bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reactions of Phosphate Rocks, Rhenania Phosphate, and Superphosphate with an Acid Soil
Authors: Chien S. H. 
Published: July 2010

AbstractThe amounts of water‐soluble P in various phosphate materials after their reaction with Weston soil (pH 4.5) at a rate of 400 ppm P followed the order: Rhenania phosphate > CSP > North Carolina rock > Araxa rock. Addition of 150 ppm Si in the form of Na2SiO3 to the soil treated with CSP significantly decreased the P‐retention capacity of the soil. The water‐soluble P level was maintained at 100–150 ppm in the soil treated with CSP and silicate during the whole course of incubation (10 weeks). Addition of silicate, however, did not eliminate P retention completely.Liming the soil with Ca(OH)2 decreased the water‐soluble P in the soil treated with CSP. In contrast, soluble silicate increased the water‐soluble P as the rate of application increased, despite the fact that soil pH increased. The amounts of water‐soluble P in the soil treated with Rhenania phosphate and CSP together at the ratio of 1:1 (as P) were found to be greater than the calculated sum of water‐soluble P in the soil treated with Rhenania phosphate and CSP separately. This suggests that the silicate in Rhenania phosphate decreased the soil P‐retention capacity and thus increased the level of water‐soluble P in the soil. It appears that Rhenania phosphate should be a potential P fertilizer source for those tropical acid soils with relatively high P‐retention capacity in some developing countries, provided its cost can be justified.
Direct In‐field Measurement of Nitrous Oxide Flux from Soils
Authors: Ryden J. C. , Lund L. J. , Focht D. D. 
Published: July 2010

AbstractA method was developed whereby nitrous oxide (N2O) effusing from a soil surface could be contained and selectively trapped for subsequent analysis. Containment of N2O was achieved by inserting a steel cover box with inlet and outlet ports into the soil. The enclosed air space above the soil surface was continuously swept by drawing external air through the cover at a flow rate of 20 liters/hour. N2O in the air swept from the enclosed airspace was adsorbed on 5Å molecular sieve. Adsorbed N2O was displaced for gas chromatographic analysis by addition of water to the molecular sieve in a closed system. N2O evolved from the soil surface was distinguished from that drawn into the cover during operation by concurrent measurement of the amount of N2O adsorbed from an equivalent flow of the external atmosphere. The adsorption and recovery of N2O by molecular sieve was affected by the N2O concentration in the air flow and the amount of N2O passed through the molecular sieve. Preliminary experiments in which N2O‐air mixtures were passed through 20g molecular sieve demonstrated that for N2O concentrations up to 34 µg N/liter, a flow rate of 20 liters/hour and sampling periods of 4 hours or less, complete recovery of N2O passed into the molecular sieve was achieved upon displacement with water. N2O released into the enclosed air space from an unsealed syringe was also quantitatively recovered providing a flow rate of at least 20 liters/hour was used to sweep the cover box. Flow rates of 10 to 40 liters/hour through covers inserted into moist soil had no effect on the measured rate of N2O evolution from the soil surface. Preliminary measurements at an irrigated, fertilized (120 kg N/ha) celery‐production block on a Haploxeroll indicated an overall mean N2O flux of 9.42 g N/ha per hour over a period of 76 hours. There was a diurnal variation in the N2O flux with mean peak fluxes of up to 15.8 g N/ha per hour occuring during the early afternoon. The method provides a basis for monitoring N2O flux from field soils under on‐going agricultural practice.
Shrub‐induced Spatial Patterns of Dry Matter, Nitrogen, and Organic Carbon
Authors: Barth R. C. , Klemmedson J. O. 
Published: July 2010

AbstractSpatial patterns of dry matter, nitrogen, and organic carbon were investigated for velvet mesquite [Prosopis juliflora (Swartz)] DC and for palo verde [Cercidium floridum Benth.] ecosystems in the Upper Sonoran Desert of Arizona. Standing understory vegetation and litter originating from the overstory shrub decreased in weight as distance from the shrub center increased. Litter originating from understory vegetation displayed weak spatial patterns in dry weight. Gradients in percentage N and percentage carbon of understory vegetation, understory litter, and shrub litter were generally lacking. However, percentage soil N and organic carbon decreased as horizontal distance from the shrub center and depth to 60 cm from the surface layer increased; soil pH under both shrubs changed with depth and horizontal distance. Quadratic response surfaces for these three soil properties differed significantly between velvet mesquite and palo verde. Limited sampling of honey mesquite (Prosopis juliflora var glanulosa Torr.) ecosystems in the Chichuahuan Desert in New Mexico showed spatial patterns of dry matter and soil properties that differed somewhat from those of Sonoran Desert shrubs.
The Applicability of Dual Gamma Scanning to Freezing Soils and the Problem of Stratification
Authors: Goit J. B. , Groenevelt P. H. , Kay B. D. , Loch J. G. P. 
Published: July 2010

AbstractThe attenuation of a dual energy gamma beam provides a powerful technique for studying the swelling phenomenon associated with soil freezing. However, the development of a stratified system due to the formation of a discrete ice lens in the same plane as the gamma beam requires special attention. Erroneous results are obtained when attenuation equations which are developed for homogeneous mixtures are applied to stratified media. The calculated dry bulk densities are then always lower than the averaged actual dry bulk densities and sometimes even negative. The calculated water contents are then always higher than the averaged actual water contents and sometimes in excess of 1 g/cm3. Stratification may also occur during the shrinking of unfrozen soil when cracks form in the same plane as the gamma beam. The equation describing the attenuation of a gamma beam in a stratified medium is formulated. A technical modification in the scanning procedure is suggested in order to solve the appropriate equations and to locate the interface.
A Comparison of Various Laboratory Methods for Predicting the Agronomic Potential of Phosphate Rocks for Direct Application
Authors: Chien S. H. , Hammond L. L. 
Published: July 2010

AbstractThe reactivity of seven phosphate rocks was estimated by five methods (neutral ammonium citrate first and second extractions, 2% citric acid, 2% formic acid, ammonium citrate pH 3, and absolute citrate solubility). These measurements were evaluated by crop response data obtained from a greenhouse experiment with guinea grass (Panicum maximum) and a field experiment with beans (Phaseolus Vulgaris L.), both on acid Colombian soils. Neutral ammonium citrate (second extraction), 2% formic acid, and ammonium citrate pH 3 solubilities were best correlated with these agronomic data.Factors such as: (i) calcite depression of apatite solubility in neutral ammonium citrate, (ii) the “grade” effect (total P content) on the apparent solubility, and (iii) the textural effect of apatite‐silica intermixing, need to be considered when correlations of chemical reactivity of the various phosphate rocks and their agronomic effectiveness are compared.
Dissolution and Transport of Gypsum in Soils: I. Theory
Authors: Glas T. K. , Klute A. , McWhorter D. B. 
Published: July 2010

AbstractA model was developed describing the dissolution and subsequent transport of gypsum from a soil column by combining the one‐dimensional convection‐dispersion equation with a kinetic expression for the dissolution process. The resulting partial differential equations were solved numerically by the method of lines. Results are presented showing the effect of the various parameters in the model on calculated concentration‐time curves.
Orthophosphoric Acid as a Phosphorus Fertilizer in Trickle Irrigation
Authors: O'Neill M. K. , Gardner B. R. , Roth R. L. 
Published: July 2010

AbstractTraditional P fertilizers have demonstrated relative immobility in soils. When used in trickle irrigation, these fertilizer materials tend to form precipitates in the irrigation lines which cause clogging problems and eventual breakdown of the system.The movement of P in Superstition sand was determined after spot placement of treble superphosphate (TSP) and injection of orthophosphoric acid (OP) with a trickle system. Rates of P application, based on the recommended rate of TSP for citrus in the Yuma, Arizona area were: check, 28 kg P/ha as TSP and 14, 28, 57, and 114 kg P/ha as OP. The experiment was conducted over the two irrigation periods; one for 3 days and the second for 24 days. Phosphorus was delivered to a greater soil volume when applied as OP than TSP, which should result in more plant available P in the root zone. The OP treatments lowered the pH of the irrigation water enough to eliminate clogging problems of P precipitates in the irrigation lines.
Boron Distribution in Soils and Waters of Egypt
Authors: Elseewi Ahmed A. , Elmalky A. E. 
Published: July 2010

AbstractSaturation extract, hot water‐soluble, acid‐soluble, and total B fractions were determined in soil samples from profiles representing six geographically diverse areas in Egypt. Saturation extract and hot water‐soluble B averaged 0.6 µg/ml and 1.3 µg/g. Acid‐soluble and total B averaged 10.2 and 113 µg/g. The acid fraction showed a curvilinear relationship with CaCO3 content of the soil, and averaged 12.5% of the total B. Total B, on the average, was twice as high in clay samples as in sandy samples, and decreased by about 32% beyond the 60‐cm depth of the soil profile. Concentrations of saturation extract B were either similar to or a reasonable multiple of Nile‐Water B, indicating that the latter is a direct source of at least water soluble B in these soils. Concentrations of water and acid‐soluble B suggest that B status in soils of Egypt is above the sufficiency level, and that under proper soil and water management the incidence of toxicity is unlikely.
Influence of Six Years of No‐tillage and Conventional Plowing on Fertilizer Response of Maize (Zea mays L.) on an Alfisol in the Tropics
Authors: Lal R. 
Published: July 2010

AbstractThe effects of four rates of N (0, 40, 80, and 120 kg/ha) and three rates of P (0, 13, and 26 kg/ha) on maize (Zea mays L.) response were investigated for no‐tillage and conventionally plowed plots on an Alfisol in southwestern Nigeria. These, experiments were conducted for three consecutive seasons. Notillage treatments yielded more than conventionally plowed plots in all three seasons. The mean yields were 2.90 and 2.42 metric tons/ha, respectively. There was no effect of P on grain yield. Nitrogen application had a significant effect on grain yield in all three seasons. Relative grain yield in the plowed plots without N application was 0.85 of that in no‐tillage plots. These results, obtained 6 years after adopting these tillage systems, are contradictory to those obtained in the first year of adopting these tillage practices. Leaf concentration of N was affected only by levels of N application.
Seasonal Weather Regimes Influence Interpretation of Pinus resinosa Foliar Analysis
Authors: Bickelhaupt Donald H. , Lea Russell , Tarbet Don D. , Leaf Albert L. 
Published: July 2010

AbstractA technique is described for quantifying the influence of seasonal precipitation and atmospheric temperature patterns (using degree‐day summations) on annual foliar analysis data. The results of this are used to adjust for the influence of climatic variation on foliar data so as to obtain a better estimate of species and soils relations. For Pinus resinosa, a species with determinate growth characteristics, precipitation and degree‐day summations over a portion of the previous snow‐free season plus the same measures for the current snow‐free season may be used to adjust annual foliar analysis data to improve these data for diagnostic purposes.
Solute Dispersion in Unsaturated Heterogeneous Soil at Field Scale: II. Applications
Authors: Bresler Eshel , Dagan Gedeon 
Published: July 2010

AbstractThe model for nonadsorbed solute spread by vertical steady‐state flow of water in a heterogeneous field soil, developed in Part 1, is applied to a Panoche soil with properties which have been investigated previously. Average solute concentration profiles as functions of depth and time are computed for various surface rates of infiltration. The average concentration over a layer extending from the soil surface to a given depth is also computed. It is shown that the concentration profile extends over an apparent mixing zone which is much larger than that predicted by a conventional diffusion‐convection (dispersion) equation in a homogeneous fictitious field, and that the latter lacks practical significance for prediction of solute spread in the field. The implications of the results for the leaching of saline field soil and crop yield estimates as they are influenced by rate of surface recharge and its uniformity are also discussed.
Cation Release from Michigan Spodosols Leached with Aspen Leaf Extracts
Authors: Adams Paul W. , Boyle James R. 
Published: July 2010

AbstractSoil samples (<2 mm) from the A horizons of three sandy Michigan Spodosols of varying productivity were leached with water extracts of Populus grandidentata Michx. leaves. Laboratory leaching experiments were used to simulate natural weathering of soil minerals by hydrogen ions of organic acids and the complexing of cations by organic compounds in the extracts. All of the soil samples released significant amounts of Mg, K, Na, and Fe, and most released Ca. Using data for Fe released by the leachings and existing data for subsoil Fe accumulation and ground water losses in similar soils, an estimate was made of the number of years of field conditions simulated by the laboratory treatments. The annual elemental release through mineral weathering in the A horizon in each soil was then estimated. Although estimated Ca weathering rates were notably low, estimated rates of Na weathering were comparable to those observed for podzol soils in New England.
A Comparison of Solid and Liquid Fertilizer for Coastal Bermudagrass Hay Production
Authors: Walker M. E. , Keisling T. C. , Marchant W. H. 
Published: July 2010

AbstractCoastal bermudagrass (Cynodon dactylon L. Pers.) response to N, P, and K fertilization has been well documented. Generally, the accepted result of previous work is a fertilization program consisting of either (i) applying a 10‐1‐4 N‐P‐K ratio or (ii) fertilizing to increase the acid extractable P and K to 25 and 50 to 70 mg/kg, respectively. Under (ii) N is applied as needed to obtain the desired forage production and protein concentration. Liquid urea‐nitrogen solutions have been investigated but little information on liquid P and K is available. An experiment with the objective of comparing liquid N, P, and K to conventional soild fertilization practices on Coastal bermudagrass was conducted on a Tifton soil (Plinthitic Paleudult; fine, loamy, siliceous, thermic) using a well established sod. A split plot design was used. Main plots were physical fertilizer form. Subplots were a complete 3 × 5 factorial with annual applications of 0, 37, and 74 kg/ha P and 0, 93, 186, 279, and 372 kg/ha K. Nitrogen was applied at 336 kg/ha for both liquid and solid forms. All fertilizer was applied each season as four equal split applications. Soil samples were analyzed for P, K, Ca, and Mg and soil pH was measured. Liquid fertilizer containing N, P, and K produced essentially the same forage digestibility as conventional solid fertilizer. Forage yield and N recovery was less with the liquid N source compared to solid fertilizer containing ammonium nitrate. The percentage digestible dry matter decreased as the % K in the forage decreased below approximately 1.5%. At the lower tissue K concentrations, the sod was infested to various degrees by Texas panicum (Panicum taxanum Buckl.), ragweed (Ambrosia artemisfolia L.), and large crabgrass (Digitaria sanguinalis L. Scop.) whose contribution to the forage yield would cause a reduction in digestibility. At 336 kg/ha N, more K was removed in the forage than was added when previously proposed N‐P‐K ratios were used. This excess removal of K by the forage could result in nutritional imbalances when soil reserves are exhausted. Applying high rates of K did not cause K accumulation in the Ap. Soil pH decreased in the upper and increased in the lower soil profile when using solid fertilizer as compared to liquid fertilizer. Extractable Mg also decreased in the upper and increased in the lower soil profile when using solid compared to liquid fertilizer. Additional work is needed to characterize the relation between forage yield level, K removal on various soils for several years, and Coastal bermudagrass stand characteristics when the soil K reserves are exhausted.
The Nature of the Phosphate‐Goethite (α‐FeOOH) Complex Formed with Ca(H2PO4)2 at Different Surface Coverage
Authors: Parfitt R. L. 
Published: July 2010

AbstractBasic information on the reaction between Ca(H2PO4)2, NaH2PO4, H3PO4, and the iron oxide goethite (α‐FeOOH) has been obtained prior to a study of the desorption of phosphate by plants. Infrared spectra of the wet phosphate‐goethite complexes suggested that the binuclear bridging complex was present with all these phosphates over the whole range from low surface coverage to maximum surface coverage. Maximum adsorption was observed when Ca(H2PO4)2 was used with 0.01M CaCl2 as the supporting electrolyte. The adsorption isotherms with phosphate and fluoride (NaF) reached a maximum value which indicated that there were 460 to 480 µmol of reactive A type OH groups on geothite. There was no evidence for phosphate adsorbed in any other form than the surface bridging complex which is formed very rapidly.
Errors in Determination of the Water Content of a Trickle Irrigated Soil Volume
Authors: Ben‐Asher J. 
Published: July 2010

AbstractA short review of the possible methods of measuring soil water content under high frequency trickle irrigation suggested that the gravimetric method was most appropriate. Three sources of errors in this method have been evaluated and discussed. The sources are those of water content by weight, bulk density, and integration based on the sampling grid. Furthermore, as the sampling mesh became coarser the results became unstable because the differences in volume of water became larger than the defined standard deviation (SD). Error analysis of measurements on uniform Bet Dagan grumusol and sandy soils of Nahal Sinai (Israel) and Yuma (Arizona) showed that coefficient of variation in volume of water within an irrigated volume element may be reduced if the sampling grid is taken properly. The analysis suggests that for a given coefficient of variation and interval of sampling depth, an optimum distance between lateral samples can be evaluated from a mathematical reorganization of the coefficient of variation.
Field Measurement of Denitrification: II. Mass Balance and Sampling Uncertainty
Authors: Rolston D. E. , Broadbent F. E. , Goldhamer D. A. 
Published: July 2010

AbstractDenitrification determined from the total production of volatile denitrification products was compared with denitrification determined from the difference of fertilizer addition, plant uptake, residual soil N, and leaching. Field plots on Yolo loam (Typic Xerorthents) were instrumented with soil atmosphere samplers, soil solution samplers, tensiometers, and thermocouples. Plots were maintained at two different water contents, at three different carbon levels (cropped, uncropped, and manure addition), and at two different temperatures. Fertilizer was applied at the rate of 300 kg N ha−1 as KNO3 enriched with 15N. The flux of gases at the soil surface was measured from the accumulation of N2O and 15N2 beneath air‐tight covers placed over the soil surface for 1 or 2 hours per day. Fertilizer N in plant, soil, and soil solution samples was determined from total N and 15N analyses. Soil 15NO3‐ vs. time and depth and soil‐water flux at several samplers were used to determine leaching of fertilizer N. Denitrification measured directly was generally 0 to 30 kg N ha−1 less than that determined by difference for the wetter treatments. For the drier treatments, denitrification measured directly was 12 to 65 kg N ha−1 less than that determined by difference due to the inability to measure very small gas fluxes of 15N2 over relatively long time periods and inability to continuously monitor gas fluxes. Uncertainties (95% confidence intervals) associated with the difference method were primarily due to the large sampling variability in leaching (±20–110% of applied N), although variability in soil residual NO3‐ (±5–30% of applied N) and residual organic N (±0–14% of applied N) measurements were also large. The uncertainty in the leaching component was also increased due to systematic error associated with overestimating the solute flux because of anion exclusion or immobile water. Although uncertainty in the direct method due to sampling variability (±0–30% of applied N) was less than that of the difference method, systematic errors may result in an underestimation of denitrification for some situations.
Overwinter Redistribution and Leaching of Fall‐applied Nitrogen
Authors: Bauder J. W. , Montgomery B. R. 
Published: July 2010

AbstractField studies were conducted on irrigated Maddock fine sandy loam (Udorthentic Haploboroll) to determine mineralization and nitrate leaching following fall application of N from Ca(NO3)2, (NH4)2SO4, and CO(NH2)2. Chloride was used to trace water and NO3‐ movement. Amount and distribution of NO3‐‐N present the following spring was considered an index of N mineralization and redistribution. Mass balance was used to determine loss during the overwinter period.Predominant depth of leaching was 80 to 115 cm each year, although estimated effective precipitation was only 10 to 20% of the soil moisture storage capacity. Some solute was leached to 180 cm. Considerable NO3‐ leaching and redistribution was observed following fall application of Ca(NO3)2. Nitrate accumulation following (NH4)2SO4 and CO(NH2)2 application was restricted to the 0‐ to 30 cm depth. From October to April net NO3‐ accumulation attributed to nitrification and mineralization averaged 58.4 kg/ha per year. Cloride leaching was not affected by N source. On the basis of these results, NO3‐‐based N sources should not be applied in the fall on these well drained sandy soils since significant N leaching may result.
A Model for Predicting Packing Density of Soils Using Particle‐Size Distribution
Authors: Gupta S. C. , Larson W. E. 
Published: July 2010

AbstractMany soil management decisions can be made from measured dry bulk density of the soil. These interpretations of soil behavior could be enhanced if soil particle‐size analysis could be used as a predictor of soil bulk density. A random‐packing model was developed utilizing soil‐particle size distribution as the principal input. Other inputs were average equivalent particle and cavity radii; bulk and particle densities of pure soil fractions determined under the same experimental conditions, like that of the final mixture; and concentrations of soil mineral and organic fractions. The model predicts random‐packing, maximum, and minimum bulk densities of a mixture of glass beads or soil fractions. Maximum and minimum bulk densities are limiting values not found in artificial or natural particle mixture. Tests of the random packing density with measured density showed a maximum deviation of 0.08 g/cm3 for multicomponent‐glass‐bead systems and 0.45 g/cm3 for mixtures of natural soil materials. Applications of the random‐packing model may delineate surface‐sealing susceptibility among soils of similar texture, describe the degree of profile devlopment among soils of different orders, and delineate soil profiles or horizons within a profile to pan formation susceptibility.