bluuebunny/crossref_metadata_2025_split huggingface dataset:
Calcium and Strontium Absorption by Corn Roots in the Presence of Chelates
Authors: Malzer G. L. , Barber S. A. 
Published: July 2010

AbstractWhile chelates have been shown to increase the flux of metal cations into roots, the mechanism has been subject to question. The objective of this research was to characterize the action of chelates on metal cation absorption. Calcium and Sr rather than micronutrient metals were used because some plant roots do not discriminate in their absorption, hence, relative flux of Ca vs. Sr could be used to evaluate uptake mechanisms. The chelates used were: EDTA (ethylenediaminetetraacetic acid), DTPA (diethylenetriaminepentaacetic acid), and HEDTA (hydroxethylenediaminetriacetic acid). Flux into corn (Zea mays L.) roots was determined by monitoring Ca, Sr, and chelate depletion from solution with time. Double labeling of Ca and Sr with 45Ca and 85Sr was used. Ligand concentrations were measured using Cd titration, 14C‐labeling, and UV‐absorption measurements of Cu‐ligand complexes.Calcium and Sr were removed from solution more rapidly than the chelate. Only 11 to 16% of the chelating ligand was absorbed over a 5‐day period whereas 90% or more of each of Ca and Sr was absorbed. The Ca/Sr ratio of uptake indicated that some of the Ca and Sr was absorbed directly from the chelate. However, where Ca2+ was maintained by continual addition, chelated Ca appeared relatively unavailable to the plant.
Rapid Determination of Unsaturated Hydraulic Conductivity in Tilled and Untilled Loess Soil
Authors: Ehlers W. 
Published: July 2010

AbstractA rapid method recently developed for determining moisture diffusivity and unsaturated hydraulic conductivity in undisturbed soil cores was employed to calculate the hydraulic functions of the upper layers of tilled and untilled loess soil. The results obtained with the new method compare well with results obtained by a field method. Diffusivity functions as influenced by tillage and depth were significantly different. Conductivities were highest in the 20–30‐cm layer of untilled soil and were lowest in the same layer of tilled soil. The number of replicates necessary to evaluate the hydraulic functions with arbitrarily specified precision was calculated. For the soil under study, five to nine samples are needed, when upper and lower limits of the 95% confidence interval of diffusity means are defined not to be different more than by a factor of three.
Simultaneous Transport of Nitrate and Gaseous Denitrification Products in Soil
Authors: Rolston D. E. , Marino M. A. 
Published: July 2010

AbstractA pulse of NO3‐ fertilizer tagged with 15N was applied to 100 cm long Yolo loam (Typic Xerorthents) topsoil and subsoil columns maintained uniformly unsaturated at soil‐water pressure heads between −20 and −140 cm of water at soil‐water fluxes between 1.0 and 0.1 cm day‐1. Nitrate, molecular nitrogen, and nitrous oxide from the applied fertilizer were measured as a function of soil depth and time until the NO3‐ pulse eluted from the column. An analytical solution describing the transport and transformation of NO3‐ was used to determine values for the first‐order denitrification rate constants within the columns. A numerical solution of the coupled equations for transport and transformation of NO3‐ and diffusion of the gaseous denitrification products was compared with measured N2 and N2O concentration profiles within columns. The gaseous concentration profiles were very much dependent upon values of the denitrification rate constant and the soil gaseous diffusion coefficient. Values of the soil gaseous diffusion coefficient, more than an order of magnitude smaller than those values measured in the upper part of the column, were required to approximately fit the numerical solution to the measured gas concentration profiles.
Effect of Pore Water Pressure on Sand Splash
Authors: Sloneker L. L. , Olson T. C. , Moldenhauer W. C. 
Published: July 2010

AbstractWe studied the effect of pore‐water pressure and particle‐size distributions on the amount of sand splash and on the instantaneous pressure changes within a packed sand core caused by single water drops falling on the surface. Both splash amounts and pore‐water pressure changes were affected by particle size, pore‐water pressure before drop impact, and by the direction of approach to the pore‐water pressure equilibrium. Pore‐water pressure increases from falling water drops were generally greater when equilibrium pressures were approached directly than when they were approached from minimum pressure. Sand splash was also generally greater when equilibrium pressure was approached directly.
Impact of Deicing Salts upon the Endomycorrhizae of Roadside Sugar Maples
Authors: Guttay A. J. R. 
Published: July 2010

AbstractTo evaluate the effects of deicing salts upon the endomycorrhizae of sugar maples (Acer saccharum Marsh.) root, soil, and leaf samples were examined from 44 roadside trees in Connecticut. Progressively greater dieback was significantly correlated with a decrease in endomycorrhizae, an increased depth to viable roots, and increased Na and chloride in roots and in the soil of the rhizosphere. Salt damage on sugar maple is attributed to a progressive root destruction as annual salt applications continue and an increasing top dieback as the diminishing root system is unable to sustain the top.
Relative Movement of Bromide and Nitrate in Soils under Three Irrigation Systems
Authors: Onken Arthur B. , Wendt C. W. , Hargrove R. S. , Wilke O. C. 
Published: July 2010

AbstractBromide has desirable characteristics as an indicator of nitrate movement in soils, although it has not been tested under field conditions. We studied its field applicability by growing sweet corn (Zea mays L.) on plots to which a mixture of sodium nitrate and sodium bromide were band applied. Irrigation was accomplished by either furrow, sprinkler or subirrigation. Nitrate and Br‐ moved together in the soil profile, but the concentrations of NO3‐‐N and Br‐ were quantitatively unrelated. The lack of a quantitative relationship was probably due to (i) NO3‐‐N was the sum of that already present, that from mineralization of organic matter, plus that applied while bromide came only from that applied, and (ii) NO3‐‐N from all three of these sources and Br‐ were removed from the soil at different rates by the growing crop.
Historical Highlights in American Soil Physics, 1776–1976
Authors: Gardner Walter H. 
Published: July 2010

AbstractAlthough there was some practice of soil physics in the first century of the nation's existence, soil physics as an identifiable discipline had its beginning in this country at the start of its second hundred years, with the most rapid growth coming in the early part of the 20th century. Particle size distribution and soil structure have been major themes in the development of the science, but these have been gradually replaced by water. Increasing attention has been given to the effect of physical properties on plant growth. Development and acceptance of theoretical concepts regarding water flow and retention in soils were enhanced by the development of instruments of measurement in the 1920's and 1930's. Modern needs appear to be for development of more comprehensive mathematical models of plant growth which may be used to help identify areas of needed research in soil physics.
Historical Developments in Soil Chemistry: Ion Exchange
Authors: Thomas G. W. 
Published: July 2010

AbstractThe early development of ideas on cation exchange from 1850 to 1900 is described. From 1900 to the present, the coverage has been divided as the work has concentrated on soil acidity, alkali soils, and classical cation exchange studies. The discovery of crystallinity in soil clays and the rediscovery of the importance of noncrystalline oxides adsorbed on crystalline clay minerals as sources of pH‐dependent acidity and anion exchange are reviewed. Some of the more important contributions made in understanding ion exchange in soils are covered in some detail. Other contributions are mentioned. It is concluded that despite the progress made, our understanding is still far from complete.
Laterally Confined, Steady Flows of Water from Sources and to Sinks in Unsaturated Soils
Authors: Raats P. A. C. 
Published: July 2010

AbstractLaterally confined, steady flows from line and point sources at arbitrary distance below the soil surface and to line and point sinks at arbitrary distance above an impermeable base are analyzed on the basis of the assumption that the hydraulic conductivity is an exponential function of the pressure head. The results include expressions describing the flow pattern, the distribution of the components of the flux, and the distributions of matric flux potential, pressure head, water content, and total head. The horizontal variations are described by trigonometric functions in problems involving line sources and sinks, and by Bessel functions in problems involving point sources and sinks. The regions below and above the sources and sinks are treated separately, subject, of course, to matching along the interface between the two regions. The vertical variations are described by exponential dampings, and surface and base reflections. For the flows to sinks, with each flow pattern there is associated an infinite variety of distributions of the matric flux potential etc., corresponding to different suctions applied at the sinks. Some problems involving partial supply by sources and interception by sinks are also treated.The application of water along lines and at points is of interest in connection with furrow, subsurface, and drip irrigation. The removal of water along lines and at points is of interest in connection with uptake of water by plant roots and a variety of devices used to extract water and measure fluxes in the laboratory and in the field.
Immobilization of Fertilizer Nitrate Applied to a Swelling Clay Soil in the Field
Authors: Kissel D. E. , Smith S. J. , Hargrove W. L. , Dillow D. W. 
Published: July 2010

AbstractLow recoveries of N fertilizer by crops on Houston Black clay prompted this investigation. Our objectives were to determine how much fertilizer nitrate can be biologically immobilized under field conditions when fertilization exceeds crop requirements and to determine when immobilization occurs during the growing season. Calcium nitrate tagged with 9.6 atom % 15N was applied to field microplots at 328 kg N/ha and grain sorghum (Sorghum bicolor L.) was planted in rows across each microplot. The various components of the N balance were measured by sampling microplots at different times during the season.Only 2.1 kg N/ha was immobilized during the first 47 days after fertilization and planting. The rate of immobilization increased rapidly during the next 60 days and an additional 60 kg N/ha was immobilized. This increase was apparently in response to an increase in soil temperature above 22°C.About 91% of the fertilizer N was recovered, indicating that no more than 9% was denitrified, in spite of ample water that was received as rain or irrigation water during the study. A net immobilization (an increase in soil organic N relative to an unfertilized plot) of 53 to 73 kg N/ha was measured on the fertilized plot. This net immobilization suggests that the organic N content of swelling clay soils that have historically been subjected to exhaustive cropping may increase slowly and gradually reach a higher equilibrium level due to N fertilizer use.
Soil Acidity from Long‐term Use of Nitrogen Fertilizer and Its Relationship to Recovery of the Nitrogen
Authors: Jolley Von D. , Pierre W. H. 
Published: July 2010

AbstractTwo N‐rate experiments in which corn (Zea mays L.) had been grown continuously for 15 and 17 years were used: (i) to study quantitatively the amounts of acidity that had been developed at different levels of N fertilization and (ii) to determine to what extent the acidity produced can be explained and predicted from the amounts of N recovered in the crops and in the soil as NO3‐N and organic N. The measured acidity was compared with the acidity calculated from N recovery, and both were expressed as percentages of the theoretical (potential) acidity developed from nitrification.No significant increases in acidity were found in either soil below a depth of 30 cm. With amounts of applied N that produced near‐maximum yields, soil nitrate accumulation was small, and the measured acidity (CaCO3 requirement) was < 30% of the theoretical or potential. When excessive amounts of N were applied, however, relatively large amounts of NO3‐N were found in the profile, and nearly 50% of the theoretical acidity was developed. The calculated CaCO3 requirements from N recovery at near‐maximum yields tended to be smaller than that measured in the soil. This difference in the Galva soil profile was accounted for in part by a decrease in acidity between 30 and 45 cm, probably caused by nitrate absorption and by denitrification in these layers. With excessive N applications, the CaCO3 requirements calculated from N recovery were in very close agreement to that measured, averaging 48% and 47% of the theoretical, respectively.Because the acidity calculated from N recovery essentially accounted for the acidity actually found and because the corresponding N recovery was only 68% (Table 6), the 32% of the N unaccounted for evidently was lost without an equivalent amount of base. Thus, the deficit in the acidity found provides corroborative evidence to the N‐recovery data that a substantial amount of the N applied in fertilizer was lost from the soils without an equivalent amount of base. Under the conditions of these experiments, this loss probably was through denitrification.
Profile Accumulation of Fertilizer‐Derived Nitrate and Total Nitrogen Recovery in Two Long‐term Nitrogen‐rate Experiments with Corn
Authors: Jolley Von D. , Pierre W. H. 
Published: July 2010

AbstractTwo long‐term N‐rate experiments with corn (Zea mays L.) which had been conducted in northwestern Iowa on the Moody and Galva silty clay loam soils for 17 and 15 years, respectively, were studied to determine the recovery of applied N (i) as NO3‐N at various soil depths, (ii) as organic or fixed N, and (iii) as N removed in the harvested corn grain. The annual N rates applied as NH4NO3 were 0, 56, 112, and 168 kg N/ha on the Moody soil and 0, 90, and 134 kg N/ha on the Galva soil. Nitrogen recovery in the fertilized plots was determined by subtracting the amounts for the unfertilized treatment from those for the fertilized treatments.The maximum amount of N recovered as nitrate in the profiles was 1,307 kg/ha in the Moody soil as contrasted to only 231 kg/ha in the Galva soil. The maximum depth of accumulation, however, was between 1.2 and 1.5 m in both soils, and there was no indication of nitrate leaching below about 2.4 to 2.7 m in either soil.The percentage of N recovered as nitrate with increasing N applications increased from 18% to 48% in the Moody experiment compared with only 7% to 12% in the Galva; conversely, the percentage N recovery in the grain decreased from 38% to 11% for the Moody, and from 40% to 28% in the Galva, with the increasing N applications.At rates of N required to obtain maximum yield in the Moody and Galva soils, the percentage N recoveries in the grain were similar, 38% and 40%, respectively. Likewise, the percentage recoveries were 18% and 7% as NO3‐N, 18% and 22% as organic N, and 74% and 68% total, respectively. Thus, at maximum yields, the percentage of the applied N not accounted for was 26% and 32% of that applied to Moody and Galva soils, respectively. At the highest rate of application (168 and 134 kg/ha, respectively) the losses increased to 37% and 46% for the respective soils. The unaccounted for N is considered to have been lost largely through denitrification. These data emphasize (i) the close relationship that exists between efficient N utilization and possible nitrate pollution, and (ii) the importance of establishing and applying rates of N no greater than required to obtain maximum yield.
Effects of Irrigation Management on the Quality of Irrigation Return Flow in Ashley Valley, Utah
Authors: Bliesner Ron D. , Hanks R. J. , King L. G. , Willardson L. S. 
Published: July 2010

AbstractThe relationship between leaching fractions obtained under field conditions and soil water salinity profiles on nature alfalfa was studied by applying three qualities of water at three leaching fractions to areas of an alfalfa field (Medicago sativa L.) having three depths to water table. The electrical conductivity of the irrigation water and of the soil solution extract at various depths was measured for each irrigation. ET measurements from several lysimeters located in the field were used to determine depths of irrigation water to apply. A sprinkler irrigation system was used for application of the irrigation water to the plots, and the depth applied was determined by measuring the depth of water caught in cans placed in a sample plot during each irrigation.The electrical conductivity of the irrigation waters applied averaged 0.98 mmhos/cm, 2.22 mmhos/cm, and 2.80 mmhos/cm for the season. Leaching fractions for the low leaching treatment of each water quality averaged 0.003. The other leaching treatments ranged from 0.082 to 0.343. Assuming an inert soil with no precipitation or dissolving of salts, there should have been increases in average soil profile salinity ranging from 1.81 mmhos/cm to 5.45 mmhos/cm during the season depending on the treatment. The largest increase measured on any treatment was 0.32 mmhos/cm. Some treatments actually caused a decrease in salinity where an increase was expected. For the condition of this study it appears that soil profile salinity is relatively insensitive to leaching fraction for short periods of time (1 or 2 years). This is attributed to the high relative concentrations of calcium and sulfate in the irrigation water and soil solution. Bearing these factors in mind, it appears that the quantity of salt removed in the drainage water varies directly with the quantity of drainage water since the concentration is relatively constant.
The Effect of Potassium Fertilization and/or Irrigation on Elemental Leaching in a Red Pine Plantation
Authors: Marion G. M. , Leaf A. L. 
Published: July 2010

AbstractOn a glacial outwash plain in the Adirondack Mountains of New York, a K fertilizer‐irrigation study on elemental leaching in red pine (Pinus resinosa Ait.) was initiated in 1966. Elemental leaching was monitored for 3 years using tension plate lysimeters. Significant leaching of K fertilizer occurred during the initial year of treatment. Despite the high mobility of K in the coarse‐textured soils of the study area, K soil leachate concentrations remained high for the 3 years of the study. The previously reported long‐term response to K fertilization on these K deficient sites may be due, at least in part, to the persistence of K in the soil surface. Potassium fertilization increased leaching of Ca, Mg, and Na. Irrigation increased the mobility of fertilizer K and may have increased elemental leaching of P. With the exception of Ca, elemental leaching losses from untreated plots were small relative to soil stores.
Evaluation of Theoretically Predicted Thermal Conductivities of Soils under Field and Laboratory Conditions
Authors: Hadas A. 
Published: July 2010

AbstractIn the literature one finds claims that the Philip‐deVries model of heat and moisture transfer fails to predict the amounts of water moved by vapor transfer.In the work reported here an attempt was made to check and verify the predictive capabilities of the deVries, Philip and deVries models for vapor transfer by evaluating the latent heat transfer carried by vapor rather than to account for vapor flow from the usually performed total moisture balance.It was found that the deVries model predicts quite accurately the transfer of heat by vapor under steady state conditions, but underestimates it under nonsteady state conditions.The possibility that the assumed diffusive vapor transport should be corrected by including “enhancement factors” so as to incorporate local thermal gradients and mass movement induced vapor transfer, not accounted by the present model is brought up and the nature of the enhancement factors and the implications to field conditions are discussed.
Evaporation and Salt Movement in Soils in the Presence of Water Table
Authors: Hassan F. A. , Ghaibeh A. Sh. 
Published: July 2010

AbstractEvaporation from homogeneous and stratified columns, in the presence of shallow water table, at steady state, was examined. Soils from Syria and Egypt were used. Their hydraulic conductivity‐moisture tension curves were determined and fitted to smooth curves represented by Gardner's empirical formula. Solutions obtained by Gardner for the steady flow equations were modified for the boundary conditions of the top and bottom layers then reduced to a dimensionless form with two variables, the relative flux density, and the relative tension at the interface. The resulting equations were used to calculate the evaporation rates. Salt profiles near the surface, at different evaporation rates, were also studied.In case of homogeneous soil columns the calculated values gave close estimates of the measured evaporation rates. However, the ratio of the calculated to measured rates was 1.3 to 1.6 for stratified columns.The salt profiles in the top dry layer indicated the polyphasic nature of water movement in this zone. The observed increase in the dispersion coefficient with the solution velocity was more pronounced in soils of wider range of pore size.
Miscible Displacement of Nitrate and Chloride under Field Conditions
Authors: Misra C. , Mishra B. K. 
Published: July 2010

AbstractIn an attempt to develop the capability for predicting the reduction loss of NO3‐N during leaching of nitrate fertilizers in an Oxisol field profile, a 2‐cm pulse of Ca(NO3)2 solution containing 304 ppm of NO3‐N was displaced through a 300‐cm by 300‐cm field plot saturated with water down to the depth of 55 cm. On the following day an identical pulse of NH4Cl solution containing 795 ppm of Cl was leached through the same plot. The results were analyzed by means of a convective diffusion type transport equation that incorporated an irreversible first‐order sink term. The agreement between the observed and the theoretical breakthrough curves allowed the determination of the first‐order reduction rate constant for NO3‐N as 0.1 hour−1 at an average soil temperature of 34°C. Under these conditions, the recovery of added NO3‐N in the leachate was 70% whereas that of Cl was 100%, approximately, when the two pulses moved past the 55‐cm soil depth. The apparent diffusion coefficients for NO3‐N and Cl were velocity dependent and ranged between 41 cm2 hour−1 to 80 cm2 hour−1, corresponding to the pore velocity range of 11.5 cm hour−1 to 17 cm hour−1. Although the present model was reasonably successful in predicting transport of ions undergoing microbial transformation in a natural soil, a more appropriate treatment should consider ion movement in stagnant and mobile phases in the soil pores in view of greater precision in working out the kinetics of biodegradable solutes.