bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetic Implications of B Horizons in Aqualfs of Northeastern Ohio
Authors: Ritchie A. , Wilding L. P. , Hall G. F. , Stahnke C. R.
Published: July 2010

A sequence of five Aqualfs with B horizons ranging from moderately expressed argillic horizons to moderately expressed fragipans was contrasted by physical, chemical, mineralogical, and morphological means. These soils have developed from illitic‐rich parent till deposits of Late Wisconsin‐age; they range in clay content from 25 to 47% and in carbonates from 3 to 15%. A noncarbonate clay content of 30% appears to represent a delicate boundary governing the direction of B horizon genesis in these soils. The genesis of the fragipan appears to be primarily a physical phenomenon; micromorphological and structural properties of the fragipan closely resemble those of the parent till. In contrast, volume changes and fabric rearrangement associated with argillic horizon genesis have largely obliterated traces of rock structure present in the parent till. A dual nomenclature is proposed for fragipan‐like zones which do not meet the current minimum root‐spacing criteria for fragipans. A large part of the in situ clay gain in argillic horizons, cambic horizons, and the upper portions of fragipan zones is attributed to the disintegration of shale lithorelics.
Phosphorus Retention in Coastal Plain Forest Soils: II. Significance to Forest Fertilization
Authors: Ballard R. , Pritchett W. L.
Published: July 2010

Phosphorus retention of 42 forest soils collected from the US Southeastern Coastal Plain was found to be significantly correlated with Al and Fe extracted by soils tests for available phosphorus. Aluminum provided better indices of P retention than Fe extracted by these tests and it accounted for more than 81% of the variation in P retention in the case of the NH4OAc (pH 4.8), 0.03N NH4F + 0.025N HCl, or 0.03N NH4F + 0.1N HCl tests.

Concentrations of Fe and Al in the foliage of 4‐year old slash pine (Pinus elliottii Engelm. var. ‘elliottii’) growing on these soils were significantly correlated with soil P retention. However, foliar Fe, the most closely correlated, accounted for only 26% of the variation in P retention.

Retention of P from concentrated superphosphate applied at the equivalent 56 or 224 kg P/ha 4 years previously to young slash pine was measured to 20 cm depth at 10 sites, and ranged from −14 to +125%. Retention was almost independent of application rate. Extractable Al values corresponding to 50% retention of the applied P were 40, 330, 400, and 120 ppm for NH4OAc, 0.03N NH4F + 0.025N HCl, 0.03N NH4F + 0.1N HCl, and 0.05N HCl + 0.025N H2SO4 extractions, respectively. It is proposed that in the interest of maintaining long‐term growth responses and minimizing possible pollution effects, these values be used for delineating soils of low P retention where less soluble sources of P, such as rock phosphate, should be used if P fertilization is required.
Seedling Growth of Sorghum in Clay‐Sand Mixtures at Various Compactions and Water Contents
Authors: Hemsath Delroy L. , Mazurak Andrew P.
Published: July 2010

Mixtures of kaolinite clay and fine sand fraction from Tripp subsoil (Typic Haplustoll) were prepared with 1.0, 3.8, 7.5, 15, and 30% clay. The clay‐sand mixtures were compacted into cylinders at bulk densities of 1.00, 1.25, 1.50, and 1.75 g · cm‐3. The cores were then subjected to matric suctions of 0.15, 0.33, 1.7, and 8.6 bars.

Penetrometer resistance of the cores increased from 0.25 to 68 kg · cm‐2 as the bulk density of clay‐sand mixture increased from 1.00 to 1.75 g·cm‐3. Matric suction of the clay‐sand mixture contributed much to the increased penetrometer resistance with a correlation coefficient of 0.57.

The elongation of sorghum [Sorghum bicolor (L.) Moench] roots in the cores increased as the clay content increased from 1.0 to 7.5% at all bulk densities when the matric suction was <1.7 bar. Further increase in the clay content decreased the root elongation. The largest negative correlation coefficient (r = −0.65) between root elongation and variables studied was with matric suction. It was considered to be the major factor affecting root length. Penetrometer resistance of clay‐sand mixture was critical in relating soil physical conditions to root growth. At a penetrometer resistance of 20 kg·cm‐2 or greater, no root growth in the clay‐sand mixtures was observed.
The Effect of Overburden Pressure on Chloride and Water Movement in Swelling Clay Soil
Authors: Kissel D. E. , Ritchie J. T.
Published: July 2010

This study was conducted to evaluate the influence of overburden pressure on the movement of water and Cl‐ through short undisturbed cores of swelling clay soil. When overburden pressure was removed from the cores, saturated flow rates increased. Subsequent miscible displacement studies revealed that the percent soil water excluding Cl‐ was also reduced. When soil cores were loaded with overburden pressure, the amount of soil water excluding Cl‐ was approximately 50%. When overburden pressure was removed, the amount of soil water excluding Cl‐ was 33%, about the same value as measured in disturbed soil cores of approximately the same water content. Differences in the quantity of soil water excluding Cl‐ between loaded and unloaded cores were due to an interaction between soil structure and the negative charge on the clay in the loaded cores. Apparently, when overburden pressure was removed, smaller pores increased in diameter, which allowed Cl‐ to diffuse more freely into these spaces.
The Solubility Product of Gibbsite at 15°, 25°, and 35°C
Authors: Singh S. Shah
Published: July 2010

The solubility product of gibbsite was found to be 10‐34.45, 10‐33.96, and 10‐33.52 at temperatures of 15, 25, and 35C, respectively. The findings are consistent with the data of others at 25C. A general equation is given for the calculation of Ksp of gibbsite at different temperatures. The heat of reaction of synthetic gibbsite in the temperature range of 15 to 35C was 18,944 calories/mole.
Soil Mottling and Drainage in a Mollic Hapludalf as Related to Suitability for Septic Tank Construction
Authors: Vepraskas M. J. , Baker F. G. , Bouma J.
Published: July 2010

The feasibility of septic tank construction in a fine silty Mollic Hapludalf, with a mottled subsoil overlying permanently unsaturated sand, was investigated by measuring K values and soil drainage rates in situ. Mottles with chromas of 2 inside peds in the silty clay loam subsoil indicated reducing conditions and channel and plane neoferrans indicated oxidative conditions in the larger pores. Physical data showed high K values and drainage rates at saturation, due to channels and planes, but a very strong drop of these values upon desaturation. Lack of extended saturation of the entire subsoil makes possible excavation of the silt cap and construction of a septic tank seepage bed in the underlying sand.
Response of Soybeans to Liming as Related to Soil Acidity, Al and Mn Toxicities, and P in Some Oxisols of Brazil
Authors: Martini J. A. , Kochhann R. A. , Siqueira O. J. , Borkert C. M.
Published: July 2010

The response of soybeans (Glycine max (L.) Merrill) to the direct and residual effect of liming in relation to soil acidity, Al and Mn toxicities and P availability was studied in five Oxisols of Southern Brazil under successive wheat (Triticum aestivum L.)‐soybean cropping. Yield responses to liming were highly significant due to the high exchangeable Al and extractable Mn, the low pH, exchangeable Ca + Mg, and available P found in these soils. Optimum yields were obtained when liming adjusted Al from 0.1 to 0.5 meq/100g (1.5% Al saturation), soil pH from 5.2 to 5.7 and Ca + Mg from 5.7 to 8.5 meq/100g. Liming also increased root nodulation and reduced P fixation and Mn levels in the soil.
Parent Material of Upper‐ and Middle‐Coastal‐Plain Soils in North Carolina
Authors: Gamble E. E. , Daniels R. B.
Published: July 2010

In the upper‐ and middle‐Coastal Plain of North Carolina, Paleudults are on the old landscapes; Hapludults, with low base status, are on the young valley side slopes. This distribution of soils suggests a parent‐material control of soil development. X‐ray and petrographic analyses of samples of the surficial sediments showed kaolinite to be the dominant clay mineral below the solum and quartz to be the primary sandsized mineral. Weatherable minerals such as feldspar are rare. The effective exchange capacity of the clay is less than 15 meq/100 g. Aluminum is the predominant cation, and the pH ranges from 4.2 to 4.8. The percent base saturation by the sum of cations is < 35% both within and below the solum. The surficial sediment is most clayey at the surface and gradually becomes coarser with depth. The Paleudults are thus developed in the most clayey part of the sedimentary unit. These facts suggest the parent material was composed primarily of quartz sand and kaolinitic clay, with a low pH and with aluminum the dominant exchangeable cation. As a consequence only Ultisols developed; the original character of the parent material has strongly influenced such things as the mineralogy, base saturation, and vertical clay distribution.
Crop Tree Thinning Increases Availability of Soil Water to Small Yellow Birch Poles
Authors: Hannah Peter R.
Published: July 2010

Measurements of soil‐moisture depletion with a neutron probe on five forest sites supporting yellow birch poles (Betula alleghaniensis Britton) in Vermont indicate moisture is depleted at slower rates around individual trees that have had “partial release” and “full release” than around trees with “no release.” The effects of thinning on depletion are cumulative over a growing season; by late August moisture depletion curves have diverged substantially. Significant differences in depletion rates due to treatment effects occurred for 20 to 40% of the measurement intervals within a growing season. Most of the significant differences are judged to occur because of oddities in the data. Measures of net soil depletion rate are extremely variable because of microsite differences. Apparent depletion rates and theoretical depletion patterns for short intervals are examined. Moisture depletion rates between soil depth classes (0–15 cm, 15–46 cm, 46–76 cm) are significantly different during most intervals within a growing season. The data obtained in this study portray only general trends, and it is questionable whether more intensive studies of this nature should be planned to obtain significant differences in results.
Unsaturated Hydraulic Conductivity from Cumulative Inflow Data
Authors: Ahuja L. R.
Published: July 2010

A method of determining the wetting‐phase unsaturated hydraulic conductivity K(θ) from the data of cumulative inflow into a uniform soil core when water enters through a porous plate of high hydraulic resistance is described and evaluated. The method is based on piecewise application of the Green and Ampt (1911) approach to the above process of infiltration. The K(θ) determined by this technique from the numerical‐solution inflow data of Yolo light clay were within 20% of the K(θ) values actually used in obtaining the numerical solution in two different cases of hydraulic resistance. Similar analysis of the experimental inflow data of Salkum silty clay loam for four different hydraulic resistances yielded the K(θ) data which closely agreed with the K(θ) values determined by detailed analysis of the soil‐water content transients.
Evaluation of Simulated Seedling Emergence through Rainfall Induced Soil Crusts
Authors: Holder C. B. , Brown K. W.
Published: July 2010

Extensive areas of cultivated soil throughout the world develop rainfall‐induced crusts which impede seedling emergence. Quantitative information is needed on the factors influencing the development of crusts and on the influence of ameliorating treatments on crust strength. A convenient method was developed to make impedance measurements. Soil was placed in boxes which were equipped with guided tubes to allow a probe (simulated seedling) to penetrate the soil crust from below. Measurements were made by means of a balance which supported the probe, as it was raised by means of a jack.

The equipment was used to collect data on the relationship between rainfall intensity and soil crust impedance. Simulated rainfall of intensities from 1.3 to 5.1 cm/hour and durations of 19 to 60 min were used to form the crusts. Determinations of crust impedance were made daily for 7 days with a 12‐hour drying cycle.

For the loam soil tested, the maximum daily average impedances were 1,766, 2,226 and 1,851 g of force for rainfall intensities of 1.3, 2.5, and 5.1 cm/hour respectively. Crust impedance for all tests increased initially as the soil dried, then declined as cracking increased.

An inverse relation was found between mechanical impedance and the percent crust moisture between 20 and 2.8% moisture; the maximum impedance occurred in the narrow range of 2.8 to 2.2% moisture. An increase in the coefficient of variability as the soil dried was associated with cracking. Different durations of rainfall at similar intensities resulted in larger differences in impedance than did different intensities for the same duration.
Rhizosphere pH as Influenced by Plants, Soils, and Nitrogen Fertilizers
Authors: Smiley R. W.
Published: July 2010

The rhizosphere pH (pHr) of field and container‐grown wheat plants was measured and compared to the nonrhizosphere soil pH (pHb). The predominant form of N supplied to the roots was a major factor influencing the pHr. The pHr was generally lower than pHb where NH4 was supplied, higher where NO3 was used, and relatively unchanged where both forms were added. Differences in pHr of up to 2.2 units were recorded for NH4‐ vs NO3‐fed wheat plants (Triticum aestivum L.) in pots. Differences of up to 1.2 units occurred in the field. The pHb and pHr also differed by as much as 1.2 units. Changes in pHr were correlated with the concentrations of NH4 in potted soils, although the acidifying influence of NH4 decreased with time, as nitrification proceeded. Reductions in pHr values persisted longer in NH4 treated, fumigated soils, and in non‐fumigated soils where NH4 fertilizers had been treated with a nitrification suppressant. The pHr differences in NH4‐ vs NO3‐N treated soils were reduced by organic amendments. Difference with respect to pHr were found among wheat varieties and plant genera. The ability of plants to alter the pHr was related to assimilation of NO3 primarily in the roots (monocots) or shoots (dicots).
Soil‐Landscape Relationships in a Closed Drainage System
Authors: Malo D. D. , Worcester B. K. , Cassel D. K. , Matzdorf K. D.
Published: July 2010

Geomorphic and geometric conditions of a small, closed drainage system on the glacial drift plain of North Dakota were related to measured properties of the soil along a linear transect. Multiple regression techniques were used to define relationships statistically between soil properties and quantitative morphometric parameters. Landscape position and soil properties were significantly related. The geomorphic processes of erosion and sedimentation were evident in the measured properties of the soil. Textural variations encountered in profiles can be attributed to erosional and sedimentational activity present on the hillslope rather than pedologic activity. The degree with which the geologic processes of erosion and sedimentation affect the soil and their properties depends on landscape position.
Kinetic and Equilibrium Studies of Boron Desorption from Soil
Authors: Griffin R. A. , Burau R. G.
Published: July 2010

Kinetics of boron desorption from soil were determined using 0.05M mannitol solutions to create pseudo first‐order reaction conditions. The results showed two separate pseudo first‐order reactions and one very slow reaction for which detailed kinetic treatment was not attempted. The relative amount of boron associated with the two fast reactions was independent of soil texture and of initial sample boron content.

It was postulated that the two reaction rates were due to desorption from two independent boron retention sites. It was speculated that the two fast reactions were due to desorption from hydroxy iron, magnesium, and aluminum materials in the clay fraction. The third or slowest reaction rate was probably due to diffusion of boron from the interior of clay minerals to solution phase.

Equilibrium studies showed that boron desorption followed a 2‐site analog of a linear form of the 1‐site Langmuir expression. Langmuir adsorption maximum values for each site corroborated those calculated from the kinetic study and supported the multisite interpretation of the kinetic data.
The Occurrence of Aluminum‐Phosphate Precipitate in Plant Roots
Authors: McCormick Larry H. , Borden F. Yates
Published: July 2010

The occurrence of an Al‐PO4 interaction in plant roots has been described by many investigators as being an adsorption‐precipitation reaction which probably occurs along the root surface and in the cell wall region near the root tip. The present investigation was designed to observe and to identify more precisely the sites of this Al‐PO4 interaction in plant roots. Molybdenum, which has a sufficient atomic weight to be electron dense, was selected as a stain because prior investigations had shown that molybdenum becomes strongly attached to prepared precipitates of Al‐PO4. Electron micrographs gave strong inferential evidence that an Al‐PO4 precipitate did occur in the plant roots as scattered globules in the mucilaginous layer along the root surface and in the intercellular regions of the root tip.
Growth of Atriplex canescens (Pursh) Nutt. Improved by Formation of Vesicular‐Arbuscular Mycorrhizae
Authors: Williams S. E. , Wollum A. G. , Aldon Earl F.
Published: July 2010

Fourwing saltbush [Atriplex canescens (Pursh) Nutt.] roots were stained for detection of endomycorrhizal fungi by simmering in an acid fuchsin‐chloral hydrate solution. Naturally occurring endomycorrhizal fungi were observed in symbiotic association with the roots.

Mycorrhizal fourwing saltbush grown in nonsterile soil had a greater dry weight and accumulated more phosphorus than nonmycorrhizal plants grown in sterile soil. Inoculation of fourwing saltbush with a known endomycorrhizal fungi, Endogone mosseae Nicol. and Gerd. tended to stimulate the plants to greater growth than uninoculated plants.
Distribution of Nonionic Surfactant in Soil Columns Following Application and Leaching
Authors: Miller W. W. , Letey J.
Published: July 2010

The distribution of 14C‐tagged surfactant (Soil Penetrant) was observed in soil columns following application of various concentrations and leaching under unsaturated flow on wettable (Pachappa) and water‐repellent (Morris Dam) soils. The maximum depth of surfactant penetration for a given leaching period was greater for Pachappa than for Morris Dam. Following leaching there was a more uniform distribution of surfactant throughout the column of Pachappa soil. Water drop penetration time (WDPT) experiments showed good correlation between experimental distribution as determined by 14C tracing and actual reduction of water repellency to a given depth. Consequently, the movement and distribution characteristics of a non‐14C‐tagged surfactant (Aqua Gro) on the Morris Dam soil following application and leaching was qualitatively examined by the WDPT method. A theoretical model was tested for its ability to qualitatively predict experimental Soil Penetrant distributions. There was reasonable agreement between experimental and calculated distributions. Specific adsorptive characteristics at low equilibrium concentrations were found to be very important to surfactant distribution in a given soil.
Determination of Soil Water Diffusivity by Sorptivity Measurements
Authors: Dirksen C.
Published: July 2010

A new method is proposed for determining the dependence of soil water diffusivity and conductivity on water content or pressure head in the tensiometer range. A weighted mean diffusivity is used to linearize the one‐dimensional absorption problem. The resulting cumulative absorption is equated to that of the exact nonlinear solution to obtain an expression for the diffusivity in terms of sorptivity. To use this result, sorptivities must be measured for a series of step‐function increases in the water content (pressure head) at the absorption interface. Such sorptivity measurements are quickly and easily made in situ.

The method was tested on a numerical example with nearly perfect results. Also, sorptivity measurements were made on laboratory soil columns and the derived hydraulic conductivities compared well with those measured directly under steady state conditions.
Evaluation of Soil Testing Methods for Predicting Growth and Response of Pinus elliottii to Phosphorus Fertilization
Authors: Ballard R. , Pritchett W. L.
Published: July 2010

Soil tests were evaluated as methods for predicting height growth or increased height growth due to P fertilization of Pinus elliottii var. elliottii Engelm. on acid Coastal Plain soils. Growth and response parameters were obtained from field and greenhouse trials fertilized at time of planting with N and P. Field trials were measured 1, 3, and 5 years after planting and the greenhouse trial, which involved unfertilized soils collected from the field trials, was measured 1 and 2 years after planting.

The amounts of P extracted by H2O or NH4OAc (pH 4.8) were the most closely correlated with height growth and response to P fertilization after 1 year of growth in both the greenhouse and field. The effectiveness of these methods declined after longer growth periods. Methods which extracted larger amounts of P—0.5M NaHCO3; 0.05N HCl + 0.025N H2SO4; 0.03N NH4F + 0.025N HCl—were more effective predictors of response to P fertilization over growth periods of 3 and 5 years in the field. Phosphorus extracted by 0.03N NH4F + 0.025N HCl was the most closely correlated with response recorded after 5 years (r2 = 0.778).

Concentrations of P in the tops of greenhouse‐grown pine seedlings after both 1 and 2 years growth were most closely related to P removed by the stronger extractants. The r2 values for the relationships between soil test values and both concentrations of P in seedling tops after 2 years and in foliage of field trees at age 4 were almost identical.
Effects of Fertilization and Thinning on the Growth of Ponderosa Pine
Authors: Youngberg C. T.
Published: July 2010

Over much of its range second growth ponderosa pine (Pinus ponderosa Laws.) occurs in greatly overstocked stands which, in combination with low annual precipitation, results in large unproductive areas. This study explored thinning and fertilizer application as a means of increasing timber production. Nitrogen, P and K were applied to thinned and unthinned stands of 45‐year‐old pine. Growth measurements after 5 years revealed fertilizer response in both thinned and unthinned stands. Responses in the latter were significant but small. Main fertilizer effects were from N. Thinning effects were greater than fertilizer effects and a combination of thinning and fertilizers gave the best growth response. Even though additional N was applied, growth at the end of the second 5‐year period had decreased, indicating that the thinned stand was still overstocked.
Ammonia Retention in Tropical Soils as Influenced by Moisture Content and Continuous Submergence
Authors: Shimpi S. S. , Savant N. K.
Published: July 2010

Under laboratory conditions, when moisture contents increased from 0 (oven‐dry) to 30%, amount of NH3 retained in noncalcareous medium black soil and lateritic soil decreased. However, subsequent increase in moisture content from 30 to 100% resulted in increased NH3‐retention in the soils. Continuous submergence favored NH3‐retention in the soils.
On Solving the Flow Equation in Unsaturated Soils by Optimization: Horizontal Infiltration
Authors: Parlange Jean‐Yves
Published: July 2010

Recently, integral methods have been developed that provide accurate approximations to the diffusion equation with rapidly varying diffusivity, but require in general some numerical iteration. In the present paper, a new analytical approach is developed which yields optimal approximations without any numerical iteration. The method is applied to the problem of one‐dimensional horizontal infiltration of water in soils. In that case it is shown that the sorptivity is an invariant, which can be expressed in terms of the sum of two integrals involving the diffusivity. The analytical results are in excellent agreement with numerical calculations for Yolo light clay.
Dissolution Rate of Gypsum in Flowing Water
Authors: Kemper W. D. , Olsen John , de Mooy C. J.
Published: July 2010

Dissolution rates of gypsum were measured in water flowing through beds of gypsum fragments as affected by fragment size, solution velocity and initial concentrations of Ca2+, SO42‐ and CO32‐ in the flowing water.

Equations were derived to describe the rates of dissolution, and a dissolution coefficient was defined which is a function of fragment size and solution velocity. Rates of dissolution are high enough to distribute quantities of gypsum, which are within economic reach of the farmer, on farm lands via the irrigation water. Sample calculations are made to show how these data may be used to design watercourse cross sections for applying given levels of gypsum to the flowing water.
The Relationship between Organic Matter Content and Exchangeable Aluminum in Acid Soil
Authors: Thomas Grant W.
Published: July 2010

Varying amounts (0–20 meq/100g) of nitric acid were added to samples from six depths of a Maury silt loam which varied in organic matter content from 5.11 to 0.80%. Aluminum extracted by 1N KCl was found to be lower as organic matter content increased at any given pH level. This finding helps to explain the successful growth of crops in killed sods where the surface soil is acid but rather high in organic matter; it also may account for some of the benefit of organic amendments on acid soils.
Model of Soil Salinity Effects on Crop Growth
Authors: Childs S. W. , Hanks R. J.
Published: July 2010

The model considers properties of the soil, water, plant, and atmospheric system to predict relative crop yield. Crop yield predictions assume a direct relation between dry matter production and transpiration. The only salinity effects considered are osmotic potential. The influence of initial soil salinity on crop growth depended upon the crop type and irrigation management. Predictions made of salt buildup over several years show that some water management systems would produce high yields for several years before salt buildup would decrease yields. Predictions show that the influence of irrigation system uniformity on salinity buildup and yield reduction is very important.
Interactions Between Organic Compounds, Minerals, and Ions in Volcanic‐ash‐derived Soils: I. Adsorption of Benzoate, p‐OH Benzoate, Salicylate, and Phthalate Ions
Authors: Appelt H. , Coleman N. T. , Pratt P. F.
Published: July 2010

The adsorption, desorption, and competitive adsorption characteristics of benzoate, p‐OH benzoate, salicylate, and phthalate were used as models to study the possible mechanisms involved in the interactions of organic compounds with amorphous materials. The studies were carried out in batch systems using subsoil samples of three Typic Dystrandept soils from Chile.

The adsorption of simple organic anions by soils derived from volcanic‐ash can be described by an adsorption‐pKa‐pH relationship. The removal of organic matter with H2O2 did not affect the adsorption of organic anions. The adsorption characteristics obtained, together with desorption and competitive studies, suggest that benzoate was adsorbed by an anion‐exchange reaction by volcanic‐ash‐derived soils. But p‐OH benzoate, salicylate, and phthalate besides anion‐exchange adsorption, were also adsorbed by ligand‐exchange reactions. It is postulated that chelation ability would represent an important property for specific adsorption.
Ammonia Volatilization from Surface Applications of Ammonium Compounds on Calcareous Soils: IV. Effect of Calcium Carbonate Content
Authors: Fenn L. B. , Kissel D. E.
Published: July 2010

The purpose of this study was to determine the effect of soil CaCO3 content on ammonia volatilization from surface applied ammonium compounds. Ammonia‐nitrogen losses from surface‐applied (NH4)2SO4 increased rapidly to 6.1% soil CaCO3, with slight NH3 loss increases from 6.1 to 9.7% soil CaCO3, and no NH3 loss increase beyond 9.7% soil CaCO3. Ammonium nitrate reached maximum NH3‐N loss at 1.3% soil CaCO3 and 110 kg NH4+‐N/ha, with lower but still increasing losses of NH3‐N at 6.1% soil CaCO3 and 550 kg NH4+‐N/ha.

The acidity of the ammonium compounds caused a reduction in final soil pH at low CaCO3 levels and high NH4+‐N application rates; but at 6.1% soil CaCO3 and above, the pH values remained at 7.5 to 7.6. The effect of soil pH on NH3‐N losses was greater for NH4NO3 than for (NH4)2SO4. For (NH4)2SO4, the percent loss of NH3‐N below 1.3% soil CaCO3 decreased as NH4+‐N application rates increased; but at 2.9% and above, NH3‐N losses were greatest at the highest rate of NH4+‐N application. In contrast, no reversal in NH3‐N losses were observed for NH4NO3 with increasing soil CaCO3 content and NH4+‐N application rates.

Multiple regression analysis of NH3‐N losses with respect to time, temperature, rate of NH4+‐N application, and soil CaCO3 content resulted in two equations with correlation coefficients (R2) of 0.88 and 0.85.
Nitrogen Fixation by Algae in Fescuegrass Soil Crusts
Authors: Reddy Gudiogopuram B. , Giddens Joel
Published: July 2010

Soil crusts and subsoil samples of different ages of tall fescuegrass (Festuca arundinacea Schreb.) were collected and analyzed for N, C, and acetylene reduction. Total N and C in the crust was 0.18% and 2.76%, respectively, in 4‐year old soil crust as compared to 0.06% and 0.67%, respectively, in fallow soil. The amount of acetylene reduction after 5 days' incubation was 13.77 µmole/flask (9.6 cm2) for the 4‐year‐old sod crust compared to 3.06 µmole/flask for the fallow control. Ammonium nitrate reduced and liming increased N fixation in the crust. Nitrogen fixation in the crust was highest at 55% shade. Blue‐green algae present in the crust were Anabaena, Nostoc, Syctonema, and Oscillatoria. Greater nitrogen fixation occurred when moss (Bryum sp.) was present in crust.
Vehicle Perturbation Effects upon a Tundra Soil‐Plant System: II. Effects on the Chemical Regime
Authors: Challinor J. L. , Gersper P. L.
Published: July 2010

Chemical regime alterations of a soil‐plant system resulting from tracked‐vehicle perturbation were determined in Tundra soils near Barrow, Alaska. The study was a contribution to the USIBP Tundra Biome Program.

Six years following the perturbation, soils within track scars had lower redox potentials (negative) and lower amounts of exchangeable acidity than undisturbed soils. Furthermore, exchangeable bases (Ca, Mg, K and Na) were higher in the track influenced soils. Consequently, soil pH and base saturation were also higher.

Soluble nutrient (Ca, Mg, K, Na, and NH4‐N) levels in soil solutions were considerably higher in track‐influenced soils than in undisturbed soils. Correspondingly, soil solution pH was also higher.

Plants growing in the altered environment of the track scars were enriched in nutrients and were larger in size. Increased productivity and quality of track‐influenced vegetation was apparently stimulated by an increase in available nutrients in less acid, warmer, nutrient enriched soils. The track perturbation also resulted in changes in floristic composition of the vegetation at different locations within track‐affected soils.

The intensity of soil alteration and resulting changes in the soil‐plant chemical regime were related to the degree of scarring of the landscape which, in turn, was related to differences in the natural drainage of soils along the tracks; scarring being greater, the poorer the natural drainage.

Results show that a slight amount of disturbance to the tundra surface may be beneficial in terms of increased productivity and nutrient content of vegetation.
Soybean and Corn Rooting in Southwestern Minnesota: I. Water‐Uptake Sink
Authors: Allmaras R. R. , Nelson W. W. , Voorhees W. B.
Published: July 2010

Sink terms in the transient soil water flow equation were estimated to provide accurate descriptions of field water uptake. Water uptakes by vertically developing root systems of three crops were described as a function of time during drying of a Nicollet soil which often has a perched water table at 1.3 to 2 m early in the growing season. During the period 1 July through 15 Aug., water uptake by corn (Zea mays L.) was compared with that by determinate and indeterminate isolines of ‘Harosoy’ soybean (Glycine max. L. Merr.). These accounts of water uptake were later compared with directly examined rooting patterns.

Water depletion measurements (with neutron probe) underestimated transpiration beginning in late July when upward water flows at 140 cm were 0.4 to 0.6 of transpiration. Depletions by soybeans occurred at shallower depths than corn. The indeterminate isoline showed greater depletions than the determinate isoline at shallow depths.

Water flows in the rooting zone were estimated from tensiometric measured hydraulic gradients and hydraulic conductivity, calculated to match in situ field estimates. Peak flows to the root system progressed with time from the shallow to deeper depths. Maximum flows at the 122‐ to 152‐cm depth ranged from −0.6 for soybeans to −0.8 cm/day for corn. Soil water potentials at maximum flow were −180 to −600 mbars with lower potentials noted for soybeans.

Sinks for soybean water uptake showed greater and earlier water extraction at shallower depths than corn. Sinks for water uptake by all three crops moved down with time until 30 July, when water extraction by soybeans became limited by depth of rooting. Pan evaporation increased significantly, and the corn root sink continued to move down.

Integrals of the sink term early in the period overestimated by 20% the sum of depletion and upward movement into the rooting depth. Later in the test period sink term integrals underestimated the same sum by 25%.
Fluometuron and Water Content Distributions During Infiltration: Measured and Calculated
Authors: Wood A. L. , Davidson J. M.
Published: July 2010

Laboratory columns of Cobb sand were used to study the movement and distribution of surface applied 1,1‐dimethyl‐3‐(α, α, α,‐trifluoro‐m‐tolyl) urea (fluometuron) for three infiltration rates and two initial soil‐water contents. Fluometuron movement showed little dependence on initial soil‐water content for a given infiltration rate. Experimental data indicated that equilibrium existed between the adsorbed and solution phases for all infiltration rates and initial soil water contents studied with the exception of the ponded infiltration into air‐dry soil case. A simultaneous numerical solution of the water and solute transport equations described a fluometuron pulse, for large infiltration rates, which lagged the experimental data. The agreement between calculated and measured distributions was improved when the infiltration rate was reduced. The shape of the fluometuron pulse was reasonably well described by the mathematical model.
Phosphate Adsorption by Soils: II. Reactions in Tropical Acid Soils
Authors: Rājan S. S. S. , Fox R. L.
Published: July 2010

Phosphate adsorption by several Hawaiian and Indian soils, and the relation of phosphate adsorption to hydroxyl, sulfate, and silicate ions released in two Hawaiian soils were studied. Adsorption isotherms of some of the soils show an abrupt increase in phosphate adsorption at high concentrations.

The isotherms were analyzed applying a binary Langmuir equation (assuming two types of sites). The curve predicted by the Langmuir parameters describes the portion of the isotherm where adsorption seems to be mainly by surface ligand exchange (at low levels of phosphate adsorbed). Where additional reactions occur the experimental points deviate from the predicted curve.

Phosphate adsorption is associated with increased pH and sulfate release at low levels of phosphate adsorbed and increased silicate release throughout. The observations suggest that at low concentrations phosphate exchanges with (i) adsorbed sulfate and adsorbed silicate, and (ii) with water and hydroxyls of metal hydrous oxides and edge aluminum of clays. At high concentrations additional phosphate is adsorbed by displacing the structural silicate of clays. The increase in phosphate adsorption by structural silicate release, over that of surface exchange reactions, is about 50 and 25% in two soils containing kaolinite and allophane clays respectively.
Determination of Arsenate, Methanearsonate, and Dimethylarsinate in Water and Sediment Extracts
Authors: Yamamoto M.
Published: July 2010

A method is described for separating and measuring arsenate, methanearsonate, and dimethylarsinate in water and sediment extracts. The arsenicals were separated by differential elution from a column of cation exchange resin; and the separates were subsequently analyzed by the arsine method. Standard arsenical solutions separated well, and 97, 93, and 95% of arsenate, methanearsonate, and dimethylarsinate, respectively, were recovered in the effluents. The method was tested with pond sediments previously treated in the laboratory with known levels of arsenicals. Recovery varied from 80 to 98%.
Effect of Temperature on Denitrification Rate in Soils
Authors: Stanford George , Dzienia Stanislaw , Vander Pol Roger A.
Published: July 2010

The effect of temperature on denitrification rate was studied with nine soils differing widely in organic matter content and chemical and physical characteristics. In the range of 15 to 35C, the temperature coefficient of denitrification, Q10, was approximately 2. Denitrification rates at 35 and 45C were similar. Between 10 and 5C, denitrification rate declined abruptly. The lower limit of the temperature range conforming to a Q10 of 2 was estimated to be 11C. In this study of water‐logged soils sealed from the atmosphere, denitrification appeared to obey first‐order kinetics.
Effects of Parent Material on Genesis of Borolls and Boralfs in South‐Central New Mexico Mountains
Authors: Anderson J. U. , Bailey O. F. , Rai Dhanpat
Published: July 2010

A field study of a 186 km2 area, a more detailed study of a 65 ha area, and laboratory analysis of four soil profiles has shown that, in this high elevation forested area in New Mexico, Borolls are forming in residuum from limestone, but Boralfs are forming where the parent material is from sandstone. These Borolls resemble the classic concept of Rendzina, but lack a udic moisture regime necessary for Rendolls. The Boralfs are distinctly different from the Borolls even though all soil‐forming factors other than parent material appear to be the same. The absence of evidence of illuviation of clay in the Borolls can probably be attributed to the presence of calcium carbonate in all soil horizons, but the very great differences in organic matter content can probably not be accounted for by the data presented.
Distribution and Properties of Some Tidal Marsh Soils of Apalachee Bay, Florida
Authors: Coultas C. L. , Gross E. R.
Published: July 2010

Tidal marshland forms a border between the Apalachee Bay area of the Gulf of Mexico and the uplands of Taylor County, Florida. The purpose of this investigation was to determine the distribution of the tidal marsh soils and to measure some of the properties used in their classification. Three pedons representative of the major soils were described and sampled. The range of electrical conductivity is from 14 to 90 mmhos/cm. Field moist pH ranges from 5.6 to 7.8 and air dried pH values are 2 to 3 pH units lower. Content of S is < 0.75% in the Psammaquents and Haplaquods to 6.8% in the Sulfaquents. Oxidation of S to sulfates was probably responsible for the increase of soil acidity after drying. Cation exchange capacity ranges from 2 to 25 meq/100g for the Psammaquents and Haplaquods and from 25 to 75 meq/100 g for the Sulfaquents. Most soils are nearly base saturated. The soils classified in order of increasing elevation are members of the coarse‐loamy, mixed, thermic Typic Sulfaquents; the sandy, siliceous, thermic Mollic Psammaquents; and the sandy, siliceous, thermic Aeric Haplaquods. Because of high potential acidity, low bearing strength, and high salinity, decisions concerning man's use of tidal marsh soils should be carefully made. Undisturbed, these are productive soils performing functions valuable to man.
Genesis of Argillic Horizons in Soils of Desert Areas of the Southwestern United States
Authors: Nettleton W. D. , Witty J. E. , Nelson R. E. , Hawley J. W.
Published: July 2010

We studied soils and landscapes in the southwestern part of the Lake Lahontan drainage basin in Nevada and soils on alluvial fans near Phoenix and Willcox, Arizona and Mojave, California. The youngest surface is less than 12,000 YBP (years before present), the oldest is pre‐Wisconsin in age. Typic Torripsamments are on surfaces younger than 12,000 YBP, finer textured Haplargids and Paleargids are on surfaces older than 12,000 YBP. The volume of clay skins in a sandy family of Xeralfic Haplargids on a late Wisconsin age, dune‐sand surface is approximately equal to the increase of clay in its B horizon, whereas clay skins are mostly lacking in the fine‐textured Haplargids and Paleargids formed in sandy alluvium. Both the distribution of quartz and total silica in the sand + silt and the distribution of volcanic fragments in the very fine sand show that the A horizons of the finer textured Haplargids and the Paleargid are as weathered as, or more weathered, than their B horizons. This is evidence that the B horizons of Argids were formed at least in part by translocation of clay. Accumulation of total Al2O3 and Fe2O3 in these argillic horizons is more direct evidence that clay translocation occurred. The older Argids have clay maxima below the calculated depth of wetting in most years. These clay maxima are near the depth of wetting expected once or twice each 100 years in the older Argids, but the present climate does not seem adequate to have produced the soils in the time involved. Rather these older Argids are probably products of moister Plestocene climates.
Effects of Grazing on Infiltration Rates in Waste Water Spray Fields
Authors: Pearson George A. , Jung Gerald A. , Fowler Richard E. , Mitchell Donald M.
Published: July 2010

Many food‐processors use grass‐covered sprayfields for treating waste water. These fields are generally mowed one or more times each year. To eliminate mowing costs, such fields could be fenced and used as irrigated pastures. However, since the primary purpose of such fields is waste water treatment, adverse effects on infiltration must be avoided, particularly in areas with shallow soils that cannot be manipulated for overland‐flow.

A portion of a food‐processor's wastewater treatment field was fenced and grazed for approximately 5 months during the summer and fall of 2 successive years. The soil series was Sassafras sandy loam and the grass species were ‘Kentucky 31’ tall fescue [Festuca elatior var. arundinacea (Schreb.) Wimm.] and orchardgrass (Dactylis glomerata, L.).

The infiltration rate at saturation was measured frequently throughout the period of grazing. It was found that trampling reduced the infiltration rate from an initial value of 2–2.5 cm/hr to a final value of 0.3 cm/hr.

If these fields are to be grazed, it will be necessary to use low wastewater application rates to avoid surface runoff and ponding in low spots.
Predicting Anion Movement in Disturbed and Undisturbed Soils
Authors: Cassel D. K. , Van Genuchten M. Th. , Wierenga P. J.
Published: July 2010

Prediction of anion displacement in soils has proven difficult owing to anion exclusion and the occurrence of anion sources or sinks within the soil system. In addition, variations in bulk density and texture with depth cause mean pore water velocity and soil water content to be functions of depth. In this paper a numerical solution of a modified convective diffusion equation, which accounts for apparent anion exclusion and variations in soil water content and mean pore water velocity as functions of depth, is discussed. Moreover, a zero‐order rate term is incorporated to account for nitrification occurring in the upper portion of the soil profile.

The model was tested using previously published NO3 and 36Cl displacement data for disturbed and undisturbed cores of Aberdeen loam. The model predicted 36Cl displacement well. Incorporation of the source term improved prediction of the nitrate breakthrough curve, but agreement of the predicted curve with observed data was only fair. When average values for water content and bulk density were used throughout the entire column, instead of depth dependent values, the description of anion movement was not as good. It is suggested, however, that the improvement in accuracy of prediction of anion displacement may be less than the variation in solute movement observed among replicate soil cores.
Potassium‐Calcium Exchange Equilibria in Volcanic‐Ash Soils
Authors: Schalscha E. B. , Pratt P. F. , de Andrade L.
Published: July 2010

Potassium‐Ca exchange equilibria were determined at potassium adsorption ratios (PAR) of 0.2, 2.0, and 20 for pH values of 4.8, 6.0, and 7.5 for four volcanic‐ash soils of southern Chile. Increases in pH produced large increases in CEC which were largely balanced by increases in the amount of Ca adsorbed. The increases in exchangeable K with increase in CEC were relatively small. The relative affinities for K versus Ca at a PAR of 0.2 indicated that for each soil a small, but nearly constant, amount of negative charge had a high specificity for K. Beyond this small amount of CEC with a high affinity for K, the affinities for K were relatively low.
Infiltration of Organic Phosphate Compounds in Soil
Authors: Rolston D. E. , Rauschkolb R. S. , Hoffman D. L.
Published: July 2010

Organic phosphate compounds may be moved greater distances into soil than is possible with inorganic phosphates inasmuch as organic phosphates must be enzymatically hydrolyzed to orthophosphate before soil reactions inhibit movement. The hydrolysis in solution and movement in soil of six organic phosphates were investigated in order to evaluate possible advantages of the compounds as fertilizers. The compounds studied were glycerophosphate, methyl ester phosphate, glycol phosphate, ethyl ester phosphate, glucose 1‐phosphate, and glucose 6‐phosphate. The infiltration of organic P compounds into Panoche clay loam soil and glycerophosphate into five soils differing in texture, clay type, organic matter, and pH and into one soil at three water contents was investigated by infiltrating organic P solution into columns of dry or moist soil at a rate of 66 kg of P/ha. Inorganic P concentration in bicarbonate extracts was measured as a function of soil depth at the termination of infiltration. The movement of P from organic compounds was compared with the movement of potassium phosphate. All the organic phosphates hydrolyzed at similar rates. The P from all the organic compounds moved to approximately the 12‐cm depth in the calcareous Panoche clay loam soil with only slight differences in P concentration above that depth, whereas inorganic phosphate moved no more than 2–3 cm. The enzymatic hydrolysis rate of glycerophosphate and the resulting P distribution after infiltration was influenced by soil type. The greatest P movement (12 cm) occurred in Panoche clay loam, and the least amount of movement occurred with Aiken clay loam. Soil‐water content had only a slight effect on glycerophosphate movement for the one soil studied.