bluuebunny/crossref_metadata_2025 huggingface dataset:
Soil Properties Affecting Formation of Nitric Oxide by Chemical Reactions of Nitrite
Authors: Blackmer A. M. , Cerrato M. E.
Published: July 2010

Gas chromatography was used to determine the amounts of nitric oxide (NO) in the headspaces above samples of 28 soils that had been autoclaved, treated with nitrite, and sealed in all‐glass flasks with He atmospheres for 18 h. When nitrite was added at a rate of 100 mg N kg−1 soil, the amounts of NO‐N found ranged from less than 1 to 35 mg kg−1 soil, and statistical analyses indicated that 95% of the variability in the amounts of NO found among the soils could be explained by a model that considered only soil organic C content, pH, and an interaction of these factors. The formation of CO2 and the ratios of NO to NO‐3 observed indicate that production of NO cannot be explained solely by self‐decomposition of nitrous acid. When various amounts of soil were added to identical samples of nitrite solution, the amounts of NO‐N found increased with amounts of soil added. These findings indicate that NO is formed by reactions of nitrite with the organic fraction of soils as well as by self‐decomposition of nitrous acid.
Relative Toxicities of Inorganic Aluminum Complexes to Barley
Authors: Cameron R. S. , Ritchie G. S. P. , Robson A. D.
Published: July 2010

The inorganic forms of Al in the soil solution that decrease plant growth in acid soils have not been clearly identified. Therefore, we examined the effects of Al and its complexes with F‐ and SO2‐4 on the root elongation of barley (Hordeum vulgare) in nutrient solutions containing 3333 µmol Ca L−1 and 6 µmol B L−1 at pH 4.5. The anions were chosen because of their presence in the soil solution at levels sufficient to complex Al. The toxicity of 0 to 100 µmol Al L−1 was studied in the presence of 0 to 10 µmol F‐ L−1 or 0‐3300 µmol SO2‐4 L−1. The elongation of roots of barley seedlings was correlated with Al3+ concentrations but not with total soluble Al or Al complexed with F‐ and SO2‐4. This could be one of the reasons why measurements of labile Al using complexing agents have not always been successful at distinguishing between Al‐toxic and nontoxic soils.
Water Table Characteristics and Water Chemistry of Seasonally Wet Soils of Southwestern Ohio
Authors: Ransom M. D. , Smeck N. E.
Published: July 2010

The seasonally high water table in Clermont (Typic Glossaqualfs) and Avonburg (Aeric Fragiaqualfs) soils of southwestern Ohio was investigated by monitoring variations in water table depth and in water chemistry of the vadose and upper saturated zones. Piezometers were installed for two pedons at three depths ranging from 70 to 180 cm, and soil‐water samples were collected using 0.1‐MPa porous ceramic cups installed in triplicate at four depths ranging from 32 to 170 cm. During the period of this study (April 1982–June 1983), the water table occurred within 30 cm of the surface during winter and early spring, fell rapidly to a depth of about 150 to 180 cm during late summer and early fall, and then returned to within 30 cm of the soil surface during late fall and early winter. Soil‐water exhibited ranges in pH (5.2–8.6), Eh (153–543 mV), electrical conductivity (7.0–91.5 mS m−1), dissolved O2 (0.6–6.1 mg L−1), Ca (2.5–64.1 mg L−1), Fe(II) (0–3.87 mg L−1), and Fe(III) (0–11.48 mg L−1). Soil‐water chemistry was a function of season and depth below the soil surface. While the dissolved O2 content decreased with depth, Eh and pH increased. Alternating periods of reduction and oxidation were suggested by significant seasonal variation in the variables monitored. Reducing conditions were indicated by the presence of Fe(II) in solution and an Eh of <400 mV, both of which occurred in the Clermont soil at the uppermost sampling depth during the April through June period. This period was characterized by saturated conditions and a soil temperature higher than 8°C. The highly variable Fe(II) and Fe(III) contents indicated that oxidation‐reduction reactions occurred primarily in microenvironments. The soil‐water system was not at internal equilibrium as evidenced by (i) the simultaneous occurrence of dissolved O2 with reduced C (organic matter) and Fe (II), and (ii) a mixed potential for Eh that did not correlate with dissolved O2 content.
Surface Soil Variability of a Map Unit on Niger River Alluvium
Authors: Ameyan Oluwole
Published: July 2010

Examination of an adequate number of sample points is a prerequisite for valid generalizations in soil surveys. The number of sample points required depends upon a host of factors, including the spatial variability of the properties under investigation. This study examines the spatial variability of textural and chemical soil properties in the surface horizon of two sample areas mapped as Ozugbi series (Typic Humaquepts). From a knowledge of the dispersion characteristics of the soil properties, the number of sample points required to estimate each property at different levels of precision was determined. There were marked contrasts in the variability levels of the soil properties, and, hence, in the number of samples required to estimate each property, between the sample sites and within the map unit as a whole. The pH is the least variable of the properties examined and, hence, needs the smallest number of samples for estimation.
Irrigating Row Crops from Sod Furrows to Reduce Erosion
Authors: Cary J. W.
Published: July 2010

Kentucky bluegrass (Poa pratensis L.) sod furrows were established to stablize the soil. The furrows were used to irrigate corn (Zea mays L.), wheat (Triticum aestivum L.), barley (Hordeum vulgaris L.), beans (Phaseolus vulgaris L.), and sugar beets (Beta vulgaris L.). The sod strips containing the furrows were 0.3‐m wide and managed as a permanent living entity. A strip moving machine and a miniature rotary ditcher were developed to maintain the sod furrows. Crops were grown in clean tilled strips 0.9‐m wide between the sod strips. Normal use of fertilizer, herbicides, and cultivation was utilized for the crop rows in the clean tilled strips. This management system eliminated soil erosion, at least doubled the infiltration rate of irrigation water, and allowed the production of satisfactory yields of wheat, barley, dry beans, and corn for silage. Sugar beet production was unacceptable due to competition from the sod.
Estimation of the Philip Infiltration Parameters from Rainfall Simulation Data
Authors: Bach L. B. , Wierenga P. J. , Ward T. J.
Published: July 2010

A new, simple technique for estimating the parameters of the two‐term Philip infiltration equation was developed and tested using field‐measured data obtained in the northern Chihuahuan desert of New Mexico. The technique simultaneously provided information on the relationship between the Philip equation parameter A, and the field‐measured hydraulic conductivity. The equation was reformulated as I − cKf = 1/2St−1/2, where I is the infiltration rate, S the sorptivity, t the time, Kf the field‐measured final infiltration rate, and c, a coefficient relating Kf to the Philip parameter A. The final, steady infiltration rate measured in the field was used for the value of Kf. Regressions of (I − cKf) vs. (1/2t−1/2) for values of c between 0 to 1 resulted in optimum c values for each treatment along with their corresponding S values. For the soils in this area, values for the coefficient c were sometimes outside the suggested range of 0.33 to 0.67, and were different for each study site. The regression analysis also showed that the value of S can be highly sensitive to changes in c. Using the values of S and c determined by the proposed method, a comparison was made between computed infiltration rates and measured infiltration rates. The results of this study showed that the prediction method provided adequate fits to field‐measured data, and that the choice of an appropriate c factor is important in determining infiltration parameters from field data.
Chloride Movement in Forest Soils of Nigeria
Authors: Ghuman B. S. , Lal R.
Published: July 2010

Chloride movement studies were conducted with forest soils at six locations in Nigeria: Ibadan, Ikenne, Ikom, Mokwa, Onne, and Zaria. The soils at Ibadan, Ikenne, Zaria, and Mokwa are classified as Alfisols, those at Ikom and Onne are Ultisols. Potassium chloride was uniformly broadcast on the surface of 145‐ by 145‐cm plots and displaced with 8, 4, 4, and 4 cm of water applied as flood irrigation, keeping a 1‐ to 2‐cm head at the soil surface, at 1‐d intervals. No evaporation was allowed during soil‐water and solute redistribution. Immediately after infiltration of each incremental application of water, duplicate solution samples were obtained using solution samplers installed at 10‐, 20‐, 30‐, 50‐, 70‐, and 90‐cm depths. After infiltration of the first water increment (8 cm) much of Cl‐ moved beyond the 90‐cm depth in the Ikom soil, a well‐structured clayey soil. Chloride concentration peaked at 70‐, 10‐, 30‐, and 20‐cm depths in the Ibadan (gravelly soil), Ikenne, Mokwa, and Onne (leached soil) soils, respectively. There were two Cl‐ concentration peaks, one at a 10‐ and the other at a 70‐cm depth in the Zaria soil, due to textural changes in the profile. There was no appreciable effect of redistribution time of 24 h on the Cl‐ content peak and its dispersion in the Ikenne and Mokwa soils. The effect of redistribution on Cl‐ distribution was considerable in the Zaria soil. Leaching efficiency, calculated as the ratio of the depth of chloride content peak and total water applied (20 cm), was the highest (3.6 cm cm−1 of applied water) in the relatively coarse Mokwa soil and the minimum (0.07 cm cm−1) in the layered Zaria soil.
Effect of Skid Trail Compaction on a Volcanic Soil in Central Oregon
Authors: Allbrook Robert F.
Published: July 2010

A skid trail in the Ochoco National Forest, Oregon, was examined to assess the degree of compaction that had occurred as a result of traffic during log harvesting. The soil, classified as a Lithic Cryorthent is a sandy loam derived from rhyolitic and tuffaceous colluvium. Measurements of bulk density and shear strength were made at five positions across the trail and two locations in undisturbed soil. Cores were taken to measure bulk density, moisture content, and moisture retention. Compaction resulted in increases in bulk density of up to 25%, in shear vane strength up to 157%, and in cone index up to 220% along with a decrease in pore space > 10 µm of 69%. Bulk density, vane shear, and penetrometer measurements were found to be highly correlated.
Spatial Variability of Soil pH and Organic Matter in Forest Plantations
Authors: Riha Susan J. , James Bruce R. , Senesac Gail P. , Pallant Eric
Published: July 2010

The spatial variability of soil pH and organic matter concentration in 0.4‐ha plots of 45‐yr old monospecific red pine (Pinus resinosa Ait.), Norway spruce [Picea abies (L.) Karst.], and sugar maple (Acer saccharum Marsh.) stands located on acid Inceptisols in south central New York was examined. Soil was sampled every 5 m along east‐west and north‐south transects and also every 30 cm around selected individual trees from next to the base to a distance of 120 cm. A geostatistical approach was used to analyze the components of variability that were systematically changing in space, correlated in space or not spatially related. There was little spatial correlation between samples with respect to pH or organic matter. However, there was systematic change in space in some horizons due to the presence of the different tree species. After 45 yr the surface mineral horizon under spruce was slightly (<0.3 pH unit) more acidic than under maple. There were also differences between stands of the different species in organic matter of the Oe horizons but not of the surface mineral horizons. The greatest variability in pH occurred between samples taken at the base of individual trees compared to samples taken 30 to 120 cm away. This effect occurred in the organic horizons of all three stands and in the surface mineral horizons under spruce and pine and was greatest for the pine. The approach employed in this study was useful in determining the effect of different tree species on soil chemical properties, where there was no plot replication.
Relative Phytotoxicity of Dicyandiamide and Availability of its Nitrogen to Cotton, Corn, and Grain Sorghum
Authors: Reeves D. W. , Touchton J. T.
Published: July 2010

The nitrification inhibitor, dicyandiamide (cyanoguanidine) (DCD), can improve fertilizer N efficiency; however, yield reductions and phytotoxicity from the use of DCD have been reported. A greenhouse experiment was designed to determine the effect of DCD on growth, chlorophyll concentration and nutrient concentration of corn (Zea mays L.), cotton (Gossypium hirsutum L.), and grain sorghum [Sorghum bicolor (L.) Moench.]. Dicyandiamide‐N/urea‐N combinations of 0:60, 5:55, 10:50, 20:40, 30:30, 40:20, 50:10, and 60:0 mg kg−1 soil were applied to pots containing a Norfolk sandy loam (fine‐loamy, siliceous, thermic, Typic Paleudults) cropped to each of the three species. Increasing the proportion of N as DCD decreased plant dry weight and leaf chlorophyll concentration and increased stem‐leaf N concentrations. Nitrogen recovery decreased curvilin‐early from 103% to 4%, from 64% to −6%, and from 72% to 4% for corn, cotton, and sorghum, respectively, with increasing proportion of N as DCD‐N. The effects of DCD‐N on stem‐leaf tissue concentraitons of P, K, Ca, Mg, Fe, Mn, Zn, and Cu varied with DCD‐N concentration, plant species, and nutrient element. At lower DCD‐N concentrations, most nutrient element concentrations were affected by uptake of NH+4‐N derived from urea; while higher concentrations of DCD‐N resulted in increased nutrient element concentrations as a result of reduced plant growth.
Estimation of Calcium Diffusion Coefficients from Electrical Conductance
Authors: Conkling B. L. , Blanchar R. W.
Published: July 2010

Diffusion coefficients for Ca in various horizons of the Bardley, Lebanon, Marshall, and Putnam soils were calculated from electrical conductivity measurements. A diffusion model which separates ion movement in solution from that along soil surfaces provided estimates of Ca movement that agreed with estimates of self‐diffusion measured using 45Ca. The equation has the form dq/dt = (ΛC/Λα) Dliq (dC/dx) + Dsur (dCe/dx), where dq/dt is the flux, ΛC/Λα the ratio of molar conductivities at the given concentration divided by that at infinite dilution, Dliq the diffusion coefficient in the liquid phase at infinite dilution, dC/dx the solution gradient, Dsur the diffusion coefficient along the soil surface, and dCe/dx the gradient of exchangeable concentration. Values of Dliq varied from 0.95 to 1.60 × 10−6 m2s−1 and Dsur from 0.61 to 1.18 × 10−6 m2s−1. Values of Dliq estimated at 0.01 mol/L CaCl2 concentration were 5 to 6% higher than those measured in 1 mol/L CaCl2 and values of Dsur are independent of salt concentration. The ratio of the quantity of Ca diffusing through solution to that along the particle surfaces was < 1 to 4 at 0.01 mol/L salt and approximately 4 to 1 at a 1 mol/L salt level. The estimated Ca diffusion coefficient along the particle surface was in all cases lower in the surface horizon samples than in those from a lower depth in the soil.
Competitive Adsorption of Phosphate with Malate and Oxalate by Tropical Soils
Authors: Lopez‐Hernandez D. , Siegert G. , Rodriguez J. V.
Published: July 2010

A study about the competition between organic anions (oxalate and malate)—currently present in the rhizosphere and phosphate for adsorption sites in tropical soils—indicate that in the presence of organic anions, phosphate adsorption by soils is reduced. The extent of such reduction is dependent on the way in which either phosphate or the organic anion are added to the soil. The organic oxyanions studied are more rapidly adsorbed to the soil surface than the phosphate; consequently those anions, when existing in the rhizosphere, can improve the phosphate status of soil.
Sorption of Bromacil, Chlortoluron, and Diuron by Soils
Authors: Madhun Yousef A. , Freed V. H. , Young J. L. , Fang S. C.
Published: July 2010

Sorption of bromacil (5‐bromo‐3‐sec‐butyl‐6‐methyluracil), chlortoluron [3‐(3‐chloro‐4‐methylphenyl),1,1‐dimethylurea], and diuron [3‐(3,4‐dichlorophenyl)1,1‐dimethylurea] by soils containing contrasting organic carbon (OC) content was studied. The sorptive capacity of the soils was assessed at 4 and 25°C by the batch equilibrium procedure over a broad range of aqueous phase herbicide concentrations. The herbicides showed the following order of increasing tendency to be sorbed: diuron > chlortoluron > bromacil. Sorption constants (Kf) were from 50‐ to 120‐fold higher for the organic soil than for the loamy sand soil, reflecting sorption dependence on soil OC. This variation in Kf was reduced to less than twofold variation in Koc by normalizing sorption to OC. Although sorption was higher at 4 than at 25°C, the difference was only minor at this temperature range. The isosteric heats of sorption (δHs) were relatively small and exothermic, suggesting the involvement of entropy driven mechanism. Water solubility (S) and octanol‐water partition coefficient (Kow) of the herbicides were determined and used to derive equations for estimating Koc with r2 ≥0.989. The practical utility of these correlations is that they allow reasonable estimates of Koc from more easily determined molecular parameters.
Nitrogen Mineralization Potentials of Revegetated Lignite Overburden in the Texas Gulf Coast
Authors: Hornby W. J. , Brown K. W. , Thomas J. C.
Published: July 2010

Fresh mine spoil is virtually devoid of organic matter (OM) and N. The needed N is commonly added as inorganic fertilizer; however, sewage sludge additions could supply both OM and N. This study was conducted to compare the mineralizable N resulting from inorganic fertilizer and sludge applications to overburden. Nitrogen mineralization potentials were determined from laboratory data on a pre‐mined native soil (Elmina fine sandy loam) and 4‐yr old reclaimed mixed overburden that received 180 kg N ha−1 yr−1 as NH4NO3 using the Stanford and Smith model (1972). In addition, the effect of anaerobically digested sewage sludge (sludge) on N‐mineralization potential of overburden was evaluated on samples collected from field plots. Treatments were as follows: 0 kg N ha−1, 212 kg N ha−1 as NH4NO3, 106 kg N ha−1 as NH4NO3 plus 106 kg N ha−1 as sludge, and 212 kg N ha−1 as sludge applied to 13.8 m2 plots of overburden. Soil and spoil samples (0–15 cm deep) were collected from these plots 2 weeks, 26 weeks, and 52 weeks after amendment. Mineralization rates were determined using columns containing 0.2 kg of soil or treated overburden plus 0.1 kg of sand which were incubated for 18 weeks at 35°C. These columns were leached with saturated CaSO4 and a N‐free nutrient solution at 0, 2, 6, 10, 14, and 18 weeks and were extracted to a tension of −0.066 MPa after each leaching. The leachate was analyzed for NH+4 and NO‐3 by colorimetric methods. Application of 56 Mg sludge ha−1 significantly (α = 0.05) increased the total N 26 and 52 weeks after application to levels present in the 4‐yr old mineral fertilized reclaimed spoil. Sludge application also resulted in a sustained release of plant available N for 52 weeks after application. Mineralization potentials 2 weeks after the plots were treated were ranked as unamended overburden = NH4NO3 treated overburden < native spoil = 4‐year old reclaimed overburden < NH4NO3 plus sludge treated overburden < sludge treated overburden.
Aggregation of a Silty Clay Loam Soil by Mycorrhizal Onion Roots
Authors: Thomas R. S. , Dakessian S. , Ames R. N. , Brown M. S. , Bethlenfalvay G. J.
Published: July 2010

Onion plants (Allium cepa L.) inoculated in the root zone with a vesicular‐arbuscular mycorrhizal (VAM) fungus, or left uninoculated, were grown in potted soil for 230 d to determine the influence of the VAM fungus (Glomus macrocarpum Tul. and Tul.) on soil structure. The silty clay loam soil was maintained at a moisture content between 25 and 30%. Paired inoculated (+M) and uninoculated (−M) plants were harvested (20 pairs over 150 d) beginning 80 d after planting. Relationships between plant, fungal, and soil parameters and changes with time were evaluated by regression analysis. Root colonization by the VAM fungus in +M plants ranged from 49% to 60% over the sampling period, while no mycorrhizae were detected in the ‐M plants. Total dry mass of VAM plants was five to six times that of the non‐VAM plants. Soil from the +M treatment was significantly better aggregated, more porous, and had greater water permeability than ‐M soil. Root dry mass and VAM hyphal density in the +M soil were both significantly correlated with the relative abundance of water‐stable soil macroaggregates. Correlation of root mass with aggregate abundance was stronger, however, suggesting that soil changes were mainly mediated by direct root effects of a host plant whose growth was stimulated dramatically by its VAM fungal endophyte.
Recovery of Fertilizer Nitrogen by Wheat as Affected by Fallow Method
Authors: Power J. F. , Wilhelm W. W. , Doran J. W.
Published: July 2010

The fate of fertilizer N applied to crops is of both environmental and economic concern. To follow fertilizer N recovery in western Nebraska, depleted‐15N NH4NO3 was surface broadcast in April on winter wheat (Triticum aestivum L.) growing on plots fallowed the previous year by plowing, subtillage, and no‐till. Quantities of labeled N taken up by the growing crop, in the upper 100 mm of soil as inorganic N, and in both visible and partially decomposed crop residues, were followed on two sets of plots through the crop‐fallow‐crop sequence (approximately 117 weeks). About 16 to 18% of the labeled N was removed in the grain of the first wheat crop, with an additional 3 to 5% in the second crop. Labeled inorganic soil N decreased to <5% within 1 yr, with little effect of fallow method. No more than 4% was in visible residues at any time for all except no‐till fallow, for which 7 to 13% of the labeled N was found in visible residues from heading of the first crop through the entire fallow period until the second crop was seeded. Likewise, 4 to 9% of the labeled N applied was found in partially decomposed residues of no‐till during this period, compared to no more than 2% for the plow and subtill treatments. Total N in both residue pools combined decreased 50% from October to April of the fallow year for N‐fertilized wheat and 25% for unfertilized wheat. Most of the labeled N in the straw found in the visible residue pool by October was transferred over winter to either the partially decomposed pool or to other undetermined pools (including soil organic matter, microbial biomass, and losses to the atmosphere). Results show that, compared to plow and subtill, no‐till fallow enhanced retention of labeled N in the several crop residue pools and increased N uptake by the two wheat crops.
Runoff and Soil Loss as Influenced by Tillage and Residue Cover
Authors: Stein O. R. , Neibling W. H. , Logan T. J. , Moldenhauer W. C.
Published: July 2010

To gain a better understanding of the interactions between soil detachment, transport capacity, and residue cover, the USDA programmable rainfall simulator was used to erode plots created on established and newly created ridge‐till areas of <1% slope with and without residue cover. A control of conventional moldboard plow‐spring disk was also included. Results showed that for all treatments, ridge sideslope erosion was three to four times greater than total soil loss, suggesting that transport capacity was the limiting factor. For most runs no significant difference in soil loss was measured between ridges of different ages. The presence of residue decreased soil loss to one‐sixth or one‐seventh on older ridges and to one‐half on new ridges. Location of residue was more important than the total amount of residue. Residue placed only on the furrow bottom was as effective in reducing soil loss as residue placed over the entire ridge and furrow, while residue placed only on the ridge side‐slope did not reduce soil loss significantly from treatments without residue.
Relationships of Dense Tillage Pans, Soil Properties, and Subsoiling To Tobacco Root Growth
Authors: Vepraskas M. J. , Miner G. S. , Peedin G. F.
Published: July 2010

Deep tillage with subsoilers can fracture tillage pans and increase root development in some soils, but little is known about the precise soil conditions for which subsoiling works best. This study evaluated relationships of soil physical properties, chemical properties, and subsoiling to root distributions in 10 Ultisols. Five sites had dense tillage pans in their E‐B horizons with bulk densities (ρb) ≥1.66 Mg m−3. At each location flue‐cured tobacco (Nicotiana tabacum L.) was grown in subsoiled and nonsubsoiled (moldboard plow/disk) tillage treatments. At approximately 100 d from transplanting, root distributions were described by the trench‐profile method. Soil properties evaluated included bulk density, texture, ped mean weight‐diameter, cone index (CI), Ca and Al saturation ratios, base saturation, and pH. Subsoiling significantly increased the proportion of roots below the E‐B horizon (0.15 m below the Ap), in three of the five sites with E‐B ρb's ≥1.66 Mg m−3, while it had no significant effect on proportion of roots below the E‐B horizon in any of the five sites whose E‐B ρb's were <1.66 Mg−3. A regression analysis showed that ρb of the E‐B horizon, B horizon sand content, and cummulative rainfall accounted for 96% of the observed variation in subsoil root development for the nonsubsoiled treatment across the 10 sites. Soil chemical properties had little effect on variation in subsoil root development across sites.
Effect of Soil Surface Sealing on Splash from a Single Waterdrop
Authors: Bradford J. M. , Remley P. A. , Ferris J. E. , Santini J. B.
Published: July 2010

Most soil erosion prediction models do not account for surface sealing and soil crusting effects on soil detachment. The objective of this research was to evaluate surface seal formation and subsequent drying effects on amount of soil detached by single waterdrop impact. Twenty soils ranging in texture from sand to clay were tested. Single drop splash and fall‐cone strength determinations were made on each soil in an uncrusted condition, in a crusted condition immediately following 1 h of simulated rainfall (63 mm/h), and after 2 to 4 weeks of drying. Splash for the uncrusted condition ranged from 8.9 to 61.0 mg/drop and from 0.8 to 13.7 mg/drop for the crusted condition. Subjecting crusted soils to one drying cycle did not significantly alter splash amount. Splash was correlated with soil strength for both uncrusted and crusted conditions for finertextured soils; however, for sands and sandy loams additional research is required for soil strength‐based splash model for crusted conditions.
Water Seepage Through Multilayered Anisotropic Hillside
Authors: Selim H. M.
Published: July 2010

A mathematical analysis is presented for the steady‐state saturated flow through multilayered hillsides or soil beddings with a sloping surface. Each soil layer was considered anisotropic in nature, i.e., κ ≠ ξ where κ and ξ are the hydraulic conductivity in the vertical and horizontal directions, respectively. The method of solution is an analytical one and is based on the Gram‐Schmidt orthonormalization technique. Potential and stream functions were obtained and flow nets are presented for two‐layered geometries with varying degrees of anisotropy. The range of values chosen were ξ = (1/25)κ to ξ = 16κ and the equivalent hydraulic conductivities for two soil layers K1/K2 were 1:1, 1:10, and 10:1. The selected cases considered illustrate the significance of the degree of anisotropy on the water flow pattern, the relative flow rate as well as the volume of water passing through individual soil layers. Moreover, the greatest influence on the relative flow rate was when the upper layer was anisotropic rather than the lower layer.
Aluminum Speciation: A Comparison of Five Methods
Authors: Hodges Steven C.
Published: July 2010

The objective of this study was to compare five methods with varying chemical approaches to the speciation of Al. The 8‐hydroxyquinoline (HQ) and ferron procedures were used to estimate the inorganic, monomeric forms of Al at reaction times of 15 and 30 s, respectively. Two other procedures, an ion exchange column procedure and a chelating resin procedure, were used primarily to measure organically bound forms of Al. These were compared with a F electrode technique which quantifies Al3+ activity using equilibrium thermodynamic calculations and measured values of F activity and total F. Stability constants are then used to calculate the speciation of inorganic forms of Al, and organically complexed forms are obtained by subtraction from total Al. Sample solutions containing 5 mmol m−3 F, and 7.9, 15.2, 44.5, and 80.4 mmol m−3 Al were synthesized, with and without addition of 1 mol m−3 (as dissolved organic C) purified fulvic acid extracted from the surface horizon of an Edneytown soil (Typic Hapludults). A soil solution extract was also obtained from the soil and analyzed. Excellent agreement (r = 0.999) between predicted and measured Al3+ was obtained for the electrode procedure in solutions without organic matter (OM). The kinetically reactive Al values obtained by the HQ procedure correlated very well with those of the F electrode procedure in predicting [Al3+] and toxic Al (Al3+ + AlOH2+ + Al(OH)+2), (r = 0.91 and 0.90, respectively), but overestimated these Al forms when the Al/organic C ratios were low. The kinetically reactive Al values obtained by the ferron procedure were greater than values obtained by the HQ and electrode procedures since ferron was also able to breakdown Al‐F complexes to a greater extent. The column and chelating resin procedures were able to separate organic and inorganic forms of Al only, thus speciation of inorganic complexes was not feasible. Organically bound Al calculated from the electrode procedure was generally lower but consistent with the values obtained by the chelating resin. The ion exchange column proceduure gave the lowest values of Al‐OM at the lowest Al/OM ratios, indicating that some degradation of Al‐OM complexes may occur during passage through the column. The F electrode procedure, though promising, should not be indiscriminately used over a wide range of pH, Al/F ratios, and DOC contents without more information on the effects of electrode interactions with organic solutes. Furthermore, the procedure is slow and requires the assumption of equilibrium conditions, which may seldom occur for Al in field conditions. It is, however, promising as a tool for the evaluation of other procedures under well controlled experimental conditions.
Dependence of the Gapon Coefficient on Exchangeable Sodium for Mineralogically Different Soils
Authors: Evangelou V. P. , Coale F. J.
Published: July 2010

The traditional nonthermodynamic Gapon exchange selectivity coefficient (KG) for Na‐Ca exchange has previously been shown in the literature to be relatively constant for only a restricted range of Na+ equivalent fractions (NNa ≤ 0.40) in the exchanger. This relationship was developed for a heterogeneous group of soils. A linear Langmuir‐type plot of the traditional Gapon equation for Na‐Ca exchange data of mineralogically different soils, clay minerals, and an exchange resin was used to demonstrate the applicability of a constant KG for NNa values >0.40 for some soils. The results demonstrate that, in general, low CEC soils are more likely to demonstrate a constant KG for NNa values >0.40 than are high CEC soils. The data show that a constant KG for NNa values >0.40 was obtained for Georgia kaolin, illite, and several soils of low CEC. However, the plot failed to predict the KG and the CEC for soils, clay minerals, and an exchange resin of high CEC. These high CEC materials exhibited a NNa dependent KG. Using solution ion concentration instead of single‐ion activity affected the magnitude of the KG but did not affect the degree of constancy of the KG for NNa values >0.40. The relationships are of practical importance in the reclamation of sodic soils with an equivalent fraction of Na+ in the exchanger phase (NNa) of >0.40.
Soil Compaction in Double‐cropped Wheat and Soybeans on an Ultisol
Authors: NeSmith D. S. , Radcliffe D. E. , Hargrove W. L. , Clark R. L. , Tollner E. W.
Published: July 2010

In recent years double‐crop winter wheat (Triticum aestivum L.) and soybeans [Glycine max (L.) Merr.] have become quite common in the southeastern USA. To minimize the time between harvest of the winter crop and planting of soybeans, many farmers have adopted reduced or no‐tillage systems. A 2‐yr experiment was conducted on an Ultisol in Georgia to assess the influence of these tillage practices on soil physical properties. Spring tillage treatments were no‐tillage, disking, and moldboard plow plus disking. Fall tillage prior to planting wheat was with a disk. Bulk density and mechanical impedance measurements indicated a compacted layer in the disked and notillage treatments at a depth of 0.15 to 0.25 m. This was attributed, in part, to the fall disking, and it persisted through the winter and into the next growing season.
Long‐term Tillage Practice Effects on Soil Aggregation Modes and Strength
Authors: Hadas A.
Published: July 2010

Air dry aggregates of two soils were collected from cultivated fields and a natural reserve, and separated into five diameter groups: 1 to 5, 5 to 10, 10 to 20, 20 to 40, and 40 to 76.4 mm. Tensile strength of aggregates from these size groups was determined by brittle fracturing the aggregates in an unconfined compression unit. Analyses in view of using the brittle fracture theory showed that soil exhibits specific structural states organized hierarchially (e.g., primary, secondary, etc). Each consecutive state has a characteristic internal strength which diminishes and a “cell” structure the size of which increases with respect to the consecutive hierarchial order. This implies that aggregates are made of mixtures of soil materials belonging to the different aggregation states, and the materials of a lower hierarchial order act as cementing or binding material between soil cells of a higher aggregation order (e.g., tertiary aggregation material binds secondary aggregates and the bound mass, consisting of tertiary and secondary aggregates, binds the primary aggregates). Tensile strength of aggregated samples in a cultivated field was greater than that of samples taken from a noncultivated virgin site of the same soil. Internal strength of the basic soil aggregation units was quadrupled under cultivation as compared to that determined for virgin samples. These findings suggest that cultivation and trafficcaused compaction affect the basic smaller structural units of the soil rather than the larger aggregation units.
An Automated Technique for Flow Measurements from Mariotte Reservoirs
Authors: Constantz Jim , Murphy Fred
Published: July 2010

The mariotte reservoir supplies water at a constant hydraulic pressure by self‐regulation of its internal gas pressure. Automated outflow measurements from mariotte reservoirs are generally difficult because of the reservoir's self‐regulation mechanism. This paper describes an automated flow meter specifically designed for use with mariotte reservoirs. The flow meter monitors changes in the mariotte reservoir's gas pressure during outflow to determine changes in the reservoir's water level. The flow measurement is performed by attaching a pressure transducer to the top of a mariotte reservoir and monitoring gas pressure changes during outflow with a programmable data logger. Using a simple linear relation between reservoir gas pressure and water‐level changes with time, the data logger converts the transducer signal into outflow‐flux values. To demonstrate the usefulness of the new technique, two constant‐head experiments are described that have vastly different flux ranges and time durations. The first experiment was a 1‐h infiltration run in which infiltration rates dropped from 0.6 to 0.2 cm/min. The second experiment was a 3‐week evaporation experiment in which the evaporation rate ranged from 1.0 to 3.0 cm/d. Results indicate that the automated flow measurement technique performed well when compared to a manual sight‐tube technique for flux measurements; the difference between the two methods was never more than 9% for the infiltration experiment and 5% for the evaporation experiment. The advantages of the new technique over previously available automated flow measurement techniques include: (i) the ability to rapidly record a large range of fluxes without restricting outflow, and (ii) the ability to accurately average the pulsing flow, which commonly occurs during outflow from the mariotte reservoir.
Copper Activity in Soil Solution: I. Measurement by Ion‐selective Electrode and Donnan Dialysis
Authors: Minnich M. M. , McBride M. B.
Published: July 2010

Copper activity in saturation extracts (2:1 soil/solution) of sludge‐ and Cu‐salt‐treated soil was estimated by ion‐selective electrode (ISE) and by Donnan dialysis. Treatments were a factorial combination of four levels of Cu additions and four levels of total sludge additions. In the Donnan system, the ionic strength of a soil saturation extract was matched with KOAc buffer on opposite sides of a cation perm‐selective membrane. At membrane equilibrium, Cu concentration was determined in the KOAc buffer by voltammetry. Extracts of sludge treatments had sufficient Cu buffering capacity to maintain the same Cu2+ activity before and after dialysis; Cu‐salt treatments exhibited a lower soil solution Cu2+ activity after dialysis indicating the procedure was inadequate for these treatments. The ISE results were more precise, but the technique is only suited for use in aerobic, Cu‐contaminated soils. Values for Cu2+ activity obtained by ISE were approximately an order of magnitude greater than Cu2+ activity values estimated by the Donnan dialysis method. By either procedure, increased total Cu resulted in higher Cu2+ activities and conversely, increased total sludge resulted in decreased Cu2+ activities. Total soluble Cu was highest in the Cu‐salt treatments; sludge rate was associated with increased soluble Cu and a decreased proportion of free Cu2+.
Reduction and Oxidation of Acid Sulfate Soils of Thailand
Authors: Charoenchamratcheep C. , Smith C. J. , Satawathananont S. , Patrick W. H.
Published: July 2010

Changes in pH, oxidation potential (Eh), and the solubility of S, Al, Ca, Mg, Fe, Mn, and Si were measured in four acid sulfate soils of Thailand following reduction and subsequent oxidation. Reduced S species accumulated under anaerobic conditions, but oxidized rapidly when the systems were aerated. The SO4 concentration in solution increased as the Eh of the soil suspensions increased and pH decreased to <4. The extreme acidity developed in all soils resulted in the dissolution of Al, Mn, Mg, and Si.
Volcanic Ash‐influenced Vertisols and Associated Mollisols of El Salvador: Physical, Chemical, and Morphological Properties
Authors: Yerima B. P. K. , Wilding L. P. , Calhoun F. G. , Hallmark C. T.
Published: July 2010

Vertisols and Mollisols have developed from Quaternary pyroclastic deposits in central El Salvador under ustic moisture and isohyperthermic temperature regimes. Pellusterts generally occupy the nearly level constructional landforms (alluvial plains, coastal plains, and concave alluvial toeslopes), are poorly drained and exhibit darkgray to black colors. Chromusterts and Pellusterts with argillic horizons and secondary silica in lower sola occupy more sloping, erosional upland landforms that are better drained. Associated Argiustolls have formed in loamy or clayey andesitic alluvium on nearly level alluvial plains. Vertisols of El Salvador have many properties in common with Usterts of the USA, i.e., high clay contents, slickensides, tilted parallelpipeds, and deep wide cracks that extend to the surface, but they lack gilgai relief, cyclic horizonation, and with a few exceptions, self‐mulching surface horizons. Most have cambic horizons. The amorphous material content of the <2 µm fraction of these soils range from 14 to 28%, pH's range from 5.4 to 7.5, base saturation is >50% (commonly >75%) with Ca and Mg dominant. COLE values are 0.06 to 0.24 and clays are smectitic or kaolinitic. Microfabrics indicate high shrink‐swell. Stress‐oriented plasmic fabrics are largely vo‐masepic, vo‐skel‐masepic and lattisepic for cambic and Bt horizons indicative of microshear failure. Undulic plasmic fabrics dominate in pumice‐rice ash mantles and pyroclastic‐rich parent materials. Illuvial channel ferri‐argillans and organo‐argillans occur in subsoils of the Chromusterts and Argiustolls, respectively. Pedogenesis and plasmolysis increase in the order: andesitic bedrock or alluvium, saprolite (from bedrock), clay‐enriched Bw and Bt horizons, and Bw horizons in upper sola with slickensides and stress‐oriented plasmic fabrics. The best Bt and silica‐enriched (Bq) horizons occur in lower sola below the more physically active upper Bw horizons.
Soils Developed in Sediments from Late Quaternary Water Bodies in Northern New York
Authors: Kern J. S. , Bryant R. B.
Published: July 2010

Extensive areas of soils in northern New York have formed in parent materials deposited in late Quaternary water bodies. In previous studies, distinctions among these lacustrine, marine, and brackish‐water deposits have relied on the identification of fossils and continuous shoreline features; however, evidence of this kind is not always present. The morphology, mineralogy, and chemistry of a number of soils were characterized to determine whether differences in soil properties were attributable to the depositional environment and if soil characterization data are useful criteria for differentiating among soils developed in these deposits. X‐ray diffraction was used to characterize clay‐sized components. Standard soil characterization procedures were used to characterize soil chemical and physical properties. Soils formed in marine and lacustrine sediments were found to have similar mineralogies, dominated by vermiculite, illite, kaolinite, and interestratified clay minerals with lesser amounts of smectite, chlorite, and clay‐sized quartz, feldspars, and amphiboles. Chemical differences between soils formed in lacustrine and marine sediments do reflect the chemistry of the depositional environments, and soil characterization data are useful for distinguishing among soils developed in these parent materials. The data support a westward influence of the Champlain Sea beyond where marine fossils have been found to date. The area appears to be contiguous with, and transitional to, freshwater drainage from the Ontario Basin. The data also support the presence of a brackish‐water phase in the St. Lawrence Valley, and a water plane for this late Champlain Sea phase is postulated.
Extraction and Determination of Sulfur in Organic Horizons of Forest Soils
Authors: Maynard D. G. , Kalra Y. P. , Radford F. G.
Published: July 2010

Little information exists on the accuracy, precision, and make‐up of extractable S in surface organic horizons of forest soils. Eight extractants (H2O, 0.01 M CaCl2, 0.01 M KCl, 0.01 M LiCl, 0.003 M NH4OAc, 0.003 and 0.01 M NH4Cl, and 500 mg P L−1 as Ca(H2PO4)2·H2O) were evaluated for the extraction and determination of SO4‐S and total extractable S in surface organic horizons of five forest soils. The analyses for SO4‐S and total extractable S were performed by ion chromatography (IC) and inductively coupled plasma atomic emission spectrometry (ICP‐AES), respectively. Each of the weak salt extractants removed similar amounts of SO4‐S and total extractable S. Water was the least desirable extractant because it removed more organic S than the salt extractants, was the most variable for IC analysis, and produced inconsistent results. The 0.01 M NH4Cl extractant, however, was found to be the most consistent extractant. The precision ranged from 3.7 to 8.9% for the IC analyses excluding the aspen (Populus tremuloides Michx.) sample and from 1.9 to 8.4% for the ICP‐AES analyses. Poor precision in the SO4‐S determination of the aspen organic horizon was due to the elution of an unidentified peak adjacent to the S peak. Quantitative recoveries from 102 to 108% and from 97 to 108% were obtained in the 0.01 M NH4Cl extract by the IC and ICP‐AES methods, respectively. The effect of varying solution to soil ratios was also determined for 0.01 M NH4Cl. The 10:1 solution to soil ratio was the most consistent. Ratios <10:1 had significantly lower concentrations of extractable S and SO4‐S for three soils and caused logistical problems in the laboratory (i.e., slower filtering, more sample required) because of the low solutin‐to‐soil ratio. Storage of airdried material at room temperature (20 ± 4 °C) for 1.5 yr resultd in increased total extractable S and SO4‐S concentrations.
Solubilization of Soil Organic Matter by Liquid Anhydrous Ammonia
Authors: Norman R. J. , Kurtz L. T. , Stevenson F. J.
Published: July 2010

A laboratory study on the solubilization of organic matter in three soils (Drummer, Typic Haplaquoll; Blount, Aeric Ochraqualf; Cisne, Mollic Albaqualf), by application of liquid anhydrous ammonia (LAA) revealed a six‐ to sevenfold increase in water‐soluble organic C in the center radial zone (0‐1.5 cm radius) around the point of application of 44 kg N ha−1 and a seven‐ to ninefold increase where 206 kg N ha−1 had been applied. Initially, a three‐ to fourfold increase in water‐soluble organic C was measured as far as 3.0 cm from the application point at the 44 kg N ha−1 rate and as far as 6.0 cm at the 206 kg N ha−1 rate. Maximum concentrations of water‐soluble organic C (700 mg C kg−1) decreased with time after LAA applications and with distance from the point of application. When pH levels were above 6.5 to 7.0, water‐soluble organic C was linearly related to both exchangeable NH+4‐N concentration and pH. As the concentration of exchangeable NH+4‐N and soil pH declined with time due to nitrification and its acidifying effects, the concentration of water‐soluble organic C also declined. After periods of 28 to 112 d, depending on application rate and soil properties, amounts of water‐soluble organic C, on a whole soil basis, declined almost to their original levels although elevated concentrations were still present in the center of the application zones. Estimates were not made of losses of solubilized organic C via microbial conversion to CO2. However, since the maximum increases in solubilized organic C were always <1% of the total organic C (calculated on a total surface soil basis), drastic declines in soil organic matter content would appear unlikely as a result of LAA applications to these soils.