bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effect of Hydroxy‐Al and Hydroxy‐Fe Polymers on Montmorillonite Particle Size
Authors: Frenkel H. , Shainberg I. 
Published: July 2010

AbstractPotentiometric and photometric titration of Al‐ and Fe‐montmorillonite suspensions with NaOH and Na2B4O7 are presented. Hydroxy‐Al polymers formed during the neutralization reaction apparently acted as cementing agents and prevented the dispersion of the structure. When an excess of NaOH is added, the hydroxy‐Al polymers disintegrate and complete dispersion of the Na‐montmorillonite takes place. No aluminates are formed upon neutralization of Al‐montmorillonites with Na3B4O7, and hence no dispersion takes place.Neutralization of Fe‐montmorillonite suspension with NaOH and Na2B4O7 resulted in gradual breakdown of the Fe‐montmorillonite particles. Hydroxy‐Fe polymers were not as effective in preventing the dispersion of the particles by adsorbed Na as hydroxy‐Al polymers.
Improved Growth of Onion and Bell Pepper in Saline Soils by Two Vesicular‐Arbuscular Mycorrhizal Fungi
Authors: Hirrel Marc C. , Gerdemann J. W. 
Published: July 2010

AbstractThe effect of 5 levels of salinity on the growth of onions (Allium cepa L. cv. ‘Early Yellow Globe’) and bell peppers (Capsicum annuum L. cv. ‘California Wonder’) inoculated with the mycorrhizal fungi, Glomus fasciculatus or Gigaspora margarita, was compared to uninoculated nonmycorrhizal controls. In soils with saturation extracts (ECe) of 1, 3, 4, 6, and 12 mmho/cm, mycorrhizal plants consistently outweighed the controls. Plants inoculated with Gl. fasciculatus, also, grew larger than those inoculated with Gi. margarita. In both onion and bell pepper, the effect of salinity on decreasing percent fresh weight was greatest in the nonmycorrhizal controls. Also, in bell pepper, decreases in percent fresh weights were less with plants infected by Gl. fasciculatus than with those infected by Gi. margarita. Thus, plants infected with mycorrhizal fungi may be more salt tolerant than uninfected nonmycorrhizal plants.
Use of Streptomycin for Suppressing Blue‐Green Algal Nitrogenase Activity During the Assessment of Nitrogenase Activity in the Rice Rhizosphere
Authors: Habte M. , Alexander M. 
Published: July 2010

AbstractThe addition of streptomycin at concentrations as low as 5 µg/ml to cell suspensions of blue‐green algae (cyanobacteria) or to blooms developing in a flooded soil caused greater than a 99% reduction in the nitrogenase activity of the cells in 24 to 72 hours. The antibiotic was not toxic to rice (Oryza sativa L.) at 250 µg/ml, and the nitrogenase activity of heterotrophs developing in puddled soils previously planted to rice was not significantly affected by concentrations as high as 50 µg/ml. The nitrogenase activity of heterotrophs developing in flooded or puddled soils not previously planted to rice was sensitive to concentrations of the antibiotic exceeding 10 µg/ml. In experiments involving the assessment of nitrogenase activity in the rice rhizosphere, streptomycin at concentrations as low as 2.5 to 5.0 µg/ml effectively curtailed the interference from blue‐green algal activity.
Effect of Gambel Oak on Forest Floor and Soil of a Ponderosa Pine Forest
Authors: Lefevre R. E. , Klemmedson J. O. 
Published: July 2010

AbstractA study was conducted on the Beaver Creek Experimental Watersheds south of Flagstaff, Arizona to determine the effect of Gambel oak (Quercus gambelii Nutt.) in ponderosa pine (Pinus ponderosa Laws.) forests on some physical, N, and C properties of the forest floor and upper soil layers. Samples of L, F, and H layers of the forest floor and of the 0‐ to 5‐, 5‐ to 15‐, and 15‐ to 30‐cm soil layers were collected from randomly chosen replicated plots in five stand types representing a range in oak basal area from 0 to 75% of total basal area.Weight, density, and thickness of L, F, and H layers responded differentially to change in oak basal area. These responses are attributed to structural features and decay characteristics of pine and oak leaf litter. With increasing oak in the stand, percentage N increased in all layers of the forest floor and in the upper 15 cm of soil. Amount of N increased in the H layer, the forest floor as a whole, and in the 0‐ to 5‐cm layer of soil. With increasing oak, percentage C remained the same in the forest floor, but increased significantly in the upper 15 cm of soil. Carbon/nitrogen ratio declined in L and F layers with increasing oak. Increased percentage C in 0‐ to 5‐ and 5‐ to 15‐cm soil layers with increased oak basal area coincided with decreased weight of these layers.
A Rapid in Situ Method of Extracting Water from Tidal Marsh Soils
Authors: Eleuterius Lionel N. 
Published: July 2010

AbstractAn inexpensive, easily constructed apparatus was developed to extract interstitial soil water from the soils of tidal marshes. Major components of the apparatus are a polypropylene bottle, polyethylene tubing, neoprene stopper, and plankton netting. The sampler can be easily placed at varying depths in the soil and left permanently in the field. The system can also be used for fertilizer and dye injection studies. Because of its simplicity, durability, and versatility this vacuum‐pressure lysimeter is well suited for use in the marsh.
Thermodynamic Study of Calcium‐Sodium and Calcium‐Magnesium Exchange in Calcareous Soils
Authors: Van Bladel R. , Gheyi H. R. 
Published: July 2010

AbstractMontmorillonite calcareous soils and a Moroccan montmorillonite clay in the Ca form were used to determine the effect of temperature and varying ionic strength on Ca‐Na and Ca‐Mg exchange. Ca was selectively adsorbed over Na and, to a lesser extent, over Mg. Affinity for Ca over Na or Mg ions was greatest in the calcareous soils and varied approximately in the same order as the soil organic matter content. In the Ca‐Na system, the selectivity coefficient was rather independent of ionic strength. Enthalpy and entropy changes were negative for the substitution of Ca by Na. These results indicate that the preference of Ca was probably due to the overall entropy change.The experimental results were compared to theory based on a constant selectivity coefficient. The agreement of experimental and theoretical Na or Mg loading, calculated from the composition of the soil solution, was satisfactory.
Influence of Water Potential on the Survival of Rhizobia in a Goldsboro Loamy Sand
Authors: Mahler R. L. , Wollum A. G. 
Published: July 2010

AbstractInoculation of soybeans [Glycine max (L.) Merr.] at planting in North Carolina is apparently ineffective due to unfavorable environmental conditions. Water potential has been suspected to be a primary factor in inoculation failure; however, the lack of a suitable method to artifically control or create desired water potentials in laboratory environments has prevented investigation.The objectives of this study were to (i) evaluate a technique designed to maintain soil water potentials for incubation studies, and (ii) to investigate the influence of water potential on the survival of 10 Rhizobium japonicum strains in a Goldsboro loamy sand (Aquic Paleudult). Dow Ziploc Storage Bags were employed to maintain desired water potentials while the most probable number (MPN) technique and plant infectivity tests were used to enumerate rhizobia.Water potential was found to have a profound effect on numbers of rhizobia in a Goldsboro loamy sand. Rhizobial numbers were from one to three log numbers lower under water potentials of −15 bars than at potentials near field capacity. There was usually a depression of one log number at −5 bars. In most cases the 9‐week rhizobial numbers were less at water potentials of −0.10 bar than at potentials of −0.50 and −0.33 bars. Total aerobic bacteria and aerobic sporeformer numbers also declined at both high and low water potentials. Differences in ability to tolerate low water potentials were noted between the 10 serogroups tested. In general, isolates from serogroups 110, 122, and 138 survived in much greater numbers at water potentials of −15 bars than the other seven serogroup isolates. Isolates of serogroups 24, 31, 94, and 123 were particularly vulnerable to water stress as populations at 9 weeks were more than four log numbers less than the initial populations. Field soil water potential data confirmed that −15 and −5 bar values which reduce rhizobial numbers are found to be quite common in North Carolina.
Fertilizer Zinc Efficiency in Flooded Calcareous Soils
Authors: Amer Fathi , Rezk A. I. , Khalid H. M. 
Published: July 2010

AbstractEffect of Zn sources and methods of application on rice (Oriza sativa var. Giza 159) was studied in relation to organic matter application and to N source. In addition to laboratory investigations, a pot experiment was conducted with 65Zn‐labelled soil (Vertic Torrifluvents) and two field experiments with labelled and nonlabelled Zn fertilizers.Zinc oxide (ZnO) was superior to ZnSO4 in increasing grain yield and Zn content of flooded rice and in maintaining higher Zn concentration in the soil solution. With different methods of ZnSO4 application, rice yield and Zn uptake were in the order: applied to surface water 2 weeks after transplanting ≫ mixed with soil = surface applied to soil. The corresponding percentages of plant Zn derived from fertilizer and of Zn utilization from the applied fertilizer were 11.2, 8.46, and 6.26%; and 2.9, 1.4, and 1.0%, respectively. Effectiveness of organic matter in increasing yield and Zn content was greater when applied 2 weeks before transplanting than when applied at transplanting, as it decreased soil solution Zn during the first 2 weeks of anaerobic decomposition. The organic matter induced a temporary reduction in Zn content early in the season, but a good correlation was obtained between grain yield and Y leaf Zn at the midtillering and panicle initiation stages.With combined Zn and organic matter application, urea as a N source resulted in higher yielding and Zn content than (NH4)2SO4. Specific activity measurements showed that under nonflooded conditions rice was largely dependent on the Zn labile pool, while flooded rice was able to derive Zn from an additional source. Results generally indicate that formation of sphalerite (ZnS) may play a major role in controlling Zn solubility in flooded calcareous soils.
Soil Temperature Regimes of the Central Appalachians
Authors: Carter Brian J. , Ciolkosz Edward J. 
Published: July 2010

AbstractSoil temperatures were measured for 3 years at depths of 25 and 50 cm at four sites in four areas on a north‐south transect from northern Pennsylvania to northern West Virginia. Each site was at a different elevation. The mean annual soil temperature (MAST) was estimated using: (i) an average of four readings (taken in mid‐January, April, July, and October; at all sites), (ii) an average of 12 readings (one taken each month; at each site in one area), and (iii) a mean annual air temperature (MAAT) at one site in each area. A prediction equation was derived from the seasonal readings at a 50‐cm depth (Y = 11.7 — 0.0061X1 — 0.0034X2, where relative latitude = X2 in kilometers, elevation =X2 in meters and Y = MAST in degrees centigrade). Using the prediction equation the mesic‐frigid soil temperature boundary was found to be 572 ± 125 m (1,875 ± 410 feet at Coudersport, Penn., 755 ± 78 m (2,475 ± 255 feet) at Philipsburg, Penn., 921 ± 35 m (3,020 ± 115 feet) at Kegg, Penn., and 1,088 ± 26 m (3,570 ± 85 feet) at Davis, W.V. The prediction equation indicates that the mesic‐frigid soil temperature boundary rises rapidly in elevation from north to south and there are areas of Pennsylvania, Maryland, West Virginia, and Virginia that have frigid soil temperature regimes. The data also indicates that: (i) MAST can be estimated from seasonal readings at 25 cm as well as 50 cm, (ii) MAST at 50 cm can be estimated from monthly or seasonal readings, and (iii) MAAT averaged 1.2°C below MAST.
Determining the Volume of Sampled Soil When Using the Four‐Electrode Technique
Authors: Nadler A. 
Published: July 2010

AbstractA theoretical discussion of the ratio between apparent resistivity and real resistivity of a soil layer as a function of (i) layer thickness/electrode spacing ratio; (ii) the soil layer thickness and resistivity of an underlying layer; and (iii) horizontal distance of a different medium from the current electrode is presented. Laboratory experimental work was carried out in order to study the effects the electrode spacing and current density have on the determination of the electrical conductivity of soil solution. It was found out that the depth sensed by a Wenner Configuration would be deeper than the inner electrode spacing for most field situations and especially where there are large variations in conductivity (due to salinity or water content) with depth. The laboratory calibration of the salinity probe should be done in a volume of about 2.5 liters or greater. The volume sensed by this method is greater the lower is the water content. The implications in laboratory calibration‐field measurements relationships are discussed.
Carbaryl Adsorption on Calcium‐Bentonite and Soils
Authors: Aly M. I. , Bakry N. , Kishk F. , El‐Sebae A. H. 
Published: July 2010

AbstractAdsorption of carbaryl on Ca‐bentonite, and two Egyptian soils, a Nile alluvial and a highly calcareous soil, was carried out at different temperatures. Carbaryl adsorption increased as the temperature decreases. Ca‐bentonite exhibited the highest degree of adsorption followed by the Nile alluvial soil and the calcareous soil.The calculated partial molar heat of adsorption ΔH* for bentonite, alluvial and calcareous soils were −3.8, −0.924 and −10.282 kcal/mol, respectively, indicating that adsorption may be physical in nature. The ΔG* values of the three systems were −0.570, −0.118, and −0.346 kcal/mol, respectively, indicating that the adsorption reaction was spontaneous in all cases. The adsorption data followed the Freundlich adsorption equation. The entropy values for the adsorption of carbaryl by the three adsorbents were −15.0, −36.7, and −8.0 entropy units indicating that carbaryl adsorption is favored by the alluvial soil that contains the highest organic matter content.
A Model of Zinc Movement to Single Roots in Soils
Authors: Bar‐Yosef B. , Fishman Svetlana , Talpaz H. 
Published: July 2010

AbstractThe movement of zinc in soils can be influenced by the pH of the soil and the presence of synthetic chelates or soluble organic matter capable of forming metal‐organic complexes. To understand how these complexes and pH may contribute to zinc uptake by plants, the basic processes involved in zinc transport and absorption by a single root were formulated and the resulting differential equation solved simultaneously.The model considers diffusive and convective flow of several zinc species, H+ and a chelating agent, flow of water to the root, and chemical equilibria between adsorbed and solution phase ions and between complexed and uncomplexed cations. The model assumes transient conditions with respect to water and ions and makes allowance for the adsorption isotherm and the biologically determined parameter relating flux of uptake to concentration to be concentration‐dependent.Within the range of studied cases, root permeability to ions and water is the most effective mechanism in controlling Zn uptake. Excretion of H+, and probably other means of reducing the pH near the root, are more effective in enhancing Zn uptake than excretion of complexing agents. A generalization of this conclusion is subject to improved experimental results of reactions between zinc‐organic complexes and soils. Among the soil characteristics, which include maximum adsorption capacity and bonding energy related coefficients for the various ions, the maximum adsorption capacity is the most important one in determining Zn uptake.
The Effects of Sodium and Organic Matter in Sewage Effluent on Water Retention Properties of Soils
Authors: Burns S. , Rawitz E. 
Published: July 2010

AbstractThe effect of 90 days of sewage effluent irrigation by drippers on water redistribution after irrigation was investigated on two soil layers of different texture and organic matter content. Changes in soil salinity, organic matter content, surface area, and water‐retention properties were monitored for 90‐ and 60‐day periods of effluent irrigation. The experiments were carried out in columns under constant temperature conditions. Soil depth was 3 cm and its mass was 100 g.The results led to the formulation of a hypothesis to explain the observed increased water retentivity of soils under effluent irrigation. The sodium and organic matter additions to soil via the waste water were found to interact in their effects on the active surface of soil particles. As a result of this interaction, drainage of the heavier soil, impaired during effluent irrigation, improved by subsequent drying. It then showed little damage upon simulated rainfall application. In contrast, drying of the sandier soil did not significantly improve its drainage properties, and subsequent “rainfall” resulted in severe clogging.
Phosphorus Nutrition of Rhizobium japonicum: Strain Differences in Phosphate Storage and Utilization
Authors: Cassman K. G. , Munns D. N. , Beck D. P. 
Published: July 2010

AbstractPhosphate accumulation from defined liquid medium was assessed in six strains of Rhizobium japonicum grown at high P (2 × 10−3M orthophosphate in solution). The total cell P concentration ranged from 1.6 to 2.4% dry mass depending on strain, and correlated with subsequent growth after transfer to medium without added P. Stored cell P could support up to four or five generations. Steps to ensure high‐P storage in inoculant cultures might have practical utility.Growth ceased when total cell P dropped to 0.3%. Electron microscopy indicated a tendency of deficient cells to become elongated, distorted, and packed with lightly staining granules (perhaps poly β hydroxybutyrate).High‐P cells of all the strains contained from 5 to 7 electrondense granules. Their total volume varied between 0.1 and 0.5% of the cell, depending on strain; and related linearly to percent of P in the cell. The granules occurred only when cell P was already high (> 1.5%) and disappeared within 1 day after transfer to medium without P. They may be polyphosphate storage granules. They provided P sufficient at most for 1 to 2 generations.Cells grown at an intermediate external solution‐P concentration buffered at 6 × 10−6M, resembling that in fertile soil, had few granules and moderate stored P (1.3 to 1.7%). Invasion of P‐depleted rhizospheres by rhizobia from soil probably cannot depend on previously stored P: it must also require efficient uptake from very dilute‐P concentrations.External gum was abundantly produced at low‐ and moderate‐P supply, but not at the high P concentrations routinely supplied in laboratory media.
Growth of Rhizobium Strains at Low Concentrations of Phosphate
Authors: Cassman K. G. , Munns D. N. , Beck D. P. 
Published: July 2010

AbstractA technique was developed for assessing effects of P on growth, in defined liquid media at orthophosphate concentrations comparable to those in soil solutions. Phosphate was supplied in sorbed form on iron oxide (goethite) separated from the liquid medium by a dialysis membrane. Depending on the level of sorbed P, concentrations in solution were established in the range 0.05 to 30 µM. Analytical monitoring indicated that concentrations above 0.1 µM were buffered against depletion by cell growth until populations exceeded 106 cells per ml.The system was used to compare P responses of seven strains of soybean and cowpea rhizobia grown from P‐depleted inocula at initial densities of 104 cells per ml. Two P‐efficient strains grew as rapidly at the lowest concentration (0.05 µM) as in a control medium at 2,000 µM. They would seem unlikely to be P‐limited in the field. Other strains were less efficient. One strain could barely grow at P concentration below 1 µM; this strain could have difficulty colonizing P‐deficient soils or normal rhizospheres.Large differences in tolerance to low P among strains may be agronomically important. The technique could be simplified for routine screening of strains; and its operation at submicromolar concentrations could be improved for research on nutrition and requirements of P‐efficient rhizobia and other organisms.
Effects of Water and Nitrogen Management on Yield and 15N‐Depleted Fertilizer Use Efficiency of Irrigated Corn
Authors: Russelle M. P. , Deibert E. J. , Hauck R. D. , Stevanovic M. , Olson R. A. 
Published: July 2010

AbstractThe objective of this experiment was to evaluate the effects of irrigation sequence and of time and rate of nitrogen application on the dry matter production and fertilizer use efficiency of irrigated corn (Zea mays L.), grown on a representative fine‐textured soil of eastern Nebraska, and to monitor the movement of fertilizer N in this soil. During 1974–1976, 15N‐depleted ammonium sulfate was banded at rates of 112, 168, or 224 kg N/ha at planting or sidedressed at the eight‐leaf growth stage. No N was applied in 1977–1979. In 1974–1977, irrigation applications of 5, 7.5, or 10 cm of water were made at 2‐, 3‐, or 4‐week intervals, respectively, until a total of 30 cm had been applied. The plots were uniformly irrigated in 1978–1979.Grain yield and N uptake in 1974–1976 were not influenced by time of N application, and were highest with light, frequent irrigation. From 1977–1978, yield increased with previous N rate in response to residual mineral N in the soil. During both treatment and residual years, fertilizer N recovery in the grain was greater with sidedressing and increased with N rate. Heavier, infrequent irrigation decreased tracer N recovery in 1974–1976. Maximum fertilizer use efficiency was obtained with the low N rate, applied as a sidedressing, and with light, frequent irrigation.
Ion Micromilling Applied to the Ultramicroscopic Study of Soils
Authors: Bresson L.‐M. 
Published: July 2010

AbstractThe electron transmission microscopic (TEM) study of undisturbed soil materials requires the preparation of thin sections of about 1,000Ä thick. This seems to be possible only by ion micromilling.This thinning technique necessitates particular precautions due to the fragility of permeated soil materials. The resins generally used for the making of thin sections are suitable as long as their polymerization is very good. Handling of the sample must be done under a stereomicrosocope with great care. It may prove useful before bombardment to glue the sample (3 mm in diam, 30 µm in thickness) between two electron microscope grids with a single central hole. The required thickness is reached when small holes appear in the sample. The thickness of the ultrathin sections can be irregular because the thinning rate of the sample varies considerably with its chemical composition, the type of its crystal lattice, and the state of its surface. Therefore, the only areas visible with a TEM appear as halos around holes. Artifacts induced by ion bombardment seem to be negligible compared with those that appear during observation by TEM. The ultrathin sections thus obtained allow the morphology of soil constituents and their ultramicroorganization to be studied at very high magnifications; hence, they are extremely useful for studies of mineral weathering, microstructures, and microfabrics.