bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Humic Acids on Nodulation and Dry Matter Production of Soybean, Peanut, and Clover
Authors: Tan K. H. , Tantiwiramanond D.
Published: July 2010

Humic substances have been reported to increase plant growth. A stimulating effect on the growth of legumes may improve biological nitrogen fixation in soils. The present investigation studied dry matter production, nodulation and N content in nodules of soybean (Glycine max L., ‘Bragg’), peanut (Arachis hypogaea L., ‘Florunner’), and clover (Trifolium vesiculosum, ‘Arrow leaf’), grown in sand cultures containing a fertilizer mixture and 0 to 800 mg kg−1 (ppm) of fulvic acid (FA) or humic acid (HA). The results indicated that FA and HA were capable of stimulating dry matter production in the plants. Dry weights of roots and nodules showed a tendency to increase over the control at 100 to 400 mg kg−1 (ppm) of FA or HA. The increases in total dry matter production were statistically significant at 800 mg kg−1 (ppm) of FA or HA, and a positive correlation was noticed between increases in dry weights of shoots, roots, and nodules and FA and HA concentrations. Fewer nodules were produced by plants receiving FA and HA treatments than the control, but the nodule mass was greater with the FA and HA treatments. The N content of nodules was little affected by the treatments, although a tendency can be noticed that 100 mg kg−1 (ppm) of FA had decreased the N content in the nodules of both soybean and peanut plants.
Effect of Pelleting, Temperature, and Soil Type on Mineral Nitrogen Release from Poultry and Dairy Manures
Authors: Hadas Aviva , Bar‐Yosef B. , Davidov Sara , Sofer M.
Published: July 2010

Pellets are produced from manures for more convenient and economical use. The rate of N mineralization of manures under different conditions is of agronomic importance, since it allows estimation of mineral N supply to plants as a function of time. Pelleted manure may have mineralization characteristics differing from those of its raw components due to the high temperatures and pressure involved in the pelleting process. The rate of N mineralization of raw manures and pelleted manure was studied in water and in soil incubation experiments. About 10% of total N in the manures was initially KCl‐extractable NH4. Within 1 d, 30 to 35% of total N in poultry manure and 18% in mixed 75% dairy and 25% poultry manure were mineralized in water. Mineralization kinetics of manures in soil showed an initial rapid process followed by a slow release of mineral N and could be described as two simultaneous first‐order reactions. During the first week, 34 to 44% of total N in poultry manure and 14 to 23% in 75% dairy + 25% poultry manure were mineralized in soil pellets releasing more N than ground manures. After 2 to 3 months, mineral N in soil was 34 to 50 and 27 to 44% of total N in poultry and 75% dairy manures, respectively, the pellets contributing equal or less mineral N to soil than the ground manures. Pelleting increased the relative amount of rapidly mineralizable N in the manures and created higher NH4‐N concentrations in soil, which under less favorable conditions for nitrification increased the susceptibility to loss of NH3‐N. Temperatures in the range of 14 to 35°C had little effect on the rate of mineralization but affected N loss from poultry manure pellets by delaying nitrification at 14 and 35°C compared with 25°C.
Albic Neoskeletans in Argillic Horizons as Indices of Seasonal Saturation and Iron Reduction
Authors: Vepraskas M. J. , Wilding L. P.
Published: July 2010

Significant periods of seasonal waterlogging in some soils of the Texas Coastal Plain have gone unrecognized because the soils lack low (≤ 2) chroma colors. A study was conducted in two soils along a forested toposequence of Alfisols to identify morphological features other than color that are indicative of ground water saturation and Fe reduction. The duration of saturation and Fe reduction had been determined previously for each soil of the toposequence. Iron nodules (> 2 mm diam) and neocutanic albic materials (albic neoskeletans) were sampled and their abundance determined. Albic neoskeletans were also characterized with respect to total Fe content, particle size distribution, and color. Sesquioxide nodules within portions of the argillic horizon had no consistent relationship to the soil structure and were found both in zones of Fe loss and accumulation. This indicated at least some nodules were relict features and that nodules could not be used for moisture regime identification in these soils. Albic neoskeletans along ped surfaces and root channels formed in place by a loss of clay and free Fe from the surfaces of macropores. Most albic neoskeletans were not overlain by other cutans and all evidence indicated they formed under the current moisture regime in each soil examined. Albic neoskeletan abundance was directly related to the duration of Fe reducing conditions, but not to the duration of saturation. Greatest development of these features occurred in a soil with a perched water table in horizons that were Fe reduced for 55 to 146 d. It is suggested that albic neoskeletans be used as diagnostic criteria for water saturation and Fe reduction despite their moist color chromas of 4 or less. It is proposed that albic neoskeletans be used, when low (≤ 2) chroma colors are absent, to identify aquic intergrades in Paleudalfs.
Tillage and Surface Residue Effects on Soil Upper Boundary Temperatures
Authors: Gupta S. C. , Larson W. E. , Linden D. R.
Published: July 2010

The effects of tillage‐surface residue interactions on soil upper boundary temperatures are described. Regression curves are developed between the maximum and minimum soil surface temperatures vs. maximum and minimum air temperatures at the 2‐m height. Soil surface temperature variations between various residue and tillage treatments were mainly due to the change in surface residue cover. During fall and spring, the maximum temperature differences were 12 and 19°C, respectively, between no residue and surface residue treatments for the same tillage condition. Soil surface temperature variation due to the disturbance of soil by tillage for the similar residue cover condition were relatively small. During the growing season, maximum and minimum soil surface temperatures under corn canopies were approximately the same for all tillage‐residue interactions. A procedure to normalize diurnal upper boundary temperatures with respect to daily maximum and minimum soil surface temperatures is suggested. This procedure simplifies the upper boundary temperature data for easy comparison between treatments, seasons, and locations. Comparison of the average normalized soil surface temperature curves suggests that the shape of the daily soil surface temperature curve is slightly different for various tillage and residue interactions, with and without a corn crop. These differences in the average normalized soil surface temperature curves suggest that residue cover delays cooling more than heating of the soil surface. Based on the regression and the average normalized soil surface temperature curves, a procedure is described to estimate the soil upper boundary temperatures for various tillage and surface residue conditions from daily maximum and minimum air temperatures. Application of these soil upper boundary temperatures is in the physically based soil temperature models to estimate the root zone soil temperatures for various tillage and residue management systems with and without a corn crop.
Irrigation Decisions Simplified with Electronics and Soil Water Sensors
Authors: Cary J. W. , Fisher H. D.
Published: July 2010

Two simple, inexpensive systems use electrical resistance measurements to provide useful, immediate information to assist decisions made on irrigation water application. In one system a microprocessor‐based circuit coupled to a programmable calculator provides an on‐site estimate of the time until the next irrigation will be required, based on field data and an operator‐supplied parameter. The second system simply signals the arrival of the wetting front at any location in the soil by giving a visual indication, such as raising a mechanical flag. The microprocessor‐based circuit measures and stores the resistance of four gypsum blocks once a day. The program in the portable calculator accesses this information and uses it to extrapolate the soil drying rate to predict the number of days until the next irrigation. By restricting the microprocessor circuit to data acquisition only and putting all number‐handling routines into the calculator program, the cost and complexity of the microprocessor circuit is minimized, whereas maximizing the programming flexibility. This makes it feasible to install a number of these devices at different locations, all serviced by the same portable calculator.

The water infiltration circuit intermittently scans eight sets of stainless steel electrodes to locate the soil wetting front during irrigation. When the resistance across the electrodes decreases, signaling the arrival of the front, the circuit trips a spring‐loaded flag. This provides a visible sign that the wetting front has reached that point in the soil. The equipment worked well. When irrigation was required in six or fewer days, the microprocessor/calculator system made correct predictions 85% of the time. An example of how easily any irrigation scheduling method may be converted to the microprocessor/calculator system is presented.
Probability Sampling Techniques for Estimating Soil Erosion
Authors: Roels J. M. , Jonker P. J.
Published: July 2010

Data on the lateral variability of soil loss from Submediterranean rangelands are presented. Modified Gerlach troughs were used to measure both rill and interrill erosion. Random, systematic, stratified random, and cluster sampling methods were tested for various numbers of plots and plot widths in order to find the method that gives the most accurate estimate of soil loss. If both the rill and interrill subpopulations are sampled, random sampling and stratified random sampling give almost identical standard errors. Cluster sampling yields larger errors and is therefore less effective. Systematic sampling, however, allows one to choose more accurate samples of an economical size, but its efficacy depends largely on the number of rills in the study area. The smallest standard errors are obtained by measuring the total rill erosion and by sampling only the interrill subpopulation. When this procedure is applied, the four sampling methods turn out to be equally accurate.
Iron Oxides in Petroferric Materials
Authors: Ibanga I. J. , Buol S. W. , Weed S. B. , Bowen L. H.
Published: July 2010

Samples of petroferric materials with a very wide range of chemical and morphological characteristics were obtained from Australia, Bolivia, Brazil, Nigeria, Thailand, and the USA. A prominent feature of all samples is a high content of Fe and/or Al oxides, relative to other constituents. Free Fe oxide is present mainly as goethite or hematite with very small amounts of lepidocrocite in some samples. Soil sample color is related to the Fe oxide mineralogy; the reddish colored samples have a high content of hematite while the yellowish samples have a high goethite content. Also, samples with a low active Fe ratio tend to have a reddish color while those with a high active Fe ratio are yellowish in color. The active Fe ratio is not predictable from a knowledge of the crystallinity or particle size of goethite present, but the presence of lepidocrocite generally increases the oxalate‐extractable Fe. Both hematite and goethite in the samples contain Al up to about 25 atom percent. Treatment of the samples with boiling 5M NaOH decreased the Al‐content of some but not all hematites and goethites.
Stability Relationships in Kaolinite, Gibbsite, and Al‐hydroxyinterlayered Vermiculite Soil Systems
Authors: Karathanasis A. D. , Adams Fred , Hajek B. F.
Published: July 2010

The stability of common soil minerals found in Ultisols was studied relative to their natural soil solution composition. The mineralogy of the clay fraction (<2 µm) ranged from 22 to 60% in kaolinite, 0 to 20% in gibbsite, 17 to 57% in hydroxyinterlayered vermiculite (HIV), and 1 to 12% in quartz. Ion activity functions (pH‐⅓pAl and pH4SiO4) of soil solutions plotted on a stability diagram along with solubility lines of soil kaolinite, gibbsite, and HIV with the formula K0.24Ca0.08(Si3.24Al0.76)(Al1.56Fe0.24Mg0.20)[Al1.45(OH)3.79]O10(OH)2 indicated all solutions to be supersaturated with respect to reference kaolinite. Only a few surface soils containing gibbsite had solutions oversaturated relative to gibbsite. Solubility products of HIV were very close to its estimated pk, indicating a near‐equilibrium condition with this mineral, especially in eluviated and transitional subsoil horizons (E and EB). Although the HIV appeared to be metastable relative to reference kaolinite, the data indicated a possible equilibrium coexistence of the two minerals with an HIV stability field below or above that of soil kaolinite, depending on the degree of Al‐hydroxyinterlayering.
Submersible Pressure Outflow Cell for Measurement of Soil Water Retention and Diffusivity from 5 to 95°C
Authors: Constantz Jim , Herkelrath W. N.
Published: July 2010

A technique was developed to measure water content in soil as a function of capillary pressure from 5 to 95°C. To overcome problems encountered at high temperature, a modified Tempe pressure cell containing a soil sample is suspended in a constant‐temperature water bath. The cell's porous plate is in direct contact with circulating bath water, thus eliminating the problem of entrapped air bubbles. A balance located above the water bath measures water content changes in the soil by weighing the entire pressure cell under water. The technique is designed to measure soil water retention characteristics and to make transient outflow estimates of the soil water diffusivity at temperatures from 5 to 95°C. We also used the technique to determine the isobaric temperature dependence of water retention in soil. Results indicate that at constant capillary pressure, the relationship between moisture content and temperature is hysteretic.
Potassium‐Calcium Exchange in a Multireactive Soil System: I. Kinetics
Authors: Jardine P. M. , Sparks D. L.
Published: July 2010

The kinetics of K exchange were investigated in Ca‐saturated samples from the Ap horizon of an Evesboro soil from Delaware. Biphasic kinetics characterized the first‐order plots for K adsorption and desorption at 283 and 298K with the two simultaneous reactions being attributed to exchange sites with varying reactivity for K and Ca ions. The rapid reaction was ascribed to exchange sites of the soil that are readily accessible to cation exchange reactions, whereas the slow reaction was attributed to exchange sites that are difficultly accessible to cation exchange reactions. Confirmation of the hiphasic kinetics was achieved through the use of cetyltrimethylammonium bromide (CTAB). Parabolic diffusion plots for K adsorption and desorption at 283 and 298 K indicated that an intraparticle diffusion process may be rate limiting for the difficultly accessible sites of the soil. The initial deviation from linearity of the parabolic plots for K desorption suggested that film diffusion may be rate limiting for desorption on readily accessible sites of the soil that form strong bonds with Ca ions. At 313 K the initial rapid kinetics of exchange was no longer present, and the exchange process was described by a single first‐order reaction. The parabolic plots at 313 K suggested that this phenomenon could possibly be attributed to the finite rate at which the polymer structure of soil organic matter changes in response to the adsorption and desorption of the two reacting cations.
Effect of pH on Saturated Hydraulic Conductivity and Soil Dispersion
Authors: Suarez D. L. , Rhoades J. D. , Lavado R. , Grieve C. M.
Published: July 2010

The adverse effects of exchangeable sodium on soil hydraulic conductivity (K) are well known, but at present only sodicity and total electrolyte concentration are used in evaluating irrigation water suitability. In arid areas, high sodicity is often associated with high dissolved carbonate and thus high pH, but in humid areas high sodicity may be associated with low pH. To evaluate the effect of pH (as an independent variable) on K, solutions with the same SAR and electrolyte level were prepared at pH 6, 7, 8, and 9. Saturated K values were determined at constant flux in columns packed at a bulk density of 1.5 Mg m−3. At pH 9, saturated K values were lower than at pH 6 for a montmorillonitic and a kaolinitic soil. For a vermiculitic soil with lower organic carbon and higher silt content, pH changes did not cause large K differences. Decreases in K were not reversible on application of waters with higher electrolyte levels. The results from the K experiments were generally consistent with optical transmission measurements of dispersion. Although anion adsorption was at or below detection limits and cation exchange capacity (CEC) was only slightly dependent on pH, differences in pH effects on K among soils are likely due to differences in quantities of variable‐charge minerals and organic matter.
Long‐Term Reactions of Copper(II) in a Contaminated Calcareous Soil
Authors: McBride M. B. , Bouldin D. R.
Published: July 2010

The concentrations of total and uncomplexed Cu(II) were measured in water extracts from a soil contaminated at least a half century ago. The total Ca concentration in the topsoil was about 3150 mg/kg of soil. Estimates of uncomplexed (free) Cu based on ion‐selective electrode data indicated that at least 99.5% of the Cu in soil solution was in an organically complexed form. This percentage was decreased by adjusting the soil pH downward. The concentration of uncomplexed Cu in soil solution increased with decreasing pH, but the total soluble Cu was relatively insensitive to pH change. Extraction of the soils with DTPA, pyrophosphate, and other selected reagents, as well as analysis of these extracts by electron spin resonance, revealed that the form of Cu2+ adsorbed in the soil was probably largely inorganic. Although solubility data indicated that the soil solution was undersaturated with respect to Cu hydroxide and hydroxy‐carbonate precipitation, malachite had crystallized on limestone surfaces.
Wheat Response to Sodium Uptake under Zonal Saline‐Sodic Conditions
Authors: Devitt D. , Jarrell W. M. , Jury W. A. , Lunt O. R. , Stolzy L. H.
Published: July 2010

Plants growing in saline‐sodic soils are usually subjected to the zonal distribution of salts. The ability of a root system to tolerate high levels of soluble salts and in particular high levels of Na+ is partially due to the compensatory uptake of water and ions in the more favorable regions, thus leading to an improved water and nutrient status of the plant. The objective of this investigation was to determine the uptake of Na+ under zonal saline‐sodic conditions and to determine what impact Na+ accumulation had on the overall water, nutrient and growth status of the plants. The experiment was conducted in lysimeters packed with four soil types, with wheat as the test crop. Electrical generating plant blowdown water (EC 6.9 dS/m) was used as the irrigation source on the treated lysimeters. A 10% leaching fraction was imposed on all lysimeters. Sodium‐22 was applied to each of the salinized lysimeters at different times to establish different 22Na positions with depth. Plant and soil samples and soil solution extracts were taken during the experiment and analyzed for Na+, K+, Ca2+, Mg2+, Cl‐, and 22Na. Electrical conductivity was also measured on soil and extracted soil water samples. Fresh to dry weight ratios of the plant and yield estimates were also obtained. An excellent correlation was found between the depth weighted ECSE/θ and the cumulative evapotranspiration. Incorporating the fractional water uptake (WJ) with the ECSE/θ values with depth improved the correlation between ECSE/θ and the cumulative evapotranspiration. Plants that had higher dry matter production and evapotranspiration rates also had higher Na+ accumulation. This we believe was manifested by a positive response to more favorable ECSE/θ regions where Na+ was effectively used in osmoregulation. Sodium‐22 results indicated that the regions closest to the surface were the most active in terms of Na+ uptake. Finally, as the evapotranspiration rate decreased so did the yield and this was directly linked to soil type. Yield estimates as high as 7.5 Mg ha−1 were obtained on the soils with the higher CEC and water holding capacities.
Sulfur Nutrition of Rapeseed II. Effect of Time of Sulfur Application
Authors: Janzen H. H. , Bettany J. R.
Published: July 2010

A growth chamber pot experiment was conducted to compare the efficiency of 35S labeled sulfate applied at various stages of growth (at seeding, rosette, bud, and flowering stages) in rapeseed grown on S‐deficient soils. Plant uptake of fertilizer S was generally higher when S was applied at later growth stages. Much of the S applied during these stages, however, accumulated in excessive amounts within the leaves and was not retranslocated despite severe S shortages during seed formation. Seed yields were not affected by time of S application except under conditions of severe S stress where S applied after the rosette stage did not allow recovery of maximum seed yields. Plant maturity was delayed when S was applied after the rosette stage. The results suggest that S deficiency diagnosis using plant tissue analysis will allow successful amendment of S deficiency in rapeseed providing sulfate is applied during or shortly after the rosette stage.
Identification of Pedogenic Carbonates using Stable Carbon Isotope and Microfabric Analyses
Authors: Rabenhorst M. C. , Wilding L. P. , West L. T.
Published: July 2010

In soils formed from limestone, it is often difficult to distinguish between inherited and pedogenic carbonate. In nature, both thermodynamic and kinetic factors have caused fractionation of C isotopes. While marine carbonates usually have δ13C values near zero, the processes of pedogenic carbonate formation result in considerably lower values, which are dependent only on the δ13C of the soil CO2 gas. Therefore, a simple proportionality may be employed to quantitatively estimate pedogenic carbonates in the soil.

Seven pedons formed over Cretaceous limestone in Central and West Texas were studied. The δ13C values were determined for the parent carbonates, soil organic matter, and for the various carbonate‐enriched horizons. Both finely disseminated carbonates in A horizons and massive indurated petrocalcic materials were confirmed by isotopic analyses to be primarily of pedogenic origin. Characteristic microfabrics were correlated with isotopic assay of massive petrocalcic materials which may be diagnostic for identification. Although generally useful, isotopic analysis underestimates the pedogenic component in certain carbonate forms, including laminar caps and some concretions and pendants. It is postulated that a different mode or environment of formation for these forms is responsible for discrepancies with theoretical values.
A Unifying Quantitative Analysis of Soil Texture
Authors: Shirazi Mostafa A. , Boersma Larry
Published: July 2010

The soil texture triangle used by the U.S. Department of Agriculture is converted into a new texture diagram which contains all information in the original triangle, but additionally, gives mean particle size and particle size standard deviation of soil samples. Thus, mechanical analysis information on percents of clay, silt, and sand together with particle‐size limits for clay, silt, and sand are found in a single unified system. The new diagram provides greater resolution in detecting classified soil samples within a texture region, it can be extended to cover coarse fragments, and other soil texture classifications can be incorporated into it.
Silicic Acid and Oxidizable Carbon Movement in a Walla Walla Silt Loam as Related to Long‐Term Management
Authors: Douglas C. L. , Allmaras R. R. , Roager N. C.
Published: July 2010

Agricultural ecosystems can alter the natural soil‐forming process, but little information is available to project the effects. Such alterations can be recognized early in soils that have little natural horizon differentiation, such as the Walla Walla silt loam (coarsesilty, mixed, mesic Typic Haploxeroll). The potential for movement of silicic acid (H4SiO4) and soluble organic carbon (C) was evaluated in selected plots subjected to residue and nitrogen (N) addition treatments for a period of 50 y. Soil samples from the four upper 15‐cm layers of a plot, assembled as a column, were leached and simultaneously monitored for solubilization and movement of H4SiO4 and oxidizable organic C. Leachate concentrations and net transfers of H4SiO4 from the 0‐ to 15‐cm layer decreased as long‐term C additions increased, soil pH increased, or both. High concentrations of H4SiO4 were noted throughout the upper 60 cm, which confirms earlier observations using perfusion and batch equilibration techniques. The large concentrations of soluble organic C and their failure to correlate with H4SiO4 movement indicated that soluble organic C was not controlling solubilization of sorbed silica. Liming decreased the release of soluble H4SiO4 from the 0‐ to 15‐cm layer. All soluble H4SiO4 observations were consistent with silicic acid release from surfaces that could be partially covered (or otherwise deactivated) by coatings of organic materials. The decrease in H4SiO4 solubilization by either liming or a high organic matter level should be examined further as a possible mechanism involved in the beneficial effects of these two managements on soil structure and physical properties.
Properties of Minesoil Reclaimed for Forest Land Use
Authors: Bussler B. H. , Byrnes W. R. , Pope P. E. , Chaney W. R.
Published: July 2010

Physical and chemical properties of minesoil reclaimed for forest land use in southwestern Indiana were evaluated to determine suitability for reforestation according to specifications of Public Law 95–87, The Surface Mining Control and Reclamation Act of 1977. Properties of reconstructed minesoil and unmined reference soils were compared. Soil types on the reference area were primarily Ava (Typic Fragiudalf) and Parke (Typic Hapludalf) silt loams and were similar to soils on the mineland prior to excavation. Both the reclaimed mineland site and reference site supported mixed upland hardwood trees and shrub vegetation prior to surface mining. Chemical properties of minesoil were similar to or more favorable for plant growth than unmined reference soils. However, physical properties in the rooting zone were less favorable in minesoil than reference soils. Minesoil had higher bulk density, lower porosity, lower permeability, higher coarse fragment and clay content, and lower available water‐holding capacity than reference soils at comparable depths. Mean bulk density of minesoil, adjusted for rock fragments > 2 mm, ranged from 1.53 Mg m−3 (g cm−3) in topsoil to 1.77 Mg m−3 in graded cast overburden. Mean available water‐holding capacity was 16.5% in topsoil and 10.8 to 11.7% (kg kg−1) in graded cast overburden layers of minesoil. Chemical properties of minesoil should be adequate for cover crop and tree seedling establishment after liming and fertilization to recommended soil test levels of NPK. However, physical properties could adversely affect plant survival and growth.
Soil Nitrogen Availability following Long‐Term Burning in an Oak‐Hickory Forest
Authors: Vance Eric D. , Henderson Gray S.
Published: July 2010

Seasonal levels of extractable ammonium and nitrate in the surface soil of oak‐hickory (Quercus spp. and Carya spp.) forest plots subjected to 30 yr of annual and periodic (4‐yr) prescribed burning were studied. Laboratory incubations were also carried out for 4‐, 14‐ and 28‐d periods at each of six dates to determine the effect of the burning treatments on mineralizable N. Ammonium was the predominant N form regardless of treatment. Burning significantly (P = 0.05) reduced quantities of extractable NH+4 over all sampling dates, with annual burning resulting in lower amounts than burning every 4 yr. Burning also significantly reduced the quantity of N mineralized during incubation. Since previous studies have not shown decreases in total N on the burned plots, the lower extractable N concentrations appear to be the result of an adverse effect of long‐term burning on substrate quality that reduced rates of mineralization. The treatment influence on mineralizable N was more apparent during the latter 24 d of laboratory incubation, whereas the initial 4 d reflected the influence of sampling date to a greater degree. From this pattern, it is hypothesized that the initial 4 d of incubation are more indicative of field environmental conditions, whereas the latter 24 d reflect the quantity of mineralizable substrate present. Although treatment differences in extractable and mineralizable N were statistically significant overall, the lack of statistical differences at some dates indicates the importance of seasonal sampling.
Sulfur‐Coated Urea for Turfgrass Fertilization
Authors: Hummel N. W. , Waddington D. V.
Published: July 2010

The acceptance of sulfur‐coated urea (SCU) as a fertilizer in the turfgrass industry requires a firm basis on which to make recommendations for its use. Three SCU materials were evaluated at different rates and timing of application for maintenance fertilization of ‘Merion’ Kentucky bluegrass (Poa pratensis L.). Two were SCU materials from the Tennessee Valley Authority (TVA): SCU‐11 and SCU‐25, having 11 and 25% 7‐d dissolution rates, respectively. The third, CIL‐30 (30% dissolution rate), was SCU prill from Canadian Industries Limited (CIL). Ammonium nitrate (AN), ureaform (UF), and isobutylidene diurea (IBDU) were also evaluated for comparison with SCU. Response to fertilization was measured by weekly determinations of clipping yields and color. Nitrogen recovery in the clippings and residual SCU pellets in the turf stand were also determined. Data were collected for three growing seasons.

The most uniform turfgrass response to SCU fertilization was produced by split applications of 245 kg N ha−1 y−1; and response to SCU‐11 was less than that to SCU‐25 and CIL‐30. When SCU‐25 and CIL‐30 were applied at a rate of 245 kg N/ha in single fall applications, there was insufficient carry‐over of residual N to maintain dark color throughout the growing season. During the first 2 y, release of N from SCU‐11 tended to be too slow to maintain good season‐long color, with only the single spring application of 245 kg N/ha maintaining good color throughout the summer. Response improved in the third year. Fertilization rates of 147 kg N ha−1 y−1 did not produce acceptable quality turf.

Pellet recovery from the turf was inversely related to N recovery in plant tissue. Two months after application, SCU dissolution ranged from 91 to 97% for CIL‐30, 60 to 80% for SCU‐25, and 38 to 53% for SCU‐11. Recovery of applied N in the clippings was highest for AN and CIL‐30 with 49 to 59% and 50 to 56% recovery, respectively. Nitrogen recoveries of 42 to 52% and 25 to 37% were obtained for SCU‐25 and SCU‐11, respectively. Recovery was 22% for UF and 46% for IBDU. Response to IBDU compared favorably to SCU‐25, while response to UF was less than from any other 245‐kg split treatment.
Short‐Term Immobilization of Fertilizer Nitrogen at the Surface of No‐Till and Plowed Soils
Authors: Rice Charles W. , Smith M. Scott
Published: July 2010

Immobilization of (NH4)2SO4 in no‐till and conventionally tilled soils was monitored after application of 15N enriched material to the surface of 20‐cm diameter plots on three soil types. Soils were collected periodically up to 35 d and 15N in organic and inorganic fractions was measured. On all three soils there was more immobilization in no‐till. After 35 d, the percentage of fertilizer applied that was immobilized was 21 and 11 on Maury silt loam, 13 and 6 on Tilsit silt loam, and 24 and 15 on Cavode silt loam for no‐till and conventional tillage, respectively. There were no consistent trends or statistically significant differences between tillage treatments with regard to total N recovery (organic plus inorganic). The increased potential for immobilization of N at the surface of no‐till soils may significantly reduce crop recovery of fertilizer N.
Organo‐Mineral Complexes and Their Study by Radiocarbon Dating
Authors: Anderson D.W. , Paul E.A.
Published: July 2010

The objective of this study was to investigate the long‐term cycling of organic C in cultivated soils by radiocarbon dating. Samples from a clayey Haploboroll soil (Indian Head) taken in 1963 and 1978 showed a general reduction in radiocarbon age of the whole soil of 20%. This was attributed to the enrichment of 14C in the atmosphere because of nuclear explosions in the 1960s, and its subsequent incorporation into organic matter. Relative decreases in age were least for nonhydrolyzable C and the aromatic HA‐A, the oldest and least active fractions. The apparent age of the humin and clay‐associated HA‐B decreased much more, indicating their greater involvement in short‐term cycling. A second clayey Haploboroll soil (Melfort) was studied by chemical fractionation and separation into size fractions after ultrasonic dispersion. The HA‐A and coarse clay‐associated organic C were oldest, with a much younger date for fine‐clay‐associated organic C. Fulvic acids purified by dialysis to eliminate materials less than 2000 molecular weight had an old date of 1140 ± 35 yr. Size fractionation of two other Boroll soils indicated young radiocarbon ages (radiocarbon enrichment) of fine clay‐associated organic C. These findings are discussed in terms of the cycling of organic matter and nutrients. Particular attention is given to clay‐humus interactions and their importance in protecting otherwise labile humic materials to provide a substantial pool of moderately available nutrients.
Effectiveness of Phosphoroamides for Retardation of Urea Hydrolysis in Soils
Authors: Martens D. A. , Bremner J. M.
Published: July 2010

The effectiveness of two phosphorodiamides (phosphorodiamidic acid, phenylphosphorodiamidate) and 10 phosphorotriamides [(N‐phenylphosphoric triamide, N‐(4‐nitrophenyl)phosphoric triamide, N‐(diaminophosphinyl)benzamide, 4‐cyano‐N‐(diaminophosphinyl)benzamide, N‐(3‐trifluoromethylphenyl)phosphoric triamide, N‐(diaminophosphinyl)‐3‐pyridinecarboxamide, 4‐chloro‐N‐(diaminophosphinyl)benzamide, 4‐fluoro‐N‐(diaminophosphinyl)benzamide, N‐(diaminophosphinyl)benzeneacetamide, and phosphoric triamide] for retardation of urea hydrolysis in soils was studied by determining the effects of 10 µg g−1 soil of each compound on the amounts of urea hydrolyzed when soils treated with urea were incubated at 20°C for 3, 7, and 14 d. The soils used were selected to obtain a wide range in properties, and the effects of the 12 phosphoroamides studied were compared with those of five compounds known to be among the most effective of the compounds thus far proposed for retardation of urea hydrolysis in soils (hydroquinone, catechol, 1,4‐benzoquinone, 2,5 dichloro‐1,4‐benzoquinone, and phenylmercuric acetate). The data obtained showed that most of the phosphoroamides studied were as effective as the compounds used in this comparison and that phenylphosphorodiamidate was considerably more effective than all other compounds studied.
Effects of Nitrogen Fertilization on Manganese Concentration and Yield of Barley and Oats
Authors: Petrie S. E. , Jackson T. L.
Published: July 2010

Response of barley (Hordeum vulgare L.) and oats (Avena sativa L.) to band application of N sources with and without Mn and the effects of band vs. broadcast application of fertilizers on the Mn concentration in leaves and yield of barley and oats were studied in the field in 1978, 1979, and 1980 on Lower Klamath Lake where Mn deficiency of oats had been observed in previous years. Experiments were established on a Tulana silt loam variant (medial, nonacid, mesic, Mollic, Andequepts). The pH of the soils ranged from 7.6 to 8.3 and the organic matter content was between 17 and 19%. Nitrogen was applied at 0, 22, or 45 kg N/ha as (NH4)2SO4, NH4Cl, urea, and various urea‐phosphate (UP) formulations. Manganese was applied at 0 or 5.6 kg Mn/ha as MnSO4. All treatments received P at 19 kg P/ha as Ca(H2PO4)2 or 25 kg P/ha in the UP fertilizers, and Cu as CuSO4 at 2.2 kg Cu/ha in 1978 and 5.6 kg Cu/ha in 1979 and 1980. ‘Cayuse’ oats and ‘Steptoe’ barley were planted at 110 kg/ha. Band application with the seed of 22 or 45 kg N/ha as (NH4)2SO4 or NH4Cl significantly increased both barley and oat leaf Mn concentrations and yields all 3 yr. Leaf Mn concentrations and yields were not increased by urea fertilization. When Mn was applied with the N fertilizer, leaf Mn concentrations and yields were similar regardless of N source. Broadcast application of fertilizers did not increase leaf Mn concentration or yield. The UP materials were intermediate in effectiveness between urea and (NH4)2SO4.
Toposequence of Oxisols from the Central Plateau of Brazil
Authors: Curi N. , Franzmeier D. P.
Published: July 2010

Landscape position is a critical factor influencing many co‐varying soil properties even in highly weathered soils that tend to have a high degree of homogeneity. The objective of this study was to learn how the position of a soil in a toposequence influences soil color, mineralogy, and some chemical and physical properties.

In a toposequence of Oxisols developed from basalt in the Central Plateau of Brazil (Goias State), moist soil color changed from dark reddish brown (2.5YR 3/4) in upper slope positions to dark yellowish brown (10YR 4/4) in lower slope positions and the following trends were observed: hematite content decreased and goethite content increased, the amount of Al substitution in the goethite structure increased, gibbsite content decreased and kaolinite content increased, and magnetic suceptibility and maghemite content of fine clay decreased. Also, the yellower soils down slope adsorbed more P and desorbed less P than the redder soils upslope, possibly because the yellower soils contain more goethite, which was found to have a smaller crystallite size and more DCB‐extractable Al than hematite. Soil color is a reliable indicator of iron oxide mineralogy which reflects the genesis of the soil and influences properties that affect plant growth. Thus, color should be used at a relatively high categorical level in soil classification systems to define classes of Latosols and Oxisols.
Characterization and Evaluation of Agricultural Benchmark Soils from Sevilla, Spain
Authors: de la Rosa D. , Mudarra J. L. , Romero R. , Martin‐Aranda J.
Published: July 2010

In Sevilla Province, southwestern Spain, benchmark soils of eight agricultural areas were defined using traditional soil pedon concepts of soil survey. The characterization emphasized morphological, chemical, and physical analyses. These eight representative soils were classified as follows: Rojo Aljarafe (Typic Rhodoxeralf), Tierranegra Campo (Typic Pelloxerert), Salino Marismas (Vertic Fluvaquent), Franco Vega (Typic Xerofluvent), Arena Terrazas (Aquic Haploxeralf), Almagra Alcores (Calcic Haploxeralf), Bujeo Campiña (Typic Chromoxerert), and Albariza Estepa (Entic Haploxeroll). By application of a computer‐based soil evaluation system developed with information from a representative zone, predicted yields were calculated for wheat (Triticum aestivum L.), field corn (Zea mays L.), and cotton (Gossypium hirsutum L.) for the selected benchmark soils. Productivity information was transferred from the representative zone to the eight agricultural areas within Sevilla Province. Soils were ranked in the following order according to predicted yields for the three crops: Bujeo Campiña > Tierranegra Campo > Franco Vega > Salino Marismas > Rojo Aljarafe > Almagra Alcores > Albariza Estepa > Arena Terrazas.
Formation of Aluminum‐Substituted Goethite in Seasonally Waterlogged Rice Soils
Authors: Karim Zahurul
Published: July 2010

Three soils (Aeric Fluvaquentic Haplaquepts, Fluvaquentic Haplaquepts, and Rhodic Paleudults) were collected from three different typical paddy fields in Bangladesh. Goethite was the only crystalline hydrous iron oxide identified by X‐ray diffraction, ranging in amount from approximately 4.78 to 12.05 mg g−1 of soil. Aluminum substitution for iron in the soil goethites ranged from 5.38 to 12.69 mole %, the largest amount being in Fluvaquentic Haplaquepts. A probable process of formation of the soil goethite is discussed. Aluminum‐substituted goethite was synthesized in simulated rice paddy conditions by the oxidation of Fe(II) solution in the presence of Si and Al. Synthetic goethites contained 3.8 to 6.4 mole % Al in their structures.
Evaluation of Aluminum‐Smectite Stability Equilibria in Naturally Acid Scoils
Authors: Karathanasis A.D. , Hajek B. F.
Published: July 2010

Stability characteristics of six Al‐smectites in naturally acid (pH < 5.0) montmorillonitic soils were determined by using structural ionic constituents and in situ soil solution compositions. Approximate solubility products (pk) for each smectite were calculated from δG0t values of hydroxide counterparts of cation structural components. Calculated ion‐activity products (pQ) of soil solutions were approximately equal (within the range of analytical uncertainties) to extimated pks of smectites in three of six soils. The other three solutions were either supersaturated (C horizon) or undersaturated (Bt horizons) relative to smectite. Solutions obtained from C horizons were supersaturated with respect to amorphous silica due to dissolution of biogenic opal and albite. In these borizons, where large quantities of smectite have been preserved, smectite stability appeared to be enhanced by high solution levels of Si and Mg. Low ratios of solution Si/Al in A and B horizons, where not compensated by relatively high pH, promoted weathering of smectite to kaolinite. Standard free energies of formation (δGot for Al‐smectites, computed from estimated pk values, ranged from −10 161 ± 1021 to −10 345 ± 1040 kJ/mol. The highest δof values were encountered in smectites with the most structural OH‐.
Influence of Mine Tailing Particle Density on Pipette Procedures
Authors: Shetron S. G. , Trettin C. C.
Published: July 2010

Water displacement and pycnometer determined particle densities were calculated for a variety of mine mill waste materials. Generally, both procedures were in agreement with each other. However, water displacement particle densities were slightly less than pycnometer determined particle densities. Particle densities for several kinds of mine mill wastes range from 2.51 to 3.77 Mg m−3. When compared to their mineralogical species composition, particle density values reflected the specific gravity of the dominant mineral found in the mine wastes. As a result of the range in particle densities, time and depth sampling for pipette determined 20 µm and 2 µm size fractions were adjusted to compensate for the variability in mine waste particle densities.
Determination of Ionic Activities in Soil Solutions and Suspensions: Principal Limitations
Authors: Amacher M. C.
Published: July 2010

A review of the theoretical and experimental limitations of the measurement and calculation of ionic activities in soil solutions and suspensions was conducted. Ion‐selective electrode methods, ion speciation models, and metal ion‐chelate equilibria methods were reviewed. The lack of sensitivity, the presence of numerous interferences, and the existence of liquid junction potentials can severely limit ion‐selective electrode methods. The completeness of the ion speciation model and the reliability of the analytical data and the species formation constants greatly affect the quality of the results of this approach. The failure of the chelate and trace metal ions to reach equilibrium with a specific solid phase in the soil in a reasonable time period limits the metal ion‐chelate equilibria methods. Further work is needed to identify and overcome limitations in the determination of ionic activities in soil solutions and suspensions.
Prediction of Ion Activities in Soil Solutions: Computer Equilibrium Modeling
Authors: Baham John
Published: July 2010

Modeling of a multicomponent natural water system, such as the soil solution, utilizing classical ion association equilibria, allows one to estimate thermodynamic activities for many chemical species for which direct measurement is either not practical or impossible. A number of computer‐based equilibrium models are presently available for use in soil chemical research. The thermodynamic formalism employed by all of the models is very nearly identical; however, small differences in the estimation of activity coefficients and temperature correction of thermodynamic data exist between models. The sophistication of the numerical routines used to obtain solutions of the problem can also vary between models. These differences are reflected in computational efficiency, but give rise to little or no difference in th epredicted activities.

The selection, extent, and flexibility of the user‐supplied thermodynamic data file (TDF) is the major difference between geochemical models. After the total concentrations of metals and ligands, temperature, and pressure are specified, equilibrium constants for all complexes allowed to form are retrieved from the TDF. The selection of a TDF, therefore, specifies the equilibrium problem to be solved. The compilation of a critically reviewed TDF for use in soil chemistry is the most important component in the attempt to model soil solution geochemistry at equilibrium.

Some recent uses of geochemical modeling of the rhizosphere have been selected from the literature to demonstrate the utility of this approach.
Influence of Long‐Term Tillage and Crop Rotation Combinations on Soil Enzyme Activities
Authors: Dick W. A.
Published: July 2010

The effects of long‐term no‐tillage practices on the activity of enzymes in soil are not well understood. Soil profile (0–30 cm) samples were collected from plots where various tillage and rotation combinations had been continuously applied to a Hoytville silty clay loam (Mollic Ochraqualfs) soil (18 yr) and a Wooster silt loam (Typic Fragiudalfs) soil (19 yr). With the exception of alkaline phosphatase activity in the Wooster soil, results indicate that the activities of acid phosphatase, alkaline phosphatase, arylsulfatase, invertase, amidase, and urease in the 0 to 7.5‐cm profile increment were significantly (P < 0.05) higher where no‐tillage (NT) compared to conventional tillage (CT) practices had been maintained. Below the 7.5‐cm depth, the effect of tillage on the enzyme activities varied with the soil and/or the enzyme studied. Enzyme activities in the 0 to 7.5‐cm profile increment in the NT plots were significantly affected by rotation with the highest activities observed for the corn (Zea mays L.)‐oats (Avena sativa L.)‐alfalfa (Medicago sativa L.) rotation and the lowest for the corn‐soybeans (Glycine max L.) rotation. The results observed for the effect of tillage and rotation on soil enzyme activities were strongly correlated with organic C concentrations. From 78 to 92% of the total variation in enzyme activities observed for the Wooster soil profile could be accounted for by organic C concentrations. For the Hoytville soil from 28 to 83% of the variation could be accounted for by organic C concentrations. Including pH in a multiple regression model increased the total variation of the alkaline phosphatase, arylsulfatase, and urease activities which could be explained in the Hoytville profile from 28 to 1%, 28 to 57%, and 41 to 59%, respectively.