bluuebunny/crossref_metadata_2025 huggingface dataset:
Amidase Activity in Soils: IV. Effects of Trace Elements and Pesticides
Authors: Frankenberger W. T. , Tabatabai M. A.
Published: July 2010

Amidase was recently detected in soils, and this study was carried out to assess the effects of 21 trace elements, 12 herbicides, 2 fungicides, and 2 insecticides on the activity of this enzyme. Results showed that most of the trace elements and pesticides studied inhibited amidase activity in soils. The degree of inhibition varied among the soils used. When the trace elements were compared by using 5 µmol/g of soil, the average inhibition of amidase in three soils showed that Ag(I), Hg(II), As(III), and Se(IV) were the most effective Inhibitors, but only Ag(I) and As(III) showed average inhibition > 50%. The least effective inhibitors (average inhibition < 3%) included Cu(I), Ba(II), Cu(II), Fe(II), Ni(II), Al(III), Fe(III), Ti(IV), V(IV), As(V), Mo(VI), and W(VI). Other elements that inhibited amidase activity in soils were Cd(II), Co(II), Mn(II), Pb(II), Sn(II), Zn(II), B(III), and Cr(III). Enzyme kinetic studies showed that As(III) was a competitive Inhibitor of amidase, whereas Ag(I), Hg(II), and Se(IV) were noncompetitive inhibitors.

When the pesticldes studied were compared by using 10µg of active ingredlent per gram of soil, the average inhibition of amidase in three soils ranged from 2% with dinitroamine, EPTC plus R‐25788, and captan to 10% with butylate. Other pesticides that inhibited amidase activity in soils were atrazine, naptalam, cbloramben, dicamba, cyanazine, 2,4‐D, alachlor, paraquat, trifluralin, maneb, diazinon, and malathion. The inhibition of amidase by diazinon, alachlor, and butylate followed noncompetitive kinetics.
A Comparison of Calcium Carbonate Precipitation and pH Depression on Calcium‐Reduced Ammonia Loss from Surface‐Applied Urea
Authors: Fenn L. B. , Matocha J. E. , Wu E.
Published: July 2010

The role of calcium (Ca) in reducing ammonia (NH3) loss from soil by way of calcium carbonate (CaCO3) precipitation and soil pH depression was investigated by applying increasing rates of urea with fixed ratios of Ca/N in the laboratory and greenhouse. Soil pH, Ca precipitation, and the rate of hydrolysis of added urea were related to reduction of NH3 loss.

Calcium/nitrogen ratios of 0.25 were equally effective in reducing NH3 loss independent of N application rates. Higher ratios of Ca/N at at 55 and 110 kg N/ha application rates did not further depress NH3 loss. At application rates of 550 and 1,100 kg N/ha, Ca levels above a Ca/N ratio of 0.25 resulted in additional large depressions of NH3 loss. This additional effect was due to a depression in soil pH from increased Ca activity and a dramatically reduced rate of urea hydrolysis. The chemical reaction of Ca with urea was complete at a Ca/N ratio of 0.25. Additional Ca, if added with a high enough rate of urea (550 and 1,100 kg N/ha) remained soluble and reduced the soil pH and was responsible for one half of the total reduction in NH3 loss.

Greenhouse data showed that the addition of Ca with urea increased plant recovery of fertilizer N more than predicted from laboratory data. Nitrogen rates as low as 55 kg/ha, applied in a surface band or as large granules, resulted in improved plant recovery of added N. Broadcast applications at 165 kg N/ha also resulted in good fertilizer N recovery at Ca/N ratios of 0.25 and 0.50.
Walkley‐Black Digestion Efficiency and Relationship to Loss on Ignition for Selected Sierra Leone Soils
Authors: Rhodes E. R. , Kamara P. Y. , Sutton P. M.
Published: July 2010

Ten top soils sampled from six physiographic positions in the Njala Survey Area of Sierra Leone, West Africa, varied in organic carbon content from 1.02 to 7.82% and in clay content from 22 to 65%. Walkley‐Black oxidation efficlency ranged from 93 to 100% and averaged 97%, using Wet Combustion as standard. Organic matter in these tropical soils is apparently in forms easily oxidized by the sulphuric acid‐dichromate digestion.

Simple correlation between organic carbon (C) and loss on ignition (L.O.I.) was very strong, r = 0.997; partial correlations showed that when organic C was held constant, 31% of the variation in L.O.I. was associated with clay content variation, and when clay content was held constant, 98% of the variation in L.O.I. was associated with organic C.

Ignition loss of organic C was closely predicted by the linear relationship y = 0.505 x − 0.094, where x = % organic C. Prediction error (about 0.5%) was proportionately greater at lower levels of ignition loss.
The Effect of Land Forming on Subsidence in the Florida Everglades' Organic Soil
Authors: Shih S. F. , Vandergrift D. E. , Myhre D. L. , Rahi G. S. , Harrison D. S.
Published: July 2010

Land forming in the Everglades Agricultural Area (EAA) can become an important practice for reducing the organic soil subsidence. Before the land forming practice can be successfully implemented in the EAA, ground elevation variation with time, concepts of ground elevation distribution, and managing different types of water table depth need to be clearly defined. A new concept of general low spot elevation was introduced. It was estimated from general deviation of ground elevation, composited from 68% of 1 standard deviation (SD) of ground elevation, 27% of 2 SD, and 5% of 3 SD. Three types of water table depths involved in this study, which were used to evaluate the impact of land forming on reducing subsidence, were conventional water table (CWT), recommended water table (RWT), and unifrom water table (UWT). The results showed that the SD of ground elevation in virgin land decreased from 6.2 cm in 1958 to 2.6 cm in 1978. the St. Augustine grass (Stenotaphrum secundatum) field had a similar trend of decrease in SD from 3.6 cm in 1958 to 2.6 cm in 1978. As the time progresses, the range of ground elevations decreases. The ground elevation in EAA is approximately a normal distribution because the probability distribution in ground elevation is similar to normal condition. The land forming has the potential of extending the life of organic soil by about 10 years in EAA with either RWT or UWT management conditions.
Effect of Particle Surface Roughness on Mechanical Impedance of Coarse‐Textured Soil Materials
Authors: Cruse R. M. , Cassel D. K. , Stitt R. E. , Averette F. G.
Published: July 2010

Packing energy required to increase bulk density in coarse‐textured soils is influenced by particle surface roughness, i.e., by interparticle friction. It was, therefore, hypothesized that particle surface roughness would influence soil resistance to movement of a cone penetrometer, because soil bulk density is increased in the zone surrounding the penetrometer tip during its advance. The cone index (C.I.) was calculated for all penetrometer measurements, and C.I. was compared in both disturbed and undisturbed coarse‐textured soil material, with each soil having a unique particle surface roughness as determined by the dense soil angle of repose measurement. For soil materials with similar particle size distributions and bulk densities, C.I. increased as particle surface roughness increased.

The role of particle surface roughness in tillage pan formation and in root growth restriction is discussed. It is suggested that, due to poorer aeration during rainy periods and higher mechanical resistance during drier conditions, tillage pans formed in soil materials having smoother‐surfaced particles will be more restrictive to root growth compared to those pans formed in soil materials having rougher‐surfaced particles. Consequently, among soils having root‐restricting tillage pans, the greater enhancement of rooting depth due to subsoiling would likely occur on soils with smooth particles compared to soils with rough soil particles.
Effects of Time and Leaching on Phosphate‐Induced Increase in Cation Exchange Capacity in Volcanic Ash Soils
Authors: Schalscha E. B. , Ahumada I. , Pratt P. F.
Published: July 2010

Incubation of phosphorus (P)‐treated soils for up to 240 days had no effect on the P‐induced cation exchange capacity (CEC) of subsoil samples of three volcanic ash‐derived soils of southern Chile. Washing one soil with large volumes of distilled water desorbed small quantities of P but had no effect on CEC.
Clays and the Survival of Rhizobium in Soil During Desiccation
Authors: Osa‐Afiana L. O. , Alexander M.
Published: July 2010

A study was conducted to assess the effect of drying on populations of two strains of Rhizobium japonicum and two cowpea rhizobia. The numbers of these bacteria fell markedly in soils undergoing drying. The extent of the decline varied with the strain and the soil. The decline in the population of a cowpea rhizobium occurred during the time of rapid water loss from four soils. The fall in numbers of three of the strains during desiccation was greater if the organisms were on glass beads than in soil. Illite did not increase survival on the beads, and kaolinite reduced the number of survivors of three strains dried on fine sand. Montmorillonite at the same concentrations protected against viability loss of two rhizobia undergoing desiccation on fine sand, but had no such effect on the more desiccation‐sensitive strain. The percent survival of three strains in a soil and in sand‐montmorillonite mixtures was directly related to the amount of water remaining after drying and was also affected by relative humidity. A possible relation between tolerance to desiccation and cell water content is suggested.
Effect of Cultural Practices on the Soil Population of Aspergillus flavus and Aspergillus parasiticus
Authors: Angle J. S. , Dunn K. A. , Wagner G. H.
Published: July 2010

Aflatoxin is a highly toxic compound and potent carcinogen produced by the fungi Aspergillus flavus and Aspergillus parasiticus. Corn infected by these organisms is frequently contaminated with aflatoxin. The infection of corn by A. flavus and A. parasiticus often occurs while the crop is still in the field. Because A. flavus and A. parasiticus are indigenous soil inhabitants, the soil is an important source of inoculum.

This study was undertaken to quantify the population of A. flavus and A. parasiticus in soil and the ability of these organisms to produce aflatoxin. Soils under 11 different cultural systems were examined to determine the effects of the different practices on A. flavus and A. parasiticus.

The maximum number of A. flavus and A. parasiticus propagules was found in soil cropped to a rotation of wheat, red clover, and corn using conventional tillage practices. In this soil, which had also been amended with manure, the count of A. flavus was 68 and that of A. parasiticus was 211 propagules per gram of dry soil. No A. flavus or A. parasiticus isolates were observed in a virgin prairie soil. Of all isolates observed from all cropping systems, 43% were A. flavus while 57% were A. parasiticus. The ability of the different isolates to produce aflatoxin varied significantly. In general, however, A. parasiticus isolates exhibited a greater ability to produce aflatoxin than did A. flavus.
Characterization of Sulfur in Fulvic Acids Extracted from Anaerobically Digested Sewage Sludge
Authors: Schaumberg Gene D. , Holtzclaw Kenneth M. , LeVesque C. S. , Sposito Garrison
Published: July 2010

A variety of analytical methods were employed to characterize 80 to 90% of the sulfur (S) in two representative fulvic acids extracted from anaerobically digested sewage sludge. As in fulvic acids extracted from soils and peats, the majority of the sulfur (69%) was present as organic ester sulfate, with smaller contributions from LAS‐type detergents, amino acids, and inorganic sulfates. Of the ester sulfate, between 20 and 30% was identified as sulfate esters of fatty alcohols, presumably of detergent origin, and about 5% was accounted for by sulfated acidic polysaccharides. It was concluded that, because of the ubiquitous distribution of sulfate esters, the disposal of anaerobically digested sewage sludge should not alter drastically the character of sulfur in natural soil and water systems. Perhaps of greater concern would be the contribution of carbon‐bonded sulfur from LAS‐type detergents, which have no common natural analogs.
Interaction of Phosphorus Rates and Soil pH on Soybean Yield and Soil Solution Composition of Two Phosphorus‐Sufficient Ultisols
Authors: Adams J. F. , Adams Fred , Odom J. W.
Published: July 2010

Because growers continue to use phosphorus (P) fertilizer on soils that test high in available P, two field experiments were conducted to determine what nutritional problem, if any, would develop in soybeans (Glycine max L.) when high levels of P were established on Ultisols. Soil pH levels, ranging from 5.0 to > 7.0, were established by differential limiting; five P rates as concentrated superphosphate were superimposed on the pH levels. Zinc (Zn) deficiency was induced by high P rates and high pH, and the magnitude of yield reduction corresponded with the intensity of deficiency symptoms on foliage. Leaf Zn, acid‐extractable soil Zn, and soil solution Zn were poor indicators of Zn deficiency. The ratio of P/Zn in leaves was a fair indicator in one soil and a poor one in the other, possibly because of differences in availability of subsoil Zn. Soil solution Zn, which ranged between 0.1 and 5.1 µM, was affected by pH but not P level. Soil solution P, which ranged between 5 and 230 µM, was affected primarily by P rates. Both SO4 and Si concentrations in soil solutions were increased by increasing P rates. Calculated ion activity products for Ca5OH(PO4)3 showed numerous soil solutions to be supersaturated with respect to hydroxyapatite.
Response of Corn and Inoculated Legumes to Urea, Lime, Phosphorus, and Sulfur on Guadalupe Clay
Authors: Jones U. S. , Samonte H. P. , Jariel D. M.
Published: July 2010

Responses of soybean (Glycine max L.), mung bean (Vigna radiata L.), and corn (Zea mays L.) to CO(NH2)2, CaCO3, Ca(H2PO4)2·H2O, and CaSO4, and of legumes to single strain Rhizobium inoculants on a Vertisol was determined during the dry season at Los Banōs, Philippines. Irrigation well water and precipitation were used to maintain soil moisture slightly below saturation in 6‐kg crocks. Relevant chemical analyses were made on soils, water, and plants. Inoculation increased N concentration of soybean tops. Soybean yield was greater with seed inoculation before planting than without, but mung bean did not respond to seed inoculation before planting. Neither legume responded to 30 kg N/ha as urea. Nodules on legume roots were greatly increased by 40 kg P/ha. All yields were more than doubled by addition of 40 kg P/ha. Increased yield of corn and soybeans resulted from the addition of 20 kg S/ha. The addition of sulfur as CaSO4 resulted in an increased soil S concentration as measured by dilute NH4C2H3O2, CH3COOH extraction.
Chemical and Mineralogical Properties of Glauconitic Soil as Related to Potassium Depletion
Authors: El‐Amamy M. M. , Page A. L. , Abudelgawad G.
Published: July 2010

The mineral glauconite has been identified in parent materials of some Libyan soils in the Barce Plateau region. Three soils, Elabiar clay loam, Elmarj silty clay, and Hamama clay, were selected to represent a weathering sequence. The cation exchange capacities (CEC) of these soils were found to increase with increased weathering intensity. This study dealt with the effects of potassium (K) depletion from clay and silt fractions on chemical and mineralogical properties of the soil glauconite. A relationship between equilibrium K concentration in the extracting solution and weathering degree was established.

Although it existed in all size fractions, glauconite (10.0, 5.0Å) was found in higher concentrations in fine silt and coarse clay fractions. Elabiar clay loam contained more glauconite and less K‐depleted glauconite than Hamama clay. Total K values were proportional to the amount of glauconite in each of the soil separates.

The results of equilibrating the clay and silt fractions with 1N NaCl indicated that more than 90% of total K was exchangeable with an equivalent increase in CEC. When the replaced K was allowed to accumulate in the extracting solution, the exchange process continued until K concentration reached a certain equilibrium level. The equilibrium K concentration was a function of K depletion regardless of particle size, solution density, or both. Because of their larger surface areas and the shorter diffusion paths, the finer fractions had shorter equilibration times and more rapid exchange rates.

The K depletion resulted in expanding the 10Å glauconite to 14 to 15Å when Mg‐saturated. Glycolation of the Mg‐treated samples did not effect the 14 to 15Å K‐depleted mineral. The results confirm those of previous research with glauconite specimens that, upon weathering, the soil glauconite produced a vermiculite‐ rather than a smectite‐type mineral.
Heavy Water Tracing of Soil‐Water Transfers Under Irrigation
Authors: Moutonnet P. , Couchat Ph.
Published: July 2010

In soil columns, a horizon was labeled with heavy (deuterated) water (D2O), and the evolution of D2O during the experiment was monitored in situ by gamma‐neutron counting. An automatic irrigation device was used for crop watering.

Based on the results of two consecutive experiments (H2O and D2O balance and water transfer analysis), the system was found to provide fully satisfactory irrigation. Deuterated water labeling, moreover, proved to be an effective technique for evaluating root uptake in a soil horizon.
Salt Generation in Pyritic Coal Spoils and its Effect on Saturated Hydraulic Conductivity
Authors: Evangelou V. P. , Phillips R. E. , Shepard J. S.
Published: July 2010

The oxidation of pyrite (FeS2) in surface‐mined coal spoils usually generates a large amount of soluble salts. These salts may impede water movement through the spoil, in some cases due to an increase in soil solution viscosity. This hypothesis was tested by the use of an 8.9‐cm diameter column filled with spoil material and outfitted with six tensiometers at 14‐cm intervals along its length. The buildup of salts in the lower portion of the column due to oxidation of pyrite was correlated with a suppression in hydraulic conductivity. A gradient in saturated hydraulic conductivity was measured starting in the upper portion of the column with a value of 0.50 cm/hour, decreasing to 0.03 cm/hour in the lower portion of the column. A gradient of salts was also encountered, with an electrical conductivity at the top of 0.12 mmho/cm and at the bottom of 16.44 mmho/cm. Upon depleting the salts from the column the saturated hydraulic conductivity of the lower portion approached that of the upper portion.
Effect of Soil Cation Exchange Capacity on the Uptake of Cadmium by Corn
Authors: Hinesly T. D. , Redborg K. E. , Ziegler E. L. , Alexander J. D.
Published: July 2010

Since many investigators examine the environmental input of sludge‐borne heavy metals through studies involving soluble metal salts, it is imperative that the equivalence of these two metal sources be tested.

Samples of B1 horizon of the Ava series (Typic Fragiudalfs) and Ap horizon of Maumee series (Typic Haplaquolls) were separately diluted with samples of the Plainfield series (Typic Udipsamments) to obtain soil mixtures having cation exchange capacities (CEC) of about 5.3, 10.6, and 15.9 meq/100 g. A mixture containing equal proportions of Ava and Maumee were also diluted with Plainfield to give an equivalent range of CEC. One portion of each of the nine experimental soils was admixed with the equivalent of 100 metric tons/ha of dried, digested sewage sludge to provide soil‐Cd concentrations of 10 mg/kg. The remaining portion was treated with CdCl2 at rates to provide equivalent soil‐Cd concentrations.

Corn (Zea mays L.) (single‐cross Mo17 × H98), selected for its inherited capacity to take up relatively high amounts of Cd, was planted in four pots of each mixture. Three plants were harvested at the end of 3 weeks and an additional three after 7 weeks. Cadmium uptake and dry weight production were affected to the greatest extent by Cd source > soil or soil mixture > CEC. Cadmium uptake and plant yields were inversely related to CEC on CdCl2‐treated soil but were not significantly different on soil mixtures treated with sludge. Less cadmium was taken up from soil mixtures that contained increasing quantities of Maumee, but there was no evidence that organic matter decreased cadmium uptake beyond that attributable to increased CEC. Total amounts of cadmium accumulated per plant were significantly different on sludge‐treated mixtures, but the magnitude of the differences were small compared to those from CdCl2‐treated soils. Biomass produced during the interval between the first and second harvest contained less cadmium than that collected during the first harvest. For the most extreme example (Ava B1 treated with CdCl2), only slightly more than 2% of the total soil cadmium was depleted by corn plants during 7 weeks of growth.
Soil Pore Structural Stability and Irrigation Water Quality: II. Sodium Stability Data
Authors: Cass A. , Sumner M. E.
Published: July 2010

The effect of mixed sodium/calcium solutions on the hydraulic conductivity (HC) of a range of soils was measured at fixed sodium absorption values and a range of cation concentrations decreasing from 800 to about 1 meq/liter. A similar series of solutions was used to measure water uptake (macroscopic swelling) of extracted soil clays. Using these data, sodium sensitivity and threshold swelling models were computed. The slope of the sodium sensitivity model was related to the smectite content, cation exchange capacity, and specific surface of pedal, nonvertisol soils through log‐log relationships having correlation coefficients of 0.67*, 0.61**, and 0.66**. It was also related to swelling by a log‐linear relationship (r = 0.64*). Some vertisols did not obey these relationships, possibly because of the effect of marked alteration to flowbed geometry during swelling. Such alteration maintained HC at higher values than would have been inferred from soil properties alone. Apedal soils containing large amounts of smectite also displayed greater stability than expected, possibly because of the stabilizing effect of sesquioxides on clay swelling. Soils with low specific surface, low CEC, and little smectite and/or sufficient sesquioxide to inhibit swelling (red, apedal) tend to be most stable in the presence of mixed Na/Ca solutions.
Kinetics of Thermal Dehydration of Gypsiferous Soils
Authors: Elprince A. M. , Al‐Shammary M. A. , Magboul A. M.
Published: July 2010

Recording the decrease in weight with time upon heating by electrically reproducible infrared (IR) radiation offers a fast method for studying the kinetics of the dehydration of gypsiferous soils. Plotting the weight loss rate against time gives a dehydration curve made of two peaks. The first peak is due to soil moisture and the second to the crystal water of gypsum. The product of dehydration is best regarded as soluble anhydrite (CaSO4 · ε H2O) rather than hemihydrate (CaSO4 · ½H2O) or insoluble anhydrite (CaSO4). This is indicated by the loss in weight and the IR spectra. The kinetic curves for the dehydration of gypsum at 156, 123, and 95°C are of sigmoidal forms. Beyond the inflexion point, most of the data fits the “diminishing sphere” kinetics formula. The rate constants and activation energies for the interface advance process shows that the soil matrix acts as a catalyst and that Na montmorillonite is a more effective catalyst than the soil matrix. A rate‐limiting step for the interface advance is the necessity for crystal water to pass through an adsorbed state. Soil minerals may offer effective adsorption sites. In contrast to the growth process soil matrix is a more effective catalyst for nucleation than Na montmorillonite.
Effect of Suspending Agent and Temperature on Survival of Rhizobium in Fertilizer
Authors: Kremer R. J. , Polo J. , Peterson H. L.
Published: July 2010

The lack of compatibility between legume inoculants and fertilizers has been widely recognized and reported. Studies involving alternative inoculant carriers and methods of inoculant preparation led to an examination of rhizobia incorporation in fertilizer. The effects of suspending agent and incubation temperature on the survival of two strains of Rhizobium in 0‐9‐12 fertilizer were determined using plate counts and most‐probable‐number methods of analyses. Results showed that oil was superior to water in maintaining the viability and effectiveness of two strains of lyophilized rhizobia. A fertilizer incorporated with lyophilized R. phaseoli suspended in oil contained nearly 104 viable cells per gram after 24 weeks of incubation at 65°C. In contrast, no R. phaseoli were recovered from a fertilizer containing a water suspension of lyophilized cells after 8 weeks of incubation at 25°C. These results strongly suggest that fertilizer and lyophilized rhizobia may be combined to form an effective inoculant if adequate precautions are taken to protect the rhizobia from rehydration.
Nodulation of Crimson Clover by Introduced Rhizobia in Mississippi Soils
Authors: Materon L. A. , Hagedorn C.
Published: July 2010

Crimson clover (Trifolium incarnatum L.) has long been recognized as an important annual legume in the winter grazing programs of the South. Considerable effort has been devoted to the development of cultivars which are resistant to disease, reseed reliably, and produce more fall and winter forage. Little information on the bacterial microsymbiont has been reported, and questions exist which concern Rhizobium strain‐host cultivar interactions, persistence of inoculum strains, and nitrogen fixation rates under field conditions. For this reason, five strains of R. trifolii were evaluated in competition with indigenous populations in nodulating crimson clover at two field sites in Mississippi. Proportions of nodules due to the introduced strains were measured by acquired and intrinsic antibiotic resistance. First season data indicated significant differences among the amended strains both within and between field locations. Three of the strains (162K10, RP113‐14, and RP111‐51) were recovered at a high frequency (>85% of the nodules sampled) in one site. At the second location, almost one‐half of the nodules assayed were produced by the indigenous rhizobia when competing with 162K10 and RP113‐14. In contrast, the proportion of nodules due to the other two strains, a local isolate (207) and an Australian culture (TA1), varied between 16 and 55% at both locations. Forage yield and percent crude protein levels reflected a positive association with the most competitive Rhizobium strains. These results indicate that selections for highly effective and adaptive Rhizobium strains can increase both crimson clover production and symbiotic nitrogen fixation.
Soil—Landscape Relationships in the Piedmont of Maryland
Authors: Darmody R. G. , Foss J. E.
Published: July 2010

A study was conducted to investigate and model the soil‐landscape relationships in the Piedmont of Maryland. The soil series of particular interest were the Chester, Glenelg, and Elioak series of Typic Hapludults. Results indicate that Elioak soil is a relict paleosol. A stone line separating strongly weathered Elioak soil material from silty overburden was revealed in several excavations. Particle‐size analyses and elemental analyses of silt fractions confirmed these discontinuities. Comparisons with known and radiocarbon‐dated loess deposits on the eastern shore of Maryland indicate that the silty overburden on the Piedmont is loess which was deposited after 10,520 ± 240 years B. P. Where the loess is thick, as on gentle slopes, Chester soils are mapped. Where the relict paleosol has been essentially eroded away, as on steeper slopes, Glenelg soils are mapped.
Estimation of the Concentration of Fe3+ and the (Fe3+)(OH‐)3 Ion Product from Equilibria of EDTA in Soil
Authors: Norvell W. A. , Lindsay W. L.
Published: July 2010

Equilibria of EDTA (ethylenediaminetetraacetic acid) chelates were used to measure the concentration of ferric ion in near‐neutral soils. Concentrations of Fe3+ and the (Fe3+)(OH‐)3 activity product were defined quantitatively by simultaneous equilibria involving EDTA4‐, Fe3+, Ca2+, and OH‐. Equilibrium between soil Fe and chelated Fe was established by varying the fraction of EDTA associated with Fe or by slightly altering the pH of the soil. Corrections were made to account for the differential sorption of various EDTA chelate species onto soils and for the formation of EDTA chelates of Zn and Cu.

Concentrations of Fe3+ in the range of 10−16 to 10−18 M were measured successfully in the presence of much higher concentrations of iron present as hydrolysis species and as unknown natural complexes. In 10 experiments using three near‐neutral soils, the negative logarithm of the (Fe3+)(OH‐)3 ion product had a mean value of 39.3 with a standard deviation of approximately 0.2. The solubility of Fe3+ in equilibrium with soil was stable for at least 6 weeks.
Conversion of Freundlich Adsorption K Values to the Mole Fraction Format and the Use of SY Values to Express Relative Adsorption of Pesticides
Authors: Bowman B. T.
Published: July 2010

Anomalies in the Freundlich isotherm equation prevent the simple conversion of K values to a common set of units for assessment of relative adsorption. Although there is a straightforward way to properly convert the units of K values, serious extrapolation errors can result because, in the new set of units, the K value may be evaluated considerably outside the concentration data range. In the mole fraction format, concentration is reported as a mole fraction, and adsorption as mol g−1, giving units of mol g−1 for K. In this format, K loses any practical meaning since it is evaluated at log Z = 0, Z = 1. An improved and more flexible method of reporting relative adsorption using SY values is presented as well as a procedure to convert existing data to this format.
A Comparison of the Effects of Monocalcium Phosphate and Diammonium Phosphate on Phosphorus and Calcium Availabilities
Authors: Adams Fred
Published: July 2010

Because monocalcium phosphate (MCP) is often a superior phosphorus (P) source to diammonium phosphate (DAP) when used at high rates, a short‐term, growth‐chamber experiment was conducted to compare the two P sources. An acid, P‐deficient Lucedale sandy loam (Rhodic Paleudult) was treated with all combinations of five lime rates and four P rates (0, 75, 150, and 300 ppm) as MCP and DAP. Other needed nutrients and a nitrification inhibitor were uniformly added, and a sorghum‐sudangrass hybrid (Sorghum bicolor × S. sudanensis L.) was grown for 14 days. Soil pH was lower and soil‐solution P and Ca were higher from MCP than DAP at each P rate. Several DAP‐treated soils produced forage yields lower than that predicted from their P levels; the lower yields were positively correlated with lower soil‐solution Ca. The critical ambient Ca level in DAP‐treated soil was significantly lower for plants growing at the rate of 300 ppm P than at that of 150 ppm, possibly because high P levels enhanced the uptake or physiological utilization of Ca.
Parameters for Describing Soil Detachment Due to Single Waterdrop Impact
Authors: Al‐Durrah M. M. , Bradford J. M.
Published: July 2010

A simple relationship that predicts soil detachment due to single raindrop impact was tested for nine soils and three drop sizes. This relationship expressed splash weight as a linear function of the ratio of raindrop kinetic energy to soil resistance expressed as the undrained shear strength. The coefficient of determination values between splash weight and the force‐resistance ratio for individual soils were high (r2 = 0.88 to 0.97); however, the coefficient of determination among all soils was lower (r2 = 0.81). This was due to differences among soils in the slope of the regression line and to uncertainties associated with the calibration of the fall‐cone penetration apparatus. The slope was highly correlated with percent clay, organic matter, surface area, exchangeable sodium, and the amount of soluble salts. A maximum coefficient of determination of 0.61 was found when soil properties other than shear strength were used as independent variables to predict soil splash.
A Permeameter Which Eliminates Boundary Flow Errors in Saturated Hydraulic Conductivity Measurements
Authors: Hill R. L. , King L. D.
Published: July 2010

A permeameter was designed to eliminate boundary flow errors that occur during saturated soil hydraulic conductivity measurement. Advantages of the permeameter are its adaptability for use with either disturbed or undisturbed soil samples, the elimination of possible problems associated with acrylic swelling, and relatively low cost. The permeameter was effective in eliminating boundary flow errors.
Control of Nickel and Strontium Sorption by Free Metal Ion Activity
Authors: Bowman R. S. , O'Connor G. A.
Published: July 2010

Formation of soluble complexes usually lowers sorption of metals by soils. The purpose of this study was to determine if changes in free Ni2+ or Sr2+ activity could explain differences in isotherms obtained in highly complexing SO2‐4 systems vs. slightly complexing Cl‐ systems. Sorption of Ni and Sr by homoionic montmorillonite and soil was studied using the batch isotherm technique. The Na+ (0.1N) and Ca2+ (0.02N) solutions of Cl‐ and SO2‐4 with Ni or Sr (10−6 to 10−4M) yielded systems in which up to 45% of soluble metal (M) was present as MSO04. Sorption was greater in the Cl‐ vs. the SO2‐4 systems at the same total M (Ni or Sr) concentration at equilibrium. Plotting data in terms of free M2+ activity at equilibrium eliminated significant differences between corresponding isotherms. Sorption thus appeared to be controlled by M2+ activity. The data supported the hypothesis that MSO04 complexes were not sorbed and MCl+ complexes sorbed only slightly if at all. Nickel sorption was greater than Sr sorption under similar conditions. The results illustrate the importance of correcting for ionic strength/ion pairing effects before making comparisons among isotherms.
Mineralization and Plant Availability of Phosphorus from Biomass of Hyaline and Melanic Fungi
Authors: Kapoor K. K. , Haider K.
Published: July 2010

This study was conducted to evaluate the mineralization and phosphorus availability to plants from fungal biomass and to determine differences between hyaline and melanic fungi in this respect. In a period of 5 weeks, wheat plants took up 6 to 16% of applied 32P in the form of fungal mycelia from soil. The availability of P from this biomass was lowest with highly melanized fungi Curvularia lunata and Stachybotrys chartarum (6 to 11%) and highest in the case of hyaline fungi Paecilomyces fusisporus and Penicillium chrysogenum (12 to 16%). This compared to >20% uptake of applied inorganic phospate. Carbon mineralization of fungal biomass during a 5‐week‐incubation period decreased with increase in melanization. Phosphorus availability to plants followed C mineralization but the correlation was not highly significant. Sixty to 70% of the P from fungal biomass was extractable with sodium bicarbonate predominantly in an organic form. Plant availability of this extractable organic P was lower in the case of melanized fungi than in hyaline.
Atmospheric Sulfur as Related to Acid Precipitation and Soil Fertility
Authors: Suarez E. L. , Jones U. S.
Published: July 2010

In experiments conducted to determine the major acidic components of precipitation in the southeastern United States, amounts of sulfur (S) deposited on the soil with rainfall were estimated and relationships between applied sulfur and crop yields in South Carolina were established.

Precipitation was collected at three locations from 10 Apr. 1979 to 8 Apr. 1980, at Clemson, S. C., Experiment, Ga., and Franklin, N. C., using a wet/dry collector. Conductivity, pH, and ionic components were determined in the rainfall and particulate matter. Sulfur in the air was collected at Clemson on a 30‐d interval in a standard lead peroxide sampler. Soil samples were taken from 15 locations in South Carolina and analyzed for sulfur.

It was observed that the average loading concentration of anions in rainwater increased during the spring‐summer months and decreased during the fall‐winter months. Sulfuric and nitric acids were found to be the major components of acid rainfall. Rainfall and air deposition contributed approximately 10.7 and 1.8 kg/ha of sulfur per year, respectively, at Clemson. Atmospheric deposition from the particulate matter contributed an estimated 3.0 kg/ha of sulfur during the year.

Increases in corn grain and silage yields were obtained with the application of 18 kg/ha of sulfur at Darlington, S. C. A relationship between applied sulfur and crop response for the other crops considered could not be established. A need for reevaluating the findings and recommendations for sulfur fertilizers was apparent because of the contribution of atmospheric‐deposited sulfur to the soil and plant sulfur supply.
Toxicity of Aluminum to Coffee Seedlings Grown in Nutrient Solution
Authors: Pavan Marcos A. , Bingham F. T.
Published: July 2010

A solution culture experiment was conducted with coffee seedlings (Coffea arabica L.) to determine the combined effect of ionic strength and aluminum (Al) concentration of nutrient solutions on Al availability. The treatments consisted of three Al concentrations: 0.0, 0.037, and 0.148 mmol dm−3. These were combined with five levels of ionic strength produced by diluting a complete nutrient solution to relative concentrations of 0.5, 0.25, 0.10, and 0.01. The phosphorus (P) concentration of each solution was adjusted to 0.1 mmol dm−3. The pH of the solutions was maintained at 4.0 ± 0.2. Shoot and root growth decreased progressively under the Al treatments. The lateral roots of Al‐stressed plants were thicker, shorter, and fewer in number than those of the control plants. The younger leaves of Al‐stressed plants were small, curled along the margins, and frequently chlorotic along the leaf margin.

At a constant Al concentration, seedling growth was reduced with dilution of the nutrient solution. This decrease in growth was best correlated with an increase in the activity of Al3+. An Al3+ activity value of 1.2 × 10−5 was associated with a 10% reduction of coffee seedling growth.
The Evaluation of Iron Deficiency Using a Bioassay‐type Test
Authors: Barak Phillip , Chen Yona
Published: July 2010

Experiments to establish a bioassay‐type pot test for the evaluation of iron deficiency in soils were performed. Peanut plants cv. Shulamit were grown in small pots (500 g of soil) for 5 weeks in six soils varying in CaCO3 content from 3.6 to 63.0%. Control and FeEDDHA (ethylenediamine di‐o‐hydroxyphenylacetic acid) treatments were employed. Chlorophyll content of the leaves was measured at the end of the growth period. A significant linear correlation was found between the relative chlorophyll content of leaves (FeEDDHA = 100) and the total CaCO3 or active lime content (r = 0.892 and 0.940, respectively). Chlorosis was completely remediable with the addition of FeEDDHA. A mountain rendzina soil containing 63% CaCO3 caused the most severe chlorosis. An experiment was conducted in which the chlorophyll content of FeEDDHA‐treated and untreated peanut plants grown on this soil was compared. This experiment was repeated at three different times of the year. Some variability was found in chlorophyll content of either treated or untreated plants when absolute numbers were compared. However, when chlorophyll content of the untreated plants was expressed as percent of that of FeEDDHA‐treated ones, the resulting relative values for the three growth periods were as close as 46.8, 41.7, and 45.0%. The same soil was used for further experimentation with the screening test. Three genotypes of peanuts were tested for Fe‐sensitivity: Congo Red, Virginia Bunch Improved, and Shulamit. Congo Red was found to be the most sensitive cultivar as known from former field studies. Iron‐enriched peat was prepared in our laboratories and tested as a possible remedy for iron deficiency of Shulamit peanuts grown on the rendzina soil. A positive response curve of plant chlorophyll to iron‐enriched peat dosage was obtained reaching levels comparable to FeEDDHA.

The growth chamber pot test described provides a simple and efficient tool for the following purposes: (i) screening soils for potential chlorosis problems in peanuts and possibly other plants; (ii) screening peanut cultivars for iron efficiency; and (iii) screening iron‐containing fertilizers, and roughly estimating their efficiency and application rates. The iron‐enriched peat which was first tested in this work exhibited positive and promising effects.
Potassium and Magnesium Recovery from Selected Soils of the Allegheny Plateau
Authors: Stout W. L.
Published: July 2010

Many soils of marginal land areas in the northeastern United States have been depleted in K and Mg by either poor soil fertility management or erosion. These soils also contain clay minerals such as mica and vermiculite that are prone to fix K and Mg. The combination of depleted levels of K and Mg and clay minerals may have an adverse effect on the recovery of K and Mg applied to these soils. The objective of this study was to determine the effect of clay minerals on the recovery of K and Mg applied to A and B horizons of seven Appalachian soils.

The recovery of K and Mg applied to the A and B horizons of seven soil series common to the Allegheny Plateau region of western Pennsylvania and northern West Virginia was determined using 1N ammonium acetate, double acid (0.05N HCl in 0.025N H2SO4), and oat seedlings. Potassium recovery by all methods ranged from approximately 60% of applied K in soils containing small amounts of mica and/or vermiculite to approximately 15% in soils containing moderate amounts of these clays. Almost all of the applied Mg was recovered by the soil testing methods, while the oat seedlings were only able to recover about 4% of the applied Mg. Recovery of Mg was not directly affected by clay type.

The ammonium acetate method was able to predict the recovery of K by the oat seedlings better than the double‐acid method. Magnesium recovery by the oat seedlings was predicted equally well by both soil testing procedures.
Salt‐affected Soils in the Platte River Valley of Central Nebraska: Properties and Classification
Authors: Al‐Janabi K. Z. , Lewis D. T.
Published: July 2010

Studies were undertaken to more fully understand and to properly classify some salt‐affected soils in central Nebraska. In spite of their location on a recent flood plain, these soils appeared to have accumulated illuvial clay in their subsoils and had evidence of removal of materials from the upper solum. A microknoll‐microdepression relief was evident in the permanent pasture, but salt accumulation did not follow expected patterns in relation to it. A thin, white salt crust was evident in irrigated parts of the area, but total salt accumulation in the pedons where the salt crust was evident was not much different from that in the other areas studied. No salic horizon was evident. Organic carbon (C) content of the upper pedon was too low, structure too weak, and consistence too firm to place these soils with Mollisols. Evidence for a Natric horizon was questionable. Therefore, placement in a fine loamy, mixed, mesic Typic Halaquept family is suggested. Since this family is presently not established, a taxadjunct to this category is a possibility. The presence of salt in these soils is most likely the result of a dilute solution of salts in the groundwater. Another mechanism is suggested, however.
Residual‐Wax Soil Treatments for Water Harvesting
Authors: Fink D. H.
Published: July 2010

Paraffin wax is being used as a soil treatment to increase the water runoff yield from precipitation. However, the increasing costs of petroleum products and occasional treatment failures prompted this laboratory study to improve treatment‐weathering resistance, decrease wax application rates, and substitute residual waxes for the more expensive paraffin. Ten residual waxes and two paraffin waxes were applied to Tremant soil (fine‐loamy, mixed, hyperthermic Typic Haplargids) at three rates (0.25, 0.50, and 1.00 kg/m2). Each wax contained three rates of antistripping agent (0, 2, and 4% by weight). Before the wax application, the soil was stabilized either by wet compaction alone, or by compaction followed by application of cellulose xanthate. The treated soils were weathered by alternately subjecting them to freeze‐thaw cycling, to erosion, and to water repellency testing. The laboratory results showed that the less costly residual wax treatments were generally more weather resistant than the paraffin treatments. Generally, the antistripping agent and cellulose xanthate improved weatherability of the waxes tested. Results also indicated that, with soil prestabilization and the addition of antistripping agent, the wax application rate for most waxes on soils similar to the one tested could be reduced to 0.25 kg/m2, which is one‐fourth to one‐eighth the currently recommended rate. The best treatments will be field‐tested to confirm these laboratory findings and to extend the use of wax treatments to other soils and climates.
Subjectivity in the Separation of Organic Horizons of the Forest Floor
Authors: Federer C. A.
Published: July 2010

Repeated measurements of the thicknesses of L, F, H, and A1 horizons for 30 years in six New Hampshire forest stands indicated that observers define and separate horizons differently. Consistent use of the new Soil Conservation Service definitions would help eliminate this difference. However, valid comparison of measurements on the forest floor among studies or over time is questionable.
Silica‐Sesquioxide Ratios as Aids in Characterization of some Temperate Region and Tropical Soil Clays
Authors: Tan K. H. , Troth P. S.
Published: July 2010

The usefulness of silica‐sesquioxide ratios in the characterization of clays was studied by comparative analysis of primary and secondary minerals, and clays isolated from selected temperate region and tropical soils. The reference minerals and the clay fractions (<2 µm), separated from A and B horizons, were analyzed for total Si, Al, and Fe contents by the lithium metaborate method and atomic absorption spectrophotometry. Characterization of the minerals was conducted by x‐ray diffraction, differential thermal analysis (DTA), and infrared analysis. The data indicated that the molar silica‐sesquioxide ratios were capable of detecting differences in mineral composition, not revealed by x‐ray diffraction or the other methods. However, a considerable overlap in values of the ratios was noted for clays of the temperate region soils. In the absence of x‐ray diffraction and/or other analysis, this overlap imposed some restrictions as to the use of the ratios in the identification of mineral species from a mixture of 2:1‐type of clays, but was not critical in the distinction of kaolinite from montmorillonite as monominerals. Kaolinite in the temperate region Ultisols and tropical soils had SiO2/R2O3 (1.41 to 2.15) and SiO2/Al2O3 (1.63 to 2.46) ratios in general agreement with those of reference kaolinite. However, the lower values of SiO2/Fe2O3 and Al2O3/Fe2O3 ratios of the soil clays distinguished them from the reference clay as being higher in iron content. The idea that increased weathering decreased the values of the silica‐sesquioxide ratios was not substantiated by the present results, since the clay minerals revealed similar if not higher silica‐sesquioxide ratios than the primary minerals.