mass‐Based Model for Estimating Fractal Dimensions of Soil Aggregates
Authors: Rasiah V. , Kay B. D. , Perfect E. 
Published: July 2010

AbstractValues of the fractal dimension, D, for soil aggregates may vary with the model used and the assumptions invoked in formulating the model. The objectives of this study were to: (i) develop a new mass‐size‐based model, not assuming that probability of failure, P, and bulk density, ρ, are scale‐invariant for the estimation of D (defined DR), and (ii) compare the values of DR with those obtained using three other procedures. In the first procedure, manually counted aggregate numbers were used in the number‐size relation model for the estimation of D (defined Dn). Aggregate numbers were computed, assuming scale‐invariant ρ, in the second procedure and these numbers were used in the same number‐size relation model for the estimation of D (defined Dm). In the third procedure, a mass‐size‐based model, which has an upper limit to D and assumes scale‐invariant ρ, was used for the estimation of D (defined DT). Aggregate‐size distributions and P for different sizes of aggregates arising from fragmentation during wet sieving in water were obtained for three soils under two cropping treatments (CT) using a modified form of the Yoder apparatus. The P of soil aggregates ranged, depending on soil type, CT, and aggregate size, from 0.30 to 0.91. Values of DR ranged from 2.02 to 3.19 and those for Dm and DT ranged from 2.32 to 3.28 and from 2.46 to 2.84, respectively. Significant 1:1 linear correlations existed only between DR and Dm and between Dm and Dn. Values of DR, Dm, and DT were strongly influenced by soil type, CT, and the estimation model used. The interaction between clay and organic matter contents and CT accounted for 74% of the variability in DR, compared with 54% for DT and 52% for Dm.
Seasonal Variations in Denitrification and Nitrous Oxide Evolution at the Landscape Scale
Authors: van Kessel C. , Pennock D. J. , Farrell R. E. 
Published: July 2010

AbstractThis study was conducted to examine the seasonal and spatial variability of denitrification in various landform elements in a pea (Pisum sativum L.) field at Blaine Lake, Saskatchewan, Canada. The distributions of denitrification activity and N2O evolution were highly skewed, and could not be log‐transformed to yield normal distributions. Consequently, ordinary statistical procedures (i.e., those based on a normal distribution) were considered inappropriate for this study, and nonparametric statistics were used to describe the data. Denitrification activity and N2O evolution exhibited similar temporal and landscape‐scale patterns and were highly correlated, suggesting that denitrification was the main source of N2O evolution. In general, N2O evolution accounted for ≅41% of the denitrification activity. Maximum rates of denitrification were low prior to spring tillage and seeding, increased during the first half of the growing season (following the addition of fertilizer N), and decreased toward the end of the growing season; denitrification had essentially ceased by the fall sampling. Statistical outliers for denitrification activity, i.e., hotspots of activity, occurred predominantly at low levels of denitrification activity and were completely absent when denitrification activity was at its maximum. Therefore, the importance of hotspots of activity for estimating seasonal rates of denitrification appears to be limited. Soil water content was the most dominant factor controlling denitrification activity, followed by the concentration of NH+4, total soil respiration, and NO−3. The intensity of denitrification was controlled largely by hydrologic processes, which, in turn, were influenced by the topography of the landscape. Nevertheless, the landscape‐scale patterns of denitrification and N2O evolution were intensity‐independent and remained consistent throughout the season.
Evaluation of Pedo‐Transfer Functions
Authors: Tietje O. , Tapkenhinrichs M. 
Published: July 2010

AbstractMeasuring unsaturated hydraulic properties, including water retention vs. tension relationships, is expensive, time consuming, and labor intensive. Several attempts have been made to estimate these relationships from available soil data such as particle‐size distribution, organic C content, and bulk density. An estimation method that describes the soil water retention relationship based on other soil characteristics is referred to as pedo‐transfer function (PTF). The PTF approach will supply data for water and transport models for the unsaturated zone. Pedo‐transfer functions were evaluated by comparing estimated with measured water retention values using test data sets with a broad range of soils. Accuracy of the retention prediction is quantified by the root of the mean squared difference (RMSD) between the measured and predicted retention function. After the application of several PTFs to many soils in a data set, the average 〈RMSD〉 was found in the range of 0.04 to 0.13 m3 m−3 depending on the PTF. When the RMSD was calculated in the range from 0.1 J kg−1 to wilting point, the lowest 〈RMSD〉 was found to be about 0.05 m3 m−3. Using a PTF to supply the water retention for unsaturated soil water flux models (Richards equation), the most practical (and the most accurate) method is to predict retention function parameters (e.g., the parameters of the van Genuchten equation). But, the prediction of the van Genuchten retention function parameters α and θr (residual water content) using a PTF was found to be inaccurate, even when the PTF is based on nonlinear regression analysis and principle factor analysis.
Nutrient Availability and Foliar Nutrient Status of Sugar Maple Saplings following Fertilization
Authors: Paré D. , Meyer W. L. , Camiré C. 
Published: July 2010

AbstractFoliar analysis of maple sugar (Acer saccharum Marsh.) saplings having low foliar K (5.4 g kg−1) and P (1.2 g kg−1) was carried out for 3 yr to investigate the effects of a single application of fertilizer P triple superphosphate [TSP], K (K2SO4) and Ca [Ca(OH)2]. Also, soll, water‐saturated soil extract, resin sacks buried in situ, and lysimeter solution analysis methods were used. Potassium and P additions significantly increased foliar K (1.81 g kg−1 increase) and P (0.25 g kg−1 increase) for the 3 yr that the observations were conducted. Calcium addition had no effect on foliar element concentrations. A Diagnosis and Recommendation Integrated System (DRIS) analysis corroborated the foliar analysis: K indices increased with increased K fertilization (from −47 to ‐23) and P indices increased with increased P fertilization (from ‐25 to −15). Calcium application significantly increased the effective cation‐exchange capacity (CEC), exchangeable Ca and Mg and water‐extractable Ca and decreased the acidity in the rooting zone for a 3‐yr period. Conventional soil analysis and resin sacks detected significant effects of P and K fertilizers on their respective elements. However, these effects did not last more than 2 yr after fertilizer application in the surface soil horizon (Ah). Lysimeter solution analysis showed that K2SO4 fertilizer caused short‐term increases in SO4 and Ca leaching. The duration of fertilizer P and K on foliar nutrition and the behavior of soil nutrients suggested that biochemical cycles are important mechanisms perpetuating fertilizer effects.
Competition in Adsorption between Phosphate and Oxalate on an Aluminum Hydroxide Montmorillonite Complex
Authors: Violante A. , Gianfreda L. 
Published: July 2010

AbstractA study was conducted to provide information on phosphate and oxalate sorption on an Al(OH)x‐montmorillonite (chlorite‐like) complex under changing conditions of pH, total solution ligand concentrations, and order of anion addition. The competitive adsorption of phosphate and oxalate on a chlorite‐like complex (3.3 mol Al kg−1 montmorillonite) was influenced by pH (5.0–9.0), order of anion addition, and initial oxalate/phosphate molar ratio (Ri). In systems containing a constant amount of phosphate (500 or 400 mmol kg−1) and increasing quantities of oxalate (Ri from 0.5 to 3.34), more phosphate than oxalate was adsorbed even when the initial concentration of oxalate was much higher than that of phosphate. Of the sites on the clay surface that were available for adsorption by both anions, 51 to 79% were occupied by phosphate at Ri = 3.34 in the range of pH studied. Minimum reduction in phosphate adsorption occurred when phosphate was added to the clay mineral before oxalate, whereas maximum reduction occurred when oxalate was introduced before phosphate. The efficiency of oxalate in inhibiting phosphate adsorption was stronger at pH 5.0 than at pH 7.0 or 9.0. At pH 5.0, by increasing Ri from 0.5 to 3.34, phosphate sorption decreased from 20 to 44% when OX was added before phosphate. Many sites of the clay mineral were highly specific for phosphate, whereas some others, common to both the anions, had a higher affinity for phosphate than for oxalate. However, some sites were specific for oxalate anions.
Soil Solution Chemistry: Effects of Bulking Soil Samples
Authors: Giesler R. , Lundström U. 
Published: July 2010

AbstractBulking of soil samples is commonly used to obtain a spatially averaged measure of soil properties. This study investigated whether bulking can affect the chemistry of soil solution extracted by the centrifuge drainage technique. The short‐range variation within a 1‐m‐wide pit face was also investigated. Systematic differences were found between the chemistry of soil solutions taken from bulked and unbulked soil samples. The soil samples studied were taken on several occasions from the upper and lower part of a Bs horizon. Samples of soil solution extracted from replicate bulked soil samples contained significantly (P ≤ 0.05) larger amounts of Si, Na, Mg, and K as well as significantly (P ≤ 0.05) smaller amounts of Al and Fe than soil solution from unbulked samples. Bulking reduced the variation in all solutes measured, although a variation remained in replicates from the bulked sample. The variation between individual core samples taken just a few tens of centimeters apart can be considerable, although the magnitude of variation differs depending on the solute studied. The results suggest that unbulked soil samples may be preferable, especially when Al or Fe chemistry is studied and a centrifuge drainage technique is used.