bluuebunny/crossref_metadata_2025_split huggingface dataset:
Soil Microsites as a Source of Denitrification Variability
Authors: Parkin Timothy B. 
Published: July 2010

AbstractThe spatial variability exhibited by soil denitrification rates is high. As is typical for natural denitrification rate measurements, the individual rates of most samples of a given data set are low; however, a few samples often exhibit extremely high rates. Such data are characterized by highly skewed sample frequency distributions. This study was initiated to investigate the underlying mechanisms responsible for these observations. It was found that “hot‐spots” of high specific denitrification activity were associated with particulate organic C material in the soil. The high specific activities of these hot‐spots (incubated under aerobic conditions with no amendments) were similar to the denitrification activity of the bulk soil measured under conditions of anaerobiosis with added glucose and NO3. This observation served as the basis of a computer model that evaluates the influence of the density and dispersion pattern of these high activity sites on the measured rates of denitrification. Histograms generated from computer simulations are very similar to histograms obtained for real data, supporting the concept that the patchy dispersion of particulate organic material in soil is a major factor influencing the variability of natural denitrification rates.
Distribution and Plant Availability of Soil Boron Fractions
Authors: Jin Jin‐yun , Martens D. C. , Zelazny L. W. 
Published: July 2010

AbstractThe fractionation of soil B and the plant availability of each fraction have not been examined extensively. This laboratory and greenhouse research was conducted to study the distribution and plant availability of B in different soil fractions. Total B in the 14 soils under study ranged from 21.5 to 96.3 mg kg−1. A trace to 0.34% of the total B was in a water‐soluble form; ≤0.23% was 0.02 M CaCl2 extractable (nonspecifically adsorbed B); from 0.05 to 0.30% was mannitol exchangeable (specifically adsorbed B); and from 0.23 to 1.52% was acidified NH2OH·HCl extractable (B occluded in Mn oxyhydroxides). Ammonium oxalate solution (pH 3.25) extracted from 2.8 to 34.4% of the total soil B in the dark (B occluded in noncrystalline Al and Fe oxyhydroxides) and from 17.5 to 73.9% under ultraviolet (UV) light (B occluded in crystalline Al and Fe oxyhydroxides). Residue B, which was considered to be in association with soil silicates, accounted for 2.4 to 79.2% of the total B. Boron concentration in corn (Zea mays L.) tissue correlated positively (α = ≤0.05) with water‐soluble B, CaCl2 extractable B, mannitol exchangeable B, and acidified NH2OH·HCl extractable B. The sum of these four fractions, which were related to B availability, accounted for only 0.4 to 2.0% of the total B in the 14 soils. Boron concentration in corn tissue was unrelated (α = 0.05) to NH4‐oxalate extractable B (either in the dark or under UV light) and to the residue B fraction. These relationships indicate that B in noncrystalline and crystalline Al and Fe oxyhydroxides and in silicates was relatively unavailable for plant uptake.
Genesis and Classification of Clay Soils with Vertic Properties in Saskatchewan
Authors: Dasog G. S. , Acton D. F. , Mermut A. R. 
Published: July 2010

AbstractClayey soils formed in glaciolacustrine sediments in semiarid and subhumid regions of Saskatchewan were studied to understand their genesis and to examine their classification according to the amended definition of Vertisols. Although slickensides were common to all soils, semiarid soils displayed weak horizons, whereas subhumid soils had argillic horizons and prominent mollic epipedons. All the soils had high potential to swell and shrink, and were characterized by seasonal moisture deficits sufficient to induce cracking. Soil displacement, as evidenced by slickensides, was attributed to differential wetting in the subsoil. Pedoturbation, as a result of such displacement, has been sufficient to prevent strong horizon formation in semiarid soils but insufficient to counter leaching and illuviation in subhumid soils. Blocky and prismatic structure, when dry, and microfabric considerations support a B horizon designation in these soils, which otherwise exhibit indistinct horizons when moist. It is suggested that Vertisols with frigid and cryic soil temperature regimes should be grouped into a new suborder, Borerts. It is also suggested that soils that have diagnostic horizons other than mollic be excluded from Vertisols even when accompanied by intersecting slickensides.
Reactive Characteristics of Certain Soils from South Nigeria
Authors: Okusami T. A. , Rust R. H. , Juo A. S. R. 
Published: July 2010

AbstractStatistical relationships were determined between soil pH, effective cation exchange capacity (ECEC), surface area, and some other soil properties for selected soils of southern Nigeria. The soils were mostly hydromorphic with a pH range of 3.6 to 8.1. Exchange acidity was virtually due to exchangeable Al (r = 0.99). Negative ΔpH values indicate a dominant silicate clay mineralogy. The ΔpH (pHKCl‐pHH2O) was correlated with exchangeable Na (r = −0.56), sand content (r = 0.51) and organic C (r = 0.34). Effective cation exchange capacity was low, average of 7.1 cmolc kg−1. No exchangeable Al was found above a soil pH (KCl) of about 4. A derived variable, ΔCEC (difference between CEC measured at pH 8.2 and ECEC), was used as a dependent variable to test pH dependence. The variability observed in ΔCEC values was found to be related to clay content (r = 0.65), exchangeable K (r = −0.11), and organic C (r = 0.34). A regression analysis with BET‐N2 (Brunauer, Emmett, and Teller) specific surface area as the dependent variable showed a strong relationship with clay content (r = 0.96) and ΔpH (r = −0.44) in the best regression equation.
Correspondence of Soil Properties and Classification Units with Sagebrush Communities in Southeastern Oregon: II. Comparisons within a Multi‐taxa Soil‐vegetation Unit
Authors: Lentz R. D. , Simonson G. H. 
Published: July 2010

AbstractA complex soil landscape composed of two dominant soil components supporting a range of heterogeneous sagebrush communities was examined in order to determine if soil properties and classification differed among plant community types. Cluster analysis of 64 vegetation samples identified six recurring plant groupings (RPGs). Properties of RPG soil profiles were statistically compared by defining aggregate horizons (tiers) that were common to all profiles. Recurring plant groupings were characterized by relative canopy cover of Artemisia arbuscula, Artemisia tridentiata ssp. wyomingensis, Festuca idahoensis, Agropyron spicatum; total grasses, and total herbs. Stepwise discriminant analysis selected thickness of mollic epipedon, surface rock fragment cover, and thickness and weighted average dry consistence of the argillic horizon as those that best distinguished between RPG associated soils. Evidence suggests that series separations are justified based on family and class distinctions of higher categories or differences in range of one or more soil properties, including (i) horizon sequence, (ii) mollic epipedon thickness, (iii) structure of BAt subhorizon, (iv) thickness, and (v) weighted average dry consistence of the argillic horizon. Phase level separations of RPG associated soils from identical families are feasible if both physiographic and soil surface criteria are utilized together.
Effect of Aluminum and Iron Oxides on Hydraulic Conductivity of Sandy Loam Soil
Authors: Shainberg I. , Singer M. J. , Janitzky P. 
Published: July 2010

AbstractIron and Al oxides and hydroxides have been shown to stabilize pure clay systems from the effect of high exchangeable sodium percentage (ESP). This study examined the effect of Fe and Al additions on the stability of a California Alfisol with serious crusting problems. Changes in saturated hydraulic conductivity were used as a measure of treatment effectiveness. Saturated hydraulic conductivity (HC) of a sandy loam equilibrated with sodium adsorption ratio (SAR) 20 CaCl2‐NaCl solution and leached with distilled water was faster for samples treated with 20 and 40 mmol kg−1 of FeCl3 or AlCl3 compared with untreated and 10 mmol kg−1 treatments. The FeCl3 treatments were more effective than AlCl3 treatments in maintaining HC. Analysis of the column effluent showed that more Al than Fe was removed during leaching. Much of the Fe added to the soils is recovered in oxalate and citrate‐bicarbonate‐dithionite (CBD) extracts, but little Al is recovered because the added Al is removed with the effluent. The stabilizing effect of hydroxy‐Fe polymers against the deleterious effect of exchangeable Na was related to the charge on the polymers and not with the total amount extracted.
Penetrometer Resistance and Bulk Density as Parameters for Predicting Root System Performance in Mine Soils
Authors: Thompson P. J. , Jansen I. J. , Hooks C. L. 
Published: July 2010

AbstractMaterial handling methods used in the construction of soils after surface mining often result in a soil with physical and structural characteristics that restrict root development. A method to quickly and easily predict root system performance and compare mine soils on the basis of their suitability for root growth is needed. This study was conducted to determine the effectiveness of penetrometer resistance (as measured by a constant rate cone penetrometer) and bulk density as parameters for predicting root system performance. Both penetrometer resistance and bulk density data fit well into a multiple linear regression model that could be used to predict root length density in the lower portion of the root zone (67–110 cm depth). Results suggest that in the mine soils studied, both bulk density (R2 = 0.81) and penetrometer resistance (R2 = 0.73) are useful predictors of root system performance.
Hydraulic Conductivity of Three Southeastern Soils as Affected by Sodium, Electrolyte Concentration, and pH
Authors: Chiang S. C. , Radcliffe D. E. , Miller W. P. , Newman K. D. 
Published: July 2010

AbstractIn the humid southeastern USA, little attention is given to the effect of electrolyte concentration or low levels of Na on clay dispersion, although dispersion‐related phenomenon such as surface crusting and erosion are common. Our objective was to determine the effect of electrolyte concentration, sodium absorption ratio (SAR), and soil pH on saturated hydraulic conductivity of three soils that differed in parent material. Cores packed with sieved soil at different pHs were leached with 10 pore volumes of solution at varying SAR and electrolyte concentrations. The relative decrease in conductivity during leaching was recorded as a measure of clay dispersion and subsequent clogging of pores. The Cecil soil (Typic Hapludult), which is derived from granitic parent material, was easily dispersed and hydraulic conductivity was sensitive to small changes in electrolyte concentration, SAR, or pH. The Davidson (Rhodic Paleudult) and Iredell (Typic Hapludalf) soils, derived from mafic parent material, were flocculated and insensitive to changes in electrolyte concentration and pH except at very high SAR. The implications are that southeastern soils may differ greatly in structural stability and this may be related to parent material. Dispersive soils need to be identified and managed in an appropriate manner.
Forest Floor and Soil Influence on Response of Douglas‐fir to Urea
Authors: Edmonds R. L. , Hsiang T. 
Published: July 2010

AbstractData from the Regional Forest Nutrition Research Project (RFNRP) in Washington and Oregon were analyzed to improve stand‐specific prediction of Douglas‐fir [Pseudotsuga menziesii (Mirb.) Franco] response to urea fertilization. The response variable (relative difference in volume growth between fertilized and control plots 4 yr after fertilization with 448 kg N/ha) was regressed against 28 stand and site variables (e.g., age, elevation, forest floor C/N ratio, soil cation exchange capacity, etc.) using stepwise multiple regression analysis. Data from 120 installations were stratified by thinning level (thinned or unthinned), geographic location (provinces), and site quality (site index and class). Forest floor C/N ratio was the dominant variable related to response. In thinned installations of high site quality (site classes 1 and 2), 60% of variation in response was explained by the forest floor C/N, and 75% of the variation in response was explained with inclusion of surface soil exchangeable K. In thinned, low site quality stands, response was not as well related to forest floor C/N. Analysis of the data by province indicated that S may be limiting in southwest Oregon and P in coastal Washington.
Phosphorus Fertilizer Solution Distribution in the Band as Affected by Application Variables
Authors: Eghball B. , Sander D.H. 
Published: July 2010

AbstractPhosphorus fertilizer applied with the seed or knifed into the soil as a band application has been shown to be more effective than broadcast P. Several experiments have shown that P fertilizer applied as a band becomes increasingly superior compared with broadcasting P as the P rate increases to the optimum rate. Phosphorus distribution in the band was judged to be a potential contributing factor. Therefore, an experiment was conducted to determine the distribution of P fertilizer solution in the band as affected by P rate and band spacing. A solution applicator was utilized to deliver fertilizer solution as ammonium polyphosphate (10‐15‐0, N‐P‐K) to application knives set about 3 cm above the surface of a catch paper. The fertilizer solution was placed on the paper and the distribution of the fertilizer droplets was measured. Knife spacings of 30, 45, 60, and 75 cm along with four P rates (7.5, 15, 22.5, and 30 kg ha−1), five traveling speeds (1.6, 2.6, 4.5, 7.1, and 9.8 km h−1), and three delivery tube sizes (0.9, 1.1, and 1.5 i.d.) were used. The results indicate that at lower rates the P solution is not distributed as a continuous band but rather as droplets of different sizes. At 7.5 and 15 kg P ha−1, the band consists of droplets at all banding spacings. Continuous bands of solution were formed at 22.5 and 30 kg P ha−1 at spacings >40 and 50 cm. Traveling speed affected the distance between droplets. The greater the speed the smaller the distance between the droplets. The increasing superiority of banding compared with broadcasting as the P rate increases may possibly be explained by the distribution of droplets in the band, where a continuous band may provide greater opportunity for the roots to utilize the fertilizer. When droplets are widely scattered, many droplet‐root contacts are necessary to supply adequate P to the plant, but in a continuous band, only one contact may be sufficient for root uptake of adequate P if the roots continue to proliferate along the continuous P fertilizer band.
Acidification and pH Buffering of Forest Soils
Authors: Magdoff F. R. , Bartlett R. J. , Ross D. S. 
Published: July 2010

AbstractHorizons (O, A, E, B, and C) of forest soils from Vermont, New York, New Hampshire, and Virginia were equilibrated with various rates of either acid (H2SO4) or base (CaCO3). Most titration curves had a logistic shape with a lower asymptote (between pH 0.3 and 3.1) and an upper asymptote (around pH 7). The lower pH asymptote was highly correlated with equilibration solution Al and with soil pH measured in 1 M NaF. The specific buffer capacity (SBC) of the 26 horizons was related to organic matter (OM). Higher OM levels caused greater SBC. The buffer capacity of the OM was 0.4 mol kg−1 OM−1 pH−1. Using pH, pHNuF, OM, and horizon depth, it is possible to estimate the amount of acid currently in the soil (compared to a reference pH), the quantity of acid needed to lower the pH by a given amount, the amount of pH decrease associated with a given amount of acid input, the lower pH asymptote, and the pH at which solution Al is above a given concentration.
An Improved Procedure for Collection and Preservation of Soil Profiles
Authors: Ottersberg R. J. , Byron T. M. 
Published: July 2010

AbstractThe monolith and lacquer peel methods of soil profile collection proved to be unworkable for an 8‐m high wall that contained both fine loams and loose gravel. A new procedure was developed that has advantages over either of the commonly used procedures. Polyurethane foam is injected as a binder and filler between the soil and the field backing board. The foam dries hard overnight making it possible for two people to remove 2‐m sections of profile on the following day. The field backing board is also the final mounting board, so less time is spent in the laboratory preparing samples than with the traditional monolith procedure. Polyurethane foam makes it possible to collect larger profiles that can be more easily managed than the traditional monolith. It can be used on a wider range of textures than the lacquer peel method, and requires less time in the field because foam requires less drying time than lacquer. The foam method is an efficient way to collect large soil profiles.
Some Personal Reflections on Soil Science and Agriculture, 1936 to 1986
Authors: Aldrich Daniel G. 
Published: July 2010

AbstractThe personal reflections of the author on soil science and agriculture, 1936 to 1986, provide graphic evidence of the changes that have taken place in soil science. By way of illustration, changes in research that have taken place in Div. S‐1, S‐2, S‐3, and S‐4 are highlighted. The forces that drive the changes in soil science relate directly to funds supporting soil and plant research. Such funding is crucial in furthering our understanding of the fundamental chemistry, physics, and biology of soils and our ability to relate and utilize this knowledge in solving soil‐plant‐water problems of agriculture, however and wherever it is practiced today. Over the past half century, U.S. Agriculture has changed dramatically, moving more and more from an independent, production‐oriented sector of the economy toward a technologically advanced, interdependent system that distributes food and fiber worldwide. As these changes in American agriculture continue to take place, the agricultural education and research system is being called upon to broaden the traditional context within which it has functioned in order to address significant societal concerns. These legitimate societal issues include concerns about preserving the viability of our agricultural infrastructure, increasing the agricultural literacy among the general population, maintaining the quality of our environment, and improving the health and nutrition of our citizens. Thus as the case is made for obtaining support for research in soil science and agriculture, it must contain evidence of how fundamental knowledge generated by research expands the foundation of applied or problem‐solving research and development that is vital to society.
Solute Transport in Undisturbed Columns of an Aggregated Tropical Soil: Preferential Flow Effects
Authors: Seyfried M. S. , Rao P. S. C. 
Published: July 2010

AbstractSolute breakthrough curves (BTC) resulting from miscible displacement of 3H2O in undisturbed soil columns under a range of soil‐water tensions were evaluated in terms of the mobile‐immobile (MIM) water model and the convective‐dispersive (CD) model. The BTC performed under tensions >0.1 kPa were approximately symmetric in shape and accurately described by the CD model, whereas BTC performed under tensions of 0 or 0.1 kPa were quite asymmetric and better described by the MIM model. Application of tension resulted in about a 10‐ to 20‐fold decrease in hydraulic conductivity [K(θ)] with relatively little change in soil‐water content (θ). Highly asymmetric BTC were attributed to bypassing or preferential flow along macropores. Thus, in terms of model selection, bypassing was significant only when soil‐water contents were at or very near saturation. Rhodamine B dye patterns obtained under saturated conditions showed that soil‐water flow (and thus convective transport) was confined to small regions within the columns. However, easily identifiable, discrete channels were not observed in these regions. It appears that flow was conducted via a series of relatively large pores, or continuous pore sequences. Application of tension appears to have disconnected the most rapidly conducting pore sequences, thus reducing the asymmetry in measured BTC and compressing the dye “solute front.” Even so, dye patterns showed that flow was very heterogeneous, as was also evidenced by high dispersion coefficients in the 3H2O experiments. Comparison of the frequency distributions of field‐measured saturated hydraulic conductivity values and measured rainfall intensities indicated that saturated conditions, and hence significant bypassing, are not expected to occur in this soil under field conditions. Observation of water table response to rainfall events supports this conclusion. From these experiments, we conclude that field‐scale models based on the CD model may adequately represent solute movement in soil at this field site.
Movement of Manganese‐54 in Calcareous Soils as Affected by Leaching Solution, Lime Content, Salinization, and Sterilization
Authors: Fahad A. A. 
Published: July 2010

AbstractMovement of 54 Mn was investigated in calcareous soil columns (untreated, partially depleted lime, salinized, and sterilized) leached with 0.05 mol CaCl2 L−1 followed by 0.03 mol EDTA L−1 (ethyle‐nediaminetetraacetic acid). Manganese was monitored along the soil columns using gamma spectrometry and measured in the effluent during the leaching course (80–120 d). Results indicated that the leaching with CaCl2 for 45 d left 63, 32, and 10% of the applied Mn in the upper 0.5 cm of the silty clay, loam, and loamy sand soils, respectively, with no Mn detected below 5.0 cm. Conversely, leaching with EDTA for 4 d resulted in a nearly uniform distribution of Mn in the 20‐cm soil columns. The various soil treatments caused a reduction in the retention capacity of the three soils for Mn with the maximum reduction occurring in the soils with partially depleted lime. In most cases, leaching with CaCl2 for 45 d produced no Mn in the column effluent except negligible amounts of Mn that were displaced from the sterilized and 50 g lime kg−1 columns. On the other hand, Mn emerged in the effluent immediately after EDTA application and continued until the end of the leaching course. The shape and the position of the breakthrough curves varied depending on the specific soil treatment.