bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Dinitrogen‐Fixing Trees on Phosphorus Biogeochemical Cycling in Contrasting Forests
Authors: Zou Xiaoming , Binkley Dan , Caldwell Bruce A. 
Published: July 2010

AbstractPhosphorus availability in soils is controlled by both geochemical and biological reactions. Dinitrogen‐fixing trees differ from non‐N2‐fixing trees in litter production and litter chemistry, and these differences may substantially alter soil P biogeochemistry. We examined the effects of two N2‐fixing tree species on labile P pools and potential P transformation rates and correlated these variables with soil acid phosphatase activity. Experimental treatments include stands of N2‐fixing red alder (Alnus rubra Bong.), conifers, and a mixture of both in Oregon, and plantations of N2‐fixing Albizia falcataria (L.) Fosberg, Eucalyptus saligna Sm., and a mixture of both in Hawaii. Data from Oregon indicated that red alder increased labile organic P (Po) levels and soil phosphatase activity. Soil labile Po concentrations in the red alder and mixed stands were twice those of the conifer stand. Labile inorganic P (Pi) pools and net P solubilization rates in soils under the mixed stand were two‐ to fivefold greater than in pure stands, suggesting that interactions between alder and conifers, rather than alder's effect, triggered changes in P geochemical reactions. In Hawaii, labile Po concentrations in both pure A. falcataria and mixed plantations were higher than in the pure E. saligna plantation. Soil acid phosphatase activity in the pure A. falcataria plantation was twice as high as that in the pure E. saligna plantation. However, labile Pi pools and P transformation rates did not differ among the three Hawaiian plantations. Our results suggest that N2‐fixing trees increase soil labile Po levels and soil phosphatase activities whereas their interactions with non‐N2‐fixing trees vary with species and may result in altering both geochemical and biological P transformations.
Absorbent Method for Measuring Solute Activities in Unsaturated Soils: Thermodynamics and Preliminary Experiments
Authors: Snyder V. A. , Martínez G. A. , Vázquez M. , Peña L. , Cavallaro N. 
Published: July 2010

AbstractCharacterizing the physico‐chemical environment in unsaturated soils has been difficult due to lack of methods for measuring solute activities at low soil water content. We describe a method where a thin sheet of insoluble and chemically nonreactive absorbent material is allowed to absorb water and solutes from the soil. Solute activities are inferred from the measured amounts of sorbed water and solutes and a generalized pressure membrane technique. Preliminary evaluations of the method used Whatman no. 42 filter paper as the absorbent. Air‐dry filter papers that had been impregnated with different known amounts of K2HPO4 were allowed to absorb water by equilibrating through the vapor phase with salt solutions of known water potential. Measured filter paper water contents and K2HPO4 molalities (mol sorbed K2HPO4 kg−1 sorbed water) related to water potential in a way consistent with theory. To examine general trends and variability of measurements in actual soil systems, filter papers were equilibrated with soil receiving different chemical pretreatments, at soil water matric potentials between −7 and −5400 J kg−1. Coefficients of variation for Ca, Mg, and K molalities in the filter papers were usually <20% for a given treatment. Predictably, cation molalities generally increased with decreasing soil water content. In CaSO4‐treated soil, however, Ca molalities decreased significantly, perhaps reflecting increased soil adsorption of CaSO4 at low water potentials. Adding Ca electrolytes to the soil generally increased K and Mg molalities, as expected from ion exchange.
Fate of l‐Phenylalanine in Soil and Its Effect on Plant Growth
Authors: Sarwar M. , Frankenberger, W. T. 
Published: July 2010

AbstractPhenylacetic acid (PAA) is a deamination product of phenylalanine (PHE) applied to soil, which can have a positive physiological effect on plant growth and development. The objective of this study was to determine the factors limiting deamination of PHE when added to soils, determine the major pathway upon detection of metabolic intermediates, and assess the growth‐promoting effect on maize (Zea mays L.) of an exogenous application of PHE to soil. The highest activity of PHE deamination in soils occurred at pH 8.5 and on incubation temperature of 40°C. The soil assay used to determine these parameters was based on the amount of NH4‐N cleaved from l‐PHE when incubated for 48 h in the presence of toluene. A sigmoidal relationship was observed between NH4‐N and PHE concentration, indicating cooperative kinetics. Both phenylpyruvic acid and PAA were detected by high‐performance liquid chromatography (HPLC) following the addition of PHE to soil. A glasshouse experiment revealed that an exogenous application of PHE as a soil drench to established uniform seedlings of maize had a significant effect on vegetative growth parameters (shoot height, shoot fresh weight, internodal distance, uppermost leaf collar base distance, and leaf width). Since PAA is a well‐established plant growth regulator, it was concluded that this metabolic product derived from PHE in soil was responsible for the stimulatory growth effects in maize.
Sodic Calcareous Soil Reclamation as Affected by Water Chemical Composition and Flow Rate
Authors: Nadler A. , Levy G. J. , Keren R. , Eisenberg H. 
Published: July 2010

AbstractSodic soils exhibit poor physical conditions that adversely influence water and air movement, soil erodibility, and plant growth. This study investigated the efficiency of naturally occurring CaCO3 in reclaiming a sodic loess soil (Calcic Haploxeralf) with an exchangeable sodium percentage of 16. Soil columns (50 or 100 mm high) were leached with distilled water (DW), 1 dS m‐1 tap water (TW), or CO2‐enriched TW at a flow rate of either 11.5 or 50 mm h‐1. The effluent from the columns was collected continuously, and its chemical composition was analyzed. When DW was used, CaCO3 dissolution was the main source (85%) for replacing exchangeable Na. When TW was used, 80% of the (Ca2+ + Mg2+) for reclaiming the sodic soil came from the leaching solution. The slow water flow rate (11.5 mm h‐1) improved reclamation by ∼30%, probably due to the higher concentration of (Ca2+ + Mg2+) from CaCO3 and the longer time available for Ca2+ diffusion into soil aggregates. The CO2‐enriched TW was the most favorable treatment for CaCO3 dissolution and thus the most efficient for soil reclamation. Our results suggest that reclamation of sodic soils can be accomplished by means of the naturally occurring CaCO3 in the soil, providing management conducive for CaCO3 dissolution is used.
Soil Emissions of Nitric Oxide and Nitrous Oxide from No‐till Corn
Authors: Thornton Frank C. , Valente Ralph J. 
Published: July 2010

AbstractFertilized agricultural soils can be a significant source of emissions of NO and N2O into the atmosphere. This study was conducted to determine the influence of N rate on the emissions of these gases in a no‐till corn (Zea mays L.) crop grown in western Tennessee. The influence of N rate was assessed for a 210‐d period on replicated plots receiving 0, 140, and 252 kg N ha−1 (0N, 140N, and 252N) as ammonium nitrate (AN). Plots were located on a Routon silt loam (fine‐silty, mixed, thermic Typic Ochraqualf) at the West Tennessee Agricultural Experiment Station in Jackson, TN. Gas fluxes were measured by static chamber boxes located on plots. The measurement technique was automated and replicate chamber estimates were made eight times daily for the entire study period. Fertilizer application significantly affected both NO and N2O emission rates. The cumulative N2O‐N lost from the fertilizer treatments was from 10 to 20‐fold that of NO. On an areal basis, the 140N treatment emitted 4.23 kg N2O‐N and 0.19 kg ha−1 of NO‐N whereas the 252N treatment emitted 6.56 kg N2O‐N and 0.50 kg ha−1 NO‐N. Soil parameters of water‐filled pore space (WFPS), NO3− and NH4+, were correlated with N2O emissions but only soil NO3− was correlated with NO flux. Our data, and more recent data in the literature, suggest that N2O emissions from fertilized soil may be considerably higher than previously thought. Emissions of N2O were 2.6 to 3.0% of the fertilizer amounts applied. These higher emissions may, in part, explain some of the reason for the shortfall in the global N2O budget.
Mechanistic Modeling of Coupled Ammonium and Nitrate Uptake by Onions Using the Finite Element Method
Authors: Abbès C. , Parent L. E. , Robert J. L. 
Published: July 2010

AbstractA two‐dimensional finite element model for predicting N uptake by onion (Allium cepa L. cv. ‘Norstar 210B’) was developed using variable space intervals in zones of high ionic gradient near the root surface and flexible grid size describing shrinkable subdomains of increasing root competition. The rationale included assumptions of the Cushman‐Barber model, the mobile layer concept, the type of elements, and the discrete variables of the system. The model can predict simultaneous NO3− and NH4+ uptake by coupling a nitrification model and plant‐specific Michaelis‐Menten kinetic paremeters. The model output was compared with measured N uptake based on ammonium sulfate and ammoniated peat (AP) applied to four soils (a silt loam, two sandy loams, and a sand) in a growth chamber. The observed N uptake was close to the predicted in all soils but one, where NH4+ uptake capacity was probably attained. Root growth rate was a sensitive parameter reducing N uptake from As compared with AP. The S‐shaped uptake curves were obtained for the silt loam and sandy loam soils receiving AP. Ammonium profiles were steep. Nitrate profiles were smoother. Nitrate was the dominant N form taken up even when NH4+ was the major available form. Total N uptake was smallest in the sand, which had a low moisture content and maintained a high NH4+ gradient, and the highest in the silt loam, which showed the smallest buffering capacity and the largest volumetric water content, both known to increase NH4+ and NO3− diffusivity.
The Effect of Raindrop Impact and Sheet Erosion on Infiltration Rate and Crust Formation
Authors: Morin Joseph , Van Winkel Jeannoux 
Published: July 2010

AbstractSoil crust formation can result from the beating action of falling drops (structural crust) or the deposition of entrained eroded suspension in shell flow (deposional crust). To determine the relative importance of the two processes, an experiment was carried out with rainfall simulation under laboratory conditions. Clay soil exposed to the beating action of rain drops produced sheet erosion, which was deposited on a layer of clean sand downslope of the same continuous slope. The thin crust that was formed on the two parts of the slope, the clay and the sand, reduced the infiltration rates in time to values of 1 to 5 mm h−1. In comparison with the uniform clay slope, the main difference was the longer time needed to reach the low infiltration rates. Preventing the sand part from any rain impact beating extended the time needed to obtain the low infiltration rates that were nearly the same as those of the clay slope. The results provoke the question is the common theory of compacted crust by rain impact such an important factor?
Nitrogen Recovery by Corn from Nitrogen‐15 Labeled Wheat Residues and Intact Roots and Soil
Authors: Hubbard Victoria C. , Jordan Diann 
Published: July 2010

AbstractConservation tillage systems, which maintain crop residues on the soil surface, are becoming more widely used. Crop residues serve as ground cover to reduce soil erosion and act as a sink‐source for plant nutrients. A better understanding of the processes involved in crop residue decomposition and N release in these systems is needed to develop more efficient residue and fertility management practices. A greenhouse study was conducted to determine N availability to corn (Zea mays L.) from wheat (Triticum aestivum L.) residues and intact roots and soil as affected by residue placement. Tracer 15N was used to quantify the N recovered by corn from wheat residues and intact roots and soil. Wheat residues were either surface‐placed or incorporated in a Mexico silt loam (fine, montmorillonitic, mesic Udollic Ochraqualf) in pots with intact wheat roots. Residue placement significantly influenced the amount of 15N recovered by corn from wheat residues but not from intact roots and soil. Corn 15N recovery was significantly higher from incorporated residues than from surface residues; however, this was not reflected in the dry weight. Corn dry weight was 12% greater from surface residues than from incorporated residues. Higher yield from surface residues was attributed to a more constant optimum soil water content.
Availability of Residual Phosphorus in Manured Soils
Authors: Sharpley Andrew N. 
Published: July 2010

AbstractIn many areas with confined animal operations, continual manure application has increased soil P above amounts sufficient for optimum crop yields. In these areas, it is of economic and environmental importance to determine how long high‐P soils will remain above crop sufficiency and identify soils where P contents would decrease most rapidly under similar management conditions. Thus, the surface 5 cm of 23 high‐P soils (85–419 mg kg−1 Mehlich‐3 P) in Oklahoma and Texas, which had received beef feedlot, poultry, or swine manure (90–1880 kg P ha−1 yr−1 for up to 35 yr) were successively extracted with Fe‐oxide‐impregnated paper strips to investigate residual soil P availability. A decrease in strip P with successive extractions followed the equation: Strip P = a(extraction number)−b (r2 of 0.88‐0.98). The rate of P release to strips (exponent b) decreased more rapidly as soil P sorption saturation increased (R2 of 0.79). Phosphorus saturation also accounted for 85% of the variation in the total amount of P released to strips from manured soils in 15 successive extractions (51–572 mg kg−1). Fractionation of soil P before and after strip extraction showed bicarbonate inorganic P contributed most of the P released to strips (46%). The above equation also described soil P release in several published field studies (r2 of 0.77–0.98). Thus, successive strip extraction of soil has the potential to describe soil factors controlling the availability of residual P and identify soils where high P contents may be less buffered and, thus, decrease more rapidly than others under similar management conditions.
Sandy Wet Spodosols: Water Tables, Chemistry, and Pedon Partitioning
Authors: Evans C. V. , Mokma D. L. 
Published: July 2010

AbstractSpodosols are notably difficult to classify in terms of moisture regime, presumably because redox colors are masked by spodic colors, or perhaps because the absence of structure in sandy Spodosols is a hindrance to detection of redox features. Some views of Spodosol pedons as a series of compartments raise the possibility that some portions of the spodic pedon are simply more responsive than others to saturation parameters. This study attempts to determine whether compartmentalization within Spodosol pedons results in differentiation of soil response to saturation and water table fluctuation. Water table and chemical data were compiled from 16 Aquod pedons. Pyrophosphate‐extractable Fe and Al, oxalate‐extractable Fe and Al, and dithionite‐extractable Fe and Al were determined for all soils; organic C was also determined for at least Bh, Bhs, and Bs horizons, and oxalate‐extractable Si and the optical density of the oxalate extract (ODOE) were also determined for eight of the pedons. Comparisons of chemical data to saturation and water table fluctuation indicated that spodic horizon chemistry was unresponsive to both saturation duration and water table fluctuation. Chemistry of E horizons was most responsive to water table fluctuation, while Al and Si levels of C horizons were more sensitive to saturation and water table fluctuations. Thus, due to compartmentalization of Spodosol pedons, interpretations of saturation and water table fluctuation can be most effectively made from the chemistry of C and E horizons, respectively. The B horizon chemistry was not a good indicator of saturation duration or of water table fluctuation patterns.
Kinetics of Phosphate Rock Dissolution in Acidic Soil Amended with Liming Materials and Cellulose
Authors: He Z. L. , Baligar V. C. , Ritchey K. D. , Martens D. C. , Kemper W. D. 
Published: July 2010

AbstractPhosphate rock (PR), coal combustion by‐product (CCBP), lime‐stone, and organic materials are promising amendments for low P, acid soils, and two or more of the amendments are commonly applied to improve crop yields in acid soil. However, the interactions between these amendments in acid soil are not fully understood. The effects of CCBP, limestone, and cellulose application on dissolution of North Carolina phosphate rock (NCPR) in an acid Lily loam (fine‐loamy, siliceous, mesicTypic Hapludult) from West Virginia were examined in an incubation study. Based on the ΔP‐NaOH estimation method, ≈ 30% of the added NCPR was dissolved after 60 d of incubation. The NCPR dissolution decreased drastically with increasing rate of CCBP, particularly when it was applied together with limestone, whereas cellulose addition tended to enhance NCPR dissolution. Dissolution of NCPR was well described by first‐order, Elovich, and Langmuir kinetic equations. The average r2 values between the experimental data of NCPR dissolution and the three models were 0.829*, 0.851**, and 0.930**, respectively, for 17 soil samples with and without amendments. Half‐life (t1/2) from the first‐order reaction could be employed as a simple measure of the NCPR dissolution rate. Constants A and b derived from the Elovich equation were related to the initial and average dissolution rate of NCPR. The potential maximum dissolution of PR from the Langmuir equation provided an estimate of the dissolution extent of NCPR. All four kinetic parameters, particularly t1/2 and A, were closely correlated with CCBP application rates. These parameters appeared useful in evaluating the effects of CCBP application on NCPR dissolution in the acid soil and might also be applicable to predicting PR dissolution for a wide range of soils with different properties.
Mechanisms of Negative Impacts of Three Forest Treatments on Nutrient Availability
Authors: Harrison Robert B. , Gessel Stanley P. , Zabowski Darlene , Henry Charles L. , Xue Dongsen , Cole Dale W. , Compton Jana E. 
Published: July 2010

AbstractMany forest management treatments are directly aimed at maintaining or enhancing forest productivity. There may also be secondary effects that detract from this goal. We discuss three case studies in Washington state in which several mechanisms may have led to adverse secondary impacts. In the first study, pulp and paper (PII) sludges were mixed into soil and growth of Douglas‐fir [Pseudotsuga menziesii (Mirb.) Franco], noble fir (Abies procera Rehder) and western white pine (Pinus monticola Douglas ex D. Don) was monitored. There was a significant negative correlation of height and diameter growth and C/N ratio for Douglas‐fir and western white pine (0.05 level). In a second study, effects of 50 yr of red alder (Alnus rubra Bong.) and Douglas‐fir growth on soil chemistry and stand productivity were compared. When the 50‐yr‐old stands were cut and red alder was established by planting into the soil of the former Douglas‐fir and red alder forests, lowered available P in the soil of the previous red alder stand was observed. In a third study, high rates of low C/N ratio organic matter (300 Mg ha−1) were added in municipal biosolids (N amount about 8000 kg ha−1) to Douglas‐fir and grand fir [Abies grandis (Dougl.) Forbes] plantations. Excess organic N in the biosolids apparently mineralized, nitrified, and contributed to soil acidification and accelerated cation leaching. Severe Mg deficiency (0.25 g kg−1 in biosolids‐treated vs. 0.93 g kg−1 in untreated area) might be the cause of observed foliar chlorosis and poor growth rates.
Importance of Soil and Role of Ecosystem Disturbance for Sustained Productivity of Cool Temperate and Boreal Forests
Authors: Kimmins J. P. 
Published: July 2010

AbstractHuman population growth places increasing demands on the world's forests. Sustaining these forests will depend to a considerable extent on sustaining soil structure and function. Traditional scientific concerns about sustaining timber production focused largely on soil fertility, but recent interest has focused attention on the plant and animal community and on “biodiversity”. Neither of these approaches is satisfactory on its own. They should be replaced with an ecosystem analysis approach that includes the biotic and abiotic components. The most fundamental issue in sustainable forest management is the long‐term productive capacity of individual sites, which is determined to a considerable extent by the availability of soil resources. Understanding the sustainability of site productivity requires knowledge of the determinants of leaf area and its photosynthetic efficiency, and of the allocation of net production. Keys that determine production ecology in boreal and cool temperate forests include low soil temperature, slow rate of litter decomposition and the resultant character of the forest floor, and, in some areas, impeded soil drainage; these lead to limitations on nutrient availability. Natural disturbance influences these factors and thereby plays a vital role in maintaining productivity and several measures of biological diversity. Without stand‐replacing disturbances, closed forest may not be the climax vegetation in many western and northern Canadian landscapes. While forests and soils should be protected from “damage”, sufficient disturbance should be sustained to respect the disturbance‐related ecology of these forests. Ecological site classification and use of ecosystem‐level management simulation models are important for the design of appropriate disturbance regimes.
Boron Sorption and Release by Allophane
Authors: Su Chunming , Suarez Donald L. 
Published: July 2010

AbstractTo predict B behavior in soils and its influence on plants, it is crucial to understand the mechanisms of B sorption by mineral phases. Because B reacts with clay minerals and Al and Fe oxides, it should also sorb to poorly crystalline aluminosilicates such as allophane. Boron sorption, with and following allophane precipitation, was studied in batch experiments. Solutions containing AlCl3 and Na2SiO3 (concentrations <47 mM with Al/Si molar ratio of 1:1) and B(OH)3 (0, 4.4, and 32 mM) were mixed and titrated to pH 8.0 with 1 M NaOH at two rates (1 and 5 mL min−1) at 23°C, then incubated at 23 and 90°C for 5 d. More B was removed from solution when B was present during allophane precipitation than when B of an equal concentration was reacted with freshly precipitated allophane. In addition, more B was removed when allophane was formed by slower mixing at a slower titration rate, with higher initial B concentration, and incubated at lower temperature. More B was released by repeated washing with dionized water from allophane precipitated in the presence of B(OH)3 than from allophane reacted with B(OH)3. Boron sorption was investigated with diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. Adsorbed B was both trigonally and tetrahedrally coordinated, with the former being predominant. Boron reacted with allophane precipitate was surface sorbed. Corprecipitated B occurred only in tetrahedrally coordinated positions, presumably by substituting for Si in the tetrahedral layer. The structurally coprecipitated B is expected to be more resistant to release than the adsorbed B.