bluuebunny/crossref_metadata_2025_split huggingface dataset:
Constant‐Flux Absorption of a Tritiated Calcium Chloride Solution by a Clay Soil with Anion Exclusion
Authors: Bond W. J. , Gardiner B. N. , Smiles D. E. 
Published: July 2010

AbstractThe distribution of water, tritium, and chloride was measured following horizontal constant‐flux absorption of a tritiated CaCl2 solution by a Ca‐saturated clay soil. Water contents throughout the soil were < 80% of saturation at all times. The position of the tritium front corresponded closely with the interface which would exist between the initial and the inflowing solutions if the former were completely displaced by the latter. There was therefore no evidence of immobile water in these experiments. The chloride front moved ahead of the tritium front and the measured chloride concentrations throughout the soil were less than the concentration of the inflowing solution, although all of the added chloride was recovered. The behavior of the chloride relative to tritium is accounted for by anion exclusion.Tritium concentration profiles were accurately predicted using a theory described earlier. Difficulties were encountered, however, in extending this theory to the case of an excluded anion but an approximate predictive scheme is discussed. Areas for further work are outlined.
Improved Corrective Fertilizer Recommendations Based on a Two‐Step Alternative Usage of Soil Tests: I. Recovery of Soil‐Equilibrated Phosphorus
Authors: McLean E. O. , Oloya T. O. , Mostaghimi S. 
Published: July 2010

AbstractThe objective of these studies was to improve corrective fertilizer P recommendations using soil quicktest methodology which measures P‐fixation (buffering) tendencies of individual soils. Actual amounts of fertilizer P required to reach a selected sufficiency level of Bray‐1 available P were measured from the added P vs. available P relationship in 10 soils with a wide range in P‐fixation tendency. The new (universal) extractant of Mehlich was found to give approximately the same indication of P fixation as did Bray‐1, indicating that both P and K may be equilibrated together thereby eliminating one extraction. Regression analyses were made between the actual and variously computed amounts of P to reach sufficiency level based on constant fraction recovery, quicktest measured recovery (one‐step), and regression‐adjusted recovery (two‐step). This showed that most of the deviations between actual and computed values can be eliminated by this quicktest‐computed, regression‐adjusted procedure. Hence fertilizer recommendations evidently can be improved correspondingly. Relatively low correlation of Bray‐1 available P with yields of corn seedlings in this preliminary study appeared to be not the fault of the soil test but the effect of plant exploitation of the small aliquots of soils used.
Toxicity of Aluminum to Coffee in Ultisols and Oxisols Amended with CaCO3, MgCO3, and CaSO4·2H2O
Authors: Pavan Marcos A. , Bingham F. T. , Pratt P. F. 
Published: July 2010

AbstractA greenhouse experiment was conducted with six acid soils from southern Brazil to investigate the effect of available Al on growth and mineral nutrition of coffee (Coffea arabica L.) seedlings. Coffee seedlings were grown for 7 months in pots containing soil treated with varying amounts of CaCO3 up to twice the lime equivalent, and amounts of MgCO3 and CaSO4·2H2O equal to the lime equivalent. Leaf samples were collected immediately before harvesting the seedlings and analyzed for Ca and Al. At this time, soil was collected from each pot and analyzed for exchangeable cations and soluble ions. The chemical composition of the soil solution was used as input data for a computer program (GEOCHEM) to chemically speciate Al in the soil solutions. Shoot and root weights were correlated with KCl‐exchangeable Al of soil, percent Al saturation of soil, the concentrations of total Al (Alt) and Al3+ (calculated), and the activity of Al3+ (calculated) in the soil solution. Growth reductions of the seedlings correlated best with the Al3+ activity value. The toxicity threshold for the Al3+ activity was approximately 4.0 × 10−6. Leaf Al concentrations likewise correlated best with Al3+ activity. Threshold leaf Al concentrations of approximately 62 and 100 µg/g, respectively, were observed for reduction in root and shoot growth.
Leaching of Fertilizer Ions in a Kaolinitic Ultisol in the High Rainfall Tropics: Leaching of Nitrate in Field Plots under Cropping and Bare Fallow
Authors: Arora Yogesh , Juo A. S. R. 
Published: July 2010

AbstractLeaching and crop recovery of nitrogen (N) applied as calcium ammonium nitrate (CAN) to bare fallow and cropped plots were studied in a coarse‐textured, kaolinitic Ultisol under high rainfall conditions (mono‐modal). Maize (Zea mays) was planted in the first cropping season (March–July) and upland rice (Oryza sativa) in the second season (August–December). Rates of N applied to maize and rice were 150 and 90 kg/ha, respectively. Soil samples up to 120 cm in depth were taken at 4‐week intervals throughout the two growing seasons. Nitrate leached readily in the fallow and cropped plots. Liming (2 t/ha) shortened the initial time lag of nitrification, increased the nitrification rate, and, consequently, increased leaching of nitrate in both fallowed and cropped plots. During the first season, substantial amounts of NH4‐N persisted in the surface soil for over 4 weeks in plots that received CAN application.Splitting of N from one to three applications reduced the leaching loss from 53 to 28% of applied N. The limed plots with single application of N lost the largest amount of N through leaching. Splitting of N into two applications significantly increased grain yield of maize and rice. Further splitting into three splits increased the yield of rice only. Percentages recovery of applied N by maize were 22, 35, and 41% and 31, 39, and 61% by rice for one application, two and three splits, respectively. With one application of N during each cropping season, bare fallow retained 37% of the total applied N (240 kg N/ha) within the 0‐ 120‐cm depth at the end of the second cropping season.
Formation of an Oxisol‐Ultisol Transition in São Paulo, Brazil: I. Double‐Water Flow Model of Soil Development
Authors: Moniz A. C. , Buol S. W. 
Published: July 2010

AbstractThis study of Oxisol‐Ultisol transitions on hill slopes in transported material with oxic properties allowed the development of a double‐water flow model explaining the formation of soil structure that occurs during the soil development. According to this view, Ultisols form from Oxic materials through the action of both lateral‐ and base‐water flow, integrated in the landscape.In the sites studied both argillic and oxic horizons are formed from the same parent material. Oxisols are formed in thick colluvium on nearly level surfaces where the lateral‐water flow is not developed and the base‐water flow is too deep to affect the solum.The argillic horizon of the Ultisols on the slopes below the Oxisols is hypothesized to form inside a layer having blocky structure initiated by saturation ⇆ desiccation‐induced compression.The formation of the compressed layer is controlled by the geomorphology, which promotes the formation of the lateral‐water flow as the relief becomes steeper, as well as by the degree of vertical textural anisotropy.
Formation of an Oxisol‐Ultisol Transition in São Paulo, Brazil: II. Lateral Dynamics of Chemical Weathering
Authors: Moniz A. C. , Buol S. W. , Weed S. B. 
Published: July 2010

AbstractDepending on the mineralogical nature of the parent material and underlying rock, Fe, Mn, Si, and bases are concentrated downslope as a result of lateral‐ and/or base‐water flow action. Dissolution at the rock‐saprolite interface is an important supplier of those elements, which are transported by the base‐water flow affecting mainly the soils in the footslope.Chemical weathering does not always proceed in the same direction. The alternate process of desilication‐resilication occurs horizontally downslope along the toposequence. This approximately corresponds to Walther's Law of Succession of Facies. The lateral resilication process is important in tropical regions because it counterbalances the allitization process and explains the occurrence of relatively less weathered clay minerals on lower slope positions in the soilscape.
Mineralogy and Iron Characterization of Plinthitic Soils on Alluvial Landforms in Venezuela
Authors: Daugherty L. A. , Arnold R. W. 
Published: July 2010

AbstractThe iron oxides and clay mineralogy were characterized for several soils of Venezuela which contain plinthite and pseudo‐plinthite. Molar ratios of SiO2/Al2O3 (Ki ratios) of the plinthite and pseudo‐plinthite zones range from below 2 to above 4 suggesting a wide range in mineral composition. Cation exchange capacity for these zones ranged from 14.6 to 65.6 meq/100 g of clay suggesting that these mottled zones are not always associated with low activity clays. Kaolinite dominated the clay minerals. Montmorillonite was identified in a few pedons.Goethite was the dominant iron oxide present in the plinthite. The percentage of iron was determined by extracting the soil with citrate‐bicarbonate‐dithionite and by extracting with ammonium oxalate. These two extractions were ratioed (OX/CBD) yielding values of >0.05 for pseudo‐plinthite and values of <0.05 for plinthite in most cases. Soils with plinthite contained most of the iron in the sand‐ and silt‐size fraction following one drying cycle while soils with pseudo‐plinthite contained most of the iron in the clay‐size fraction.
Runoff and Soil Loss in Trinidad under Different Crops and Soil Management
Authors: Gumbs F. A. , Lindsay J. I. 
Published: July 2010

AbstractErosion caused by some of the farming practices on the major soil type (Orthoxic Tropudult) in the northern mountain range in Trinidad was assessed by measuring the runoff and soil loss from maize (Zea mays L.) and cowpea (Vigna unguiculata L. Walp) plots on 11, 22, and 52% slopes with and without tillage during the wet seasons in 2 consecutive years. The total rainfall for each of the three periods over which the experiments were conducted was 38.8, 22.4, and 82.5 cm, respectively.At the lower levels of rainfall there was generally a significant increase in soil loss (but not runoff) from the bare plots with an increase in slope from 11 to 22 to 52%; but a nonsignificant increase in both runoff and soil loss from the cropped plots. At the higher rainfall level, there were significant increases in soil loss from the bare and both of the cropped plots with an increase in slope from 11 to 22% only.The effect of tillage of the 22% slope on runoff and soil loss seems to have depended on the level and distribution of the rainfall and on the crop type. When rainfall is low, no‐tillage does not significantly affect runoff or soil loss, but it significantly (P = 0.05) reduces soil loss from bare plots if there are intense storms. At the highest rainfall level, no‐tillage still resulted in high soil losses (28 to 55 t/ha) and maize and cowpea (particularly maize) were less effective than at lower rainfall in reducing soil loss. Because of the high level of rainfall experienced in these hills the bare soil should not be exposed in the wet season and the clean cultivation of maize and cowpea in the wet season should not be recommended for slopes >11%.
Hydraulic Conductivity of Soil as Determined from Cumulative Runoff
Authors: Schroeder S. A. , Foster G. R. , Moldenhauer W. C. , Mannering J. V. 
Published: July 2010

AbstractHydraulic conductivity measurements using a Purdue sprinkling infiltrometer were performed on plots with the resultant data of cumulative runoff vs. time analyzed to determine values of hydraulic conductivity through the use of a cumulative runoff equation based on an infiltration equation proposed by Swartzendruber. Comparisons made with a differentiated form of an infiltration equation by Swartzendruber and Youngs (similar to the form of Philip's) or Swartzendruber's proposed infiltration equation were not, generally, greatly different. Additions of random errors in the data through computer simulation also did not change the resultant hydraulic conductivity values in the cumulative runoff method very much from the original data's determined hydraulic conductivity values. Thus using cumulative runoff versus time to determine hydraulic conductivity has shown to be reliable.
Effect of Soil pH on Adsorption of Lead, Copper, Zinc, and Nickel
Authors: Harter Robert D. 
Published: July 2010

AbstractLead, copper, nickel, and zinc adsorption by and desorption from pH‐adjusted soils has been studied. Surface and subsurface horizon samples of two soils were equilibrated with varying amounts of Ca(OH)2 prior to metal addition. The amount of all four metals retained was dependent upon pH of the soil sample, with retention dramatically increasing above pH 7.0 to 7.5. With the exception of Ni, at least 70 to 75% of the retained metal was extractable in 0.01N HCl. Nickel was somewhat less extractable, with that sorbed by the highest pH soils being the least extractable. Based on subsequent extractability, the soils used appeared to have specific adsorption sites for Pb, Ni, and Cu but little or none for Zn. These studies cast some doubt on the concept of pH management for immobilizing heavy metals placed on the land in that sorbed metals were substantially extractable by 0.01M HCl, which has been used to estimate plant availability of soil ions.
Evaluation of Irrigation‐Nitrogen Management Practices for Celery using Continuous‐Variable Irrigation
Authors: Stark J. C. , Jarrell W. M. , Letey J. 
Published: July 2010

AbstractThe interaction between N source and irrigation rate and the resultant effects on NO‐3 leaching were characterized for celery, using a modified line‐source sprinkler system which applied water across fertilizer plots at rates varying from replacement of evapotranspiration (ET) to 1.8 ET. Nitrogen, as (NH4)2SO4 (AS), was applied at a rate of 300 kg/ha in split applications (AS300); sulfur‐coated urea (SCU) was applied alone at 300 kg N/ha (SCU300), all preplant, or in a combination with 150 kg N/ha SCU preplant and 150 kg N/ha AS sidedressed (SCU150AS150). Plants with the AS300 and SCU300 treatments removed significantly less N at the lowest irrigation rate than those with the SCU150AS150 treatment, but this difference was not observed at high irrigation rates. All three N treatments produced large accumulations of NO‐3 beneath the root zone which increased with increased leaching. Yields from the fertilized treatments were significantly higher at all irrigation levels than yields from unfertilized plots, but were not different from each other. Yields also did not vary substantially across the range of irrigation rates, indicating that deep percolation of water and NO‐3 can be minimized through improved irrigation management without reducing celery yield.
Phosphorus and Potassium Fertilization of Irrigated Alfalfa on Calcareous Soils: I. Soil Test Maintenance Requirements
Authors: Fixen P. E. , Ludwick A. E. 
Published: July 2010

AbstractField experiments with irrigated alfalfa (Medicago sativa L.) were established in far eastern Colorado on a Keith soil and in far western Colorado on a Ravola soil in 1976. Concentrated superphosphate was applied at rates of 25 and 50 kg P/ha annually for 3 years or 75 kg P/ha in a single application at seeding. Muriate of potash was applied at rates of 140 and 280 kg K/ha annually for 3 years or 420 kg K/ha in a single application at seeding. Soil profile changes in NaHCO3‐P and exchangeable K were determined. At a location having low to medium available‐P status (crop response to P expected), 2.2 times the P removed by the alfalfa was required to maintain the initial NaHCO3‐P level. At a location with medium to high available‐P status (no P response expected), only 1.4 times the removed P was required for maintenance. The two locations required a fertilizer K rate of 0.75 and 0.22 times the K removed by alfalfa uptake to maintain their respective initial exchangeable‐K levels. The low maintenance requirement of the latter soil was apparently due to the K minerals present which buffered the exchangeable K near 100 mg·kg−1.
Phosphorus and Potassium Fertilization of Irrigated Alfalfa on Calcareous Soils: II. Soil Phosphorus Solubility Relationships
Authors: Fixen P. E. , Ludwick A. E. , Olsen S. R. 
Published: July 2010

AbstractAlfalfa (Medicago sativa L.) was established at two field locations in Colorado in 1976 and triple superphosphate applied at rates of 25 and 50 kg P/ha annually or 75 kg/ha in a single application at seeding. The initial P applications were incorporated while subsequent applications were topdressed. Soil profile changes in NaHCO3‐extractable P and in P solubility measured in 0.01M CaCl2 were determined over a three‐year period. The resulting calcium hydroxide and monocalcium phosphate potentials were related to known solubility products for distinct P mineral phases including octacalcium phosphate (OCP) and β‐tricalcium phosphate (TCP). Octacalcium phosphate controlled solution P if the NaHCO3‐extractable P rose above 35 mg·kg−1 while TCP or a similar mineral phase dominated P intensity in the range of 10 to 25 mg·kg−1. Relating these potentials to the changing NaHCO3‐P levels indicated that considerable Ca8H2(PO4)6·5H2O, octacalcium phosphate (OCP), accumulated in one soil. Solubility data from both soils also indicated significant buffering of soil P on or near the solubility isotherm of β‐Ca3(PO4)2, tricalcium phosphate.
The Kinetics of Gibbsite Dissolution in Nitric Acid
Authors: Bloom P. R. 
Published: July 2010

AbstractThe kinetics of dissolution of two synthetic gibbsite preparations was studied in nitric acid solutions with pH values that ranged from 1.5 to 3.3. Dissolution rates were determined at 298 K for both gibbsites and additional rate experiments were conducted at 313 K and 328 K with one of the gibbsites. Dissolution was controlled by reactions at the solid‐solution interface and not by diffusion. The rate of reaction did not increase monotonically with H+ activity; rather, there was a minimum rate of about pH = 2.25. Two different mechanisms with different rate‐controlling steps were suggested. At pH < 2.1 the rate‐controlling step was probably protonation of positively charged surface sites while at pH > 2.4 the rate‐controlling step was probably water attack of surface Al.
The Effect of Suspended Solids in Wastewater on Soil Hydraulic Conductivity: I. Suspended Solids Labelling Method
Authors: Vinten A. J. A. , Mingelgrin U. , Yaron B. 
Published: July 2010

AbstractA method for labelling suspended solids in sewage effluent with 14C‐DDT [1,1,1, trichloro‐2,2‐bis(p‐chlorophenyl)ethane] is presented. The method allows the vertical distribution of deposited solids in a soil, following leaching with effluent, to be determined. A simple physical model which describes transport of labelled suspension through the soil is developed. This enables the conditions necessary for successful utilization of the method to be defined. Procedures for the estimation of the parameters required for the model are presented and the application of the method is demonstrated for two soils. It is shown that the method for tracing the fate of suspended solids is valid, as long as the label is sufficiently strongly adsorbed on suspended solids. It is also required that the rate of desorption of label from suspended solids be low compared with the residence time of mobile suspended solids in the soil.
Leaching Characteristics of a Stony Desert Soil
Authors: Russo David 
Published: July 2010

AbstractThe leaching characteristics of a stony desert soil were studied. The functional relationships between pressure potential head and gravimetric water content for the different soil layers were determined in the laboratory under drying conditions using samples in which the stony fractions (> 2 mm) were excluded. These gravimetric water content values were converted to field volumetric water contents, using the field‐measured values of the field bulk density and the stone fraction (on a mass basis). For a given pressure potential head, volumetric water content decreased with depth. Unsaturated soil hydraulic conductivity functions for the different soil depths were determined by the transient drainage profile method, using tensiometers and the appropriate soil water characteristics functions. The saturated hydraulic conductivities were estimated from the steady‐state infiltration rate and the appropriate hydraulic head gradients. Measured saturated hydraulic conductivity values decrease with soil depth while for a given pressure potential head, the unsaturated hydraulic conductivity increases with depth. A leaching experiment was conducted in the field, by operating a sprinkler system at a rate of 7.6 mm/h. The time variations of the electrical conductivity (EC) of the soil solution as well as the concentrations of Na+, Ca2+, Mg2+, Cl‐, and SO2‐4 were recorded by extracting soil solution samples from four soil suction probes located at a depth of 0.45 m and spaced 12 by 12 m apart. The initial average EC of 165 dS/m was reduced to 7.5 dS/m as 800 mm of water were applied to the soil. This final value of the EC of the soil solution is three times higher than the EC of the irrigation water, as a result of the presence of gypsum and relatively high ESP in the solid phase of the soil profile. Measured values of the EC of the soil solution were used to estimate the value of the dispersivity for longitudinal dispersion, λ. The resulting λ = 2.91 cm is in relatively good agreement with published field data of λ for another soil, but is much smaller than the value of the equivalent field‐scale dispersivity calculated for two different soils.
Effect of Soil Properties on the Kinetics of Phosphorus Desorption
Authors: Sharpley A. N. 
Published: July 2010

AbstractRelationships between the constants of a semilogarithmic modified Elovich and a logarithmic equation describing the kinetics of soil P desorption and physical and chemical properties of 60 soils, collected from throughout the USA, and volcanic ash were investigated. These relationships are needed for application of the equations to modeling soluble P transport in runoff from agricultural watersheds. The constants of the semilogarithmic equation (a and b) were significantly related to the extractable Al and CaCO3 content of acidic and basic calcareous soils, respectively. For the logarithmic equation, constants (K, α, and β) were related to the ratio of Fe‐ or clay‐organic C content of the acidic soils and CaCO3‐ or clay‐organic C content of the basic calcareous soils. It is suggested that these ratios represent an index of interactive specific surface area involved with P adsorption‐desorption for a given soil. In contrast to the logarithmic equation, constants of the modified Elovich equation varied with soil P status and water‐to‐soil ratio. Thus, the former equation may have a wide application to describing soil P desorption in water quality models.