bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Rhizobial Extracellular Polysaccharide on Solution Phosphate Levels of Acid Soils
Authors: Cunningham Scott D. , Munns Donald N. 
Published: July 2010

AbstractPrevious work has shown a positive correlation between the ability of a strain to colonize acidic agar and its production of extracellular polysaccharide (EPS) in solution culture. This paper examines the relationship between EPS production and phosphate levels in solution, determining: (i) the interaction of EPS with an oxide (gibbsite) surface, (ii) the effect of EPS on phosphate sorption, and (iii) the effect of EPS on previously sorbed phosphate. Rhizobial EPS was readily adsorbed onto gibbsite. When EPS was present before the addition of phosphate, both the quantity of EPS and its source significantly influenced the amount of phosphate sorbed. Addition of standard amounts of EPS from different strains to a gibbsite suspension with previously sorbed phosphate produced solution phosphate levels which differed significantly. The pH of the EPS added to the gibbsite‐phosphate suspension was also varied; added EPS decreased solution phosphate levels if the EPS was more acidic than the gibbsite suspension, and increased solution phosphate levels if it was more alkaline. Rhizobium in an acid soil may be able to influence the phosphate level of their immediate micro‐environment through the excretion of extracellular polysaccharide at an appropriate pH.
An Evaluation of Aromatic Fraction in Humic Substances
Authors: Ghosal M. , Chian E. S. K. 
Published: July 2010

AbstractThe fraction of aromatic carbon (AC) present in humic substances was reported to be determined by carbon magnetic resonance (CMR). A second method for determining AC is based on the weights of aromatic degradation products obtained by permanganate oxidation of humics. A correct method of computing AC from such data, not available so far, has been developed. AC values thus calculated are found to be much lower than those determined by CMR. The probable cause for such discrepency may be the presence of rings with low aromaticity, like furans, in the structure of humic substances.
Changes in Soil Carbon and Nitrogen Due to Irrigation Development in Nebraska's Sandhill Soils
Authors: Lueking M. A. , Schepers J. S. 
Published: July 2010

AbstractCarbon and N parameters were compared for nondeveloped and developed soils (predominantly mixed mesic, Typic Ustipsamments, and sandy, mixed mesic Entic Haplustolls). Soil samples were collected from four developed center pivot irrigation sites and from the nondeveloped corners at depth increments of 0‐ to 75‐, 75‐ to 150‐, and 150‐ to 300‐mm. Total C, total Kjeldahl N (TKN), hydrolyzable N, and mineralizable N by autoclave and by a 112‐d incubation study were determined. Changes in TKN were not significant in the 0‐ to 75‐mm depth, but in the second depth increment, TKN increased with development (507 to 569 kg ha−1). Total C also increased at this depth (5650 to 6400 kg ha−1). The C/N ratio increased with development in the surface 75 mm (11.5 to 12.2). Inorganic N increased in the top 300 mm due to development. Mineralizable N by both techniques increased in the 75‐ to 150‐ and 150‐ to 300‐mm depth increments. Steady state values for ln TKN were calculated to be 6.6, 6.4, and 6.8 kg ha−1 for soil depth increments of 0‐ to 75‐, 75‐ to 150‐, and 150‐ to 300‐mm, respectively. The ln total C steady‐state values were 9.1, 8.8, and 9.1 kg ha−1. In some cases, undeveloped soil contained more N and C than these steady‐state values, suggesting that development tended to decrease the soil test values. If the undeveloped soil was lower in N or C than the steady‐state value, development tended to increase the test value. Total C, TKN, hydrolyzable N, mineralizable N (both techniques), and inorganic soil N were all highly correlated. Changes in TKN and total C were not correlated to landscape position or time since development.
Phytotron Experiments to Evaluate the Effect of Growing Plants on Denitrification
Authors: Haider K. , Mosier A. , Heinemeyer O. 
Published: July 2010

AbstractThe amount and availability of plant rhizosphere carbon deposits and their influence on microbial denitrification in soil are not clearly defined. To evaluate this possibly important facet of fertilizer N loss from agricultural soils a study was conducted to simultaneously quantify the carbon fixed by plants and the fate of fertilizer nitrogen applied to the soil during a plant growing season. Corn (Zea mays) or wheat (Triticum aestivum) was grown in a phytotron under a continuous supply of 14CO2 in 15N fertilized soil. The results of the studies show that denitrification was not stimulated in soils planted with corn or wheat compared to unplanted soil. About 60% of the root biomass carbon could be found in the soil as rhizodeposited carbon at the termination of the experiments. Only 5 to 7% of this carbon was, however, extractable with water or 2 M Na2SO4. This suggests that even though a sufficient quantity of carbon was deposited in the soil by the plants that the carbon was not available for denitrification.
Soil‐Landscape Relationships of a Climax Forest in the Allegheny High Plateau, Pennsylvania
Authors: Aguilar Richard , Arnold R. W. 
Published: July 2010

AbstractThe Tionesta Research Natural Area, located in the Allegheny National Forest of northwestern Pennsylvania, is a unique remnant of the old growth American beech (Fagus grandifolia L.)‐Eastern hemlock (Tsuga canadensis L.) forest that once covered over 2400 ha of the Allegheny Plateau. During a detailed soil survey, the soils occurring on the various landscapes in the area were characterized and the relationships between the vegetation and the soils were evaluated. The development of the landscapes in the Tionesta area has been strongly influenced by the contrasting erodibility of alternating layers of sandstone, siltstone, and shale bedrock. The gentle, regional dip of the bedrock in a southwesterly direction has favored the preferential erosion of the south‐facing slopes. The area experienced a periglacial climate during the Late Wisconsin Glaciation. Evidence of this former cold climate is expressed by colluvial (solifluction) deposits and boulder fields on the ground surfaces of the footslope landscapes. Seven distinct soils occur on the various landscapes. These soils are extremely acid to very strongly acid and high in exchangeable aluminum. Low cation exchange capacity and base saturation reflect the abundance of quartz and other primary minerals which are highly resistant to weathering. Podzolization processes are evident and most pronounced in the coarse‐textured, free‐leaching soils under hemlock stands. Drainage appears to be an overriding soil factor influencing the vegetation patterns on the different landscapes with hemlock dominating the stands in wetter areas. Shade‐intolerant species, such as black cherry (Prunus serotina L.), commonly occur on shallow soils on steep slopes where frequent canopy openings associated with blow‐downs have allowed their establishment.
Chemical and Stubble‐Mulch Fallow Influences on Seasonal Soil Water Contents
Authors: Tanaka D. L. 
Published: July 2010

AbstractA study was conducted in the northern Great Plains to determine the effect of chemical and stubble‐mulch fallow of a Williams loam (fine‐loamy mixed, Typic Argiborolls) on soil water contents during 14‐and 21‐month fallow periods. Soil water contents to a depth of 1.70 m were measured by use of the neutron‐scatter technique for two 14‐and three 21‐month fallow periods. The amount of surface residue after harvest ranged from 0.6 to 3.6 Mg/ha during the study. Chemical fallow maintained more surface residue than stubble‐mulch fallow, but no significant differences in soil water contents to 1.70‐m soil depth occurred between the treatments. Gain in soil water occurred after harvest and over the first winter with soil water loss generally occurring during summer for 14‐ and 21‐months of fallow. No gain in soil water contents occurred over the second winter when chemically fallowed for 21‐months. Precipitation frequency and distribution may be just as important as quantity and position of surface residue for chemical fallow to effectively store more soil water than stubble‐mulch fallow.
Phosphorus Application Frequency and Sources for Grain Sorghum
Authors: Janssen K. A. , Whitney D. A. , Kissel D. E. 
Published: July 2010

AbstractA field study was conducted for 8 yr on an initially low soil test P, Woodson silt loam soil (fine, montmorillonitic, thermic Abruptic Argiaquolls) in east‐central Kansas to determine the effectiveness of ortho‐and polyphosphate fertilizers applied annually at 25 kg ha−1, every 2 yr at 50 kg ha−1, and every 4 yr at 100 kg ha−1 for grain sorghum (Sorghum bicolor L.) production. The first year, yield was higher with the larger, less frequent P applications because of the low P status of the soil. Second‐and third‐year yields were not statistically different. The fourth year, when the time span was longest since the every 4‐yr P application had been applied, yield was lower with the every 4‐yr P application compared to annual P. The every 2‐yr P treatment produced intermediate results. Total grain production for the first 4 yr did not differ significantly with the P application frequency treatments. During the second 4 yr, when soil P levels were higher, the P application frequency treatments produced no significant differences in yearly or total yield. The ortho‐and poly‐phosphate P sources, in general, produced similar response applied annually, or at infrequent intervals. These data suggest that there are Argiaquolls in east‐central Kansas on which infrequent P fertilizer applications can perform similarly to annual P applications.
Classification of Soils with Andic Properties from the Oregon Coast
Authors: Baham John , Simonson G. H. 
Published: July 2010

AbstractFourteen pedons from three northern Oregon coastal counties were evaluated for their chemical and physical properties for inclusion in the proposed soil order Andisol (Leamy, 1984). Seven pedons were found to meet the criteria for bulk density, aluminum solubility in ammonium oxalate (Alo), depth, and phosphate retention, and were provisionally classified as Udands. Data for four representative pedons with andic properties are presented. Most of the measured Alp/Alo values for the andic horizons were >0.5 (Table 2), indicating that much of the Al is present in the form of humus‐metal complexes. The relatively low values for oxalate‐extractable Si suggest that these soils contain only small amounts of allophane and/or imogolite. These soils are similar to the nonallophanic, humus rich Udands that have been described in northeastern Japan. The proposed classification is discussed with respect to the guidelines presented in the 6th ICOMAND letter (Leamy, 1984).
Comparison of Liquid Retention Curves with Polar and Nonpolar Liquids
Authors: Lenhard Robert J. , Brooks Royal H. 
Published: July 2010

AbstractCapillary pressure‐saturation data obtained on unconsolidated porous media containing different clay minerals with different liquids are compared to evaluate the effect of clay‐water interactions on liquid retention characteristics. The clay minerals used were a well‐crystallized kaolinite, an illite, and a Ca‐montmorillonite. The wetting fluids were distilled water and a light hydrocarbon, soltrol, which was assumed not to interact with the clays. The hydraulic variables, capillary pressure and saturation, are transformed to account for differences in contact angle, density, and surface tension of the liquids. The liquid retention functions obtained from the different wetting fluids for the kaolinite samples are statistically similar. For Ca‐montmorillonite and illite, the retention functions are statistically different. The explanation for the difference in retention functions for Ca‐montmorillonite samples is the swelling that occurs with water. The difference in retention functions for illite samples can be accounted for by an immobile water layer.
Effects of Manure Amendment on Soil Chemical Properties and Hydrous Oxides
Authors: Miller W. P. , Martens D. C. , Zelazny L. W. 
Published: July 2010

AbstractThree Virginia soils with low, moderate, and high amounts of Fe and Mn oxides were amended with swine (Sus scrofa L.) manure at a rate of 100 mt ha−1 in an incubation experiment conducted in the laboratory over 29 days. Changes in pH, redox potential (Eh), and forms of Fe and Mn were monitored in order to assess the effect of high rates of manure loading on the chemical properties of these soils. Manure additions caused immediate reductions of 175 to 325 mv in soil Eh by day 4, although Eh recovered to near untreated soil levels by the end of the study. Minimum Eh levels were related to initial Fe and Mn contents of the soils. Soil pH increased to 7 to 8 in all soils, and organic matter contents, initially 25 g kg−1 higher than control soils, decreased as decomposition proceeded. Soil Mn was rapidly solubilized under the reducing conditions present early in the incubation, as shown by increases in soluble, exchangeable, and adsorbed forms of Mn determined by sequential extraction. Reprecipitation of MnO2 occurred in the high‐Mn soil by day 8, as Eh began to recover. Iron was reduced to more soluble forms only in limited amounts in the soils with the high and medium Fe oxide contents, while significant reduction of amorphous Fe oxide was observed in the soil with low oxide content. These results suggest that toxicities of Fe and especially Mn, along with other trace metals associated with these oxides in soils, may result from high rates of organic waste addition to soils where reducing conditions may persist for some time.
Natric Horizons on Some Erosional Landscapes in Northwestern South Dakota
Authors: Johnson W. F. , Mausbach M. J. , Gamble E. E. , Nelson R. E. 
Published: July 2010

AbstractSoils with natric horizons, associated slickspots, and soils with argillic horizons were sampled to study landscape relationships. These soils occur in microtopographic sequences that recur in spacings of 15 m or more. At two sites soils were sampled from trenches that transected the microtopographic sequence. At each site soils had a continuous argillic/natric horizon that was exposed at the surface in slickspots. Slickspots have an upslope scarp and appear to be dynamic erosion surfaces that migrate upslope. Salt content in and below the argillic horizon was highest in the slickspot and in pedons closest to the slickspot and decreased with distance outward from the slickspot. Content of soluble salt also appears to vary in the parent rock. It is suggested that lateral movement of salts and content of salt in the parent material are important in formation of the soils and that salts may be redistributed by the movement of the slickspots.
Effects of Subsoiling and Irrigation on Corn Production
Authors: Cassel D. K. , Edwards E. C. 
Published: July 2010

AbstractDeep tillage and irrigation are two soil management techniques that have been used separately to alleviate water shortages for crops growing on soils having root restricting tillage pans. The purpose of this study was to evaluate the effects of in‐row‐subsoiling (S), irrigation (I), and in‐row‐subsoiling plus irrigation on corn (Zea mays L.) production on Wagram soil (fine‐loamy, siliceous, thermic Arenic Paleudults) having a dense tillage pan. Main plot treatments were: CD (conventional tillage [double disking], dryland); CI (conventional tillage, irrigated when soil water pressure [SWP] at the 0.25‐m depth reached −40 kPa); SD (in‐row‐subsoiled and bedded, dryland); and SI (in‐row‐subsoiled and bedded, irrigation when SWP < −40 kPa at 0.30‐m depth). Total growing season precipitation in 1979, although poorly distributed, was near normal; 1980 and 1981 were both drought years. The 3‐yr mean amounts of irrigation water applied were 179 mm for the CI and 145 mm for the SI treatments. The CI, SD, and SI treatments always had significantly higher yields of grain and stover and lower numbers of barren plants compared to treatment CD. Maximum corn height was greatest (2.68 m) for treatment SI and leaf area indices for treatments CI, SD, and SI were 23, 28, and 36% greater, respectively, than the 2.56 value for CD. Mean grain yields for treatments CI, SD, and SI were 215, 197, and 277% greater, respectively, than the 2.58 Mg ha−1 CD yield. Root length and root mass in the 0.1 to 0.6‐m soil depth were greater for the dryland treatments. Apparent irrigation water use efficiencies were 0.031 and 0.014 Mg ha−1 mm−1 for treatments CI and SI, respectively. Estimates of subsoil water utilization using neutron attenuation and tensiometer data were 50 mm yr−1 which resulted in an apparent subsoil water use efficiency of 0.10 Mg ha−1 mm−1.
A Modified Miscible Displacement Technique for Investigating Adsorption‐desorption Kinetics in Soils
Authors: Carski T. H. , Sparks D. L. 
Published: July 2010

AbstractThe use of miscible displacement techniques to study kinetics of ion exchange in clay minerals and soils is increasing. Although only 1 g or less of adsorbent is often used, some of the adsorbate solution will always be retained by the adsorbent. The dilution of the incoming solution by the retained solution is easily mistaken for either adsorption or desorption, resulting in an overestimation of either process. A device that ensures constant dilution volumes, regardless of adsorbent, was developed to differentiate the adsorption‐desorption process from the dilution process.
Plant Response to Mycorrhizal Fungi: Host, Endophyte, and Soil Effects
Authors: Bethlenfalvay Gabor J. , Ulrich Jane M. , Brown Milford S. 
Published: July 2010

AbstractInteractions and growth responses in soybean [Glycine max (L.) Merr.] and sorghum [Sorghum bicolor (L.) Moench] colonized by the vesicular‐arbuscular mycorrhizal (VAM) fungi [Glomus fasciculatum (Thaxt. sensu Gerd.) Gerd. and Trappe] or [Glomus mosseae (Nicol. & Gerd.) Gerd. and Trappe] as grown in three northern California soil types were investigated in a 2 by 2 by 3 factorial experiment. Growth and development of both symbiotic partners were significantly influenced by all three factors (host plant, endophyte, soil). Growth responses to VAM‐fungal colonization varied with soil type from −10 to 400%. Phosphorus concentrations increased significantly in all soybean and some sorghum plants relative to non‐VAM controls as a result of VAM‐fungal colonization. Shoot dry matter as percent of fresh weight increased significantly in only those VAM plants which had also experienced a significant growth enhancement. Root/shoot ratios of most VAM plants were lower than those of the controls. Changes in root/shoot ratios were inversely related to changes in dry weight. The results show that soil type, as well as the host‐endophyte combination, is a significant factor in modifying the VAM growth effect independently of mineral nutrient availability.
Synthesis and Characterization of Lansfordite and Nesquehonite
Authors: Ming Douglas W. , Franklin William T. 
Published: July 2010

AbstractChemically pure lansfordite (MgCO3·5H2O) and nesquehonite (MgCO3·3H2O) were synthesized from CO2‐saturated Mg(HCO3)2 solutions by degasation with air for varying periods of time depending upon equilibration temperature. Crystalline and chemical properties of the synthesized minerals were determined and the results were compared with the properties reported for geologic specimen minerals. Crystalline data determined for synthesized lansfordite are: monoclinic; a = 1.249 nm, b = 0.762 nm, c = 0.743 nm, β = 1.785 ± 0.002 rad, a/b/c = 1.638:1:0.976, Z = 4. Nesquehonite is monoclinic (pseudo‐orthorhombic); a = 1.199 nm, b = 0.769 nm, c = 0.537 nm, β = 1.573 ± 0.012 rad, a/b/c = 1.557:1:0.697, Z = 4. Lansfordite is unstable when exposed to the atmosphere at temperatures > 10°C. Large lansfordite crystals (>150 µm) were observed with scanning electron microscopy (SEM) to undergo dehydration above 10°C. X‐ray diffraction data and SEM observations indicate that upon dehydration large lansfordite crystals convert to nesquehonite but remain pseudomorphic after lansfordite. Small lansfordite crystals (<20 µm) appeared to dissolve upon an increase in temperature above 10°C when viewed with SEM. Crystal forms of nesquehonite, lansfordite, and dehydration states of lansfordite are shown in SEM microphotographs.
A Pneumatic Fracture Method for Measuring the Tensile Strength of Unsaturated Soils
Authors: Snyder V. A. , Miller R. D. 
Published: July 2010

AbstractA new technique for measuring tensile strength of unsaturated soils is discussed, wherein applied stress, pore‐air pressure, and pore‐water pressure can be simultaneously and independently controlled. The method essentially involves enclosing the test sample in an adhesive membrane which is impervious to air, and then decreasing the external applied stress relative to the pore‐air pressure until the sample ruptures or literally explodes due to the pressure difference across the adhesive membrane. Applied stress is hydrostatic, eliminating the need for knowing sample dimensions and ensuring the absence of unwanted bending moments which are a common source of error in most direct tension procedures. The system is designed in such a way that sample equilibration and tensile strength measurements are carried out in the same apparatus, avoiding dangers associated with the transfer of very weak samples from one apparatus to another. The method is shown to produce comparable results to those obtained by a direct tension procedure.
Lanthanide Solid Phase Speciation
Authors: Essington M. E. , Mattigod S. V. 
Published: July 2010

AbstractThe solid phase speciation of La, Ce, and Nd in the Ln2O3‐CaO‐SO4‐PO4‐F‐O2‐CO2‐H2O (where Ln = La, Ce, and Nd) equilibrium system were evaluated using three‐dimensional activity diagrams. Diagrams were constructed from thermodynamic data and interpreted with a knowledge of the ligands associated with La, Ce, and Nd in sewage sludge and sludge‐amended soil particles as characterized by scanning electron microscopy. Throughout a wide range of equilibrium conditions at 298.15 K and 0.101 MPa, the activities of dissolved lanthanides were controlled by a small number of solid phases. These solids were cerianite [CeO2], lanthanite [La2(CO3)3·8H2O] and Nd‐lanthanite [Nd2(CO3)3·8H2O], and La and Nd sulfates [(La,Nd)2(SO4)3·8H2O] in the presence of gypsum. In general, the stable lanthanide solid phases predicted from the thermochemical evaluation were consistent with those directly observed in chemically well‐defined sewage sludge and sludge‐amended soil; thus, illustrating the applicability of such an evaluation when applied to well characterized environments.