bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Landscape‐Scale Assessment of the Nitrogen and Non‐Nitrogen Rotation Benefits of Pea
Authors: Stevenson F. C. , van Kessel C. 
Published: July 2010

AbstractThe inclusion of a pulse crop in a rotation often leads to an increase in seed yield of the succeeding cereal crop. Landscape‐scale and small‐plot studies were established in 1993 to assess the N and non‐N rotation benefit by pea (Pisum sativum L.) to the subsequent wheat (Triticum aestivum L.) crop. In the second rotation phase, wheat seed yields were 982 kg ha−1 greater and total N accumulation increased by 46 kg ha−1 in the pea‐wheat rotation. Reduced leaf disease severity and grassy weed infestation were related to 91% of the yield advantage in the pea‐wheat rotation, the non‐N rotation benefit. A 129 N kg ha−1 increase in the A value (soil N supplying power) was related to 9% of the yield advantage in the pea‐wheat rotation, the N benefit. In both rotations, seed yield was about 400 kg ha−1 lower in the high‐catchment footslopes than the low‐catchment footslopes and shoulders. The landform effect on seed yield in the pea‐wheat rotation was related to greater soil water and N content in the high‐catchment footslopes. Increased grassy weed infestation in the high‐catchment areas of the wheat‐wheat rotation was related to lower seed yields in this same area. The rotation benefit of pea to wheat was 34% greater in the landscape‐scale vs. the small‐plot study. Topographic variation interacted with factors responsible for the non‐N rotation benefit. A landscape‐scale assessment of the rotation benefit from legumes can be used to develop site‐specific management strategies that consider the effect of crop rotation.
A Rule‐based System to Map Soil Properties
Authors: Cook S. E. , Corner R. J. , Grealish G. , Gessler P. E. , Chartres C. J. 
Published: July 2010

AbstractConventional soil mapping is limited in its capabilities in that it presents a summary of the soil surveyor's conceptual view of soil variation. As such, the method conveys little regarding what is known about the variation of individual soil properties, or the quantitative nature of their variation. We developed a new method for soil mapping, based on the concepts employed in the PROSPECTOR mineral exploration system, which builds on existing soil surveyor knowledge to construct quantitative statements about individual soil properties via the development of a network of rules. These rules operate within a system of Bayesian inference to assign the varying probability of occurrence of a soil property of interest within an area, given evidence that relates to it in a known way. Permissible evidence includes the range of attributes normally used by a soil surveyor, such as landform, vegetation, land use, or parent material, and can also include remotely sensed digital data. Evidence is weighted according to the uncertainty associated with it, and combined to produce a single estimate of probability of a given attribute. The relationship between the evidence and prediction is stated explicitly at each stage of the procedure and is thus repeatable in a consistent manner. The system has the advantage that while it does not discard the evidence and knowledge used in conventional soil survey, it produces quantitative estimates of the distribution of soil properties, which can be used for a wide range of applications. The data produced is amenable to storage in geographic information systems and related data bases. As such, it can be updated or enhanced as new information or knowledge becomes available.
Experimental Soil Acidification and Recovery at the Bear Brook Watershed in Maine
Authors: Rustad L. E. , Fernandez I. J. , David M. B. , Mitchell M. J. , Nadelhoffer K. J. , Fuller R. B. 
Published: July 2010

AbstractThe response and subsequent recovery of soils (Typic Haplorthods) to acidification by dilute H2SO4 (2000 and 4000 molc ha−1 yr−1 of SO4), HNO3 (2000 and 4000 molc ha−1 yr−1 of NO3), and combined H2SO4‐HNO3 (2000 molc ha−1 yr−1 each of SO4 and NO3) were studied at the Bear Brook Watershed in Maine. Treatments were delivered to eighteen 15 by 15 m plots (three plots per treatment) during four field seasons from 1988–1991. Recovery was monitored for the ensuing two years. Changes in soil and soil solution chemistry were evaluated using tension lysimeters and buried mineral soil bags. Soil solutions responded rapidly to all treatments with increased concentrations of SO4 (four to eight times ambient) and NO3 (39 to 88 times ambient), depending on treatment, accompanied by increased concentrations of Ca and Mg (three to five times ambient) from the upper B horizon. As solutions passed through the upper 25 cm of the pedon, concentrations of SO4 and the sum of base cations decreased significantly. Results from buried mineral soil bags located directly below the forest floor indicated that a relatively reversible SO4 sorption mechanism was responsible for attenuating most SO4 losses from these soils. Following 4 yr of acid inputs and 2 yr of recovery, soil and soil solution chemistry were remarkably unchanged, demonstrating that this hardwood forest soil was not irreversibly altered and could quickly recover.
Mineralogical Properties of a Collapsible Lateritic Soil from Minas Gerais, Brazil
Authors: de Brito Galvão T. C. , Schulze D. G. 
Published: July 2010

AbstractSoils weathered from limestone and sediments of the Bambuí Formation in parts of Minas Gerais, Brazil, are prone to near‐surface subsidence, resulting in damage to buildings and roads, and loss of life. Engineers consider them “collapsible soils” because they exhibit large decreases in volume and associated settlements with no increase in applied stress when wetting occurs. The objective of this study was to determine a possible mineralogical or chemical basis for this behavior. Three horizons to a depth of 170 cm from a Rhodic Hapludox near Sete Lagoas were analyzed by x‐ray diffraction, infrared absorption, electron microscopy, and wet chemical methods. All horizons were mineralogically very homogeneous, with kaolinite, gibbsite, and hematite dominant, but (dioctahedral) mica, hydroxy‐interlayered vermiculite, goethite, anatase, rutile, quartz, and perhaps cristobalite also present. More than 850 g kg−1 of each horizon consists of minerals with particles <2 µm, but aggregation of particles by Fe oxides results in a silt content of about 300 g kg−1. The pH of each horizon is at or very near to its zero point of charge. The physical properties of this soil are apparently dominated by: (i) the residual nature of the soil, which has weathered in place a very long time, resulting in high porosity and low bulk density, (ii) the aggregation of kaolinite and gibbsite by Fe oxides to form silt‐sized aggregates, and (iii) the variable surface charge of the dominant minerals. Future soil mechanics research on these soils should consider the consequences of chemical changes that might alter interparticle forces important in soil stability.
Modeling the Probabilities of Groundwater Contamination by Pesticides
Authors: Di H. J. , Aylmore L. A. G. 
Published: July 2010

AbstractField soils show significant spatial variations in properties, such as organic matter content, bulk density, and moisture content, that can affect the mobility and persistence and thus fate of organic pesticides in the soil environment. A simple model incorporating the variations in soil and pesticide parameters has been developed to assess the groundwater contamination potential of pesticides. The model is based on linear, equilibrium, and reversible sorption, first‐order degradation, and steady piston flow, and allows the unsaturated soil zone to be divided into a number of layers of different thickness and properties. For each input parameter, 500 random data were generated from normal distributions that characterize the variability of the parameters. The fate of 29 pesticides were assessed using soil and environmental conditions of the Swan Coastal Plains of Western Australia and pesticide properties reported in the literature. The predicted pesticide residue fractions remaining at 150‐, 300‐, and 500‐cm depths were described by beta distributions, and the corresponding travel times by normal distributions. Fourteen out of the 29 pesticides are predicted to reach 150 and 300 cm and 13 are predicted to reach the 500‐cm depth with mean residue fractions ≥ 0.01%. The predicted mean travel times for pesticides that may reach 300 cm vary from about 2 mo to about 18 yr. Significant standard deviations are associated with these mean residue fractions and travel times. Six pesticides, fenamiphos, simazine, metribuzin, linuron, fenarimol, and metalaxyl, have been identified as having high cumulative probabilities of 0.82 to 1.00 for residue concentrations to be >0.01% at the 300‐cm depth.
Seasonal Variation of Hydraulic Properties of Soils Measured using a Tension Disk Infiltrometer
Authors: Angulo‐Jaramillo R. , Thony J. L. , Vachaud G. , Moreno F. , Fernandez‐Boy E. , Cayuela J. A. , Clothier B. E. 
Published: July 2010

AbstractFor sound land management, it is important to understand the temporal changes that soil hydraulic properties undergo. Estimation of the unsaturated characteristics of the hydraulic conductivity, sorptivity, and mean pore radius was performed using tension‐disk infiltrometers in two different soils of the Mediterranean region: a sandy soil (Xerochrept) and a heterogeneous, stony, and sandy soil (Alfisol). Both soils were cropped with maize (Zea mays L.) and underwent conventional tillage and different irrigation practices, namely furrow irrigation and gun irrigation. The mobile water content was also deduced from soil samples extracted underneath the disk following a period of infiltration with the tension infiltrometer filled with a Cl− tracer. Results are presented here of measurements made after plowing and again at the end of the growing season. During the growing season, the sandy soil under furrow irrigation showed a significant decrease in its hydraulic properties. This followed an increase in the bulk density and was a result of sealing of the small interconnected pores at the soil surface. Strong nonlinearity in the hydraulic conductivity was found for the stony soil, yet there was no significant change in this nonlinearity during the growing season. However, from the tracer results, it is stated that for this soil, the structure of the fine fraction changes from a well‐interconnected microporous network to a poorly connected one. This results in an increase of the mobile water content during the growing season. It is shown that a good understanding of the porous network can be obtained from tension infiltrometers and can explain changes in both the hydraulic conductivity and the sorptivity. These changes were also partially corroborated by the mobile water content measurements obtained from tracer observations under the disk.
Image Analysis for Determination of Dye Tracer Concentrations in Sand Columns
Authors: Aeby P. , Forrer J. , Flühler H. , Steinmeier C. 
Published: July 2010

AbstractDye tracers can be used to visualize flow paths in soils. We used digital image analysis to determine the spatial distribution of dye concentrations in a quartz sand column. Color slides and near‐infrared black‐and‐white photographs were taken from a sand column that was cut in halves longitudinally after a point‐source dye infiltration experiment. In a separate calibration experiment, sand samples were prepared with known water content and dye concentration. Photographs of such sample arrays were used as training areas for image analysis. Image analysis is a viable way for obtaining a high spatial resolution of tracer concentrations and provides a quantitative basis for describing different solute mixing regimes.
Combining Scanning Tunneling Microscopy and Computer Simulation of Humic Substances: Citric Acid, a Model
Authors: Bailey George W. , Shevchenko Sergey M. , Yu Y. Shane , Kamermans Heleen 
Published: July 2010

AbstractCitric acid (CA) is a model for soil humic substances and an important participant in many biochemical processes. Humic and humic‐like materials play crucial roles in the bioavailability and mobility of organic and inorganic pollutants in aquatic and terrestrial ecosystems. Scanning tunneling microscopy (STM) was used to image and analyze the morphological character of CA aggregates on graphite. Nano‐scale images of CA also were simulated and interpreted using a molecular mechanics technique. The effects of intermolecular association and hydration on the electronic properties and chemical reactivity of CA were analyzed in relation to the behavior of similar compounds in natural processes. Computer‐assisted STM proved to be a powerful technique to investigate structure, morphology, and chemical reactivity of soil organic matter components and their aggregates. The CA molecule aggregation and hydration do not affect the electronic properties significantly. However, electrostatic potential is highly sensitive to the conformation of the molecule and the morphology of the ensuing molecular aggregate.
Effects of Adsorbed Humic Acid on Surface Charge and Flocculation of Kaolinite
Authors: Kretzschmar Ruben , Sticher Hans , Hesterberg Dean 
Published: July 2010

AbstractThe behavior of clays in soils, groundwater aquifers, and aquatic environments is controlled to a large extent by flocculation and dispersion phenomena. Dispersed clay particles can become mobile and facilitate the translocation of strongly sorbed pollutants in the environment. In this study, the adsorption of a soil humic acid to Na‐kaolinite and the resulting effects on surface charge and colloidal stability of kaolinite were investigated in dilute aqueous suspensions. The pH dependence (pH 3–11) of humic acid adsorption to kaolinite in a NaClO4 background electrolyte was studied with batch experiments at three different ionic strengths (0.001, 0.01, and 0.1 M). Sorption of humic acid increased with decreasing pH or increasing ionic strength, a behavior that is typical for anionic polyelectrolytes with carboxylic functional groups. Electrophoretic mobility measurements showed that pure kaolinite had positive net total particle surface charge at low pH and negative surface charge at high pH, with an isoelectric point at pH 4.8 (in 0.01 M NaClO4). With increasing amounts of humic acid sorbed to the kaolinite surface, the electrophoretic mobility was continuously shifted to more negative values. At low pH, this resulted in charge reversal from positive to negative net total particle surface charge. Additions of small amounts of humic acid to the kaolinite suspensions resulted in large increases in colloidal stability. At low pH, this was probably due to reversal of edge charge from positive to negative preventing edge‐to‐face flocculation. In addition, a general increase in negative surface charge density and steric stabilization effects may contribute to the influence of adsorbed humic acid on the colloidal stability of kaolinite.
A Model of the Physical Protection of Organic Matter in Soils
Authors: Hassink Jan , Whitmore Andrew P. 
Published: July 2010

AbstractCurrent computer simulation models do not treat the physical protection of organic matter in soil mechanistically. A model is presented that describes physical protection explicitly as a function of the capacity of clay particles and aggregates to hold organic matter. The net rate of decomposition of organic matter depends not simply on soil texture but on the degree to which the protective capacity of the soil is already occupied. The rate at which organic matter becomes protected depends on both the amount of free organic matter and the degree to which the protective capacity is filled. The rate at which organic matter is released from protection depends only on the amount of protected organic matter. The model closely followed the buildup and decline of organic matter in 10 soils to which grass residues were added each year for a period of 10 yr and then left without addition for a further 10 yr. An estimate made with the model of the maximum capacity of each of these soils to protect organic matter was closely correlated with the clay fraction in the soils. With this model, we were better able to predict the buildup and decline in amounts of soil organic matter in soils of different textures and initial organic matter contents than with conventional, implicit descriptions of protection. Our model accounted for 80% of the variance in the experimental data compared with 77 and 75% using the other two models. Secondly and importantly, the capacity of soil to protect organic matter was found to be positively and well related with the clay content of the soil in our model, whereas similar relationships were not found between soil texture and the parameters controlling protection in the other models.
A Chloride‐Deficient Leaf Spot Syndrome of Wheat
Authors: Engel R. E. , Bruckner P. L. , Mathre D. E. , Brumfield S. K. Z. 
Published: July 2010

AbstractA leaf spot complex that results in tissue necrosis and whose origin is unknown frequently damages selected winter wheat (Triticum aestivum L.) cultivars in Montana and neighboring regions. This study was undertaken to determine leaf spot origin (physiologic or pathogenic), cultivar susceptibility, and response to Cl nutrition. Winter wheat studies at seven sites (1993–1995) compared cultivars (Redwin, Tiber, CDC Kestrel, Manning, Stephens, Sierra, and Promontory), propiconazole (1‐[[2‐(2,4‐dichlorophenyl)‐4‐propyl‐1,3‐dioxolan‐2‐yl]methyl]‐1H‐1,2,4‐triazole) fungicide treatments, and multiple Cl fertilizer rates (0–90 kg ha−1). Chlorotic or necrotic lesions developed at all sites, but not all cultivars were affected similarly. CDC Kestrel was the most susceptible cultivar. Flag leaf spot severity (portion of tissue area affected) was as great as 40% in this cultivar. Redwin, Sierra, and Promontory were the next most susceptible cultivars, followed by Stephens and Manning. Tiber, a variant line row selection of Redwin, was leaf spot tolerant. Multiple propiconazole applications had no effect on leaf spot severity, and infectious organism(s) could not be isolated from symptomatic tissue. Thus, leaf spot origin was probably physiologic and not infectious. Chloride fertilization (11–22 kg ha−1) greatly suppressed or eliminated leaf spotting, and increased yield in one or more cultivars at six of seven sites (up to 998 kg ha−1). Physiologic leaf spot occurrence and severity in affected cultivars was linked to inadequate Cl nutrition, and a possible osmotic imbalance in leaf mesophyll cells. Damage was usually minor when whole‐plant Cl at head emergence was ≥ 1.0 g kg−1. Leaf spot damage increased exponentially as plant Cl dropped below this concentration. The name Cl‐deficient leaf spot syndrome is proposed to describe this phenomenon in wheat.
Yield and Nitrogen Uptake Prediction by CERES‐Maize Model under Semiarid Conditions
Authors: Pang X. P. , Letey J. , Wu L. 
Published: July 2010

AbstractQuantitative relationships between N and irrigation management on crop yield and NO3− leaching is urgently needed for economical and environmental analyses. Validity of the CERES‐Maize (version 2.10) model under arid conditions was evaluated for 3‐yr irrigation and fertilizer management trials conducted at Davis, CA. The N was applied at rates of 0, 90, 180, and 360 kg N ha and irrigation amounts were 20, 60, and 100 cm. The slope of the regression line between measured and simulated grain yield was 1.003 with r2 = 0.936. The slope of the regression line between measured and simulated N uptake was 1.013 with r2 = 0.946. We concluded that the CERES‐Maize model may be applied with confidence to study effects of N and irrigation management on corn (Zea mays L.) yield and N uptake under irrigated semiarid or arid conditions.
Effect of Compaction on Soil Physical and Hydraulic Properties: Experimental Results and Modeling
Authors: Assouline S. , Tessier D. , Tavares‐Filho J. 
Published: July 2010

AbstractSoil compaction affects soil physical properties and, eventually, crop production. A severe drop in the productivity of the state of Parana, southern Brazil, was observed due to soil compaction. Two oxisols from this region, a Haplic Acrothox from the site of Cascavel and a Haplic Eutrothox from the site of Palotina, presenting different compaction behaviors in the field, are studied under laboratory conditions. Uniaxial compressive pressures, from 50 to 1000 kPa, are applied to soil samples at different initial matric potentials, varying from −0.1 to −1000 kPa. The bulk density of the Palotina soil is always higher than that of the Cascavel soil and is the highest when the initial matric tension is − 32 kPa. Differences in pH, cation‐exchange capacity, organic matter, and clay particle thickness also tend to explain the different compaction behaviors. A model of the soil bulk density increase during compaction is proposed and compared with a multiplicative model and a logarithmic model. The performances of the proposed and the multiplicative models are practically similar and better than those of the logarithmic model. The major advantage of the proposed model is that it has one fitting parameter less than the multiplicative model. Compaction affects the soil water retention curves for the whole range of matric tensions, up to − 100 MPa. An approach that allows the evaluation of the hydraulic conductivity functions of the compacted samples is proposed. Applied to the Brooks and Corey relationship, the main drying curves of the compacted samples are well reproduced using one fitting parameter only.
Changes of Soil Phosphorous Fractions under Long‐Term Corn Monoculture
Authors: Zhang T. Q. , MacKenzie A. F. 
Published: July 2010

AbstractCorn (Zea mays L.) monoculture is a common management practice due to high production levels with economic and agronomic advantages. Phosphorus reactions in soil affect sustainable, economic corn management and environmental quality. Our objectives were to quantify changes in soil P fractions as related to additions of manure and inorganic P with time using a modified Hedley fractionation scheme. A field experiment was conducted on a Chicot sandy clay loam soil (fine‐loamy, mixed, frigid Typic Hapludalf) from 1984 to 1993. With an annual rate of 60 kg P ha−1 manure P plus 44 kg P ha−1 inorganic P, labile inorganic P (Pi; Bicarb‐Pi) increased and moderately labile Pi (NaOH‐Pi) decreased. A higher annual P rate of 132 kg P ha−1 plus manure P increased soil Pi through Bicarb‐Pi, NaOH‐Pi, and stable Ca‐bound Pi (HCl‐Pi). Inorganic P at either rate combined with manure P decreased labile Bicarb‐Po fractions and increased moderately labile NaOH‐Po, with the result that total extractable soil organic P (Po) increased. Without manure, 44 kg P ha−1, approximately equal to P removal by the crop, resulted in no change in soil P fractions except for residual P (Res‐P), which decreased. Soil Po and Pi levels increased continuously in soil fertilized with 132 kg P ha−1 yr−1 inorganic P only. With the manure‐inorganic system, 86% of the Bicarb‐Pi was supplied from added inorganic P, indicating reduced P fixation compared with the inorganic P system. The NaOH‐Pi and Res‐P were soil P sinks, with Res‐P being supplied from both the NaOH‐Po and HCl‐Pi fractions. In contrast, NaOH‐Pi in the inorganic P system was the major source for Bicarb‐Pi.