bluuebunny/crossref_metadata_2025_split huggingface dataset:
Winter Cover Crop Effects on Soil Organic Carbon and Carbohydrate in Soil
Authors: Kuo S. , Sainju U. M. , Jellum E. J. 
Published: July 2010

AbstractWinter cover crops may increase soil organic carbon (SOC) levels or reduce their rate of depletion. Selection of appropriate cover crops to increase SOC requires an adequate knowledge of the quality and quantity of plant biomass produced and its rate of decomposition in soil. This study examined the SOC and carbohydrate concentrations in soil as affected by several leguminous and nonleguminous cover crops after 6 yr of a corn (Zea mays L.) cover crop double cropping system in a temperate, humid region. The vegetation in the control treatment without cover crops was primarily shepherd's‐purse [Capsella bursa‐pastoris (L.) Medikus]. The cover crops had a variable effect on SOC and soil carbohydrate concentrations due to a significant difference in total organic C and carbohydrate produced by the cover crops. The buried bag technique showed that the biomass C from the aboveground biomass of the cover crops decomposed rapidly in the soil with a half‐life averaging 30.9 ± 9.4 (SD) d in 1992 and 55.2 ± 7.8 (SD) d in 1993. The decomposition of carbohydrate in the aboveground biomass in the soil was also rapid with an average half‐life of 40.0 ± 13.1 (SD) d in 1992 and 50.5 ± 11.8 (SD) d in 1993. The overriding cover crop effect on SOC and carbohydrate was due to the magnitude of the C inputs from the cover crops. With more than 4 Mg ha−1 of top biomass, cereal rye (Secale cereale L.) and annual ryegrass (Lolium multiflorum Lam.) were better suited as winter cover crops for building SOC levels in this region than Austrian winter pea (Lathyrus hirsutus L.), hairy vetch (Vicia villosa Roth), and canola (Brassica napus L.).
Genesis of Non‐Allophanic E Horizons in Tephra‐Influenced Spodosols
Authors: McDaniel P. A. , Falen A. L. , Fosberg M. A. 
Published: July 2010

AbstractHolocene volcanic ash from the cataclysmic eruption of Mount Mazama in southwestern Oregon is an important component of many soils of the Pacific Northwest region. High‐elevation forested soils of northern Idaho containing Mazama tephra have developed E‐Bhs horizon sequences and are accordingly classified as Spodosols. In this study, we report on the formation and expression of E horizons in a developmental sequence of volcanic‐ash‐influenced Spodosols from this region. Results suggest that development of E horizons in these volcanic‐ash‐influenced soils proceeds systematically along an elevational gradient. The lightest colored, thickest E horizons are associated with the highest elevation soils of the subalpine fir [Abies lasiocarpa (Hook.) Nutt.] forest zone, and E horizons are more weakly expressed and then absent with decreasing elevation. Microprobe analysis of volcanic glass shows that E and Bhs horizons contain the same tephra, indicating that substantial pedogenesis has taken place in these horizons. Formation and eluviation of Al‐humus complexes has given rise to E horizons whose mineralogy and chemistry are consistent with that of non‐allophanic Andisols and differ markedly from underlying horizons. Beidellite, an Al‐rich smectite, dominates the clay fraction of the well‐developed, very strongly acid E horizons at the expense of allophanic clays and metal‐humus complexes; other than beidellite, opaline SiO2 is the major secondary Si‐bearing phase. Chemical and mineralogical properties of illuvial B horizons are consistent with those of allophanic soils; short‐range‐order aluminosilicates and metal‐humus complexes dominate the clay fractions. Results indicate that coupled eluvial‐illuvial processes associated with podzolization are responsible for the non‐allophanic character of E horizons and the allophanic character of Bhs horizons in these forested, volcanic‐ash‐influenced ecosystems.
Mapping Wind‐Blown Mass Transport by Modeling Variability in Space and Time
Authors: Sterk G. , Stein A. 
Published: July 2010

AbstractField observations of wind‐blown particle transport are often characterized by a considerable spatial variation, which makes quantitative modeling of wind erosion difficult. This study examines how the horizontal distribution, or pattern, of mass transport can be determined from a limited number of point measurements. Twenty‐one sediment catchers were installed in an experimental plot in the Sahelian zone of Niger, on a sandy, siliceous, isohyperthermic Psammentic Paleustalf. Mass transport values during four storms ranged from 24.0 to 213.6 kg m−1, 7.2 to 26.0 kg m−1, 9.6 to 68.9 kg m−1, and 68.9 to 282.7 kg m−1. Geostatistical theory was applied to produce storm based maps by modeling the spatial correlation structure with the variogram. To estimate the variogram from 21 observations, the four storms were treated as independent temporal replicates. Two geostatistical mapping techniques were applied. Kriging (a spatial interpolation technique) produced maps of mass transport providing the best possible estimates of net soil losses from the plot, equal to 12.5, 2.0, 4.6, and 26.8 Mg ha−1, respectively. To overcome smoothing, possible realizations of actual mass transport were created by stochastic simulations with simulated annealing. The simulated maps reproduced the statistical properties of the observations and allowed a distinction between erosion and deposition areas within the experimental plot.
Growth and Survival of Jack Pine Exposed to Simulated Acid Rain as Seedlings
Authors: MacDonald Neil W. , Ducsay Brandon J. 
Published: July 2010

AbstractIn a previous study, jack pine (Pinus banksiana Lambert) seedlings grown under pH 2.5 simulated rain had larger shoot/root ratios and altered nutrition compared with seedlings grown with pH 4.7 rain. The objective of this study was to determine if these differences in initial seedling characteristics produced long‐term effects on survival or growth of outplanted seedlings. Significantly (P < 0.05) greater diameter increment (4.3 vs. 4.0 cm) between ages 6 and 10 of jack pine treated with pH 2.5 rain as seedlings was consistent with a carryover effect from the initial treatments. However, no differences between treatments in jack pine diameter, height, or survival persisted to age 14. Results support recent recommendations that extended measurement periods may be necessary to fully assess the long‐term effects of pollutant increases or decreases on growth of immature trees.
Field Evaluation and Error Analysis of Soil Water Content Measurement using the Capacitance Probe Method
Authors: Ould Mohamed S. , Bruand A. , Raison L. , Bertuzzi P. , Bruckler L. 
Published: July 2010

AbstractThe volumetric water content of a silty clay loam soil was measured using the capacitance probe method (CPM) for three successive winter‐spring periods. The results were compared with those obtained using the neutron scattering method (NSM). The CPM was calibrated using gravimetric water content measurements, whereas the NSM was calibrated using a theoretical calibration which requires chemical analysis of soil samples. The calibration curves of CPM were linear for volumetric water content ranging from 0.25 to 0.40 m3 m−3. The correlation coefficients (r) ranged from 0.87 to 0.98. The advantages of the CPM were discussed, and it was demonstrated that, for low differentiated soils, this method can be a better alternative to the NSM, which is commonly used for the determination of soil water content. The CPM and NSM measurements were compared and root mean squared errors between these two methods ranged from 0.0098 to 0.0159 m3 m−3. The precision of NSM and CPM in a field calibration exercise was calculated. For CPM, this study discusses unbiased and biased statistical treatments to establish the calibration curves. The unbiased treatment greatly decreased the total variance in volumetric water content. The standard deviation of volumetric water content ranged from 0.0194 to 0.0248 m3 m−3 and from 0.0108 to 0.0136 m3 m−3 for biased and unbiased statistical method, respectively. Finally, the soil water storage and associated errors were calculated using CPM and NSM.
Concentration of Uranium Particulates from Soils Using a Novel Density‐Separation Technique
Authors: Elless M. P. , Timpson M. E. , Lee S. Y. 
Published: July 2010

AbstractSoils contaminated with heavy metals or radionuclides at concentrations above regulatory limits pose an environmental and human health risk. Whereas regulatory limits are only concerned with the “extent” of the contamination, knowledge of the “nature” of the contamination (e.g., oxidation state and mineralogy of the contaminant, particulate vs. adsorbed form, etc.) is necessary for developing optimal treatment strategies. Mineralogical identification of the contaminants provides important information concerning the nature of the contamination because once the mineral form is known, its properties can then be determined from geochemical data. To this end, a new density‐fractionation technique called the Magstream density separator was used to concentrate U particulates from U‐contaminated soils at a former U.S. Department of Energy U‐metal production facility. Results from neutron‐activation analysis of each density fraction showed that the U had been concentrated (up to 11‐fold) in the heavier fractions. Mineralogical analyses of the density fractions of these soils using x‐ray diffraction, scanning‐electron microscopy, and an electron microprobe showed the predominance of an autunite [Ca(UO2)2(PO4)2 · 10–12 H2O]‐like mineral with lesser amounts of uraninite (UO2) and coffinite (USiO4) as the U‐bearing minerals in these soils. The presence of reduced forms of U in these soils suggests that the optimal remediation strategy requires treatment with an oxidizing agent in addition to a carbonate‐based leachant to solubilize and remove U from these soils.
Time Series Analysis of Field‐Measured Water Content of a Sandy Soil
Authors: Wu L. , Jury W. A. , Chang A. C. , Allmaras R. R. 
Published: July 2010

AbstractPrediction of the field soil water regime is important for assessing agrochemical transport and scheduling irrigation. This research was conducted to evaluate the potential for employing the time series analysis technique to predict average water content (WAVG) of a soil profile and water content at depths of interest from measurements made at a single depth. Volumetric water content of a Zimmerman fine sand (mixed, frigid Argic Udipsamment) in Princeton, MN, was measured in situ by time domain reflectometry at six depths during the early 1993 growing season. The time series made up of hourly measurements of soil water content was first‐order differenced to obtain stationarity. The differenced data were used to conduct analyses in the frequency domain to evaluate the coherence and cross‐amplitude between two soil water content time series and were subsequently fitted to autoregressive moving average models to obtain coefficients for the transfer function models in the time domain. The transfer function models were then used to predict water contents at depths of interest (50‐, 75‐, and 100‐cm depths) and WAVG in the top 100‐cm profile from measured water content at the 25‐cm depth. Overall, the predictions were reasonable, with accuracy increasing as the separation distance from the 25‐cm depth decreased.
Statistical Mixing Model for the Apparent Dielectric Constant of Unsaturated Porous Media
Authors: Friedman Shmulik P. 
Published: July 2010

AbstractA statistical model is proposed that relates the apparent dielectric constant of an unsaturated porous medium to its porosity and volumetric water content. It is assumed that the solid, water, and air components are randomly distributed in space. The unsaturated soil, or other porous media, are considered as a three‐dimensional network of capacitors, with a distribution of capacitance values according to the volume fractions of the three components. Taking into consideration the simplifying assumptions embedded in the model and the fact that no calibration is required, a fair agreement was demonstrated between its prediction and the widely used empirical function of Topp. The basic model presented can be further developed to account for other soil properties by lifting some of the simplifying assumptions. The objectives of this study were to provide some additional insight into the way the volume fractions of the three soil phases determine its apparent dielectric constant, and to introduce a new approach for further investigation of this phenomenon. It is not intended to propose a new universal model relating the volumetric water content to its measured apparent dielectric constant.
Inorganic Nitrogen in Soil Solution Collected with Tensionic Samplers
Authors: Moutonnet P. , Fardeau J. C. 
Published: July 2010

AbstractTraditionally, porous ceramic cups are used for monitoring ion concentration in soil solutions with time and depth. To calculate the actual N losses through leaching, the cups must be associated with tensiometers, which provide the hydraulic head gradient. This study was conducted to assess how tensionics can determine mineral‐N concentration in soil solution, compared with traditional porous ceramic cups. In field conditions under maize (Zea mays L.), five sets of four tensionics buried at depths between 40 and 130 cm were used throughout the 1992 growing season to assess the concentrations of NO3‐N, NO2‐N, and NH4‐N in the soil solution. Samples were obtained every 10 d for 60 d using two successive methods. The first method was the “tensionic mode” functioning by ionic diffusion through the porous ceramic cup and requiring an 8‐ to 10‐d time step. The second method was the more standard method using soil solution samplers kept 4 h under vacuum to extract the soil solution. For both methods, the same devices were used. Regression analysis on >100 samples showed that NO3‐N recovery was similar for both methods (slope = 0.91; r2 = 0.93). With the tensionic method, NO2‐N and NH4‐N concentrations were, respectively, 5.4 and 7.9 times greater than those obtained by the standard method. These results are explained on the basis of the different ionic concentrations contained in the macro‐ and micropores of the soil. Samples obtained throughout the season (12 series) with devices working in “tensionic mode” were analyzed for inorganic‐N content. In 1992, a rather rainy year, NO3‐N leaching occurred with a surprising downward flux of NO2‐N, which at certain times during the year might pose a threat to groundwater quality.
A Selective Dissolution Analysis Optimized for Measurement of Weathering Products in a Soil
Authors: Benoit Gaboury , Rozan Tim F. , April Richard H. 
Published: July 2010

AbstractSoil weathering is an important source of nutrient cations and P for development of forested ecosystems, but the rates at which these nutrients are released are not well known. Measurement of weathering products can be used in long‐term (5–10 yr) mesocosm studies to evaluate soil weathering rates. In this study, a method was developed to optimize extraction of nutrient cations in weathering products (organic matter, transition‐metal oxyhydroxides, and amorphous Al and Si compounds) while dissblving minimal amounts of primary minerals. For organic matter destruction, dry ashing was compared with peroxide oxidation. Reducing agents (hydroxylamine hydrochloride, oxalate, dithionite) were evaluated for efficacy in extracting transition‐metal oxyhydroxides. Treatment with hydroxide solutions (NaOH, NH4OH) was tested for dissolving amorphous and poorly crystalline Al and Si compounds. Two methods were used to test for undesirable destruction of unweathered minerals: (i) parallel extraction tests on pure primary minerals, and (ii) release of Rb. The greatest variability in effectiveness of the extractants involved the reduction step. For most elements, the completeness of extraction followed the sequence dithionite > oxalate > hydroxylamine. A wash with HCl was needed to redissolve any carbonates that precipitated in the dithionite step. The best overall protocol involves (i) dry ashing, (ii) extraction with a mixture of citrate, bicarbonate, and dithionite, (iii) washing with HCl, and (iv) treatment with NaOH. This last step was found to release mainly Al and Si and only negligible amounts of cations (K, Ca, Mg, Fe, Mn). With this procedure, destruction of primary minerals can be held to ≈0.4%, well below the quantity of weathering products.
Sensitivity of Isotopically Exchangeable Phosphate in Soil Suspensions to the Supporting Solution
Authors: Morel C. , Torrent J. 
Published: July 2010

AbstractThe isotopically exchangeable quantity (Et) of phosphate measured in 1:10 soil/solution suspensions with deionized water has been identified as the reserve of plant‐available phosphate in agricultural soils. We studied the effects of two supporting solutions, 0.01 M CaCl2 and deionized water, on Et values in 27 calcareous agricultural soils. For three soils, Et was also measured after adding increasing phosphate quantities as KH2PO4, and equilibrating for 24 h, to assess changes in Et with phosphate concentration in solution (Cp). In unamended and phosphate‐enriched soils, Cp(CaCl2) was smaller than and related to Cp(H2O). The initial rapidly and the subsequent slowly isotopically exchangeable phosphate were both affected by the use of CaCl2 solution. Since both the rapid and slow isotopically exchangeable phosphate are Cp dependent, the overall effect of CaCl2 solution was analyzed considering two components: (i) a nonspecific effect attributed to the decrease in Cp and (ii) a specific effect attributed to phosphate reactions (i.e., adsorption or precipitation) in calcareous soils. Modifications in Et are the result of both nonspecific and specific effects. The change in Et due to the use of 0.01 M CaCl2 instead of deionized water varies with the soil sample, and can be positive, negative or nil depending on the time of exchange. For instance, after 24 h of exchange, the ratio {[E24h(CaCl2) − E24h(H2O)]100/E24h(H2O)} ranged from −30 to 340% for the 27 soils. The 0.01 M CaCl2 solution thus introduces complex and unpredictable changes in isotopic exchanged phosphate, and its use is not recommended to estimate plant‐available phosphate in soil.
Competition‐Induced Reductions in Soil Water Availability Reduced Pine Root Extension Rates
Authors: Ludovici K. H. , Morris L. A. 
Published: July 2010

AbstractThe relationship between soil water availability, root extension, and shoot growth of loblolly pine seedlings (Pinus taeda L.) was evaluated in a rhizotron sand mixture in the absence and presence of crabgrass (Digitaria spp.) competition. Heights and diameters of seedlings grown with crabgrass were reduced 33 and 50%, respectively, compared with seedlings grown in pine monoculture. Furthermore, survival of seedlings was reduced by 16% in the mixed species treatments compared with pine monoculture cells. Soil water contents at all depths were at least 50% lower in mixed species treatments compared with pine monocultures during a dry‐down cycle. Maximum loblolly pine root extension rate was 0.10 m wk−1 in pine monoculture compared with 0.02 m wk−1 in the presence of grass. Pine seedling root extension ceased in the presence of grass during prolonged periods of induced water stress. Crabgrass roots extended at a rate of 0.6 m wk−1, a rate largely unaffected by watering regime or differences in water content within the rhizotron. Pine root distributions, at the end of one growing season, were different for seedlings grown with grass than for those in pine monoculture; however, when seedlings of similar size were compared, root distributions were not different. Our results indicate that competition‐induced reductions in soil water availability reduced the rate of pine root extension and thus the volume of soil exploited, thereby reducing resource availability and three growth.
Improving Exposed Subsoils with Fertilizers and Crop Rotations
Authors: Robbins C. W. , Freeborn L. L. , Mackey B. E. 
Published: July 2010

AbstractIrrigation‐induced erosion and land leveling have decreased crop yields on approximately 800 000 ha of south‐central Idaho silt loam soils. Previous attempts to increase subsoil productivity to that of the topsoil have not been successful on these soils. This study was conducted to find a method(s) for increasing the productivity of freshly exposed subsoil to that of the topsoil and to determine the factor(s) limiting subsoil production. A 4‐yr study was initiated by removing the surface 0.3 m of topsoil from strips between undisturbed topsoil strips of a Portneuf silt loam (coarse‐silty, mixed, mesic Durixerollic Calciorthid). Different crop rotations were established within the strips and fertility treatments were applied across the strips. The fertilizer treatments were conventional fertilizer application according to soil test, dairy manure, and two cottage cheese (acid) whey rates. During the fourth year, dry edible bean (Phaseolus vulgaris L., cv. Viva) were grown on the entire plot area as a test crop. The application of 44 Mg manure ha−1 in the spring and 93 Mg manure ha−1 in the fall of 1991 (first year of study) was the only treatment that restored subsoil bean production to that of the topsoil plots. Plant Zn and soil organic C concentrations were the only measured factors that correlated with bean yield increases on the subsoil.
Methane Emission from a Freshwater Wetland in Belgium
Authors: Boeckx Pascal , Van Cleemput Oswald 
Published: July 2010

AbstractSome factors influencing methane emission from a freshwater wetland in Belgium were studied. Seasonal fluctuations of methane emission rates, influence of drainage capacity and depth of methane production on methane emission, as well as in situ methane oxidation were monitored. From March until December, methane fluxes varying between 0 and 102 mg CH4 m−2 d−1 were measured. During this period, a total emission of 60 kg CH4 ha−1 was calculated. Statistical analysis of these emission data showed that soil moisture was a more important controlling parameter than soil temperature. Depending on the drainage capacity of the selected area, different emission rates were observed. Sites with a “bad natural drainage” and a “fairly bad natural drainage” showed average fluxes of 5.41 and 2.04 mg CH4 m−2 d−1, respectively, during July. The area with an “insufficient natural drainage” had an emission of 1.44 mg CH4 m−2 d−1. Using methyl fluoride as a specific inhibitor for methane oxidation, it was found that 34 to 67% of the produced methane could be oxidized. Methane emission was found to decrease with increasing soil depth. With diffusion chambers placed on the soil surface, a CH4 release of 40.0 kg CH4 ha−1 (March–June) was found. With chambers placed at 150‐ and 300‐mm depths, emission rates of 11.3 and 3.3 kg CH4 ha−1, respectively, were calculated. Obviously, most of the emitted methane was produced in the upper organic soil layer.