bluuebunny/crossref_metadata_2025_split huggingface dataset:
Morphology of a Paralithic Contact in a Soil Over Soft Sandstone
Authors: Schafer W. M. , Nielsen G. A. , Nettleton W. D. 
Published: July 2010

AbstractRoot distribution was studied in a soil having a paralithic contact in southeastern Montana. An abrupt change in root abundance was the most useful criterion for locating the paralithic contact. The soft rock below the contact is part of the Tongue River member of the Ft. Union formation. The soft rock is indistinguishable from the overlying soil in texture, color, structure, and water‐holding capacity, but has a bulk density of 1.50 g/cm3 and is hard whereas the soil has a bulk density of only 1.35 g/cm3 and is soft when dry. The soil, which has a paralithic contact within 50 cm, supplied 86% as much water to plants during the 1976 growing season as a nearby, texturally similar, deep soil. The difference was less than expected. Removal of water from the soft rock apparently occurred through a few roots which follow widely spaced, vertical pockets of soil deep into the soft rock. Roots from the pockets proliferate horizontally along natural laminations and planes of weakness in the soft rock. Water is removed from as deep as 30 cm below the paralithic contact during the growing season.Present interpretation of paralithic contacts is discussed as it relates to this research. Proposed revisions to the definition are considered and further research is suggested.
Physical Model of the Hydrology of Sloping Heterogeneous Fields
Authors: Hillel D. , Hornberger G. M. 
Published: July 2010

AbstractA model simulating water flow and storage in a 2‐dimensional section of a sloping field, in which surface runoff, infiltration, evaporation, unsaturated soil moisture movement and ground‐water flow are represented as a series of interacting 1‐dimensional processes, was adapted to cases of horizontally heterogeneous fields. The model is illustrated in a series of simulation trials with variously constituted hypothetical fields of loam and clay soils, subjected to a 108‐mm rainstorm. Runoff was found to depend on the fraction of the slope occupied by clay, and on the relative location of the clay (whether upslope or downslope with respect to the loam). Ground‐water recharge was found to be greater in the loam, as was the rate of lateral drainage. The capability of the model is discussed.
Solute Dispersion in Unsaturated Heterogeneous Soil at Field Scale: I. Theory
Authors: Dagan Gedeon , Bresler Eshel 
Published: July 2010

AbstractIn a heterogenous field whose hydraulic properties vary from point to point the transport of solute also differs from profile to profile. In this paper solute concentration on the field scale was treated as a random variable. The field heterogeneity was described in terms of the statistical distribution of the hydraulic parameters, which implies a corresponding distribution of the concentration. Equations for computing this distribution, as well as its average and variance, in a heterogeneous field were derived explicitly for a simple, but representative case, of leaching under random recharge distribution on the surface. The water and solute flow in unsaturated soil was assumed to be vertical and steady. The randomness of the hydraulic properties was reduced to that of the saturated hydraulic conductivity by adopting a scaling hypothesis and a log normal distribution.
Conservation Bench Terraces for Rice in a Subhumid Climate
Authors: Bhushan L. S. 
Published: July 2010

AbstractRain‐fed crops in northern India produce less than the potential maximum due to moisture stress at crucial stages of plant development. Research was initiated on a conservation bench terrace (CBT) system to evaluate its potential to increase water supply for increasing and stabilizing rice production on 2.5% sloping land in the subhumid climate. The width ratios of the contributing area to the collection area (terrace benches) were 0:1, 1:1, 2:1, and 3:1. The contributing area was cropped with corn planted on the contour.Six years of research have shown that levelled benches received 0.25, 0.50, and 0.76 m3/m2 of estimated runoff from the 1:1, 2:1, and 3:1 ratios, respectively. Consequently, measured soil water in the level benches was greater than the storage in level benches without a contributing area at the time of panicle emergence. The rice yields in the level benches with contributing areas were 21, 47, and 88%, respectively, greater on three ratios than yields on the level check without a contributing area. The 84% increase in rice grain yield on the 3:1 CBT was attributed to increased soil water content at panicle emergence.A major advantage of the CBT system was that chances of crop failure were reduced. The probability of obtaining rice yields of < 1,400 kg/ha was decreased from 50% on level bench to 16% in level benches with a 3:1 ratio. Similarly, the probability of achieving yields > 3,500 kg/ha was 50% in the 3:1 CBT system and 0% in the level bench (NW). Total dry matter production for the 3:1 CBT system was 1.7 times greater than the level check.
Particle Shape and Size of Two Sodium Calcium Montmorillonite Clays
Authors: Dufey Joseph E. , Banin Amos 
Published: July 2010

AbstractViscosity measurements of Na‐Ca montmorillonite suspensions (Wyoming and Camp‐Berteau) were performed at five temperatures (11 to 35°C). At a given composition of the surface phase, discontinuous variations of intrinsic viscosity were observed with changing temperature. According to similar observations from the literature, variations would be due to structural modifications of water layers surrounding the clay particles.By combining those results with optical density spectra, we have pointed out different characteristics for the Wyoming and Camp‐Berteau clays. The single plates of Camp‐Berteau montmorillonite are smaller than those of Wyoming. At high Ca‐loading, the formation of thicker particles by parallel condensation of single plates does not involve any marked increase of average major axis in the case of the Wyoming clay. On the other hand, the Camp‐Berteau plates are likely to overlap when they condense; that results in an increasing major axis with increasing Ca‐loading, leading to similar shapes for both pure Ca‐clays. Those results were confirmed by measurements of water content in clay sediments.
Aluminum Organic Matter in Acid Soils: Salt‐Extractable Aluminum
Authors: Bloom P. R. , McBride M. B. , Weaver R. M. 
Published: July 2010

AbstractSample horizons of an acid Inceptisol from New York, an Oxisol from Brazil, and an aluminum‐peat complex containing 1 mole of Al per mole of peat carboxyl groups were extracted with 1N KCl and 1N LaCl3. For all three materials, LaCl3 extracted significantly more Al. The quantity of Al extracted expressed as a fraction of the BaCl2‐TEA acidity was greater for the peat than the soils. It was concluded that the fraction of Al bound by organic matter is important in determining the quantity of Al extracted from surface soils by neutral salts and that “exchangeable aluminum” and “effective cation exchange capacity” are defined by the cation and concentration of the extracting salt.
Water Vapor Movement in Soil: Reconciliation of Theory and Experiment
Authors: Jury W. A. , Letey J. 
Published: July 2010

AbstractA large number of separate experimental studies of water vapor movement in response to thermal gradients are shown to be independent of water content over a wide range of water contents. Two models, proposed by J. R. Philip and D. A. de Vries (1957) and J. W. Cary (1963), are rewritten in a compatible form and compared to the data. The phenomenological model of Cary describes the data if the phenomenological coefficient β has a value between 1.0 and 3.5, whereas the mechanistic theory of Philip and de Vries underpredicts the vapor transport observed in the experiments in all cases.A modification of the theory of Philip and de Vries is proposed which increases the influence of liquid water on vapor transport. In the new formulation the experimental information is adequately described and both models are rendered compatible. Both experimental and theoretical results suggest that water vapor movement may be described by a simple expression which is a known function of temperature, and is independent of water content over a wide range of saturation. Even without calibration it is suggested that this expression can describe water vapor flux to within a factor of 2.
Diffusion of a Biodegradable Pesticide: I. In a Biologically Inactive Soil
Authors: Gerstl Z. , Yaron B. , Nye P. H. 
Published: July 2010

AbstractThe diffusion of parathion (O,O‐diethyl O‐p‐nitrophenyl phosphorothioate) in a biologically inert (“sterile”) loamy soil (Gilat − Israel) was investigated. It was found that the diffusion coefficient (D) of parathion in Gilat soil over a large range of moisture contents varies between 0.66 × 10−7 and 3.39 × 10−7 cm2/sec. The main factors affecting the diffusion of parathion in a “sterile” soil are the adsorption coefficient of the compound on the soil surfaces (K), the moisture content, and the impedance factor (f). The variables K and f were measured independently and the experimental values of D were compared with the theoretical values. Only a small fraction of adsorbed parathion was undergoing diffusion, the mobile fraction of the adsorbed molecules being about 10% of the total adsorbed parathion.
Diffusion of a Biodegradable Pesticide: II. As Affected by Microbial Decomposition
Authors: Gerstl Z. , Nye P. H. , Yaron B. 
Published: July 2010

AbstractThe diffusion of parathion (O,O‐diethyl O‐p‐nitrophenyl phosphorothioate) was investigated and a model which involves treating microbial activity in the diffusion system was developed. The kinetics of parathion degradation during 7 days of incubation at three moisture content (θ = 0.14, 0.24, and 0.34) was determined and compared with the calculated values. It was found that the rate of parathion decomposition rises with increasing water content. The amount of parathion decomposed at any time increased with the increase in the initial concentration. The calculated course of decomposition of parathion fits the experimental results obtained over 7 days, which was the longest period in the diffusion. The experimental results and predicted distribution of parathion and of the metabolite formed (diethylthiophosphate) are presented as affected by time and soil moisture content. The proposed model—which considers the rate of decomposition at any distance and time, and depends on the local concentration of parathion and on the microbial activity—satisfactorily fits the experimental results.
Biomass Response of Loblolly Pine to Selected Cultural Treatments
Authors: Haines Sharon G. , Davey C. B. 
Published: July 2010

AbstractThe effects of site preparation and other cultural treatments on the biomass of 1‐ and 2‐year‐old loblolly pine (Pinus taeda L.) seedlings were examined. Treatments included various combinations of disking, applying herbicides, fertilizing, subsoiling, fumigating the soil, irrigating, and mowing. Oven‐dry weights of stems, needles, roots, and branches were determined. Root collar diameter was significantly affected by treatment after both 1 and 2 growing seasons and was as effective an indicator of treatment response as other variables singly or in combination.
Measured and Approximate Flux‐Concentration Relations for Absorption of Water by Soil
Authors: White I. 
Published: July 2010

AbstractThe flux‐concentration relation of Philip (1973) is calculated using moisture profiles measured during absorption of water by a fine sand when water was supplied at both constant hydraulic potential and constant rate. The general behavior of the measured flux‐concentration relations was found to be consistent with those of the model soils calculated by Philip. Within the accuracy of the measurements, no significant time‐dependence of the relation was found for the constant flux boundary condition over a large time span. Measurements of the time‐averaged flux‐concentration relation, however, suggest some significant time‐dependence for short times. Simple approximations for the flux‐concentration relation, based on these observations, are suggested. These approximations enable easily evaluated predictions to be made of the salient features of constant rate application of water to soil, which are sufficiently accurate for most practical purposes.
Use of Selective Agents for Recovery of Rhizobium meliloti from Soil
Authors: Barber Lynn E. 
Published: July 2010

AbstractThis study was planned to develop a useful selective medium for differentiating Rhizobium meliloti in soils or inocula. The objective was to define a medium which will permit growth of rhizobia and restrain growth of other microorganisms which might inhibit or mask growth of the desired strains of Rhizobium. A yeast mannitol agar medium reinforced with 500 µg/ml pentachloronitrobenzene, 1.5 µg/ml brilliant green, 1.0 µg/ml sodium azide, and 25 µg/ml Congo red proved to be very effective in differentiating R. meliloti from other species of rhizobia as well as other forms of soil microorganisms native to Oregon. Antibiotic resistance as a marker can also be used in association with the selective medium to study the ecology of rhizobia in soil or other environments. However, antibiotic resistance is apparently not a stable character and deserves frequent testing, particularly in long‐term studies.
Variability of Minesoils and Natural Soils in Southeastern Montana
Authors: Schafer William M. 
Published: July 2010

AbstractA study of minesoil variability near Colstrip, Montana, showed that different kinds of soils exist within mine areas, and that individual soil bodies are large enough to map at a scale of >1:10,000. Minesoils were more variable than natural soils at the local scale (0–10 m lateral spacing), while natural soils were more variable at the landscape scale (>500 m lateral spacing). Fourteen soil families were recognized in a 300‐ha natural landscape while only two soil families were found on mined land. Variation in natural soil properties was correlated with geomorphic variables while minesoil variability was related to mining and reclamation methods. Problems were encountered while attempting to classify soils according to Soil Taxonomy.
Influence of a Compact Zone on Solute Transport During Infiltration of Water
Authors: Hira G. S. , Singh N. T. 
Published: July 2010

AbstractIn most soils, continuous plowing results in the formation of a compact zone below the plowing depth. Laboratory studies were conducted to examine the effect of such a zone on the displacement of chloride (Cl‐) during infiltration of water. A compact zone of 4‐ or 8‐cm thickness of 1.62 g/cm3 or 1.80 g/cm3 bulk density was created at a depth of 8 cm in soil columns. A surface‐applied slug of calcium chloride was leached with 4 or 6 cm of distilled water. The presence of a compact zone in the soil profile pushed the Cl‐ peak deeper, dispersed the ions in a narrower region, and increased the peak Cl‐ concentration. Increasing bulk density and thickness of a compact zone increased the depth of the peak Cl‐ concentration.
The Gapon Coefficient and the Exchangeable Sodium Percentage‐Sodium Adsorption Ratio Relation
Authors: Oster J. D. , Sposito Garrison 
Published: July 2010

AbstractA recent, corrected thermodynamic equation for the Gapon cation exchange selectivity coefficient produces a relation between the exchangeable sodium ratio (ESR) and the sodium adsorption ratio (SAR) that is indistinguishable from the widely used, empirical ESR‐SAR relation when SAR ≤ 40. In this sense, the thermodynamic theory of cation exchange is consistent with the empirical ESR‐SAR relation over the range of SAR values that has practical importance in the management of sodium‐affected soils.
Amidase Activity in Soils: I. Method of Assay
Authors: Frankenberger W. T. , Tabatabai M. A. 
Published: July 2010

AbstractAmidase [acylamide amidohydrolase, EC (Enzyme Commission) 3.5.1.4] is the enzyme that catalyzes the hydrolysis of amides and produces the corresponding carboxylic acid and ammonia. The detection of this enzyme in soils is reported, and a simple, sensitive, and precise method to assay amidase is described. The method involves determination by steam distillation of the NH4+ produced by amidase activity when soil is incubated with buffered (0.1M THAM, pH 8.5) amide solution and toluene at 37°C. The amide compounds studied included formamide, acetamide, and propionamide. The procedure developed gives quantitative recovery of NH4‐N added to soils and does not cause chemical hydrolysis of the substrates. Results showed that this soil enzyme has its optimum activity at buffer pH 8.5 and is inactivated at temperatures above 60°C. By varying the substrate concentration it was found that the initial velocity of the amidase reaction is optimum at 0.05M substrate. The initial rates of NH4‐N released obeyed zero‐order kinetics. Steam sterilization destroyed, and formaldehyde, sodium fluoride, and sodium arsenite inhibited, amidase activity in soils. Assay of amidase activity in the absence of toluene indicated that acetamide and propionamide may induce the synthesis of this enzyme by soil microorganisms.
Changes in Solution of Forest Soils with Waterlogging and Three Levels of Base Saturation
Authors: McKee William H. 
Published: July 2010

AbstractWaterlogging and subsequent reduction significantly increased soil pH, except at high base saturation levels, for three Coastal Plain A horizon forest soils. When soils had high base levels, solution levels of Ca usually increased with soil reduction; Mg, Fe, and Mn levels increased with or without increase in base saturation. The effect of ion pairing was more proounced at low base saturation and on more weakly‐charged colloid soils. The sharp increase in cation levels in the soil solution, caused by waterlogging and the influence of bicarbonate pairing, emphasizes the importance of the soil reduction in determining levels of nutrients available to trees on seasonally waterlogged soils.
Nonionic Surfactant Effects on Adsorption and Degradation of 2,4‐D
Authors: Amonette J. , O'Connor G. A. 
Published: July 2010

AbstractThe effects of three nonionic surfactants on 2,4‐D (2,4‐dichlorophenoxyacetic acid) adsorption and degradation was determined for two soils in laboratory studies. The surfactants varied in water solubilities and hydrophilic‐lipophilic balance (HLB) values.Adsorption of 2,4‐D was significantly decreased in both soils by the least water‐soluble surfactant, X‐35. Degradation of 2,4‐D was also significantly delayed by X‐35 to various extents in both soils. However, extent of degradation was independent of treatments after 70 days. Various hypotheses, based on surfactant properties, are offered to explain the adsorption and degradation results. When surfactant concentrations remain above the critical micrelle concentration, nonionic surfactants with low HLB values can significantly alter 2,4‐D behavior in soil. Surfactants with high HLB values appear to have little effect on 2,4‐D behavior.
Response of Semiarid Grassland Sites to Nitrogen Fertilization: I. Plant Growth and Water Use
Authors: Power J. F. 
Published: July 2010

AbstractAlthough it has been repeatedly demonstrated that most perennial grassland ecosystems respond to N fertilization, knowledge of factors controlling N transformations involved in such responses is fragmentary. Eight rate‐of‐N‐fertilizer experiments were conducted for 5 or 6 years on established perennial grass sites near Mandan, North Dakota. Experiments were conducted within essentially the same precipitation and temperature regimes on sites differing in soil type, exposure, and grass species to determine their influence on N response. Above‐ground vegetation response to N fertilization depended primarily upon species — smooth bromegrass (Bromus inermis) was generally more responsive than crested wheatgrass (Agropyron desertorum) or native mixed prairie. No consistent patterns of root biomass response to N fertilization were obvious. At some sites or in certain years root biomass responses were fairly consistent, whereas at other sites or in other years, little response to N occurred. Water use efficiency (WUE) was greatest for bromegrass and least for native grasses, and was generally increased by N fertilization. WUE increased as aboveground growth increased, whether as a result of N fertilization or because of less evaporation at more protected sites. Cumulative dry matter response to N fertilization was highly correlated with cumulative fertilizer N added, with a different curvilinear relationships for each site.These results indicated that the magnitude of fertilizer N responses by perennial grasslands is site specific. Although the same general mechanisms seem to operate at the different sites, magnitude of response was controlled by the plant species present and by some soil type × location factors that are presently ill‐defined. These latter factors appear to influence the capacity of the soil to immobilize fertilizer N, capability of above‐ground plant growth to take up fertilizer N, and many other N transformations, and may be related to relative availability of water. Consequently interpretations of fertilizer experiments conducted on only one soil type or with only one species must be interpreted with caution.
Response of Semiarid Grassland Sites to Nitrogen Fertilization: II. Fertilizer Recovery
Authors: Power J. F. 
Published: July 2010

AbstractThe fate of N fertilizer applied annually for 5 or 6 years at rates up to 200 kg N ha−1 year−1 was determined on eight perennial grassland sites in western North Dakota. The amount of fertilizer N found in plant tops, roots, and as residual soil inorganic N, and the sum of these three fractions were determined for each site. The amount of fertilizer N recovered in each of these fractions was linearly correlated with the amount of fertilizer N applied to each site in almost all instances. Fertilizer N recovered in top growth was highest for smooth bromegrass (Bromus inermis) (about 80% of that applied), and least for the native prairie grasses (about 15% of applied), with intermediate values for crested wheatgrass (Agropyron desertorum). Likewise fertilizer N recovered in roots was greatest for bromegrass (near 15%), whereas soil inorganic N content was usually greatest under native range. Total fertilizer N recovered in these three fractions was usually near 50% for bromegrass sites, but only about 30% for native range sites. There was no evidence of appreciable runoff or deep percolation of nitrates. Fertilizer N not recovered was either immobilized in other forms of soil organic matter or lost to the atmosphere in gaseous forms. Available evidence indicates that only small quantities of fertilizer N would be expected to be immobilized in organic forms other than in plant roots, thereby suggesting that gaseous loss of applied N may have been significant at these dryland perennial grass sites.
Forest Soil Variability on Northeastern Flood Plains
Authors: Mollitor A. V. , Leaf A. L. , Morris L. A. 
Published: July 2010

AbstractFlood plain areas in eastern New York and western Vermont were sampled for 19 surface and 19 subsurface soil properties. On the basis of physiography, two site types were identified for stratification of data: (i) lateral accretion deposits and (ii) vertical accretion deposits. Nested analyses of variance of the 38 soil properties of these alluvial Entisols and Inceptisols shows that, of the variables measured, all with the exception of surface K concentration, K and P content and subsurface K content were significantly less variable within sample plots than among plots. It also shows that surface reaction, P concentration and P content, subsurface clay, silt plus clay, bulk density, reaction, P concentration, Ca concentration, and P content were less variable within types than between types. Sample size requirements to estimate plot means for each property were calculated. Surface soils tend to be less variable than subsurface soils and vertical accretion soils are less variable than lateral accretion soils.