bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Wetting and Drying, and of Exchangeable Cations, on Boron Adsorption and Release by Montmorillonite
Authors: Keren R. , Gast R. G. 
Published: July 2010

AbstractThe effect of drying and rewetting sequences on boron adsorption and desorption by Na‐ and Ca‐montmorillonite suspensions was determined with (i) nondried suspensions, (ii) suspensions dried prior to boron addition, and (iii) suspensions dried once or twice after boron adsorption. Boron adsorption in the nondried suspensions was completely reversible for both the Na‐ and Ca‐systems. There was little effect of exchangeable cation species (Na+ vs. Ca2+) on boron adsorption in the pH values of 7.0 and 7.2. There was a significant exchangeable cation effect, however, at higher pH's, with the Ca‐system adsorbing the greatest amount of boron. Boron adsorption on clays dried prior to boron addition was essentially the same for the nondried systems, indicating that the drying and rewetting sequence does not have any effect on the adsorption sites of the clay. The amount of boron adsorbed increased with drying and wetting after boron addition for both the Na‐ and Ca‐systems, with the greatest increase occurring after the first drying‐wetting cycle for both systems. Drying and rewetting of the clay suspensions after boron addition not only increased the amount of boron adsorbed, but significantly reduced the reversibility of the adsorption process as well. The relative amount of reversibility of adsorbed boron is a complex function of the drying and rewetting cycles, pH, and type of exchangeable cations.
The Kinetics of Phosphorus Desorption from Soil
Authors: Sharpley A. N. , Ahuja L. R. , Yamamoto M. , Menzel R. G. 
Published: July 2010

AbstractThe kinetics of P desorption for several soils was investigated at different water/soil ratios, during a short period of time, so that the results could be related to P release from agricultural soil to rainfall and runoff water. For all soils the logarithm of P release (Pd) was linearly related to the logarithm of contact time (t) at any given water/soil ratio (W) and P amendment and to logarithm of W at any given contact time and P amendment. The amount of P released was also directly proportional to the amount of desorbable P (Po) in the soil initially. The following simplified empirical model was developed to describe the desorption of soil P,Pd = KPotαWβ,where K, α, and β are constants. The simplified model gave a reasonably good description of P desorption from five southwestern soils and provided similar values of the constants K, α, and β, for each soil, over a range of experimental conditions. Consequently, we suggest that average values of the constants for each soil can be used in the model to describe P release for general applications.
Characterization of Diverse Rhizobium trifolii Isolates
Authors: Hagedorn C. , Caldwell B. A. 
Published: July 2010

AbstractForty cultures of Rhizobium trifolii isolated from diverse soils in western Oregon were characterized on the basis of host‐plant specificity and serological and cultural reactions. There was large variation in effectiveness when the rhizobia were examined on 12 cultivars of subclover (Trifolium subterraneum L.), although most of the strains demonstrated fair to average effectiveness on the majority of the subclover cultivars. The rhizobia were of generally poor effectiveness with other Trifolium species. Antibiotic resistant mutants were selected for two of the strains, and these were tested on the subclover cultivars as a mixed inoculum. Six cultivars were preferentially nodulated by one of the two strains, and individual plants that contained one of the strains in the majority of its nodules were identified. Thirty‐four of the isolates could be categorized into six serological groups based on whole‐cell agglutination reactions, whereas three cultures demonstrated very specific antibody reactions and could be identified on this basis. All 40 strains grew in acid broth at pH 4.5, but only 12 out of 40 grew at pH 3.0. At neutral pH, the mean generation time was 1½ to 3 hours, although there were a few that grew faster. At pH 4.5 the generation times were increased for most of the cultures but usually by only 1 or 2 hours. The serological groupings and growth characteristics were not found to be related to the effectiveness categories of the strains in any apparent way. The possibilities for selecting clover lines that are preferentially nodulated by a specific Rhizobium strain and identifying isolates that have research potential based on effectiveness patterns among different host‐plant cultivars are described.
Land Forming Effects on Dryland Sorghum Production in the Southern Great Plains
Authors: Jones O. R. 
Published: July 2010

AbstractThe effectiveness of selected low‐cost, water‐conserving land forming systems in preventing runoff and increasing dryland grain sorghum [Sorghum bicolor (L.) Moench] yields on Pullman clay loam was evaluated for 4 years (1975–1978) at Bushland, Tex. Systems investigated were mini‐bench terraces (5 m wide), conservation mini‐bench terraces (9 m wide with a ratio of watershed to level bench area of 1:1), and three configurations of contour furrows. Runoff was measured from conventional graded furrows (0.25% grade) that were used for the check treatment. Total runoff for the 4 years was 258 mm, about 15% of total precipitation. All systems that retained runoff on the field produced significantly greater yields and had greater water‐use efficiencies than the graded furrow system. Grain yield and water‐use efficiency were significantly greater with mini‐bench terraces than with any other treatment. Mean annual grain yield on mini‐bench terraces was 2,380 kg/ha, compared to 1,210 kg/ha on conventional graded furrows. Minibenches, conservation mini‐benches, and large contour furrows controlled erosion and retained all precipitation from a storm of 75‐year expected frequency. In that storm, conventional furrows overtopped and failed to retain runoff.
A Method for Measuring the Vertical and Horizontal Ksat of Clay Soils with Macropores
Authors: Bouma J. , Dekker L. W. 
Published: July 2010

AbstractA field method is presented for measuring the vertical and horizontal Ksat of a cube of soil (25 × 25 × 25 cm) which is carved out in situ and covered with gypsum. A vertical Ksat is measured by infiltrating water into the exposed upper surface and by collecting it below the exposed lower surface of the cube. The cube is then turned. The two open surfaces are covered with gypsum, which is removed from the other two vertical sidewalls. These turn into surfaces for percolation after again turning the cube. A vertical Ksat is now measured which represents the horizontal Ksat of the cube in its original position in the soil. The method is inexpensive and simple, creates the required large sample in clay soils, does not involve compaction of soil, can be used above the water table, and defines Ksat in terms of direction.
Spatial Variability of Steady‐State Infiltration Rates as a Stochastic Process
Authors: Sisson J. B. , Wierenga P. J. 
Published: July 2010

AbstractSteady‐state infiltration rates were measured in a field plot with infiltrometers of 5‐, 25‐, and 127‐cm inside diameter. Measurements were made with the three ringsizes along five parallel transects, spaced 125 cm apart. The infiltrometers were placed adjacent to each other along each transect (i.e., one hundred twenty‐five 5‐cm rings, twenty‐five 25‐cm rings, and five 127‐cm rings per transect). Infiltration rates were found to be lognormally distributed for all ringsizes and autocorrelated for the 5‐cm ringsize. The 5‐cm data showed that a large fraction of the water infiltrated through a small fraction of the plot area. Autocorrelation functions were determined and power spectrums computed. A first‐order autoregressive process was found to describe the 5‐cm data, and variances of samples composited along a transect agreed with sample variances. The variances for the 25‐ and 127‐cm infiltrometers were compared with sample variances, assuming a simple two‐dimensional autocovariance function. Agreement was found for the 127‐cm rings, but not for the 25‐cm rings.
Distribution and Plant Availability of Soil Zinc Fractions
Authors: Iyengar S. S. , Martens D. C. , Miller W. P. 
Published: July 2010

AbstractThis laboratory and greenhouse investigation was under‐taken to study the distribution and plant availability of zinc in different soil fractions. Total Zn (TZn) in 19 soils, which varied widely in chemical and physical properties, was fractionated into water‐soluble plus exchangeable (CA‐Zn), specifically adsorbed (AC‐Zn), organically bound (PYRO‐Zn), Mn‐oxide bound (HAH‐Zn), Al‐ and Fe‐oxide bound (AMOX‐Zn), and residual (RES‐Zn) forms. There was a wide variation in the magnitude of these fractions among soils. Most of the TZn, on an average, was present in the AMOX‐Zn (∼25%) and RES‐Zn (∼70%) fractions. The CA‐Zn, AC‐Zn, PYRO‐Zn, and HAH‐Zn fractions averaged 0.4, 3.3, 2.5, and 2.0% of the TZn, respectively. The CA‐Zn in the 19 soils increased with a decrease in soil pH, whereas the AC‐Zn increased with an increase in soil pH. The PYRO‐Zn in the soils varied directly with organic C and soil pH, HAH‐Zn increased with an increase in both soil pH and free Mn, AMOX‐Zn correlated more closely with free Al than with free Fe, and RES‐Zn varied positively with soil clay. A seven‐variable regression model, which included the six Zn fractions and soil pH, accounted for 94% of the variability in Zn uptake by corn plants (Zea mays L.) from these soils. This model separated soils that supplied inadequate amounts of Zn from those that supplied adequate amounts.
Effect of Long‐term Lime and Potassium Applications on Quantity‐Intensity (Q/I) Relationships in Sandy Soil
Authors: Sparks D. L. , Liebhardt W. C. 
Published: July 2010

AbstractThe effects of long‐term lime and K applications on quantity‐intensity (Q/I) relationships were investigated on the Ap and B21t horizons of a Kalmia soil (a fine‐loamy over sandy or sandy‐skeletal, siliceous thermic (Typic Hapludults) from the Delaware Coastal Plain. The predominant mineral suite of the <2µm clay fraction was mica, vermiculite, and chloritized vermiculite. Soil pH and exchangeable bases increased with depth and with lime additions. The equilibrium potassium activity ratio (ARke) decreased with profile depth due to greater K fixation by specific sites for K in the B21t horizon. The ARke decreased in the Ap horizon and increased in the B21t horizon with lime additions. The magnitude of ARke [> 0.01 (moles/liter)½] suggests that K adsorption in the Ap horizon occurred on planar positions while adsorption at specific sites was predominant in the B21t horizon [> 0.006 (moles/liter)½]. The parameter δKo, which measures labile K, became more negative with increased lime and K additions, indicating a greater K release into soil solution. While the quantity of K extracted by NH4OAc compared favorably to δKo in the Ap horizon, it exceeded δKo in the B21t horizon, suggesting K exchange involving specific sites in the B21t horizon. The number of specific sites (Kx) increased with K fertilization and with soil depth. The decreased Kx with increased lime additions could be ascribed to increased neutralization of hydroxyaluminum interlayer material, resulting in an increase in interlayer “islands.” The potential buffer capacity (PBCk) parameter increased with lime additions due to increased pH‐dependent cation exchange capacity (CEC).
Potential for Phosphorus Toxicity in Zinc‐Stressed Corn and Potato
Authors: Christensen N. W. , Jackson T. L. 
Published: July 2010

AbstractCorn (Zea mays L., ‘Illinois WF 9 × 38‐11’) and potato (Solanum tuberosum L., ‘Russet Burbank’) were grown in dithizone purified nutrient solutions to contrast relationships between dry matter yield, tissue phosphorus (P) concentration, and tissue zinc (Zn) concentration as they influence the development of Zn deficiency and P toxicity. Treatments consisted of Zn at 0, 0.14, and 0.41 µM in factorial combination with P at 0.02, 0.10, 1.0, and 3.0 mM. Yield and tissue concentration of P and Zn were affected by statistically significant P‐Zn treatment interactions in both species. Corn plants developed Zn deficiency symptoms and responded to nutrient solution Zn when plant growth was not limited by inadequate nutrient solution P. Corn plants grown in nutrient solutions containing 0 µM Zn and 3.0 mM P contained 3.39% P in leaf tissue and had significantly lower yields than did plants grown in nutrient solutions containing 1.0 mM P. Even though no visual symptoms were evident, P toxicity probably was responsible for the reduction in yield. Potato plants responded to nutrient solution Zn when growth was not limited by inadequate P but did not exhibit visual symptoms of Zn deficiency. Zinc‐deficient potato plants containing in excess of 2.22% P in leaf tissue exhibited probable P toxicity symptoms characterized by puckering of leaf edges, thickening and upward curling of leaves, and leaf necrosis. Excessive concentration of P in leaf tissue of Zn‐deficient potato was the result of increased mobilization and translocation of P from roots to above‐ground parts, increased total P uptake, and concentration of P resulting from restricted growth. Excessive levels of P in corn leaf tissue were primarily the result of concentration of P due to restricted growth. Zinc concentration in tissue of both species was reduced by growth response dilution, but Zn uptake by plants receiving low levels of Zn was not reduced by increasing nutrient solution P concentrations. Apparent accentuation of Zn deficiency by P application is explained on the basis of accumulation of toxic levels of P in Zn‐deficient plants. Species such as potato which show increased P uptake and increased mobilization and translocation of P to tops when under Zn stress are probably more susceptible to P toxicity.
Long‐Term Tillage Effects on Interrow Runoff and Infiltration
Authors: Lindstrom M. J. , Voorhees W. B. , Randall G. W. 
Published: July 2010

AbstractSimulated rainfall trials were conducted in wheel‐tracked and nonwheel‐tracked interrows for three continuous corn (Zea mays L.) tillage systems (fall moldboard plow with spring field cultivate, fall chisel with field cultivate, and no till designated as conventional, conservation, and no till, respectively) in the 10th year of the tillage and crop system in south central Minnesota to determine the effect of long‐term tillage systems on interrow runoff and infiltration. Wheeltracked interrow refers to tractor tire tracks from the planting operation. Simulated rainfall was applied with a sprinkling‐type infiltrometer at a rate of 12.7 cm/hour simultaneously to wheel‐tracked and nonwheel‐tracked interrows. Differences were observed in random roughness and soil bulk density of the surface 7.6 cm between wheel‐tracked variables, tillage systems, or both. Energy required to initiate runoff, reported as rainfall kinetic energy (KE), was significantly different among tillage systems for each wheel‐tracked variable. Ranking of the treatments was conservation > conventional > no till for the nonwheel‐tracked interrow, and conservation = conventional > no till for the wheel tracked interrow in relation to KE required to start runoff. The conservation and conventional nonwheel‐tracked interrows had a greater infiltration rate after runoff started than the wheel‐tracked interrows and the no till system. Evidence from this study indicates that the no till system may result in a consolidated soil surface with a low infiltration capacity that is persistent with time and susceptible to high volumes of runoff during severe rainstorm events.
Evaluation of Slow‐Release Nitrogen Sources on Baron Kentucky Bluegrass
Authors: Hummel N. W. , Waddington D. V. 
Published: July 2010

AbstractAs new nitrogen (N) sources are introduced, it is important that they be evaluated and their release characteristics determined in order to provide us with a basis on which to make fertilizer recommendations. In this study, several N sources were evaluated for maintenance fertilization of Kentucky bluegrass (Poa pratensis L.) turf. Treatments included isobutylidene diurea (IBDU) materials of two particle‐size ranges, sulfur‐coated ureas (SCU) in two size ranges from Canadian Industries Limited (CIL), SCU from the Tennessee Valley Authority (TVA), ureaformaldehyde (UF), activated sewage sludges, Organiform, soluble N sources, and combinations of slow‐release and soluble N. All N sources were applied at a rate of 197 kg N·ha−1·yr−1, divided into equal fall and spring applications for 3 consecutive years. Weekly clipping yields, color ratings, and annual N recovery were the response criteria.Sulfur‐coated urea produced a more uniform growth and had higher N recovery than IBDU, which was characterized by a delayed response following fertilization. Turfgrass response to the CIL and TVA SCU materials applied alone was similar. Particle‐size effects with CIL SCU were slight; however, N release was quicker from fine IBDU than coarse IBDU. Slow‐release characteristics were also observed for ureaform, Organiform, and the sludges, but turf quality was generally poor for these treatments. Substituting soluble N for a portion of the SCU N gave inferior turfgrass response as compared to SCU applied alone. When soluble N was used in conjunction with ureaform, Organiform LT, and IBDU, turfgrass response was improved over that obtained when these N sources were used alone. Recovery of N in the clippings was greatest for soluble N sources and SCU treatments (48 to 52%), while lowest values (15 to 29%) were associated with ureaform, Organiform, and sludges.
The Manufacture and Agronomic Efficiency of a Partially Acidulated Phosphate Rock Fertilizer
Authors: Garbouchev I. P. 
Published: July 2010

AbstractNorth Africa phosphate rock, Gafsa type (PR), and different PR/H3PO4 ratios were investigated to find an efficient, partially acidulated PR fertilizer (PAPR). A monocalcium phosphate (MCP)/PR ratio of approximately 60/40, produced by 26 to 30% acidulation of PR by H3PO4, was the most efficient PAPR product; it requires 68 to 70% less H3PO4 than the amount required for manufacture of triple superphosphate (TSP).PAPR products made in pilot plants by the “Door‐Oliver” process were more efficient than those produced by the “Batch” process. Field experiments with PAPR fertilizer were carried out from 1970 to 1978. Agronomic results showed that the above product was generally equal or slightly superior to TSP in terms of P availability as detected by routine soil test methods. Models on control of the P status in several soils were established on the basis of greenhouse experiments with increasing P rates for ryegrass (Lolium perenne L).Commercial factory production of PAPR by the “Door Oliver” process costs 30 to 35% less than that of TSP because of lower total energy and less H3PO4 used. An additional advantage appears to be a 50 to 65% increase in fertilizer output in factory‐scale installation. In practice, higher available soil P was maintained, and at least equal crop yields were obtained with a higher rate, less frequently applied, than with the same total P rate applied more often in fractional applications. This was especially true for PAPR.
A Comparison of Three Extractants for Soil Zinc
Authors: Kennedy A. C. , Brown J. R. 
Published: July 2010

AbstractAn HEDTA (hydroxyethylenediaminetriacetic acid) soil zinc (Zn) extractant was compared to 0.1M HCL (1) and DTPA [diethylenetri‐aminepentacetic acid; (4)] for their value in detecting zinc deficient sites. Published formation constants suggested that HEDTA should be an effective chelator of soil zinc below pH 7.0. Calculations based upon these formation constants were the impetus for further investigation of HEDTA as a zinc extractant. The extractant consisted of 0.005M HEDTA in a 0.1M calcium acetate buffer adjusted to pH 6.0. Ten grams of air‐dried soil were shaken with 20 ml of extractant for 30 min. After filtration the concentration of zinc in the filtrate was determined.Three extractants, HCI, DTPA, and HEDTA, were compared for their ability to extract zinc from soils at 11 sites in Missouri. The three tests were equally successful at separating deficient from nondeficient soils. Zinc extracted by HEDTA varied less within each site than did that extracted by HCI to DTPA.
Spatial Variability of Field‐Measured Infiltration Rate
Authors: Vieira S. R. , Nielsen D. R. , Biggar J. W. 
Published: July 2010

AbstractSpatial variability of 1,280 field‐measured infiltration rates on Yolo loam (fine‐silty, mixed, nonacid, thermic Typic Xerorthents) was studied using geostatistical concepts. The measurements were made at the nodes of an irregular grid consisting of 160 rows and eight columns. Sample spacing within columns was 1 m. Columns were spaced irregularly at 1, 5, 15, and 19 m.A variogram for the 1,280 measurements was used to krige 800 additional values within five more columns and to draw a contour map of the area.The large number of measured values made it possible to calculate the minimum number of samples necessary to reproduce the infiltration rate measurements with a fairly large approximation. As a result, it could be concluded that a minimum of 128 samples was enough to obtain nearly the same information as with 1,280 samples. A suggestion on how to use autocorrelograms in sampling schemes is presented.
Aromaticity of Humic Substances in Soils
Authors: Hatcher Patrick G. , Schnitzer Morris , Dennis Larry W. , Maciel Gary E. 
Published: July 2010

AbstractHumic acids from different climatic zones and a fulvic acid from an Armadale soil, Prince Edward Island, Canada, have been examined by cross polarization, magic‐angle spinning 13C nuclear magnetic resonance (NMR). Aromaticities calculated from the NMR spectral data are generally high, ranging from 35 to 92%, in general agreement with values obtained from the results of chemical oxidation/gas chromatographic mass spectrometric studies. Most NMR spectra, however, indicate the presence of significant aliphatic structures that generally were not observed by chemical oxidation studies. Chemical techniques have overestimated the degree of aromaticity of humic substances. Phenolic carbons that have always been considered to be major “building blocks” of humic substances are not observed as intense signals by NMR; this fact suggests that these carbons may be minor rather than major components. Carboxyl contents calculated from NMR spectra are greater than those calculated by chemical techniques and approximate the concentrations of total acidic groups.