bluuebunny/crossref_metadata_2025_split huggingface dataset:
Water Movement in Bare and Cropped Soil Under Isolated Trickle Emitters: II. Analysis of Cropped Soil Experiments
Authors: Earl K. D. , Jury W. A. 
Published: July 2010

AbstractSoil moisture and plant root distributions were evaluated when plots of summer squash (Cucurbita pepo var. Zucchini) were trickle irrigated with two contrasting frequencies of water application. Replicated plots receiving the same total volumes of water were irrigated three times daily and once weekly, with irrigation volumes adjusted according to evapotranspiration and tensiometric data. In the presence of actively growing zucchini, weekly irrigations produced a greater movement of water both laterally and vertically downward than daily irrigations. Plant roots were distributed according to the wetted volume of soil, with roots of weekly irrigated plots being more evenly distributed than in daily irrigated plots where roots were concentrated beneath the emitter. The imposition of a water stress demonstrated a marked increase in root density beneath the emitters as a result of proliferation of fine root material.Zucchini yields in the outer ring of weekly irrigated plants (100 cm from emitter radially) were 30% higher than the most productive daily irrigated plot. Furthermore, total green matter and dry matter yields were greater in weekly irrigated plots.
Reactions of Aluminosilicates, Aluminum Hydrous Oxides, and Aluminum Oxide with o‐Phosphate: The Formation of X‐ray Amorphous Analogs of Variscite and Montebrasite
Authors: Veith J. A. , Sposito Garrison 
Published: July 2010

AbstractThe formation of X‐ray amorphous analogs of variscite and Namontebrasite was demonstrated to occur when Al2O3 · nH2O, synthetic allophanes, and allophanic soils were reacted with sodium o‐phosphates, Na3‐AHAPO4, of varying acidity A. The formation of the two amorphous Al‐phosphates, Al(OH)2H2PO4 and AlOHNaPO4, respectively, was favored both by an increase in lability of Al (i.e., by large values of the hydration number n in Al2O3·nH2O or the presence of Si‐O‐Al bonds in the aluminosilicates) and by an increase in the acidity A of the added o‐phosphate solution.Evidence for the formation of amorphous Al‐phosphates by secondary precipitation rather than the formation of a surface o‐phosphate phase by adsorption was indicated by the slowness of the reaction between o‐phosphate and Al‐containing material, by the immediate and significant increase of Si in solution when aluminosilicates were reacted, and by the large amounts of P reacted (e.g., 82% of the P added as equimolar H3PO4 reacted with synthetic allophane). The presence of amorphous Al(OH)2H2PO4 in the products was demonstrated by showing that a solid phase, Al‐P compound was formed in all of the reactions studied that had the same pH stability limites (2.5 ≤ pH ≤ 9) and solubility product pKso (28.1 ± 0.1) as were observed in a previous investigation for amorphous Al(OH)2H2PO4 formed directly from the reaction of Al‐hydroxy‐chlorides and o‐phosphate. The presence of amorphous AlOHNaPO4 in the products was inferred from an analysis of their formation curves (P in a solid phase vs. pH) and from measurements of the amount of Na bound with Al and P, corrected for adsorption of Na, as a function of pH. The formation of the amorphous, basic, Na‐containing AlOHNaPO4 begins at pH ≃ 6 and ends with the appearance of Al(OH)4‐ at pH ≃ 10.
Lead Adsorption by Montmorillonite Using A Competitive Langmuir Equation
Authors: Griffin R. A. , Au A. K. 
Published: July 2010

AbstractThe adsorption of Pb from pure Pb(NO3)2 solutions by Ca‐montmorillonite at pH 5.00 and 25°C was found to be sensitive to the weight of the clay sample. This apparent sensitivity of the adsorption of Pb to the weight of the sample was attributed to Ca competition for exchange sites as determined from Pb/Ca ratios found in the solutions. Adsorption of Pb from 0.1M Ca(ClO4)2 solutions was substantially lower and was insensitive to the weight of the clay sample. This further supported our conclusion that adsorption of Pb was dependent on the Pb/Ca ratio.Application of the “simple” Langmuir equation to Pb adsorption by 0.05 and 0.10 g of clay resulted in a linear relation over the entire concentration range (0 to 1,200 ppm Pb). However, increasing non‐linearity was observed at the lower Pb concentrations when 0.50 and 1.00 g of clay were used, respectively. These Langmuir plots yielded lower adsorption maxima than maxima obtained from the two lower weights of clay and the shapes of the isotherms indicated two distinct regions of adsorption. The data were then plotted according to a “competitive” Langmuir equation, which successfully resolved the data for all four weights of clay into a single linear adsorption plot.
Gas Chromatographic Analysis of Soil Atmospheres
Authors: Blackmer A. M. , Bremner J. M. 
Published: July 2010

AbstractA gas chromatographic procedure is described that permits rapid, specific, and precise determination of N2, O2, Ar, CO2, CH4, N2O, and other gases in soil atmospheres. It involves use of an ultrasonic detector and two columns of Porapak Q at different temperatures, and it does not require temperature programming, column conditioning, stream splitting, column switching, or switching of recorder polarity. Unlike thermal conductivity and helium ionization detectors previously used for gas chromatographic analysis of soil atmospheres, the ultrasonic detector is not adversely affected by gases found in soil atmospheres and permits determination of these gases at concentrations ranging from <10 ng/ml to 100%.
Decomposition of Carbon‐14 Labeled Plant Material Under Tropical Conditions
Authors: Jenkinson D. S. , Ayanaba A. 
Published: July 2010

AbstractRyegrass (Lolium multiflorum) and maize (Zea mays) tissue uniformly labeled with 14C were mixed with soil and allowed to decompose under field conditions in the open or under shade. The incubations were done in the forest zone of Nigeria, using a range of contrasting Nigerian soils. Of the ryegrass Coriginally added to the soil, 20% remained after 1 year, falling to 14% after 2 years. After 1 year the soil retained slightly less maize C than ryegrass C, but the difference was small and the overall pattern of decomposition similar. There was little difference between the rate of decomposition under shade or in the open, even though soil temperatures were considerably greater in the open. A soil containing 6% clay (Apomu series) retained slightly less maize C after 1 year than a soil with 16% clay (Egbeda series), but in general the decomposition rates in the different soils were similar.For ryegrass, the decomposition pattern was very similar under Nigerian conditions to that previously observed for the same plant material in England, except that the whole decomposition process was four times faster in Nigeria.
The Function of Different Types of Macropores During Saturated Flow through Four Swelling Soil Horizons
Authors: Bouma J. , Jongerius A. , Boersma O. , Jager A. , Schoonderbeek D. 
Published: July 2010

AbstractThe hydraulic function of three types of macropores during saturated flow through four swelling fine clayey and very fine clayey soil horizons was characterized with methylene blue as a tracer, and was quantified in large thin sections with the Quantimet 720. All three types of macropores, described as channels, vughs, and planar voids, contributed to flow. Distinction between “smooth” and “rough” ped faces in field structure descriptions proved meaningful for three soils with high linear extensibility values, because vertical flow did not occur along interconnected planar voids adjacent to “smooth” peds, whereas it did occur along “rough” peds. However, flow did occur along “smooth” ped faces in the fourth soil, which had significantly lower extensibility values. Calculations of hydraulic conductivity Ksat, based on the observed dye patterns, are difficult because the dye solution flowed in interrupted patterns along the walls of the macropores without apparently filling them, due to the occurrence of smaller pore “necks” in overlying soil. But the number and percentages of colored pores for each of the three macropore‐types showed (with one exception for planar voids) consistant differences among the four soils, which corresponded with differences in measured Ksat values.
Spodic Horizon Brittleness in Leon (Aeric Haplaquod) Soils
Authors: Brandon C. E. , Buol S. W. , Gamble E. E. , Pope R. A. 
Published: July 2010

AbstractThree delineations of Leon soils (Aeric Haplaquod; sandy, siliceous, thermic) on two geomorphic surfaces in the lower Coastal Plain of North Carolina were studied. Consistence of the upper part of the spodic horizon ranges from friable to brittle. Brittleness was associated with mineral material that was slightly finer in mean particle size, less well sorted, and slightly more fine skewed than spodic horizons that were not brittle. No chemical, mineralogical, or organic matter composition was related to brittleness. Brittle spodic layers are very different from nonbrittle layers in micromorphology, having their macropacking voids filled with organic matter and silt‐sized mineral material.
Effects of Fertilizer Nitrogen on Tree Growth, Foliar Nitrogen, and Herbage in Eastern Cottonwood Plantations
Authors: Blackmon B. G. 
Published: July 2010

AbstractWhen five rates of nitrogen fertilizer (0 to 672 kg/ha) were tested in two eastern cottonwood (Populus deltoides Bartr.) plantations 7 and 10 years old in the Mississippi River floodplain, first season volume growth was more than doubled by fertilization. By the end of the third season, the direct effect of fertilization had apparently disappeared although a volume advantage caused by the large initial response was still evident. In one plantation, volume growth for the 3 years after fertilization was greatest at 336 kg N/ha, and in the other volume growth was greatest at 672 kg N/ha. However, lower rates gave more volume growth per unit of applied N. Fertilizer also increased the N content of herbaceous plants.
Anion‐Aluminum Hydroxide Gel Interactions
Authors: Serna Carlos J. , White J. L. , Hem Stanley L. 
Published: July 2010

AbstractThe interaction of the nitrate, sulfate, and carbonate anion with aluminum hydroxide gel was studied by infrared spectroscopy. A lowering in the anion symmetry due to the interaction with the aluminum hydroxide surface was observed. Evidence suggests that the nitrate anion interaction is outside of the coordination sphere of the aluminum cation and therefore is mainly electrostatic. However, the sulfate and carbonate anions both show evidence of coordination with the surface aluminum cations. The carbonate interaction appears to be the strongest and is believed to be responsible for the relatively high degree of stability of carbonate‐containing aluminum hydroxide gel.
Fluorine Content of Soil from Morrow Plots Over a Period of 67 Years
Authors: Omueti J. A. I. , Jones Robert L. 
Published: July 2010

AbstractBetween 1904 and 1971, F content in Morrow Plot soils varied from a mean of 275 to 381 mg/kg. The cause of variation in F content was shown to be related to phosphorus fertilization practices. Much of the F added to the soils in the form of rock phosphate between 1904 and 1924 was retained by 1955. Average loss of F from the soil per annum between 1924 and 1944 was calculated to be about 2.5‐mg F/kg. Recent samplings contain large, unaccounted‐for variability.
Evaluation of Antimetabolites for Retardation of Urea Hydrolysis in Soils
Authors: Mulvaney R. L. , Bremner J. M. 
Published: July 2010

AbstractStudies to evaluate three antimetabolites patented as inhibitors of urea hydrolysis in soils (pyridine‐3‐sulfonic acid, desthiobiotin, and oxythiamine chloride) showed that they had no effect on production of urease by soil microorganisms and did not retard urea hydrolysis in soils or reduce gaseous loss of urea N as ammonia, even when applied at rates far exceeding those recommended for inhibition of urea hydrolysis.
Water Uptake by Plants: I. Divided Root Experiments
Authors: Herkelrath W. N. , Miller E. E. , Gardner W. R. 
Published: July 2010

AbstractThe influence of soil water content and soil water potential upon root water uptake was investigated in a controlled laboratory environment. Water extraction rates by roots of winter wheat were measured in situ in a soil column instrumented with a gamma‐ray attenuation water‐content meter, tensiometers, and psychrometers. In addition, the leaf water potential was measured with an in situ leaf hygrometer. In order to measure the vertical distribution of water uptake, the column was divided into five sections by wax layers which were penetrated by roots, but which prevented movement of water between sections in the soil. A measurement of the average root potential was obtained by allowing a thin “test section” of soil to dry toward equilibrium with the root water potential while the rest of the soil was kept wet. Although 86% of the root zone soil was at a water potential above about −0.1 bar, the roots dried the test section to a potential of −5 hars, indicating a root potential at least this low. Because the average leaf water potential was also −5 bars, the data imply that whereas there was little flow resistance between the roots and the leaves, the resistance to flow between the soil and the root xylem was large. Root extraction rates hegan to decrease rapldly when the soil water content fell below about 0.10 cm3 water/cm3, corresponding to a soil water potential of about −0.1 bar. This result agrees with data in the literature, but is at variance with the soil‐water diffusivity‐based root uptake model, which predicts little effect of soil dryness upon root uptake at high soil moisture potential.
Water Uptake By Plants: II. The Root Contact Model
Authors: Herkelrath W. N. , Miller E. E. , Gardner W. R. 
Published: July 2010

AbstractIn the standard analysis of root water uptake, it is assumed there is a constant root membrane resistance in series with a soil resistance which is dependent upon the soil moisture diffusivity. The relation of root extraction rate to soil water content and to soil water potential predicted by this standard model was compared to the results of divided root experiments. The extraction rates predicted by the theory were as much as eight times larger than the measured values. A reasonable fit between theory and experiment could only be obtained by assuming in the theoretical calculations that the rooting density was 100 times smaller than that measured in the experiments. An alternative model emphasizing the possibility of a root‐soil contact effect was developed. It was assumed that as the soil dried, the surface area of the roots in contact with the soil decreased, which caused an increase in the root membrane resistance. By assuming that the effective root membrane permeability was simply proportional to the relative saturation of the soil, a much better fit to the data was obtained than by using the conventional theory.
An Evaluation of Several Methods of Estimating Soil Volume Change
Authors: Parker J. C. , Amos D. F. , Kaster D. L. 
Published: July 2010

AbstractThe accuracy of several previously proposed methods of estimating potential soil volume change was evaluated using samples from the B2 horizons of three pedons of each of five soil series having various swelling characteristics. Models involving swell index, plasticity index, clay content, activity index, initial and final water contents, shrinkage limit, shrinkage ratio, liquid limit, linear shrinkage, and hygroscopic moisture content were evaluated by regression analysis with percent volume change of natural clods as the dependent variable. Most methods were found to be either too imprecise or too involved to be useful. The most practical correlations were with swell index (r2 = 0.92) and with plasticity index (r2 = 0.79). Estimates using these procedures should be used cautiously since their accuracy is only ± 12 to 18% volume change, respectively, at the 95% confidence level.
Applications and Misapplications of the Langmuir Equation to Soil Adsorption Phenomena
Authors: Harter Robert D. , Baker Dale E. 
Published: July 2010

AbstractWhen the development of the Langmuir adsorption equation is critically examined, it is evident that the equation soil scientists have been using [C/x/m = C/k + I/kb, where C is concentration of adsorbate, x/m is the amount adsorbed per unit weight adsorbent, k is the adsorption maximum, and b is a constant] is in the wrong form. This error is of no great importance when the equation is merely used to obtain a calculated adsorption maximum for comparison to other adsorbent properties. However, it does become important when attempts are made to understand adsorption dynamics and bonding strengths. The commonly reported curvilinear nature of the C/x/m vs. C plots is simply the result of not considering the effect of desorbed ions in the equilibrium solution, rather than being due to multiple adsorption mechanisms. When the equation is corrected by considering desorbed ions, the isotherm becomes linear. In addition, the constant, b, of the Langmuir equation is not simply related to the bonding energy of the adsorbed ion, but to the ratio of adsorbed and desorbed ion bonding energies.
Proton Binding in Fulvic Acid Extracted From Sewage Sludge‐soil Mixtures
Authors: Sposito Garrison , Holtzclaw Kenneth M. , Keech D. A. 
Published: July 2010

AbstractAqueous solutions of two fulvic acids (FA) extracted from sludge‐soil mixtures and converted to K‐fulvates were titrated potentiometrically at 25°C with HCl in ionic media of 0.1M and 0.2M KCl. Data were obtained for a range of concentrations of FA, although during a titration experiment both FA concentration and ionic strength were rigorously held constant. A simple model was employed to interpret the formation functions calculated using the titration data. This model ascribes the acidic properties of a FA solution to an assembly of hypothetical macromolecules (“mean fulvic acid units”) that contain several distinct classes of functional group and are able to associate through hydrogen bonding. Conditional protonation constants were computed for each class of acidic functional group that protonates in the pH range 3–11. The common logarithms of the average protonation constants at 25°C were found to be 3.9, 6.5, and 9.4 for the three classes of weakly acidic functional groups studied. These values were independent (within experimental error) of FA composition and concentration, and of ionic strength in the range investigated.
Potassium Accumulation and Movement In an Irrigated Soil Treated With Animal Manures
Authors: Pratt P. F. , Laag A. E. 
Published: July 2010

AbstractData from a 4‐year experiment with animal manures are reported. Soluble and exchangeable K and K/Cl ratios indicated that K moved into the 90‐ to 120‐cm depth, but little if any moved below the 120‐cm depth. Potassium/Cl ratios indicated that K moved down in a relatively abrupt front, that the 0‐ to 30‐cm and 30‐ to 60‐cm depths had nearly equilibrated with the K input, but that deeper layers had not. Soluble K accumulated in the soil in proportion to the amount of manure added and reached a maximum of 36.5% of the total soluble cations in the saturation extract of the surface layer of the plots that received the highest rate of manure. The maximum exchangeable K was found in the 30‐ to 60‐cm depth of the same plots. The K fixed in the soil appeared to be greater than the reduction in CEC.
The Stratigraphy and Geomorphology of the Hofmann Forest Pocosin
Authors: Daniels R. B. , Gamble E. E. , Wheeler W. H. , Holzhey C. S. 
Published: July 2010

AbstractHofmann Forest is a 34,000 ha pocosin (swamp‐on‐a‐hill) that has about 25,000 ha of Histosols 0.4 to 2‐m thick. The pocosin is about 17 m above sea level, and large organic areas are uncommon at these altitudes in North Carolina. A stratigraphic and geomorphic study of Hofmann Forest was made to determine what factors were responsible for the accumulation of organic materials.The organic materials of the pocosin mantle a gentle undulating marine plain that was exposed to subaerial weathering about 220,000 years ago. Few streams drain the area and the organic materials occupy the undissected interstream divides where the distance between streams is from approximately 0.5 km to 8 km. Flux rates indicate that the very low hydraulic conductivity of the pre‐Croatan formations and their closeness to the surface prevent significant removal of excess water through the permeable thin surficial beds to the adjacent streams. Rainfall exceeds evapotranspiration and the excess water must be removed primarily by overland flow to the streams.The shallow depth to the pre‐Croatan aquicludes, the large distance between streams, and an excess of rainfall over evapotranspiration are the three major reasons why organic materials mantle a gently undulating plain about 17 m above sea level. The first two have remained nearly unchanged over the major part of the Hofmann Forest organic areas for the last 220,000 years. These conditions make the pocosin a potential area for organic accumulation. It is possible that organic deposits have been discontinuous during the last 220,000 years because of wide fluctuations in temperature and presumably in rainfall.
Comparison of Sulfur‐coated Urea and Ammonium Nitrate as Fertilizers for Pensacola Bahiagrass on a Spodosol
Authors: Blue W. G. 
Published: July 2010

AbstractTwo slowly available experimental sulfur‐coated urea (SCU) materials produced by the Tennessee Valley Authority were compared with ammonium nitrate as N sources for ‘Pensacola’ bahiagrass (Paspalum notatum Flugge) on Myakka fine sand (sandy, siliceous, hyperthermic Aeric Haplaquod). One of the SCU materials contained 35.4% N with a S coating of 23% while the other contained 40.2% N with a 12.6% coating which included S plus 2% diatomaceous earth and 0.25% coal tar. Four levels of N (0, 112, 224, and 336 kg/ha) were applied annually for 3 years to an established grass sod which had not been fertilized with N during the previous 2 years. Ammonium nitrate was applied in single and split applications, and the SCU materials were applied in single annual applications. Single applications were made in late March of each year. For the split applications of ammonium nitrate, one‐half was applied in late March and one‐half approximately 1 July. Forage growth increased with each level of N from all sources. Nitrogen utilization efficiency was higher (67%) from the 224‐ and 336‐kg/ha N rates than from the 112‐kg/ha rate (57%). Forage yield increase from the SCU (35.4% N) material was relatively poor the first year; pellets of this material were found consistently in the grass thatch at the soil surface 1 year after application. However, forage yields and N contents for each N rate over the 3‐year comparison period were not affected by N source or number of applications. The residual effect of SCU materials during the fourth year as measured by N content of forage ranged from 2 to 7% of the total N applied. These quantities of N were generally less than the decline in N content of the stolon‐root system. Forage production and N content distribution with time were not drastically altered by these slow release materials compared with ammonium nitrate.
Nature of the Organic Coating on Sand Grains of Nonwettable Golf Greens
Authors: Miller R. H. , Wilkinson J. F. 
Published: July 2010

AbstractThe organic coating of nonwettable sand grains from localized dry spots on sand golf greens was extracted with 5% NaOH. An infrared spectrum of resin purified, freeze‐dried extract was similar to spectra of soil fulvic acids. All other supporting data such as solubility, color, failure to precipitate upon acidification, noncrystalline nature, and a high extinction coefficient were consistent with the conclusion that the organic coating was fulvic acid. The relationship of the synthesis of fulvic acids to basidiomycete hyphae in the affected soil layer is discussed.