bluuebunny/crossref_metadata_2025_split huggingface dataset:
UNSATCHEM: Unsaturated Water and Solute Transport Model with Equilibrium and Kinetic Chemistry
Authors: Suarez D. L. , Šimůnek J. 
Published: July 2010

AbstractNumerous models have been developed for predicting major ion chemistry in the soil zone and in recharge to groundwater. Soils that contain CaCO3 are prevalent in arid and semiarid regions, as well as in humid and temperate regions that have been glaciated or contain carbonate bedrock. Under these conditions, carbonate‐solution reactions and ion exchange are the dominant chemical processes. In this model we couple one‐dimensional unsaturated water and solute transport with a major ion chemistry routine and plant water uptake. The model has several unique features, including expressions relating reductions in hydraulic conductivity to chemical factors, prediction of CO2 partial pressure in the root zone based on a CO2 production‐multiphase transport submodel, kinetic expressions for silicate weathering, calcite precipitation‐dissolution, and dolomite dissolution, representation of B adsorption using the constant capacitance model, a new method for predicting cation‐exchange selectivity, the option to use Pitzer ion interaction expressions for high ionic strength, and a plant growth submodel that includes water, salinity, and O2 stress. The chemical submodel considers equilibrium ion exchange, as well as various equilibrium and kinetic expressions for precipitation and dissolution of soil minerals, including gypsum, Mg carbonates, and sepiolite. The use of a predictive submodel for CO2 production and transport allows for the calculation of CO2 concentrations with depth and time. This enables us to avoid the assumption of constant CO2 distribution or constant pH required by previous models. Use of kinetic expressions for carbonate chemistry allows a more realistic simulation of soil and groundwater solution composition as well as simulations of carbonate redistribution and climatic change with time.
Soil Survey Input in Exploratory Modeling of Sustainable Soil Management Practices
Authors: Droogers P. , Bouma J. 
Published: July 2010

AbstractSoil survey information combined with exploratory simulation modeling was used to define indicators for sustainable land management. In one soil series in the Netherlands (the genoform), three different phenoforms were formed as a result of different management practices. Locations were identified using a soil map and interviews with farmers. Organic matter, bulk densities, and porosities were significantly different for the three phenoforms: biodynamic management (Bio), conventional management (Conv), and permanent grassland (Perm). By applying a dynamic simulation model for water movement, crop growth and N dynamics, the three phenoforms were analyzed in terms of sustainability indicators by defining four scenarios based on productivity and N leaching to the groundwater: (i) potential production, (ii) water‐limited production, (iii) current management, and (iv) the environmental scenario. The latter was divided into EnvA: never exceeding the N‐leaching threshold of 11.3 mg L‐1; EnvB: exceedance occurring in one out of 30 yr; and EnvC: exceedance occurring in three out of 30 yr. Biodynamic management obtained the lowest yield under current management, while yields for Perm were highest. EnvA could not be reached for Perm as a result of high mineralization rates. Obtainable yields for scenarios EnvA, EnvB, and EnvC differed substantially, illustrating the importance of selecting “acceptable” risks in environmental regulation. The presented methodology demonstrates the importance of pedological input in sustainability studies.
Application Effects of Controlled‐Availability Fertilizer on Dynamics of Soil Solution Composition
Authors: Yanai Junta , Kosaki Takashi , Nakano Aiko , Kyuma Kazutake 
Published: July 2010

AbstractThe effect of a controlled‐availability fertilizer (CAF) on plant uptake and leaching potential of soil nutrients, in relation to the dynamics of the chemical composition of the soil solution, was evaluated using a pot experiment with three N treatments [CAF or ordinary fertilizer applied as Ca(NO3)2 and an unfertilized treatment], with or without wheat (Triticum aestivum L.) plants. Soil solutions were collected nondestructively with looped hollow fiber samplers from the root zone in situ six times during the 49‐d growing period. Wheat plants were also collected at the second, fourth, and last collection date. Concentrations of NO3 and K in the soil solution were significantly lower for the CAF treatment than for the ordinary fertilizer treatment at all sampling times. Leaching potential of N and K in the CAF treatment was accordingly reduced compared with the ordinary fertilizer treatment, especially at the early stages of plant growth. The concentration of P was low, and not affected significantly by the N treatments, and the leaching potential was negligible. Moreover, plant growth, nutrient uptake of N, P, and K, and their supplying meachanisms in soil were not affected significantly by the N treatments in this experiment. Therefore, the ability of CAF to reduce the leaching potential of soil nutrients without exerting adverse effects on the growth and nutrient uptake of plants was demonstrated for N and K, based on the dynamics of the soil solution composition in the root zone.
Modeling Ammonia Volatilization from Biosolids Applied to Semiarid Rangeland
Authors: Harmel R. D. , Zartman R. E. , Mouron C. , Wester D. B. , Sosebee R. E. 
Published: July 2010

AbstractOne fate of N from land‐applied biosolids is NH3 volatilization. This study was conducted to: (i) quantify NH3 volatilization from anaerobically digested, dewatered biosolids; and (ii) develop equations to predict volatilization losses. Ammonia was collected under natural field conditions with semi‐open, dynamic collection systems. Volatilization was measured using a phenol‐nitroprusside method for 210 h following biosolid applications of 0.0, 6.7, and 17.9 dry Mg ha‐1. Volatilization studies using two soils (a Ustollic Calciorthid and a Ustollic Haplargid) with similar chemical properties but with different surface gravel contents were conducted under hot (20–36°C), intermediate (6–23°C), and cool (−4–14°C) temperature regimes. Volatilization followed a diurnal fluctuating pattern for both the hot and intermediate temperature regime trials and was significantly reduced 3 d after application for all trials. Cumulative volatilization losses ranged from 11.5 kg NH3‐N ha‐1 in the cool‐season trial for the 6.7 dry Mg ha‐1 application rate to 35.5 kg NH3‐N ha‐1 in the hot‐season trial for the 17.9 dry Mg ha‐1 rate. The influence of gravel content on NH3 volatilization was not statistically significant (P = 0.01). Empirical equations were developed to predict volatilization losses as a function of site‐ and season‐specific potential evapotranspiration, biosolid NH3‐N content, application rate, and time after application. The prediction equations for NH3 volatilization from applied biosolids as affected by temperature had a range of r2 values of 0.90 to 0.97.
Nitrous Oxide Emission through Plants
Authors: Chang C. , Janzen H. H. , Nakonechny E. M. , Cho C. M. 
Published: July 2010

AbstractAgricultural soils are a major source of N2O that has been linked to an enhanced greenhouse effect and the depletion of stratospheric ozone. The N2O produced in the soil is usually assumed to enter the atmosphere by diffusion. We postulated that significant amounts of N2O may also be emitted via plant transpiration, and conducted a controlled environment study to test this hypothesis. The shoots of canola (Brassica napus L.) were enclosed in chambers, and N2O emission from the foliage was quantified by measuring changes in N2O concentration following various soil treatments. At field capacity, a treatment not conducive to denitrification, there was no measurable emission of N2O from the plant foliage. At saturation, however, N2O concentration within the shoot chamber increased consistently with time. By the end of the sampling period, the N2O concentration in the shoot chamber was 0.45 L L−1, well above that in the soil head space (0.35 L L−1), demonstrating that N2O was released from the shoots and not the soil. Watering the soil with a N2O solution with a concentration of approximately 8 mL L−1 resulted in almost immediate release of N2O from the shoots, indicating that the N2O was not generated by the plants directly, but merely conveyed to the atmosphere by the transpiration stream. Experiments using barley (Hordeum vulgare L.) produced results similar to those with canola, suggesting that emission of N2O from plants may be a common phenomenon. These results demonstrate a mechanism for N2O emission from upland crops, and imply that measurement of N2O release solely from the soil surface may underestimate actual fluxes from agroecosystems.
Hydraulic Conductivity Variability for Two Sandy Soils
Authors: Bosch D. D. , West L. T. 
Published: July 2010

AbstractReliable estimates of saturated hydraulic conductivity are a prerequisite for accurate estimations of water flow and chemical transport through soil profiles. While informative, mean estimates of flow and transport have been shown to be inadequate for modeling purposes. Distributions and variances along with mean predictions provide a better form of model input. The spatial variability of field‐measured saturated hydraulic conductivity (Kfs) was investigated on a transect across a 1‐ha field in west‐central Georgia. The field includes two soil types, a Pine Flat loamy sand (coarse‐loamy, siliceous, thermic Typic Paleudult) and a Troup sand (loamy, siliceous, thermic Grossarenic Kandiudult). Estimates of Kfs were calculated using data collected with a constant‐head permeameter. Mean, variance, and distribution data were determined for each soil and four selected horizons. Calculated values in the top 2 m of the soil profiles ranged from 0.07 to 117 mm h−1 for the Pine Flat loamy sand and from 23 to 406 mm h−1 for the Troup sand. Statistical differences between Kfs data calculated for the lower soil profiles coincide with soil textural differences observed with depth and across the plot. Semivariances for ln Kfs data were calculated and models fit to the semivariograms. Random behavior, with little spatial correlation, dominated the In Kfs data for the upper 0.5 m of the Pine Flat soil and the 2.0‐m measurement for the Troup soil. Observed correlation ranges varied from 2 to 166 m. Large statistical differences in Kfs were observed for the adjacent soils.
Retardation Coefficients of Nonionic Organic Compounds Determined by Batch and Column Techniques
Authors: Maraqa M. A. , Zhao X. , Wallace R. B. , Voice T. C. 
Published: July 2010

AbstractBatch and column techniques were utilized to determine retardation coefficients of two nonionic organic compounds: benzene and dimethylphthalate. Three sandy soil materials with medium to high organic C content were used as sorbents. Batch data consistently overestimated retardation coefficients of the two compounds. Several previously reported factors that may cause discrepancy between the two techniques were experimentally investigated. Sorption nonsingularity, sorption nonequilibrium, presence of immobile water regions in the column, and reduction in particle spacing in the column were eliminated as the cause of this discrepancy. Loss of sorbent from the column is unlikely to be the cause of the discrepancy. Although rapidly mixed batch tubes are subjected to soil abrasion, it causes no apparent impact on the value of sorption distribution coefficients. Batch isotherms at two solids concentrations were identical, indicating that differences in solids concentration between batch and column setup is not a significant factor. This was also confirmed by a column study. Sorption nonlinearity was found to have a minor impact. Column residence time had a major impact on one of the cases studied, but no effect on the other cases. When column residence time was accounted for, some differences in sorption distribution coefficients, which seemed to be independent of the organic C content, were noticed. In this study, all previously suggested causes for the discrepancy between batch‐ and column‐determined retardation coefficients were investigated and rejected. It remains unclear why the values determined by the two techniques were different.
Carbon Dynamics in Corn‐Soybean Sequences as Estimated from Natural Carbon‐13 Abundance
Authors: Huggins D. R. , Clapp C. E. , Allmaras R. R. , Lamb J. A. , Layese M. F. 
Published: July 2010

AbstractCarbon flow in terrestrial ecosystems regulates partitioning between soil organic C (SOC) and atmospheric CO2. Our objectives were to assess SOC dynamics using natural 13C abundance in corn (Zea mays L., a C4 species)‐soybean [Glycine max (L.) Merr., a C3 species] sequences. Fifteen treatments of continuous corn, continuous soybean, various sequences of corn and soybean, and fallow were initiated in 1981 at Lamberton, MN, on a Webster clay loam (fine‐loamy, mixed, mesic Typic Haplaquoll). In 1991, soil and aboveground shoot samples from all treatments were analyzed for total organic C and δ13C. Carbon inputs, δ13C, and SOC were integrated into a two‐pool model to evaluate C dynamics of corn and soybean. Total SOC was similar across all treatments after 10 yr; however, differences in soil δ13C occurred between continuous corn (δ13C = −17.2‰) and continuous soybean (δ13C = −18.2‰). Modeled C dynamics showed SOC decay rates of 0.011 yr−1 for C4‐derived C and 0.007 yr−1 for C3‐derived C, and humification rates of 0.16 yr−1 for corn and 0.11 yr−1 for soybean. Decay and humification rates were slightly lower than those found in other Corn Belt studies. Levels of SOC were predicted to decline an additional 7 to 18% with current C inputs from either corn or soybean, respectively. Annual C additions required for SOC maintenance averaged 5.6 Mg C ha−1, 1.4 to 2.1 times greater than previously reported estimates. Controlled variation in natural 13C abundance in corn‐soybean rotations during a 10‐yr period adequately traced C dynamics.
Vertical Distribution of Roots and Soil Nitrate: Tree Species and Phosphorus Effects
Authors: Jama Bashir , Ndufa J. K. , Buresh R. J. , Shepherd K. D. 
Published: July 2010

AbstractWe hypothesized that trees can rapidly root into subsoil and capture NO3, which can accumulate in the subsoil of agricultural soils with high anion sorption. The vertical distribution of root length and inorganic N (NO3 and NH4) to 3.95‐m soil depth was compared for 11‐mo‐old stands of eucalyptus (Eucalyptus grandis W. Hill ex Maiden), sesbania [Sesbania sesban (L.) Merr.], calliandra (Calliandra calothyrsus Meissner), markhamia [Markhamia lutea (Benth.) Schumann], and grevillea (Grevillea robusta A. Cunn. ex R. Br.) grown at two P levels (no added P and 500 kg added P ha−1) on a Kandiudalfic Eutrudox in Kenya. The trees were planted at a 1 by 1 m spacing in a randomized complete block with three replications. Added P had no effect on root length, soil NO3, and soil NH4 even though the soil was low in available P. Total root length was greater for calliandra (15.5 km m−2) than other trees (1.2–5.6 km m−2). The slope for the model of natural logarithm root length density (cm cm−3) as a function of soil depth was affected by tree species (P < 0.01), indicating differences among trees in the tendency for deep rooting. Root length densities, averaged for the two P levels, were ≥0.1 cm cm−3 to depths of 2.2 m with calliandra, 1.8 m with sesbania, 1.2 m with eucalyptus, 0.45 m with grevillea, and 0.3 m with markhamia. Calliandra and sesbania reduced soil NO3 in the top 2 m by about 150 to 200 kg N ha−1 within 11 mo after establishment and effectively captured subsoil NO3. Fast‐growing trees with high root length densities can rapidly reduce subsoil NO3.
Modeling Moisture Retention in Peat Soils
Authors: Weiss R. , Alm J. , Laiho R. , Laine J. 
Published: July 2010

AbstractSoil moisture governs many biogeochemical processes in peatlands. Modeling of those processes relative to climate and anthropogenic influences requires knowledge of the basic hydraulic properties of different peat soils in a function form. Water retention of undisturbed surface peat samples, collected at four depths at each of 38 undrained and drained pine (Pinus sylvestris L.) mire sites, was measured for suction pressures of −0.98, −3.10, −6.19, −9.81, −98.1, and −1554.25 kPa. The obtained data were used to test several well‐known water retention models commonly applied to mineral soils. The most suitable model was found to be van Genuchten's model if the residual water content was omitted. Peat characteristics were used to explain the variation in the model's shape parameters. Accounting for the remains of Sphagnum, Carex, Eriophorum, and lignin and the distinction between shallow and deep peat layers considerably improved the moisture retention predictions compared with using bulk density only. The different behavior of the shallow vs. the deep peat layers was mainly attributed to the Sphagnum and lignin residues, but not to the Carex residues. We developed a semiempirical model with only one shape parameter, which was clearly better explained by the peat characteristics than the two shape parameters of the van Genuchten model. We recommend that for statistical investigations or investigations requiring a robust model, the semiempirical model be used. The van Genuchten model is to be preferred in predicting the moisture conditions near saturation.
Characterization of Dissolved Organic Matter Extracted from Composted Municipal Solid Waste
Authors: Chefetz Benny , Chen Yona , Hadar Yitzhak , Hatcher Patrick G. 
Published: July 2010

AbstractThe properties and transformation of dissolved organic matter (DOM) extracted from municipal solid waste compost at five stages of composting were studied using a chemical fractionation scheme. We fractionated the DOM into hydrophobic or hydrophilic neutrals, acids, and bases, and obtained solid‐state cross polarization magic angle spinning (CPMAS) 13C‐nuclear magnetic resonance (NMR) spectra of the unfractionated DOM and of the different fractions. The hydrophobic acid (HoA) fraction was the dominant hydrophobic fraction, exhibiting a moderate increase during composting. The hydrophobic neutral (HoN) fraction increased sharply while the hydrophobic bases (HoB) fraction decreased during composting. The hydrophilic neutrals (HiN) represented the major fraction of the hydrophiles until 120 d of composting, decreasing thereafter by 38%. The 13C‐NMR spectra of the unfractionated DOM revealed an increasing level of aromatic structures in the residual DOM with composting time. The 13C‐NMR spectra of the HoA fraction suggested a polyphenol‐humic structure, whereas the HoN spectra exhibited strong aliphatic features. The spectra of the HiN fraction confirmed its polysaccharide nature and the hydrophilic bases (HiB) fraction contained mainly proteins and carbohydrate‐amino complexes. A comparison between the 13C‐NMR spectra of HoA and fulvic acid (FA) indicated the former to be the most soluble FA fraction. The steady DOM concentration and the relative decrease of HiN as the HoA and HoN fractions increased indicates that DOM at the final stage of composting contained less bioavailable organic matter and more macromolecules related to humic substances. The constant level of DOM observed during the curing and maturation stages represents a steady‐state situation during which the chemical composition is continually changing.
Comparison of Methods to Estimate Occluded and Resistant Soil Phosphorus
Authors: Bowman R. A. , Rodriguez J. B. , Self J. R. 
Published: July 2010

AbstractWeathering, pH changes, and biotic interactions through geologic times have created a gradation of easily released (labile) to strongly stabilized (resistant) P pools. While methodologies for fertility indices and labile P are well established, methods for quantifying less labile P, such as the occluded and resistant or residual P, are less well established. We reexamined existing methods for these pools, and suggested new procedures to improve their precision and timeliness. Specifically, we compared two methods for reductant‐soluble (occluded) P, and two existing and a new procedure for the resistant P. Occluded P was difficult to reproduce from a sequential extraction procedure because of problems associated with molybdate blue reaction, which required extra molybdate or persulfate oxidation to minimize citrate interference. However, use of inductively coupled plasma (ICP) spectroscopy eliminated this problem. Measurement of P by ICP for surface and occluded P in the total free Fe oxide pool was more quantitative and reproducible [average coefficient of variation (CV) = 5%] than in the sequential extraction (average CV = 7%) procedure. Results for the proposed resistant P method (total soil P minus acid‐extractable P in an ignited sample) approximated the two sequential extraction procedures (total soil P — total acid‐ and base‐extractable organic and inorganic P) and is easier, and more reproducible. Both procedures for all soils except the Molokai showed essentially the same amounts of occluded P. An average of about 26% of the total soil P (TP) was resistant, with the more weathered Cecil soil containing about 50% resistant P.
Loessial Soils of Delaware: Taxonomy and Map‐Unit Assessment
Authors: Rebertus R. A. 
Published: July 2010

AbstractMap units named for the Matapeake series (fine‐silty, mixed, mesic Typic Hapludults) comprise one‐third of the Coastal Plain in the soil survey of northern Delaware. The concept was one of well‐drained soils formed in thin loess over coarse‐textured fluvial sediments. This study uses characterization data from pedons within the loess‐blanketed terrain of northern Delaware to assess the taxonomy and composition of Matapeake map units. All pedons are Alfisols rather than Ultisols, and this status has not been influenced by liming. Fine‐loamy rather than fine‐silty soils typically occur where loess is <80 cm thick. Much soil variability exists on interfluves where thin loess discontinuously blankets the irregular surface of the sandy Pensauken Formation. This results in an inability to map specific consociations, even for large‐scale, detailed surveys. The existing soil survey used specific map units — consociations named for phases of soil series — that do not adequately depict the diversity on mappable landscapes. The Matapeake and associated series used in this area are too narrowly defined in ranges of characteristics, are too general in geographic setting, have loess thickness limits that are not concordant with particle‐size classes, and leave gaps in the lithologic‐hydrologic continuum. They therefore provide little utility for organizing knowledge, understanding relationships, or as objects for research. Soil survey in this area requires more generalized map units, greater emphasis on stratigraphy and geomorphology and their interaction to influence hydrology and lithology, and less emphasis on artificial conceptual groupings at the lowest taxonomic category, the series.