bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of Drainage Equations for the Gravity Drainage of Stratified Profiles
Authors: Watson K. K. , Whisler F. D. 
Published: July 2010

AbstractThe output from a computer‐based numerical analysis of the gravity drainage of a sand profile through an underlying impeding layer is used as the data for testing the manner in which algebraic equations are capable of describing the stratified drainage process. The comparisons indicate that no single equation is satisfactory in describing the wide range of nonlinear behavior that occurs with eight cases analyzed. However, when specific coefficients determined from a least squares analysis are used in an equation of the Jackson and Whisler type satisfactory correspondence is achieved.
Effects of Liquid‐phase Electrical Conductivity, Water Content, and Surface Conductivity on Bulk Soil Electrical Conductivity
Authors: Rhoades J. D. , Raats P. A. C. , Prather R. J. 
Published: July 2010

AbstractRecent research has demonstrated that field soil salinity can be inferred from four‐electrode soil electrical conductivity (ECa), if the soil profile is near “field capacity” and calibration curves, based on saturation extract salinity (ECe), are available. To extend the use of this field method to arbitrary water contents, we studied EC in the laboratory as a function of water content (θ) and in situ soil water conductivity (ECw). We collected undisturbed cores of four soil types (fsl, vfsl, l, cl) using Lucite column inserts, which were tapped for later insertion of electrodes. The cells were equilibrated with waters of a desired ECw and, using a pressure membrane apparatus, adjusted to a desired θ. Values of ECa were calculated for each ECw − θ equilibration from measured four‐electrode resistances and an appropriate cell constant. Our results indicated that over the θ‐range of practical concern, ECa = (transmission coefficient) × θ × ECw + surface conductivity. This relationship is derived using a simple capillary model, which assumes that liquid phase and surface conductivities (via exchangeable cations) behave as resistors in parallel.
Nitrogen, Phosphorus, and Potassium Utilization in the Plant‐soil System: An Analytical Model
Authors: Smith O. L. 
Published: July 2010

AbstractAn intermediate‐resolution analytical model of nitrogen, phosphorus, and potassium utilization in the plant‐soil system was developed and tested. Starting from specified natural or artificial sources in the soil, element transport to root absorption surfaces was modeled in terms of diffusion, mass flow, and soil buffering mechanisms. Element uptake was described by carrier theory formalism, and assimilation was based on four premises about the roles of N, P, K, and photosynthate in cell chemistry. There were three main objectives of the model. The first was to predict the first‐order interactive growth response of particular plant species to any combination of these macronutrients supplied in the soil medium. Species parameters required by the model include root absorption rate and certain cell chemistry reaction rates. The second objective was to make the model sufficiently general to describe a broad range of species. It was built upon common denominator principles of physiology condensed from available experimental data on corn (Zea mays L.), bean (Phaseolus vulgaris), pine (Pinus elliottii Var. elliottii), etc. In this generic sense it is a measure of what plants have in common. The third objective was to use the model to test several well‐known theories of plant growth.The model was validated against reported experiments on ryegrass (Lolium perenne L.), oat (Avena sativa), a legume (Stylosanthes humilis), and rutabaga (Brassica napobrassica, Mill.), in which dry matter yield was measured as a function of factorial application of N, P, and K to the soil. The model shows that much of the deficient, optimal, toxic, and interactive response of plants to N, P, and K can be explained in terms of strong linear response of cell chemistry to low nutrient concentrations and inhibition by N, P, and K at high nutrient concentrations. Applying the model in a test of plant response to suboptimal nutrient concentrations, the model strongly confirms the Liebig Law of the Minimum and refutes the opposing multi‐limiting‐element Baule Product Law. The model also shows that the Liebig theory of linear growth response to nutrient concentration and the opposing, nonlinear Mitscherlich Law of Diminishing Return are not necessarily in disagreement, but rather may apply to different parts of the nutrient concentration range. And the model confirms that the effects on growth of nitrogen, phosphorus, and potassium levels are more often additive on the reciprocal scale than on either the logarithmic or untransformed scales.
Water Use and Productivity of Wheat under Five Irrigation Treatments
Authors: Ehlig C. F. , LeMert R. D. 
Published: July 2010

AbstractWater use and yield of wheat (Triticum aestivum L. em. Thell, cultivar Bluebird 2) were compared under five irrigation treatments using wheat planted in a silty clay loam soil in December and harvested in May. Water was applied at five rates from 11% more to 23% less than evapotranspiration (ET) from a weighing lysimeter planted to the same crop. Equal quantities of water per irrigation were applied at 76 mm in the pre‐emergence and the first postemergence irrigations and 102 mm in later irrigations. For a 102‐mm application, an irrigation was scheduled whenever cumulative ET from the lysimeter reached 91, 102, 112, 122, and 132 mm of water, since the last scheduled irrigation for the treatments. Total amounts of 485 to 688 mm of water were applied in five to seven irrigations. Soil water content to 1.5 m decreased progressively with water applications below ET. The soil water content was determined gravimetrically before each irrigation and water use determined from differences in soil water content between irrigations plus the amount of applied water. Seasonal water use decreased progressively from 677 to 540 mm as irrigation frequency decreased, although water use in all treatments was similar for the first 120 days.Yields decreased as water applications decreased, except between the treatments equal to ET and at 10% below ET. At the three driest treatments yield decreased proportionately with water use, indicating that water use efficiency was not increased by restricting water use below ET from adequately watered wheat. A relationship between grain yield (Y), in g/m2, and water use (X), in mm water, was characterized by the expression: Y = −9548 + 46.42X − 0.06866X2 + 0.00003390X3 (r = 0.98). Seed weight was unaffected by irrigation treatment. Cumulative total dry weight was similar on all treatments for the first 120 days. Plants headed 7 to 10 days earlier and matured 5 or 6 days earlier on the driest treatment than on the wettest treatments. Earlier maturity could have accounted for most of the differences in water use and total dry matter between treatments, although water stress was also important in the driest treatment. Plants produced more heads on the drier than on the wetter treatments and were shorter on the driest treatment. Data on the salt balance of the soil profile were inconclusive. The significance of these data to irrigation scheduling is discussed.
Surface Soil Moisture within a Watershed—Variations, Factors Influencing, and Relationship to Surface Runoff
Authors: Henninger D. L. , Petersen G. W. , Engman E. T. 
Published: July 2010

AbstractSurface soil moisture was measured within the upper 15 cm using neutron‐scattering equipment on six soil series within a 57.8‐ha Pennsylvania watershed during the 19 May to 11 Nov. 1971 period. Surface soil moisture was responsive to individual storm events, showed discernible seasonal trends, and displayed larger fluctuations at higher moisture levels than at lower moisture levels. An analysis of variance showed that well‐drained soils had significantly different surface soil moisture levels than the more poorly drained soils and could be grouped into a hydrologic unit distinct from the more poorly drained soils. Surface soil moisture measurements along parallel transects approximately perpendicular to the slope contours showed high surface soil moisture contents proximal to the stream indicating that these areas contribute more to surface runoff in a shorter period of time than areas distant from the stream channel. Multiple regression equations using pan evaporation and surface soil moisture for each soil series were used to show the relative importance of the internal soil drainage class in predicting surface runoff.
Simulation of Profile Water Storage as Related to Soil Hydraulic Properties
Authors: Hillel Daniel , van Bavel C. H. M. 
Published: July 2010

AbstractA previously published numerical model of soil‐water dynamics was used to simulate the separate and combined processes of infiltration, drainage, and evaporation, as determined by hydraulic properties.Three hypothetical soils were compared: sand, loam, and clay. Typical soil moisture characteristic functions were assigned to each, and the respective hydraulic conductivity functions were calculated. Uniform profiles of these soils were then subjected to various sequences of rainstorms and dry periods. The sandy soil provided the least evaporation and the most rapid downward flow. This resulted in the most effective storage under a relatively dry regime. The situation was reversed in the case of the clay soil, which stored the most water under a relatively wet regime, while the loam exhibited intermediate behavior. Some consequences of this pattern affecting arid zone ecology are discussed.
Cation‐Exchange Capacity of Acid Soils Using Aluminum Chloride and Barium Chloride‐Triethanolamine
Authors: Alexander E. B. 
Published: July 2010

AbstractBase saturation is such an important criterion for classifying soils in the U.S. Soil Taxonomy that a procedure has been developed for scantily equipped field laboratories. Exchange acidity and cation‐exchange capacity (CEC) are determined in sequence with the same samples. The procedure involves (i) displacement of exchangeable hydrogen and Al with BaCl2‐triethanolamine solution and back‐titration with HCl to determine the exchange acidity, (ii) saturation with Al from AlCl3 solution, (iii) removal of excess Al with water, (iv) displacement of Al with BaCl2‐triethanolamine solution and back‐titration with HCl to determine the exchange capacity, and (v) estimation of basic cations by the difference between the CEC and the exchange acidity. This is an extension of a well‐established procedure for determining exchange acidity. The CEC results compare closely with the sums of cations for acid subsoils, but are low for Al horizons with much organic matter.
Soil Elastic Constants: II. Application to Analysis of Soil Cracking
Authors: Briones A. A. , Uehara G. 
Published: July 2010

AbstractSoil briquets from a Vertisol and two Oxisols, equilibrated over a range of 15 to 936 bar water tension were subjected to a constant rate of strain. The trend in measured flexure and stress at rupture was adequately predicted by theory, but the measured values differed from calculated values by a large factor. The breaking stress or modulus of rupture followed the same trend as the ratio of the material's surface tension to a parameter which measures pre‐existing, microcracks. Elastic constants were necessary, but not sufficient to accurately predict cracking. The precursor to cracking appears to be prefailure microcrack formation which determines the manner of soil cracking.
Model of Salt Flow in Soil with a Source‐sink Term
Authors: Melamed D. , Hanks R. J. , Willardson L. S. 
Published: July 2010

AbstractIrrigation management practices require a knowledge of the salinity in the root zone. Models which simulate the simultaneous movement of water and soils, but ignore the buffering property of the soil fall to predict the root zone salinity distribution in many field situations. The present work develops a model that takes into consideration source and sink processes and tests it under laboratory and field situations.In determining a “source‐sink” term to be included in the model, it was assumed that precipitation and dissolution were the most important source processes and that the rate of the processes was a function of the surrounding concentration.The parameters for the “sink‐source” term for soil columns were determined from effluent data, and were found suitable for predicting the salinity of the entire soil column. Under field conditions, individual parameters for each layer were needed for good prediction.
A Technique to Index Soil Pores and Aggregates Larger than 20 Micrometers
Authors: Wilkins D. E. , Buchele W. F. , Lovely W. G. 
Published: July 2010

AbstractA laboratory technique was developed to measure soil pore size, soil aggregate size, and orientation of soil pores and soil aggregates. The technique consisted of fixing soil samples with a fluorescent polyester resin, sectioning the soil samples, and taking a photograph under black light. The black light provides sharp contrast between pores and soil aggregates. The photographs were scanned with a Flying Spot Particle Analyzer (FSPA). From the FSPA scanning information, means, and variances of soil aggregate size, soil pore size, and apparent soil porosity were calculated. This technique is limited to nonswelling soils with pore and aggregate intercepts > 20 µm.
Historical Highlights in Soil Genesis, Morphology, and Classification
Authors: Cline M. G. 
Published: July 2010

AbstractAlthough E. W. Hilgard and G. N. Coffey pioneered, it remained for C. F. Marbut to integrate concepts in a comprehensive model of soil that found acceptance in America. Establishment of the Soil Survey by the controversial Milton Whitney created a major instrument for progress in the subject matter of Division S‐V. The Soil Survey responded to the philosophies of Marbut and survived a bitter controversy during the early years of the USDA Soil Conservation Service.Division S‐5 originated as an association of soil survey workers in 1920. The association gradually broadened its scope from primary concern with soil survey affairs to include most elements of soil science. In 1936 it merged with the Soils Section of ASA as the Soil Science Society of America, with its Division S‐V responsible for the subject matter of the original association.The approaches to soil morphology, genesis, and classification have been dominated by requirements of the soil survey. From largely qualitative concepts, the work has progressed to the quantitative approaches characterized by the Soil Survey Manual of 1951 and Soil Taxonomy of 1975. Increased awareness of geomorphic history has made age a much more important element in concepts of genesis. The quantitative limits of Soil Taxonomy have focused attention on the heterogeneity of mapping units. The greatly increased amount of data and modern data processing methods promise major opportunities for advances in soil genesis and soil interpretation.
Modeling Nitrate Movement and Dissipation in Fertilized Soils
Authors: Saxton K. E. , Schuman G. E. , Burwell R. E. 
Published: July 2010

AbstractIt is important to know the fate of nitrogen (N) fertilizers to ensure crop production and avoid pollution, but frequent measurement of soil N is difficult. Therefore, we developed a digital model to calculate the occurrence, movement, and dissipation of nitrate‐nitrogen (NO3‐N) within the soil profile of fertilized agricultural lands. Daily NO3‐N amounts and distributions within a 1.8‐m soil profile were calculated by representing the major processes influencing NO3‐N for the entire year. Daily soil moisture amounts and movement were predicted by a previously developed soil moisture‐evapotranspiration model.Profiles of NO3‐N measured periodically on two research watersheds in western Iowa, one normally fertilized (168 kg/ha per year) and the other excessively fertilized (448 kg/ha per year) with N were used for model verification. The daily calculations for the fertilized cornfields (Zea mays L.) with moderately permeable soils included NO3‐N movement, dissipation, and profile leaching. The predicted NO3‐N profiles closely represented those measured.
Mass Transfer Studies in Sorbing Porous Media: II. Experimental Evaluation with Tritium (3H2O)
Authors: van Genuchten M. Th. , Wierenga P. J. 
Published: July 2010

AbstractA comparison is made between observed tritium effluent concentration distributions and those calculated with a previously published analytical solution for the movement of chemicals through unsaturated, aggregated sorbing media. In the analytical model the liquid phase of the soil is divided into mobile and immobile regions, with transfer between the two regions diffusion controlled. Effluent data obtained from several displacements of tritium through 30‐cm long columns of Glendale clay loam were used to determine the different parameters in the analytical solution by curve fitting. The data indicate some adsorption or isotopic exchange of tritium during its flow through the soil columns. The amount of immobile water increases with decreasing flow velocity and increasing aggregate size, and varies between 6 and 45% of the total volume of water in the columns. The analytical solution provides an excellent description of the experimental effluent data, and shows that tailing can be explained satisfactorily by diffusional exchange of tritium between mobile and immobile regions of the soil.
A Comparison of Numerical Simulation Models For One‐Dimensional Infiltration
Authors: Haverkamp R. , Vauclin M. , Touma J. , Wierenga P. J. , Vachaud G. 
Published: July 2010

AbstractSix models, employing different ways of discretization of the nonlinear infiltration equation were compared in terms of execution time, accuracy, and programming considerations. All models yielded excellent agreement with water content profiles measured at various times in a sand column. The two explicit models, the θ‐based CSMP model and the h‐based explicit model, used between 5 and 10 times more computer time than the implicit models. Results obtained with the two models which used the Kirchhoff integral transformation were no better than those obtained with the two h‐based implicit models. The implicit schemes with implicit, or explicit evaluation of the hydraulic conductivity and water capacity functions appear to have the widest range of applicability for predicting water movement in soil with both saturated and nonsaturated regions. Excellent agreement was obtained between water content distributions, infiltration rates, and cumulative infiltration volumes calculated with the implicit finite difference model and Philip's quasi‐analytical solution.
Kinetics of Pyro‐ and Tripolyphosphate Hydrolyses in the Presence of Corn and Soybean Roots as Determined by NMR Spectroscopy
Authors: Subbarao Y. V. , Ellis R. , Paulsen G. M. , Paukstelis J. V. 
Published: July 2010

AbstractKinetics of pyro‐ and tripolyphosphate hydrolyses by corn (Zea mays L. var. ‘NK P × 50 A’) and soybean (Glycine max L. Merv. var. ‘Cutler 71’) roots were studied using a split‐root technique to supply nutrients and to prevent precipitation reactions between phosphate sources and other nutrients. Phosphate species were determined by nuclear magnetic resonance (NMR) spectroscopy after freeze drying to concentrate the sample. A chelating agent eliminated interference by ions in sample solutions.Hydrolyses of pyro‐ and tripolyphosphates at substrate concentrations of 75 ppm P followed zero‐order kinetics. Pyro‐ and tripolyphosphates were hydrolyzed faster by corn roots than by soybean roots under the conditions studied. The zero‐order rate constant for hydrolysis of pyrophosphate was 4.36 × 10−2 mmoles hour−1 in the presence of corn roots and 1.38 × 10−2 mmoles hour−1 in the presence of soybean roots. During tripolyphosphate hydrolyses by corn and soybean roots, tripolyphosphate concentration decreased linearly and orthophosphate concentration increased linearly; pyrophosphate hydrolyzed faster than tripolyphosphate. Rate constants for hydrolysis of tripolyphosphate were 2.50 × 10−2 mmoles hour−1 and 5.42 × 10−3 mmoles hour−1 by corn and soybean roots, respectively.
Ammonia Volatilization from Surface Applications of Ammonium Compounds to Calcareous Soils: VI. Effects of Initial Soil Water Content and Quantity of Applied Water
Authors: Fenn L. B. , Escarzaga R. 
Published: July 2010

AbstractAmmonia losses from (NH4)2SO4 (AS) and NH4NO3 (AN) applied to the surface of initially wet and initially dry soils, when followed by irrigation, were generally greater from the initially wet soils, especially when water application rates were < 2.5 cm. The greatest NH3 loss occurred at the lowest water addition and the least loss at the highest water addition. The addition of 20.3 cm of water to a Harkey silty clay loam did not reduce NH3 loss below that found with the addition of 5.1 cm of water. Ammonium was moved deeper into the soil by water in the initially wet soil than into the initially dry soil.Approximately a twofold increase in NH3 loss was observed following the application of AS and AN to the soil through irrigation water compared with NH3 loss following broadcast fertilizer application and subsequent irrigation. Again, initial soil water content influenced total NH3 loss with greater loss occurring from initially wet soil.A direct relationship was found between the loss of water and NH3 in sand. This relationship was not changed by placing a barrier to capillary water and N movement in the soil profile. The barrier greatly reduced absolute NH3 and H2O losses but did not influence the ratio of NH3 to H2O loss.
Characterization of Yield and Economic Loss from Nonuniform Fertilizer Distribution Using Computer Simulation
Authors: Sorensen R. C. , Wiese R. A. 
Published: July 2010

AbstractA simple computer program has been developed to predict yield losses from uneven broadcast fertilizer distribution on the basis of distribution pattern, yield response curve, fertilizer rate, soil test rating and amount of fertilizer swath overlap.Losses were serious only on soils classed “very low” in nutrient supply. Losses for a highly responsive crop are less than for a less responsive crop. Overlapping succeeding swaths may improve the appearance of a field, but has a small effect on yield loss unless the amount of overlap is > 50%. Visually evident streaks in plant growth patterns may not necessarily indicate high yield loss.