bluuebunny/crossref_metadata_2025 huggingface dataset:
Nitric Oxide Sorption by Calcareous Soils: III. Effects of Temperature and Lack of Oxygen on Capacity and Rate
Authors: Prather R. J. , Miyamoto S.
Published: July 2010

The sorption of NO by oven‐dry soils from dry air (relative humidity < 5%) containing a concentration of 1.5% NO by volume decreases exponentially with increasing temperature from 24 to 120C. From a moist stream (relative humidity > 95%), both NO and H2O sorption capacities and rates decrease with increasing temperature from 24 to 77C. The sorption capacity of NO relative to H2O changes little, while the relative sorption rate to that of H2O decreases markedly when the temperature increases from 24 to 36C but not for higher temperatures. The lack of gaseous oxygen severely inhibits the sorption of NO from both dry and moist nitrogen gas streams.
Effect of Hydrogen Clay on Calcium and Potassium Activities and Uptake by Excised Soybean Roots from Vermiculite and Kaolinite Suspensions
Authors: Baweja A. S. , McLean E. O.
Published: July 2010

Libby vermiculite and Peerless kaolinite clay suspensions were H‐saturated by resin treatment, and then Ca‐ or K‐saturated by addition of the respective hydroxides. Reciprocal saturations of Ca‐H, K‐H, and Ca‐K with variable amounts of H‐clay added were prepared. Activities of Ca and K in the suspensions were measured by specific‐ion electrodes. Excised‐soybean root (Glycine max L., var. ‘Corsoy’) uptake from the suspension phases of membrane‐equilibrated systems of both clays was measured using 45Ca and 86Rb as tracers for Ca and K, respectively.

Cationic fractions active in Ca‐H and K‐H systems reached minimal values in kaolinite, but only when the H‐saturation reached almost twice the measured pH‐dependent CEC (30 vs 18%), while those in vermiculite did not reach minima when H‐saturation was nearly three times the measured pH‐dependent CEC (20 vs 7%). Additions of H‐clay to the Ca‐K systems progressively decreased cationic activities (or dialyzate concentrations) and uptake; the effect being more pronounced for Ca than for K. In general, the uptake of each cation was highly correlated with its effective concentration in solution. Failure of root uptake to reflect marked increases in Ca concentration of dialyzates when Ca saturation increased from 80 to 100% suggested that much of the Ca uptake at lower Ca saturations was the result of direct root‐clay contact in the mechanically‐shaken systems. Consequently, the uptake of Ca was more highly correlated with total concentration of Ca in the systems than with the dialyzate concentrations of Ca. Average Ca/K upake ratios were about 2.5 times higher from kaolinite than from vermiculite clays, and the ratios decreased significantly with increasing levels of H‐clay added in kaolinite but much less so in vermiculite.
Nitrification and Denitrification during Miscible Displacement in Unsaturated Soil
Authors: Kirda C. , Starr J. L. , Misra C. , Biggar J. W. , Nielsen D. R.
Published: July 2010

Nitrification and denitrification during the leaching of a pulse of NH4NO3 applied to the surface of soil columns are analyzed experimentally and theoretically. Experimentally, unsaturated soil columns of two lengths were leached steadily with a tracee solution containing NH4NO3 while the air‐filled portions of the columns were being flushed simultaneously with air. During these steady state conditions, a pulse of tracer solution containing either 15NH4+ or 15NO3‐ was leached through the columns. The words tracee and tracer signify that both solutions were chemically identical with the latter containing a greater proportion of 15N. Steady‐state tracee concentration distributions within the columns as well as the transient tracer concentration distributions in the effluent were analyzed assuming first‐order kinetics. Values of both the rate coefficients and the concentration distributions stemming from the tracee and tracer measurements were in general agreement. The agreement between the measured and theoretical results are discussed in terms of soil water properties and the kinetics of microbial populations.
Rice Response to Nitrogen and Phosphorus in Flooded and Nonflooded Soils
Authors: Terman G. L. , Allen S. E.
Published: July 2010

Pot experiments were conducted in a greenhouse to study nutrition of rice (Oryza sativa L., cv. Nato) under flooding and upland conditions. Yields of rice grown in one experiment on Mountview silt loam increased rectilinearly with 0‐, 400‐, and 800‐mg rates of N/pot (5 kg of soil). Concentrations of N in grain + straw at maturity were uniformly low. Yields with the various water regimes were in the order: no flooding < flooding after 10 weeks < flooding after 6 weeks < flooding after 3 weeks. Multiple rates of N from 250 to 2,000 mg/pot and P from 0 to 1,000 mg/pot (6.25 kg of soil) were applied for Nato rice grown on Mountview silt loam and Sango silty clay loam in a second experiment. Marked yield responses to N and P were obtained. Yields of straw and of grain + straw, N uptake, and N recovery were higher on nonflooded than on flooded soils. Grain yields, however, were slightly higher with flooding.

Uptake of N, P, Ca, Mg, Mn, and Zn increased with yield response to N and P, while K uptake decreased on the Mountview soil. Concentrations of N and P increased with applied N and P, respectively, while concentrations of other nutrients were diluted in most situations with yield response to N or P on both flooded and nonflooded soils.

These results indicate that with adequate applied nutrients, especially N, yields of rice with adequate water but without flooding can equal or even exceed those under flooding.
The Effect of Calcium Salts on the Degradation of Parathion in Sand and Soil
Authors: Mingelgrin Uri , Yaron Bruno
Published: July 2010

The effect of CaCO3 and CaSO4 on 0,0‐diethyl 0‐(P‐nitrophenyl) phosphorothioate (parathion) degradation was investigated. The decomposition in dry acid‐washed sand as a relatively inert matrix, as well as in two dry soils, was measured. As shown previously in the case of other Ca‐containing surfaces, both CaCO3 and CaSO4 enhanced parathion degradation in the inert medium. In every soil‐salt mixture the parathion decomposition curves were different. In one soil CaCO3 even slowed down the decomposition. In another soil, CaSO4 enhanced decomposition up to 5% salt concentration, but additional CaSO4 did not produce further enhancement.
Microbial Degradation of 2‐Carbon‐14 Bromacil and Terbacil
Authors: Wolf D. C. , Martin J. P.
Published: July 2010

Studies were conducted to determine the degradation rate of 2.88 ppm 2‐14C bromacil, 3‐sec‐butyl‐5‐bromo‐6‐methyluracil, and terbacil, 3‐tert‐butyl‐5‐chloro‐6‐methyluracil, in a neutral sandy loam soil. After a 600‐day incubation period at 60% water holding capacity (approximately ⅓ bar), 22.1% of the added 14C from bromacil was recovered as 14CO2. The addition of 0.5% corn stalks (Zea mays L.) or lima bean straw (Phaseolus limensis) increased the value to 32.5% and 33.6%, respectively. Under the same conditions, 27.5% of the activity added as 2‐14C terbacil was recovered as 14CO2 and the addition of 0.5% corn stalks or lima bean straw increased this value to 37.0% and 38.2%, respectively. No 14CO2 was evolved from sterile soil. Under saturated conditions less than 0.5% of the added activity for both bromacil and terbacil was evolved as 14CO2 in 145 days but essentially all of the activity in the bromacil treated soil was present as a metabolite. In a second test about 53% of added bromacil was still present as the parent compound after 115 days. The presence of bromacil or terbacil in the soil did not affect the activity of the soil microbial population as measured by total CO2 production.
The Physical and Chemical Properties of the Gray Hydromorphic Soils of the Hawaiian Islands
Authors: Hussain M. S. , Swindale L. D.
Published: July 2010

Gray hydromorphics, a heterogeneous group of soils of the Hawaiian Islands, have developed some common characteristics during pedogenesis under impeded drainage. These soils are characterized by their poor physical properties, high moisture‐holding capacity, and high clay content. The mean clay/15‐bar moisture ratio is 2.56.

Under the gleization process of soil formation, free iron and free manganese were found to be concentrated near the surface and above the fluctuating groundwater table. A net loss of these elements was observed from the soil profiles. The gray hydromorphic soils were found to constitute a typical hydrologic sequence. The SiO2/R2O3 and SiO2/Al2O3 ratios of the soils increased with increasing degree of hydromorphism. The SiO2/R2O3 and SiO2/Al2O3 ratios in the fine clay fractions of the soils increased with increasing drainage impedance. Al2O3/Fe2O3 ratios in the fine clays of these soils decreased with increasing degree of hydromorphism and increasing percentage of montmorillonite. Conditions of poor drainage maintained a ferrous ion activity in the soil solution sufficient to allow increasing formation of iron‐rich montmorillonite clays.
New Concepts in Soil Survey Interpretations for On‐Site Disposal of Septic Tank Effluent
Authors: Bouma J.
Published: July 2010

Soil survey interpretations for on‐site disposal of septic tank effluent are made in terms of soil limitations using existing technology. New technology, based on a detailed analysis of liquid movement and associated purification, can be used to overcome severe and very severe limitations and to reduce slight and moderate limitations. Experimental data obtained and technology derived from single experimental innovative disposal systems are relevant only if extrapolations can be made to other soils shown to be identical. Three procedures of extrapolation are discussed: (i) detailed on‐site spot checks of key properties; (ii) on‐site taxonomic soil classifications and (iii) taxonomic soil classifications at the experimental site followed by extrapolation to mapping units named after the same soil series. Largely unknown variability of key properties for liquid waste disposal in soil series or in mapping units may reduce the practical value of the latter two procedures but potential advantages are (i) reductions of expensive on‐site inspections and (ii) use of soil maps for showing potential changes in land‐use patterns following introduction of innovative technology. This approach emphasizes soil potential rather than soil limitations.
Feedlot Waste Effects on Soil Conditions and Water Evaporation
Authors: Unger Paul W. , Stewart B. A.
Published: July 2010

Feedlot wastes were applied to field plots at 0, 22, 67, 134, or 268 metric tons/ha for 4 successive years. Core and bulk soil samples from the plots were used to evaluate treatment effects on soil water retention, bulk density, strength, porosity, organic matter content, and water‐stable aggregates. Evaporation was determined from laboratory columns containing feedlot‐wastetreated soil at the surface and untreated soil below the treated soil. For soils treated with feedlot wastes at high rates, water contents at saturation and at −0.2 and −1.5 bars matric potential were significantly higher, and bulk densities were significantly lower, than for untreated soils or those treated at low rates. Soil strength, porosity index values, and water contents at −15 bars matric potential were not significantly affected by waste applications. Soil organic matter and aggregation increased and evaporation decreased as waste application rates increased.
Removal of Iron Oxides and Amorphous Material From Soil Clays—Treatment Sequence Effect
Authors: Johnson Leon J. , Yeh Ching‐Hwan
Published: July 2010

In the great majority of soil samples, more iron, alumina, and silica were found when iron removal preceded extraction of alkali‐soluble amorphous material. Iron oxyhydroxide is postulated to be present as a protective surficial coating whose removal makes accessible more alkali soluble silica and alumina. Iron may also be part of an amorphous component whose solubility in alkali is increased after removal of the contained iron by a dithionite treatment. Prior alkali treatment reduces the susceptibility of iron oxyhydroxides to the dithionite treatment.
A Procedure for Placing Large Undisturbed Monoliths in Lysimeters
Authors: Brown K. W. , Gerard C. J. , Hipp B. W. , Ritchie J. T.
Published: July 2010

Increasing need for studies of leaching water and possible pollutants through soil profiles led to the development of a method for placing large undisturbed soil monoliths in metal boxes for use as drainage lysimeters. Materials and equipment used in the technique are usually available or can be leased from local contractors. Monoliths as large as 1.5 m deep and with surface areas of 3 m have been taken. The technique could be used for even larger monoliths. Thus far, lysimeters have been installed in clay, sandy clay, loam and sand soils. The upper lip of several of the lysimeters described here was buried 25 cm below the surface to allow normal tillage, bed preparation and furrow irrigation.
Influence of Moisture on Rice Straw Decomposition in Soils
Authors: Pal D. , Broadbent F. E.
Published: July 2010

Laboratory incubation experiments were conducted for 4 months at 22 ± 0.5C with two fine‐textured soils amended with doubly tagged (13C and 15N) rice straw (Oryza sativa L.) under different moisture regimes. The moisture levels were 30, 60, and 150% of water‐holding capacity, (WHC). The extent of straw decomposition was found to be a power function of time. Differential equations were derived to give rate functions for each moisture level.

Native soil organic carbon loss was depressed by added energy materials when either moisture or oxygen supply limited decomposition. At 30% WHC, priming ratios were < 1.0 initially, and increased with time of incubation but did not reach unity within 4 months incubation. At 60% WHC, the ratios were > 1.0 and decreased with time of incubation but remained above 1.0 throughout incubation. At 150% WHC, priming ratios were < 1.0 and did not vary much during the entire decomposition period. The net release of straw‐N at 60% WHC was higher than at 30% WHC. At 150% WHC, straw‐N released during decomposition was lost from the system, presumably by denitrification. Soil inorganic nitrogen changes followed trends similar to net release of straw‐N. The influence of moisture variables on soil organic nitrogen transformations was more pronounced than the influence of decomposing straw.
Microcombustion Method for the Determination of Carbon‐14‐Labeled Pesticide Residues in Soil
Authors: Beard W. E. , Guenzi W. D.
Published: July 2010

A dry combustion procedure commonly used for total carbon analysis was modified and used to determine the concentration of 14C‐labeled pesticides in soil. Modifications included replacement of the Ascarite®3 CO2 trap with a solution of an organic base compatible with liquid scintillation solvents, and minor carrier gas flow changes. Recovery of three pesticides from four soils ranged from 83 to 99% and averaged 94%.
Amount of Clay Needed for Optimum X‐Ray Diffraction Analysis
Authors: Rich C. I.
Published: July 2010

The amount of clay necessary for optimum X‐ray diffraction patterns is reported. The calculations are based on the mass absorption coefficient, the angle of diffraction, and the use of the slide.
A Field Study of Soil Water Depletion Patterns in Presence of Growing Soybean Roots: II. Effect of Plant Growth on Soil Water Pressure and Water Loss Patterns
Authors: Arya L. M. , Blake G. R. , Farrell D. A.
Published: July 2010

Soil‐water pressure and water‐loss patterns in the root zone of soybean (Glycine max L.) genotype P.I. 79.648 were determined from daily observations during irrigation‐drying cycles for four growth periods after planting. Tensiometric measurements of soil water pressure were made on a 10‐cm square grid from one plant row to an adjacent one spaced 80 cm apart, and between 10‐ and 70‐cm depths. Water contents were inferred from pressure‐water content relationships.

During the first irrigation‐drying cycle, soil‐water pressures were marked by strong lateral and vertical gradients. As plants aged from one irrigation‐drying cycle to the next, these gradients decreased; soil‐water pressures at most depths decreased more slowly with the drying time. The proportional contribution of surface layers to the total water loss from the 10‐ to 70‐cm depth interval decreased as the plants matured while contributions from the lower layers increased. These changing patterns of soil‐water pressure and water loss are consistent with the expected shift in root activity.
Methods for Measuring Short‐Chain Fatty Acids and Ammonia from Animal Wastes
Authors: Elliott L. F. , Travis T. A.
Published: July 2010

Methods for measuring free fatty acids and ammonia‐nitrogen are discussed. Free fatty acids can be separated easily from manure constituents by steam distillation. The free acids were subsequently analyzed by flame ionization gas chromatography, following concentration and acidification of the distillate. Linear detection limits for the flame ionization detector ranged from 15 to 300 µg of acid/ml of sample with a 1‐µliter injection. Linear detection limits were increased to 1.5 µg with a 10‐µliter injection. Percent recoveries of the fatty acids ranged from 61 to 95%. Ammonia‐N was separated from light‐chain amines using the Nessler technique. Interference by methylamine and ethylamine‐N with the NH4‐N determination was only about 6% of the equivalent NH4‐N.
Nutrient Transport in Surface Runoff as Influenced by Soil Cover and Seasonal Periods
Authors: Burwell R. E. , Timmons D. R. , Holt R. F.
Published: July 2010

Nitrogen (N), phosphorus (P), and potassium (K) losses in surface runoff water and sediment were determined for five soil cover conditions on a Barnes loam soil in west‐central Minnesota. The five soil cover conditions studied were: (1) continuous, clean‐cultivated fallow; (2) continuous corn (Zea mays L.); (3) corn in rotation; (4) oats (Avena sativa L.) in rotation; and (5) hay in rotation.

Losses of water, sediment, and nutrients were determined for three seasonal periods; (P1) critical runoff period caused by melting snow and ice, (P2) critical erosion period from corn planting to 2 months later and (P3) noncritical runoff‐erosion period exclusive of periods 1 and 2.

Much of the annual sediment and nutrient losses occurred during the critical erosion period (P2). Snowmelt runoff (P1) accounted for much of the annual water and soluble nutrient losses.

Average annual quantities of NH4‐N and NO3‐N contributed by precipitation exceeded the annual losses in surface runoff, but ortho‐P losses in surface runoff were greater than the amount contributed by precipitation.
Weathering and Authigenic Halloysite in Soil Developed in Mazama Ash
Authors: Dudas M. J. , Harward M. E.
Published: July 2010

Hydrated halloysite is the dominant clay mineral formed by weathering of Mazama dacitic tephra. Allophane was also identified as a weathering product in some soils developing in this volcanic deposit. The amount of weathering and clay formation is related to soil moisture contents. In well drained upland soils, localized formation of clay occurred in pumiceous ash and lapilli near the contact with the palesols. Alteration of tephra in lower portions of these profiles was related to an area of higher moisture content above the less permeable paleosols. In poorly drained areas, considerable weathering of the Mazama tephra has occurred. This is evidenced by relatively high clay contents (15–20%) and easy physical disintegration of particles to a slippery paste. The Mazama tephra often appears relatively fresh even though deposition occurred 6,600 years ago. Limited weathering in upper horizons of well‐drained soils is attributed to inadequate moisture when temperatures are favorable for alteration processes.

The authigenic halloysite in Mazama ash soils has a low degree of crystallinity suggesting early stages of formation. Low degree of order is indicated by loss of diffraction peaks after heating to 300C for 2 hours and low endothermic peak temperatures during differential thermal analysis.
Chemical Weathering of Glauconite
Authors: Abudelgawad Gilani , Page A. L. , Lund L. J.
Published: July 2010

Glauconite samples were collected from geologic cuts in the Barce Plateau in the eastern part of Libya. The glauconite was associated with limestone, dolomitic limestone, marl, marl stone, chert, and kaolinite. Samples of the glauconite from the area of study after removal of carbonates gave X‐ray diffraction spacings of 10.0, 7.2, 5.0, 3.6 and 3.3 Å. Spacings of 10.0, 5.0, and 3.3 Å represent the 001, 002, and 003 reflection of micaceous components. Spacings of 7.2 and 3.6 Å were due to kaolinite. No 060 reflection was observed for random samples. The absence of this spacing, although not entirely specific for glauconite, is indicative of glauconite‐like minerals. Petrographic analysis and chemical composition confirmed that the micaceous mineral studied was glauconite. (The term glauconite in the area of the study was given by the field geologist based upon the morphology of the micaceous material.)

Potassium depletion of the glauconite by sodium tetraphenyl boron (NaTPB) treatment produced diffraction spacings of 14 to 15 Å when Mg saturated. Amounts of K removed by NaTPB and by exhaustive treatments with 1N NaCl were 183 and 179 meq/100 grams, respectively, which were about 95% of the total potassium as determined by Na2CO3 fusion. This demonstrated that essentially all of the K in the glauconite is of interlayer origin.

Equilibrium studies showed that the rate of K removed from the glauconite by 1N NaCl was dependent upon contact time and suspension density. Selectivity coefficients for the exchange of K by Na at equilibrium were about 2500. Infrared spectra of K‐depleted glauconites were quite similar to the IR spectrum of the specimen layer silicate nontronite. Amounts of K removed by and cation exchange capacities following selective K depletion techniques, the chemical composition, X‐ray diffraction and the infrared spectra show that K‐depletion of glauconite gives rise to an iron rich vermiculite.
Simple Flow Plugs for Regulating Gas Composition
Authors: Miller D. E.
Published: July 2010

Oxygen and nitrogen contents in a gas were accurately controlled by passing compressed air and nitrogen at regulated pressure through flow plugs. The flow plugs were constructed from bronze oxygen hose couplers with porous plastic dises as flow restrictors. Gas flow rate through a plug was varied by changing the number and porosity of disks and the applied gas pressure.
Decomposition of Carbon‐14 Labeled Plant Materials in a Grassland Soil Under Field Conditions
Authors: Nyhan J. W.
Published: July 2010

A study was made of decomposition of plant materials under field conditions using carbon‐14 labeled blue grama (Bouteloua gracilis [H.B.K.] Lag. x Steud.). A grassland soil was amended with blue grama herbage and roots in February 1971 and sampled at intervals until March 1972. For ground blue‐grama herbage buried in the top 2.6 cm of soil at two amendment levels (128 and 1,280 kg/ha) 54–57% of initially added carbon‐14 was lost in 412 days. For plant‐root material at amendment levels of 384 and 1,920 kg/ha, only 26–37% of the carbon was lost in this time period. Rates of carbon loss were significantly affected by season of burial; plants buried in February and May exhibited losses of 56% in 335 days and 42% in 314 days, respectively. Segments of blue‐grama herbage mixed with soil and placed on the soil surface for 412 days showed carbon losses of 39 and 50%, respectively. Additions of fresh, blue‐grama herbage to soil containing partially degraded, labeled plant material had no significant effect on radiocarbon loss rates.

The experimental technique used to estimate blue grama carbon losses under field conditions is evaluated and the decomposition results are discussed relative to decay patterns of native blue grama.
Climate, Time, and Organisms in Relation to Podzol Development in Michigan Sands; II. Relationships Between Chemical Element Concentrations in Mature Tree Foliage and Upper Humic Horizons
Authors: Messenger A. S.
Published: July 2010

Comparison of the chemical composition of northern hardwood and conifer foliage within polypedons of several sandy Podzols (Spodic Udipsamments and Typic Haplorthods) in northern Michigan indicates a succession to hardwoods resulting in a significant increase in concentrations of foliar N and most other macronutrient elements accompanied by a decrease in foliar Al concentrations. These successional changes appear independent of the degree of soil acidity developed under conifers.

Upper humic horizons under forest stands dominated by white pine (Pinus strobus L.) and/or hemlock [Tsuga canadensis (L.) Carr.] contain high levels of extractable aluminum and large capacities for production of crenic acid. The foliar composition of these species suggests a mechanism for considerable flux of aluminum in soil profiles and depletion of basic cations in eluvial horizons.

Foliar compositions of northern hardwoods favor humus types and microflora that produce much reduced or negligible quantities of crenic acid.
Maryland Soils Developed in Residuum from Chloritic Metabasalt Having High Amounts of Vermiculite in Sand and Silt Fractions
Authors: Coffman C. B. , Fanning D. S.
Published: July 2010

From 60 to 90% of the calcium exchange capacity (pH 7 Ca acetate saturation, Mg acetate replacement) was attributable to > 2µm particles in subsoil horizons of an Ultic Hapludalf developed in residuum from chloritic metabasalt in Maryland's Middletown Valley. Vermiculite was the dominant reactive mineral in several soils examined from the area. For material above the rock from which organic matter and free iron oxides had been removed, the fraction of CaEC attributable to “vermiculite” (measured by CEC methods) interlayers increased with increasing particle size and (for whole soils) with increasing depth. The vermiculite appears to have formed from chlorite at the rock‐saprolite boundary, since vermiculite is absent in the rocks and chlorite is absent in the saprolite and micas are rare in both rocks and saprolites. Weathering also produces kaolinite and free iron oxides and eventually destroys vermiculite as shown by examination of soils of differing degrees of development.

Most of the pedons examined in the present and in related studies were included in the Myersville and Fauquier soil series by concepts used for a soil survey of the study area published in 1960. Both soil series are placed in Ultic Hapludulfs in the current Soil Taxonomy, but many pedons mapped as Fauquier and Myersville in the 1960 survey appear to be Dystric Eutrochrepts and some on steep slopes are Udorthents. The soils examined do not meet requirements for vermiculitic family mineralogy in present Soil Taxonomy, even though cation exchange properties appeared governed by vermiculite. Substitute criteria are proposed to base vermiculitic family mineralogy on the “vermiculite” content of whole‐soils.
The Activity Concept of Phosphate‐Rock Solubility
Authors: Chien S. H. , Black C. A.
Published: July 2010

Variously treated samples of a finely ground Florida phosphate rock were equilibrated with dilute HCl solutions, and the ion‐activity product of the carbonate apatite mineral in the phosphate rock was then determined from analyses made on the solutions. Constant ion‐activity products or solubility‐product constants were found within a certain pH range in each instance. The solubility, as reflected by the numerical value of the constant, decreased with an increase in the proportion of the phosphate rock dissolved in the solubility determination or prior thereto. After a certain portion of the phosphate rock had been dissolved, however, no further decrease in solubility was found with further extraction of the phosphate rock. These results are similar to those obtained previously with synthetic hydroxyapatite and were interpreted in the same way, namely, that the solids are not uniform but exist in a range of activities.
Analytical Characteristics of Humic and Fulvic Acids Extracted from Tropical Volcanic Soils
Authors: Griffith S. M. , Schnitzer M.
Published: July 2010

Certain tropical soils formed on materials of volcanic origin on islands in the West Indies, tend to accumulate substantial amounts of organic matter but are so infertile that the addition of lime and fertilizers does not increase crop response. To obtain a better understanding of this unusual behavior, humic and fulvic acids were extracted from problem soils on the island of Dominica, and characterized by chemical and spectroscopic methods.

Elementary and functional group analyses as well as optical and IR data for humic and fulvic acids extracted from the tropical soils were similar to those of humic and fulvic acids from soils from widely differing climatic zones. The only major difference was the tenacity with which the tropical fulvic acids retained (in water‐soluble form) relatively large amounts of ash (between 9.4 and 12.6% of oven‐dry weights), rich in silica. Our data suggest that the unusually high resistance to degradation of organic matter in these soils is, at least in part, related to the formation of stable silica‐fulvic acid “complexes.”
Variations in the Natural Abundance of 15N of Wheat Plants in Relation to Fertilizer Nitrogen Applications
Authors: Shearer Georgia , Legg J. O.
Published: July 2010

Measurements were made by two laboratories of the δ15N (per mill 15N excess) of winter wheat plants (Triticum aestivum L.) grown at five locations in Pennsylvania on experimental plots. The plots were fertilized with N at various rates. The results from both laboratories showed a consistent decline in δ15N with increasing rates of N application. Such a decrease in δ15N is consistent with increasing contributions of fertilizer N to the plants as the rate of application increased, given that fertilizer N has a lower 15N content than the soil N. The coefficients of regression of δ15N of wheat on N application rate were always negative and usually significantly different from zero. The regression coefficients computed from the results of the two laboratories were not significantly different from each other in 12 of 16 experiments. There was, however, a systematic, unexplained difference in the results from the two laboratories. A regression of one set of data on the other resulted in a regression coefficient significantly different from one, the theoretically expected value.
Thermal Conductivity of a Red Pine Forest Floor
Authors: Pennypacker S. P. , Sopper W. E. , Kardos L. T.
Published: July 2010

The insulating value of red pine (Pinus resinosa Ait.) forest floor litter was determined by measuring thermal conductivity, k, using a heat line source method. Test specimens consisted of natural forest floor and individual samples of reconstituted needle and humus components that had respective average dry weight bulk densities of 0.058, 0.229, and 0.233 g/cm3. Measurements were taken of the organic material under both frozen and unfrozen conditions at moisture contents ranging from oven‐dry to approximately 300% by weight. The conductivity of the three materials was expressed as a function of moisture content and density at temperatures of approximately — 16 and 25C. Freezing increased conductivities in reconstructed samples of organic particles, but not in natural samples. The failure to obtain increased conductivities in natural samples is probably due to the absence of an ice formation or a structure of adjoining ice crystals within the porous humus layer.
Changes in the Physical Properties of Soil Clays Due to Precipitated Aluminum and Iron Hydroxides: I. Swelling and Aggregate Stability After Drying
Authors: El‐Swaify S. A. , Emerson W. W.
Published: July 2010

Compressed discs of an illite, a kaolinite, and a mixture of the two were formed from freeze‐dried dispersed suspensions of the clays, into which one level of Fe(OH)3 and two levels of Al(OH)3 had been precipitated. The precipitated Fe was found to consist of particles about 40Å in diameter and amorphous to X‐ray, rather than the acicular goethite that precipitates under similar conditions in the absence of clay. It was deduced from N2 and water vapor sorption measurements that the precipitated Al was present as very thin layers on the surface of the clay particles, which in the case of the illite could bridge some of the particles. Their form was generally indeterminate, in contrast to the well‐crystallized bayerite formed in the absence of clay.

All three hydroxy treatments inhibited the double‐layer swelling of the Na‐illite and Na‐kaolinite/illite mixture in dilute NaCl solutions. Both on weight percent and on an equimolar basis, Al was more effective than Fe in reducing the slaking of dry clay discs and in increasing the resistance of clay to dispersion in pyrophosphate solutions. Possible bonding mechanisms between the precipitate and the clays are discussed.
Reaction Products of Polyphosphates and Orthophosphates with Soils and Influence on Uptake of Phosphorus by Plants
Authors: Subbarao Y. V. , Ellis Roscoe
Published: July 2010

Ammonium polyphosphate and diammonium phosphate were compared as sources of P for corn (Zea mays L.) in a growth chamber experiment with an alkaline‐calcareous soil and a slightly‐acid soil. Reaction products of the two P sources in soils and soil extracts correlated with results obtained in the growth chamber.

Applied P increased dry weights, uptake of P by the plants, and available soil P in the slightly acid soil. Both sources of P effectively supplied P for plant growth on this soil. Ammonium and magnesium orthophosphates, formed as reaction products in the laboratory experiments when the two P fertilizer materials were added, should furnish sufficient P for plant growth.

Neither source of P increased dry weights, uptake of P by plants, or available soil P in the alkaline‐calcareous soil as much as with the slightly‐acid soil. Dry weights of plants and uptake of P were significantly less with polyphosphate than with orthophosphate, both at 36 ppm applied P. Polyphosphate also failed to increase the available soil P. A reaction product, Ca(NH4)2P2O7·H2O, that is highly stable in alkaline‐calcareous soil was formed when ammonium polyphosphate was added. Its stability and low solubility explain the limited availability of P. The compounds, Mg2KH(PO4)2·15H2O and Ca4H(PO4)3·2.5 H2O, formed when diammonium phosphate was added. They provided more P for plants at the highest rate of application, but uptake of P was limited for both sources of P in this soil.
Protein and Free Amino Acid Composition of Sesame Meal as Affected by Nitrogen, Phosphorus, and Potassium Nutrition
Authors: Mitchell G. A. , Bingham F. T. , Labanauskas C. K. , Yermanos D. M.
Published: July 2010

Protein and free amino acid composition of lipid‐free sesame (Sesamum indicum L.) meal was studied for effects of increasing substrate levels of N, P, and K in sand culture experiments. Concentrations of individual protein amino acids were increased in the seed meal with increasing substrate levels of N and K nutrition due primarily to increases in protein content. Increasing P supply had no significant effect on amino acid composition.

Increasing levels of N resulted in increases in nonamino acid forms of N. Nitrogen increased individual free amino acids while P had no effect. Potassium deficiency resulted in accumulations of all individual free amino acids except cystine. These accumulations coupled with the observed decreases in protein amino acids in K‐deficient plants support the view that adequate K supply is required for proper utilization of amino acids in protein synthesis.

The pattern of essential amino acids expressed as a fraction of the total essential amino acids was little affected by N, P, and K nutrition when compared to the large increases resulting from increased seed yield and meal protein content.
Variability of Hydraulic Conductivity in Two Subsurface Horizons of Two Silt Loam Soils
Authors: Baker F. G. , Bouma J.
Published: July 2010

Hydraulic conductivity was measured in the B22t and B31t horizons of 12 pedons of two soils developed in loess deposits overlying glacial till. Conductivity measurements were made with the crust test technique for unsaturated conditions and with a new related in situ method for saturated conditions. Nonlinear regression yielded simple well‐fitting curves of the form log K = log(bψ‐c). Variability within and between major horizons in these soil series was found to be relatively low. The four horizons in these two silt loam soils had statistically identical hydraulic conductivity characteristics, even though morphological soil structure and soil genesis differed significantly.
Sampling the Unsaturated Zone in Irrigated Field Plots
Authors: Pratt P. F. , Warneke J. E. , Nash P. A.
Published: July 2010

Data obtained from samples from each of 10 holes/plot for one plot from each of three soils were subjected to statistical analysis and used to formulate plans for sampling the 1.5‐ to 4.5‐m depth of 48 experimental plots that had received animal manures. The statistical analysis of these three plots suggested that 10 holes/plot and 10 samples/hole would provide plot means within about 20% of the true means for nitrate and chloride concentrations and electrical conductivity of saturation extracts, ECe, except for one soil which had residual salts in highly variable concentrations at the 3.0‐ to 4.5‐m depth. The sampling procedure developed gave satisfactory results when statistical analysis of the effects of manure treatments, soils and irrigation levels on nitrate, chloride and ECe were measured.
Sulfuric Acid for the Treatment of Ammoniated Irrigation Water: II. Reducing Calcium Precipitation and Sodium Hazard
Authors: Miyamoto S. , Ryan J.
Published: July 2010

Effects of ammonia (NH3 or NH4OH) and sulfuric acid (H2SO4) applied to ammoniated water on Ca precipitation and Na‐hazard of irrigation water are evaluated theoretically using known relations of ion equilibria and tested with laboratory and greenhouse experiments. Results show a severe precipitation of Ca2+ when ammonia is applied to alkaline irrigation waters. At ammonia rates ranging from 25 to 100 mg/liter, for instance, 80 to 95% of Ca2+ present in water may precipitate as CaCO3 even under a closed system. Ammonia application also increases exchangeable Na and NH4, and can reduce water infiltration rates, especially when irrigation waters contain high Na+ relative to Mg2+ and Ca2+. Sulfuric acid applied to ammoniated water neutralizes OH‐ produced by ammonia application. Thus it reduces Ca precipitation and exchangeable Na, and consequently prevents a decline in infiltration rates. Sulfuric acid, which is now available as a pollution abatement byproduct in the Southwest, can be used for correcting excessive lime incrustation or poor water penetration induced by the use of anhydrous or aqua ammonia without corroding irrigation systems.
Thermodynamic Stability and The Law of Corresponding States in Swelling Soils
Authors: Sposito Garrison , Giráldez Juan V.
Published: July 2010

Following a heuristic suggestion by Groenevelt and Parlange, a thermodynamic description is given of a postulated order‐disorder transformation in a swelling soil. This transformation is shown to correspond to a phase transition of the second order at the air entry point, wherein the onset of a microscopic ordering process among the clay crystals in the soil occurs and there is a consequent discontinuity in the slope of the swelling curve. The available experimental swelling curves with which this prediction can be checked are organized on the basis of a new application of the law of corresponding states that permits all of the data to be plotted as a single, universal function of a reduced gravimetric water content variable. Scatter in the swelling curve data is sufficiently great at present to preclude a definite conclusion as to whether a second‐order phase transition actually occurs in swelling soil.
Electric Charges on Sesquioxidic Soil Clays
Authors: Fey M. V. , le Roux J.
Published: July 2010

The effects of pH, phosphate, oxalate, pyrophosphate, citratedithionite‐bicarbonate and Na2CO3 pretreatments on the positive and negative exchange charges of sesquioxidic clays from soils of South Africa, Australia, Brazil, Japan, and New Zealand were measured using 0.05N KCl as index electrolyte according to a method which obviates a washing step for removal of excess salt prior to replacement of the index ions, Behavior of clays rich in allophane was compared to that of three synthetic amorphous, aluminosilica gels.

Hysteretic, pH‐dependent net negative exchange charge appears to arise from positive exchange charge hysteresis only, CEC being fully reversible by titration with strong acid.

The methodology of cation and anion exchange capacity determinations is discussed with special reference to the problem of surface charge density variations encountered in different materials.
Potassium Release from Sand, Silt, and Clay Soil Separates
Authors: Munn D. A. , Wilding L. P. , McLean E. O.
Published: July 2010

Four Ohio soils of divergent mineralogy were fractionated into sand, silt, and clay‐sized separates after dispersion with an ultrasonic probe. Samples were extracted for 10 days with 0.01M CaCl2 with the solution being changed each day. There was a wide range in daily and cumulative K release among the four soils for the same particle size and for different particle sizes within the same soil. When weighted according to particle size distribution of the soil, the clay was found to contribute 30–74%; silt 24–56%; and sand 3–21% of the total K released by the sum of the three separates. In all four soils, the clay separate released the most K per unit weight. The apparent rate constants for K release from the sand and clay separates were similar and renerally higher than that for the silt separates.
Particle‐Size Distribution Characterization for the Coarse Fraction of a Granite Soil: II. Disintegrating Granite
Authors: Russell D. A.
Published: July 2010

The object of this study was to test the incomplete gamma function previously developed as a descriptor for grapite disintegration. Samples of disintegrating granite were taken from several sites at three locations in a hot semiarid environment in south‐central Africa (southern Rhodesia). These samples were from surface rock, profile corestones, and disintegrating rock at the base of the soil profile. Particlesize distributions were obtained using the standard sieving and pipette method. For materials > 10 mm, Martin's diameter was measured directly.

The incomplete gamma function was fitted to these data, and also to U.S. and French data from the literature, for granite in an apparently similar state of disintegration. The values for the degree‐of‐disintegration parameter were fairly uniform. The mode of disintegration appeared the same regardless of site. The two‐parameter incomplete gamma distribution was found to be a reasonably good descriptor of the particle‐size distribution of disintegrating granite. The mean size appeared to be a sensitive and useful single‐valued descriptor for these distributions.
Particle‐Size Distribution Characterization for the Coarse Fraction of a Granite Soil: III. The Coarse Fraction of a Granite Sand
Authors: Russell D. A.
Published: July 2010

The object of this study was to test the previously developed two‐parameter incomplete gamma function as a descriptor for the > 0.002‐mm fraction of some semiarid, sandy, granite‐derived soils from south‐central Africa (southern Rhodesia). Samples were taken from profiles at five locations. Three of these locations had been previously selected for sampling disintegrating granite, and one was a medium rainfall site. Particle‐size distributions were obtained using the standard sieving and pipette method. For materials > 10 mm Martin's diameter was measured directly. The incomplete gamma described the data reasonably well. The two distribution parameters, α, the weathering index, and ρ, the scale factor, varied as expected. The mean and standard deviation increased with depth as expected. On the basis of the behavior of ρ the profiles tested were separated into two groups. Grouping according to the variation of α yielded the same two groups. The difference between the two groups could perhaps be the degree of development. However, more comparisons are necessary to check this.
High‐frequency Irrigation for Water Nutrient Management in Humid Regions
Authors: Phene C. J. , Beale O. W.
Published: July 2010

A water‐nutrient management method was designed to prevent plant‐water and nutrient stresses while maximizing the available soil water storage to accommodate rainfall. This method minimized the need for the soil as a storage reservoir for water and nutrients by frequently irrigating a portion of the root zone with small amounts of water and nutrients. The optimal range of soil matric potential, based on soil oxygen diffusion rate, soil strength, water desorption characteristics, and unsaturated hydraulic conductivity was used to determine high‐frequency irrigation criteria for sweet corn (Zea mays L.). Trickle‐irrigated plots yielded 12 and 14% more corn than did the furrow‐ and sprinkler‐irrigated plots. When fertilizers were broadcast and banded, soil NO3‐N profiles measured near the end of the growing season showed that, compared to furrow and sprinkler irrigation, trickle irrigation reduced NO3‐N losses from the root zone.

Optimal ear yield was produced with high‐frequency trickle irrigation when the soil matric potential at the 15‐cm soil depth was controlled at about −0.2 bar and plants were fertilized with 168 kg/ha each of N and K. Ear yield for this treatment was 66% higher than that for nonirrigated corn fertilized at the same rate. Soil NO3‐N did not accumulate in the profile with depth and time in plots fertilized at the 168‐kg/ha rate, but did accumulate in plots fertilized with 336 kg/ha. Generally, plots trickle‐irrigated with fertilizer solution had a higher soil NO3‐N content on the row than 50 cm from the row.

The results of this research indicate that water use efficiency, N‐use efficiency, and N leaching can be controlled in sandy soils when N and K are applied with high‐frequency trickle irrigation systems and N and K rates are adjusted to maintain an optimal N‐level in corn plants.
Relation Between the Kinetics of Nitrogen Transformation and Biomass Distribution in a Soil Column During Continuous Leaching
Authors: Starr J. L. , Parlange J.‐Y.
Published: July 2010

Nitrogen concentration profiles in soil columns with associated microbial distributions have been used in the past to deduce the kinetics of nitrogen transformations during steady leaching. Owing to the many factors which control microbial reaction kinetics in continuous flow systems, the effect of biomass variation and order of reaction cannot be separated by simply measuring steady‐state concentrations profiles. It is shown here that in practice these measurements only lead to some average kinetics for the system observed, even when the microbe distribution is measured independently. Previously published experimental data in conjunction with a derived expression are used to illustrate the point.
Coupling Phenomena in Saturated Homo‐ionic Montmorillonite: I. Experimental
Authors: Elrick D. E. , Smiles D. E. , Baumgartner N. , Groenevelt P. H.
Published: July 2010

A series of experiments was performed to observe the effects of salt concentration differences across a thin layer of homo‐ionic montmorillonite. The water pressure difference, concentration difference, and voltage difference measured with electrodes reversible to the anion were observed as functions of time. A qualitative explanation of the observations is proposed.