bluuebunny/crossref_metadata_2025_split huggingface dataset:
Production of Thiocysteine (Sulfide) in Cysteine Amended Soils
Authors: Morra M. J. , Dick W. A. 
Published: July 2010

AbstractLittle information is currently available concerning the formation in soils of hydrogen sulfide, an important intermediate in the cycling of sulfur within the earth's environment. Studies were performed in which 3 g of air‐dry soil were treated with 10 mM cysteine HCl (pH 6.0) and incubated for 24 h at 37°C. Results indicated that a dithio sulfur compound, thiocysteine (2‐amino‐2‐carboxyethyl hydrodisulfide), was produced. Production of thiocysteine occurs as a result of cystathionine γ‐lyase (EC 4.4.1.1) activity and the actual substrate of the enzyme is cystine, the oxidized form of cysteine. The procedure to measure thiocysteine involved a second addition of cysteine, used as a reagent, after the 24‐h incubation. Cysteine causes a nonenzymatic breakdown of thiocysteine, producing hydrogen sulfide, which was then collected in zinc acetate and determined colorimetrically. The amount of thiocysteine (sulfide) measured in the four soils studied after the 24‐h incubation period ranged from 7.8 to 16 mg kg−1 soil. The biological nature of the reaction was demonstrated when the production of thiocysteine (sulfide) was inhibited when soils were treated with 0.1 mL of 0.5 M sodium azide or steam sterilized for 1 h at 121°C. Complete inhibition also occurred upon the addition of 0.2 mL of toluene or formaldehyde. Addition of 10 mM propargylglycine (16.7 µmol g soil−1), a specific inhibitor of cystathionine γ‐lyase, reduced thiocysteine (sulfide) production by 58 to 91%. The formation of hydrogen sulfide as a result of the combination of cystathionine γ‐lyase activity and the nonenzymatic degradation of thiocysteine to produce hydrogen sulfide may represent an important pathway in the cycling of sulfur through the soil system.
Phosphorus Cycling in Unfertilized and Fertilized Agricultural Soils
Authors: Sharpley A. N. 
Published: July 2010

AbstractSurface soil samples (0–50 mm depth) were taken from several grassed and cropped, unfertilized and P‐fertilized soils at monthly intervals for 2 yr, to investigate seasonal variations in amounts and forms of P and relative importance of inorganic and organic P as sources of plant available P. Although no consistent seasonal variation in inorganic P content was observed for the unfertilized soils, amounts increased after fertilizer P addition. Organic P content was higher in the winter (Oct.–Mar.) than spring months (May–June) for both unfertilized and fertilized soils. Consequently, mineralization of organic P during the growing season, which contributed similar amounts of P (20–74 kg P ha−1) as added in fertilizer (13–100 kgP ha−1), was not inhibited by fertilizer P addition. Organic P variation was mainly due to changes in moderately labile organic P, with more labile and resistant pools remaining constant. The most labile organic P pool was maintained at a constant level possibly by mineralization and formation from moderately labile organic P. Little change in P content of unfertilized subsurface soil (50–150 mm) was observed, although inorganic and available P contents increased slightly following fertilizer P application. Available P (Bray‐I P) was closely correlated with organic P in unfertilized soils and with inorganic P in fertilized soils. Slopes of these relationships were related to phosphatase enzyme activity and P sorption maximum for organic and inorganic P, respectively. The importance of organic P as a source of available P in both unfertilized and fertilized soils was demonstrated. The need to include organic P in soil‐P fertility tests, especially with the increasing use of reduced‐tillage practices, is emphasized.
Soil Bulk Density Recovery on Compacted Skid Trails in Central Idaho
Authors: Froehlich H. A. , Miles D. W. R. , Robbins R. W. 
Published: July 2010

AbstractIn west‐central Idaho, the bulk densities of soil in major skid trails were compared with those of adjacent undisturbed soil in order to determine rates of recovery. Five study sites on each of two soils, one formed from granitic material (mixed, frigid, Typic Xeropsamments) and the other from volcanic material (fine‐loamy, mixed Dystric Cryochrepts), provided two chronosequences (five 5‐yr periods) of time since logging. Bulk density was measured at 5.1‐, 15.2‐, and 30.5‐cm depths. The percent increase in bulk density of soil on a skid trail over that on an adjacent undisturbed area was greater in the volcanic than the granitic soil, but recovery rates (slope of the regression line) for the two soils were not significantly different. Linear regression models showed a significant (p < 0.05) recovery trend for all depths except the 15.2‐cm depth on the volcanic site. Except for the surface 5.1 cm of the granitic soil, none of the bulk densities in skid trails had returned to the undisturbed values in the 23 yr since logging.
Soil and Stand Characteristics and Elemental Concentration of Tall Shrub Twigs
Authors: Kernik L. K. , Grigal D. F. 
Published: July 2010

AbstractWoody twigs (⩽ 3 mm diam) of tall shrubs were collected during winter in 18 forest stands in the Superior National Forest of northeastern Minnesota. Elemental concentration of the twigs was examined with respect to variation due to site characteristics including vegetation type, soil properties, management history, and stand age. The stands ranged from young Pinus resinosa Ait. plantations to natural pine and hardwood stands to lowland conifer stands on organic soils. Levels of most elements in twigs were not significantly related to soil properties. Twigs from stands on organic soils were higher in Mg and Zn concentration than were twigs from the stands on mineral soils, and Ca was lower in twigs on soils with coarser texture. Although significant differences were found in elemental concentrations of Ca, Mg, Zn, Fe, and Mn among stands classified by vegetation type, these differences were small among the upland stands. There were no differences in concentration related to differences in site preparation; K, Ca, and Zn varied with method of release of plantations. Stand age did not appear to have a major influence on elemental concentration, but twigs in younger stands had higher K and lower Fe concentrations than did twigs in older stands. Two consistent trends emerged from the analysis, those of differences in Ca and Zn associated with vegetation and soil, and of differences in K associated with stand development. The relatively small size of the study area, 185 km2, may have led to few differences.
Aging of Partially Neutralized Aluminum Solutions of Sodium Hydroxide/Aluminum Molar Ratio = 2.2
Authors: Tsai Ping Ping , Hsu Pa Ho 
Published: July 2010

AbstractAluminum hydroxide developed in all solutions in this study (0.02 M in AlCl3, NaOH/Al molar ratio in preparation = 2.2) after prolonged aging. The induction period and the rate of aluminum hydroxide [Al(OH)3] crystallization varied greatly among solutions, however. The Al ions in the freshly prepared solutions were predominantly OH‐Al polymers that reacted with ferron rapidly and yielded tetrahedral crystals of basic aluminum sulfate, of composition Na0.08Al(OH)2.46(SO4)0.31(H2O)x, upon the addition of sodium sulfate. During aging, the initial OH‐Al polymers gradually converted to either more stable polymers of similar basicity or Al(OH)3 precipitate. The conversion of metastable to stable polymers probably proceeded through internal structural rearrangement, but the development of Al(OH)3 proceeded through redissolution and crystallization. The variation in the induction period was attributed to the initial number of nuclei present as a result of localized high alkalinity during solution preparation. The variation in the rate of Al(OH)3 crystallization was attributed to the distribution of metastable and stable OH‐Al polymers at the time of crystallization. The crystallization of Al(OH)3 was faster from metastable polymers than from stable ones.
Collecting and Testing Barrel Sized Undisturbed Soil Monoliths
Authors: Brown K. W. , Thomas J. C. , Aurelius M. W. 
Published: July 2010

AbstractA procedure was developed for encasing undisturbed soil monoliths in a 0.57‐m diam, 0.85‐m deep steel casing. The casings are available from barrel manufacturing companies, and other equipment is easily made or leased locally. This equipment includes a specially designed frame that holds the thin walled casings during filling. The technique has been successfully used in soils with textures ranging from sandy loam to clay. Bromide breakthrough curves were symmetric for the majority of the encased monoliths. This suggests that side wall boundary flow contributes little to solute mobility through the encased soils. This simple test will allow the user to discard defective monoliths.
Spatial Variability of Field‐measured Soil‐water Characteristics
Authors: Greminger P. J. , Sud Y. K. , Nielsen D. R. 
Published: July 2010

AbstractOne hundred neutron access pipes were placed 1‐m apart along a 100‐m transect together with tensiometers located at soil depths of 0.3 and 0.6 m. After ponding the experimental site with water for at least 4 d, the site was allowed to drain and covered with 0.3 m of straw to reduce evaporation. Measurements of soil‐water content θ and soil‐water pressure head (h) initially made at 2‐h intervals were made less frequently as redistribution proceeded. The (θ,h|t)—observations were fitted to the five‐parameter van Genuchten model. Spatial autocorrelations and cross‐correlations of θ, h, and percentage sand manifested significant coefficients for distances as great as 10 m. The practical significance of this research is that it addresses the impact of the separation distance between a tensiometer and a neutron meter access tube on the precision of the measured soil‐water characteristic curve. Greater precision is obtained for separation distances < 10 m.
Colonization of Winter Wheat Roots by Inhibitory Rhizobacteria
Authors: Fredrickson J. K. , Elliott L. F. 
Published: July 2010

AbstractColonization of the winter wheat (Triticum aestivum L.) rhizoplane by root‐inhibiting nonfluorescent pseudomonads was investigated in laboratory and greenhouse studies with genetically marked (rifampicin resistant) isolates. Colonization was similar at root zone temperatures of 5, 10, and 15°C but was dependent on soil type, with higher populations occurring in the soil with lower organic matter and microbial biomass. Rhizoplane populations of test strains were over tenfold higher on roots in pasteurized soil than in non‐pasteurized soil or vermiculite. Deleterious effects on growth of winter wheat were related to the extent of rhizoplane colonization by the bacteria; approximately 106 colony forming units (cfu) mg−1 root were required for significant inhibition of root growth. The shoots and roots of winter wheat were significantly shorter on plants inoculated with the inhibitory bacteria in pasteurized or methyl bromide fumigated soil as well as in nonpasteurized Ritzville soil (Calciorthidic Haploxerolls). The difference in early stages of plant growth, especially shoots, between bacterized (seed treated with antibiotic‐resistant inhibitory bacteria) and nonbacterized winter wheat increased with time. The antibiotic‐resistant bacteria maintained a high population on the roots during this period. The bacteria were observed to extensively colonize winter wheat roots (rhizobacteria) and are considered a potential constraint on winter wheat yield in the Pacific Northwest.
Sulfate Retention by an Acid BE Horizon of an Ultisol
Authors: Hue N. V. , Adams Fred , Evans C. E. 
Published: July 2010

AbstractMany apparently conflicting reports on sulfate (SO2‐4) retention by soils suggest that a single, inclusive mechanism may not be adequate in explaining SO2‐4‐soil reactions and that additional experimentation is needed for different soils. An acid Benndale (Typic Paleudults) BE horizon, predominantly kaolinite and gibbsite in the clay fraction, was initially treated with either five lime rates or five gypsum rates. After 14‐d of incubation at field capacity, previously limed soils were amended with gypsum, and previously gypsum‐treated soils were limed. All samples were again incubated moist for 14 d, after which soil solutions were displaced and their chemical compositions determined. The sequence of Ca(OH)2 and CaSO4 additions did not affect SO2‐4 retention. Furthermore, SO2‐4 retention isotherms indicated that multiple mechanisms were involved because at low pH (<5.1) an adsorption‐precipitation type mechanism dominated, while at high pH (>5.6) electrolyte adsorption was dominant. This was further supported by the decrease in the ratio of OH‐ gain to SO2‐4 retention as soil pH increased. Sulfate retention was also accompanied by an increase in total exchangeable cations. Cation increases, however, varied with pH and SO2‐4 rates. The combined increases in OH‐ and exchangeable cations, particularly at low pH and high SO2‐4 rates, are inexplicable with current SO2‐4‐soil reaction models.
Fertilizer Nitrogen and Nitrogen‐15 in Three Warm‐season Grasses Grown on a Florida Spodosol
Authors: Impithuksa V. , Blue W. G. 
Published: July 2010

AbstractRecovery of fertilizer N in plant tops is generally considered to be about 50% of that applied. With increasing cost of fertilizer N and concern for environmental contamination by N lost from soilplant systems, it is important that absorption of fertilizer N be maximized. Introduced warm‐season grasses have different morphological characteristics, and they may differentially absorb N. To investigate this possibility, a field study with enriched 15NH415NO3 was superimposed in March 1977 on a nontracer N experiment with three warm‐season grasses—Ona stargrass (Cynodon nlemfuensis Vanderyst), Transvala digitgrass (Digitaria decumbens Stent), and Pensacola bahiagrass (Paspalum notatum Flugge)— on EauGallie fine sand (sandy, siliceous, hyperthermic Alfic Haplaquods) at the Agricultural Research Center, Ona, FL. Two N rates (100 and 200 kg ha−1) were the subplots, and three times of 15N‐labeled fertilizer N application were the sub‐subplots. In 1977, quantities of total and 15N‐labeled fertilizer N in forages did not differ among grass species, but they were largest in the Pensacola bahiagrass stolon‐root mass. Recovery of fertilizer N in forage as averages of the two N rates and the three times of 15N‐labeled fertilizer application was 35, 40, and 35% of that applied to Ona stargrass, Transvala digitgrass, and Pensacola bahiagrass, respectively; 13, 9, and 20% of that applied was in the stolon‐root masses; and 22, 17, and 20% of that applied was in the soil presumably in organic form, since it was neither water‐soluble nor exchangeable. Approximately 50% of the N in forages came from the 15N‐labeled fertilizer and 50% from nonfertilizer sources, Recoveries of fertilizer N in soil‐plant systems were 70, 66, and 75% of that applied to Ona stargrass, Transvala digitgrass, and Pensacola bahiagrass, respectively. The sums of fertilizer N in forages from 1977 and 1978, and in the stolon‐root masses and soil at the end of 1978, did not differ significantly from amounts accounted for at the end of 1977. Results from the study indicated (i) essentially equal quantities of labeled N in the three soil‐warm season grass systems, (ii) relatively large retention of labeled N in these sandy soils, and (iii) a large amount of nonfertilizer N in forages in 1977, the year of 15N‐labeled fertilizer application.
Availability and Transformation of Applied Phosphorus In Calcareous Lebanese Soils
Authors: Ryan J. , Hasan H. M. , Baasiri M. , Tabbara H. S. 
Published: July 2010

AbstractThough the initial reactions of P in soils are important with respect to plant growth and efficient fertilizer use, the reactions that occur with time have received less research attention, and may have even more important implications for these aspects. In order to monitor changes in applied P after fertilization, six calcareous soils were incubated up to 200 d with P solutions and periodically extracted with NaHCO3, and inorganically fractioned. Soil batches were equilibrated with P solutions ranging from 0 to 40 mg P L−1 for adsorption isotherm data after 0, 60, and 200‐d incubation. Desorption curves were obtained by water extraction for eight consecutive days. Extractable P values declined rapidly within the first day, and uniformly thereafter. The amounts of P retained against NaHCO3 extraction were closely related to citrate‐dithionite‐bicarbonate (CDB)‐Fe. With the longer incubation period, generally less P was released in the water extraction. Similarly, desorbed P was inversely related to CDB‐Fe. While P additions mainly enriched the NH4Cl‐ and NaOH‐P fractions, the amounts recovered decreased with time. Increasing prior soil‐P contact time also caused a shift in the adsorption isotherms, reflecting changes in retained P and the soils' retention capacity. Thus, free Fe oxides may modify longer‐term P reactions and residual P availability in CaCO3‐rich soils.
Measurement of Shear Strength and Bulk Density of Soil Aggregates
Authors: Benjamin J. G. , Cruse R. M. 
Published: July 2010

AbstractA method was developed to measure soil aggregate shear strength and bulk density at soil water matric potentials <0. Strength measurements were made with the Swedish fall‐cone penetrometer, and bulk density measurements were made by gamma‐ray attenuation. The method allowed both density and strength measurement on the same aggregate. Tests were conducted at soil water matric potentials of −0.2, −1.1, and −4.0 kPa. As the matric potential decreased, the shear strength of the soil aggregates increased. The method described by this paper is an improvement on the standard wet‐sieve technique for determination of aggregate stability as follows: (i) it allows the measurement of aggregate strength at matric potentials <0, (ii) the strength measurement is in units of stress, and (iii) the aggregate density as well as aggregate strength can be measured on each sample. The disadvantage is that aggregates with diameters ≥ 2 cm are required for the measurement.
Statistical Analysis of Sorghum Yield: A Stochastic Approach
Authors: Morkoc F. , Biggar J. W. , Millar R. J. , Nielsen D. R. 
Published: July 2010

AbstractThe spatial variability of the yield of a sorghum (Sorghum vulgare Pers.) crop irrigated by a two line source sprinkler system is analyzed. This system, with two different qualities of irrigation water, produced a uniform water but varying salt application between the irrigation lines. On the outside of the irrigation lines both the amount of applied water and salt varied. Maximum yield was obtained around the low salt line and the yield decreased from the low (EC = 1.50 dS m−1) to high (EC = 4.02 dS m−1) salt line. On the outside of the irrigation lines the sorghum yield decreased approximately linearly with distance from each sprinkler line. The sorghum was harvested with 1‐m sampling intervals along five 45‐m transects normal to the irrigation lines. Sample autocorrelation function (SACF) of the mean yield showed high correlation values at the first two lags and a slow decay thereafter, indicating the nonstationary behavior caused by the controlled water application. A fourth‐order polynomial removed the deterministic component of the yield. The sample autocorrelation function of the residuals showed spatial structure with a significant peak at lag 1 and indicated that the stationarity condition is achieved. Further analysis of the residuals using the sample partial autocorrelation function (SPACF) revealed significant peaks at lags 1 and 2. The behavior of SACF and SPACF indicated that the spatial structure of residuals related to the effect of soil salinity variation on the sorghum yield is well described by a second order autoregressive process with a white noise (identically and independently distributed with mean (x) zero and variance σ2).
Ethylene Biosynthesis in Soil: I. Method of Assay in Conversion of 1‐aminocyclopropane‐1‐carboxylic Acid to Ethylene
Authors: Frankenberger W. T. , Phelan Patrick J. 
Published: July 2010

AbstractEthylene (C2H4) is a common biologically active secondary metabolite produced by soil microorganisms which can have a tremendous potential impact on crop yield. Methionine (MET) has been shown to be the major substrate for C2H4 biosynthesis in higher plants and soil microorganisms. Although 1‐aminocyclopropane‐1‐carboxylic acid (ACC) is an intermediate in the conversion of MET to C2H4 in plant tissues, the immediate precursor of C2H4 and its biosynthetic pathway in soils has yet to be established. The primary objective of this study is to develop a method of assay to characterize the microbial conversion of ACC to C2H4 in soil. Results showed that the rate of C2H4 released from soil was enhanced with increasing pH (up to pH 9.0). The reaction rates of this transformation approached zero‐order kinetics when 9.9 mM ACC was added to soils. Under standard conditions, the accumulation of C2H4 was linear with time of incubation for at least 7 d. Maximum reaction rates in the conversion of ACC to C2H4 were observed at 50°C with enzyme denaturation occurring at 55°C. ACC derived‐C2H4 production in soils was enhanced under highly oxidized conditions and severely inhibited under anaerobiosis. Among various pretreatments that affected the conversion of ACC to C2H4, toluene, CoCl, and oscillation enhanced C2H4 biosynthesis, whereas, DMSO, formaldehyde, EDTA, 2‐mercaptoethanol, 2,4‐dinitrophenol, NaF, KCN, KNO2, and KNO3 inhibited this reaction.
Specific Adsorption of Lithium, Sodium, Potassium, and Strontium to Montmorillonite: Observations and Predictions
Authors: Nir S. , Hirsch D. , Navrot J. , Banin A. 
Published: July 2010

AbstractThe adsorption of Li, Na, K, Cs, and Sr to montmorillonite is studied within the framework of a model that accounts for specific binding as well as adsorption in the double layer region. Variations in solution concentrations of cations due to adsorption are explicitly considered. The experimental data include adsorption measurements in binary and ternary systems of cations as well as adsorption data taken from the literature. Solution and adsorbed concentrations of cations are well simulated and predicted by the calculations for a wide range of variations of cation ratios, ionic strengths, and clay concentrations. The values determined for the binding coefficients are: KLi = 0.6 M−1, KNa = 1 M−1, KK = 2 M−1, KCs = 200 M−1.
Specific and Nonspecific Cation Adsorption to Clays: Solution Concentrations and Surface Potentials
Authors: Nir Shlomo 
Published: July 2010

AbstractA model for cation adsorption to negatively charged surfaces is developed by taking into account specific cation binding to the surface sites and adsorption in the double layer region. Equations are given for any combination of mono and divalent cations in solution and for one type of binding site. Variations in solution concentrations of cations due to adsorption are explicitly included in the model in the framework of an iterative procedure. The results indicate that a Langmuir type of adsorption isotherm may represent the data over a certain range of cation concentrations. When a certain cation is present in such small concentrations that it does not affect the surface potential, then an increase in its concentration results in a proportional increase in its adsorbed amount. For a wide range of concentrations the amount of cation adsorbed appears to be independent of its concentration in solution. However, the adsorbed amounts are very sensitive to cation competition. An increase in the concentration of surface sites results in as reduction in the fractional binding per sits. A source of difference between sorption and desorption of cations is explained.