bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of the Root Zone Water Quality Model for Conditions in Central Nebraska
Authors: Martin Derrel L. , Watts Darrell G. 
Published: July 2010

AbstractThe Root Zone Water Quality Model (RZWQM) was evaluated for a region that has a long history of irrigated corn (Zea mays L.). Imprecise irrigation and plentiful fertilizer applications have contributed to the buildup of NO3‐N in ground water, where concentrations often exceed 30 mg L−1. Experiments were conducted to evaluate the effects of management practices on corn yield, N uptake, plant biomass, leaf area development, soil water content, and soil N. Field‐measured results from 1992 were used to calibrate RZWQM. The model was evaluated by simulating three irrigation levels and five fertilizer rates for 1993 and 1994. The model simulated the soil water pattern satisfactorily during most of the growing season; however, the simulated soil profile water content was lower than field conditions in the spring and fall. Transpiration appears to be excessive when the leaf area index (LAI) is small. Simulated yields exceeded measured values, with the largest errors for small fertilizer applications in 1993 and for large fertilizer applications in 1994. The mean error between measured and modeled yields was 2.9 Mg ha−1, with a root mean square error (RMSE) equal to 46% of the mean yield for all treatments over the 3 years. Estimates of LAI and aboveground biomass were closer to measured values, with mean errors of 5% for leaf area and 1% for biomass. The relative RMSE for LAI and biomass was 26 and 17%, respectively. The model underestimated aboveground N uptake, with a mean error of 25 kg N ha−1 and a relative RMSE of 41%. While development of the comprehensive RZWQM has been constructive, improvements are still needed. Excessive depletions in the spring and fall overstate storage of off‐season precipitation, and this leads to underestimating annual leaching losses. Combining excessive yield predictions with low N uptake estimates exaggerates the N use efficiency. These discrepancies will have a profound effect on the simulated impact of management practices. Leaching losses and yield effects will be understated, which may lead to development of policies that affect producers more severely than the model implies.
Effect of 39 Years of Cropping Practices on Wind Erodibility and Related Properties of an Irrigated Chestnut Soil
Authors: Mazurak A. P. , Zingg A. W. , Chepil W. S. 
Published: July 2010

AbstractIn April 1951, a portable wind tunnel was set up at the Scotts Bluff Substation on plots that were planted to sugar beets and potatoes. The soil losses from wind under controlled conditions were measured on manured and non‐manured plots from (i) a 3‐year rotation of barley, potatoes and sugar beets and (ii) a 6‐year rotation of barley with alfalfa, alfalfa 3‐years, potatoes and sugar beets. On these and other plots, size‐fractions of air‐dried clods from the surface 2‐inches of soil were separated by means of rotary sieves. Each size‐fraction was analyzed for the apparent density of clods, total nitrogen content, and moisture content at 15‐atmosphere tension.The cropping and manurial practices showed a marked effect on the soil losses from wind. Alfalfa in the rotation was superior to manure application in reducing soil losses. Application of 12 tons of barnyard manure on potato plots in a 3‐year rotation reduced the soil loss from 74,500 pounds per acre to 2,720. The soil loss on non‐manured plots in the 6‐year rotation was 970 pounds per acre. The beet plots, in a cropping system and manurial application similar to potato plots showed a smaller regimen of soil losses.Mechanical stability of clods was determined by their resistance to break‐down as a result of resieving. It was greatest in plots cropped to continuous barley, followed in order by beets, corn, and potatoes. Mechanical stability was greater in manured plots than in non‐manured.The application of manure or growing of alfalfa in the rotation effected a marked reduction in the apparent density of clods and increased the total nitrogen content and the moisture content at 15‐atmosphere tension. Alfalfa was superior to manure in effecting these changes in soil properties.
Effect of Autoclaving on X‐Ray Characteristics of Clay Minerals
Authors: Stotzky G. , DeMumbrum L. E. 
Published: July 2010

AbstractA variety of tropical and temperate zone soils differing in clay mineral composition and moisture content were autoclaved for 1 hour at 121 C, 15 psi, and fast exhaust. Various purified clay minerals were similarly autoclaved for 15 min in a nutrient medium used for the culture of microorganisms. Autoclaving did not significantly alter the diagnostic d values of the clay minerals contained in either the soils or the nutrient medium, regardless of the moisture content (from oven‐dry to saturation) of the soils at the time of autoclaving.
A Plinthaquult of the Aripo Savannas, North Trinidad II. Mineralogy and Genesis
Authors: Ahmad N. , Jones Robert L. 
Published: July 2010

AbstractThe Aripo Savanna Fine Sand, a Plinthaquult, has developed on water‐transported erosion products derived from the Northern Range in Trinidad. The profile consists of a surface‐bleached layer of 25 cm thickness composed of silt and fine sand, underlain by an intensely red‐ and yellow‐mottled argillic layer. The first 10 cm of this layer has ochreous diffuse mottling and is very rich in Fe. Deeper, the mottles are more distinct and red in color on an almost grey matrix. On exposure, these mottles (plinthite) harden irreversibly to nodules. Chemical and mineralogical properties of nodular material thus formed ranging from 1 to 30 years of age were examined. With time, the nodules become firmer and richer in Fe. The intensity of red coloration within the nodules is directly related to the amount of Fe present. All nodules are very low in Mn; Ti is inversely related to Fe but Ca is evenly distributed throughout all nodular materials regardless of age. No crystalline Fe minerals occur, but lepidocrocite and goethite are present in the ochreous mottles in a thin horizon above the nodule‐producing layer.The soil is derived from micaceous (muscovite) parent materials, but mica content is low; kaolinite derived from mica weathering is the dominant mineral. There are also identifiable amounts of montmorillonite or vermiculite‐type mineral thought to be derived from weathering of mica and representing intermediates in the formation of kaolinite. Cation exchange capacity and surface area values are in accordance with this mineral assemblage. The silt and sand fractions are almost pure quartz. Absence of feldspars in the silt fraction is confirmed by only trace amounts of Ca and Na found by chemical analysis. The data indicate that this soil is perhaps the most weathered of Trinidadian soils.
Soil‐Water Regimes in Brookston and Crosby Soils
Authors: Harlan P. W. , Franzmeier D. P. 
Published: July 2010

AbstractHydraulic conductivity and seasonal patterns of water content were measured and related to soil formation in associated very poorly drained Brookston soils (Typic Argiaquolls) and somewhat poorly drained Crosby soils (Aeric Ochraqualfs) in central Indiana. In the Brookston soil the water table was near the surface for only a short time during periods of heavy rainfall in the winter and spring. The water table then stabilized near 125 cm deep, where it was controlled by tile drains. In Crosby, also tile‐drained, the water table stayed near the surface longer in the spring, then became deeper than in Brookston. The hydraulic conductivity is relatively high in the Brookston B and C and Crosby B horizons but very low in the Crosby C horizon, compact glacial till. Since downward movement is restricted in the Crosby C horizon, water tends to move laterally through the B horizon into the Brookston soil where the tile are in more permeable horizons than they are in Crosby.Available water capacities of soils can be estimated by measuring the field water contents in a profile at the beginning of the growing season and during dry periods for several years using a soil under perennial vegetation. In these two soils, however, it appears that water movement from Crosby to Brookston and the profile storage capacity are both important in determining the water‐supplying capacity of the soils.
Effect of Soil Acidity Factors on Yields and Foliar Composition of Tropical Root Crops
Authors: Abruña‐Rodríguez Fernando , Vicente‐Chandler José , Rivera Edmundo , Rodríguez José 
Published: July 2010

AbstractTropical root crops, a major source of food for subsistence farmers, varied in their sensitivity to soil acidity factors. Tolerance to soil acidity is an important characteristic of crops for the humid tropics where soils are often very acid and lime‐scarce and expensive. Experiments on two Ultisols and an Oxisol showed that three tropical root crops differed markedly in sensitivity to soil acidity factors. Yams (Dioscorea alata L.) were very sensitive to soil acidity with yields on a Ultisol decreasing from 70% of maximum when Al saturation of the effective cation exchange capacity of the soil was 10 to 25% of maximum when Al saturation was 40%. On the other hand, Cassava (Manihot esculenta Crantz) was very tolerant to high levels of soil acidity, yielding about 85% of maximum with 60% Al saturation. Taniers (Xanthosoma sp.) were intermediate between yams and cassava in their tolerance to soil acidity yielding about 60% of maximum with 50% Al saturation of the soil. Foliar composition of cassava was not affected by soil acidity levels and that of yams and taniers was also unaffected except for Ca content which decreased with decreasing soil pH and increasing Al saturation. Response of these tropical root crops to soil acidity components was far more striking on Ultisols than on the Oxisol. For yams, soils should be limed to about pH 5.5 with essentially no exchangeable Al3+ present whereas high yields of taniers can be obtained at about pH 4.8 with 20% exchangeable Al3+ and of cassava at pH as low as 4.5 with 60% exchangeable Al3+.
A Chemical Model of Phosphate Adsorption by Soils: I. Reference Oxide Minerals
Authors: Goldberg Sabine , Sposito Garrison 
Published: July 2010

AbstractThe Constant Capacitance model is shown to provide a quantitative description of o‐phosphate adsorption by a variety of aluminum and iron hydrous oxides, including the effect of varying pH values. This model, based on a ligand exchange mechanism for o‐phosphate adsorption, comprises six adjustable parameters: two surface protonation‐dissociation constants, three o‐phosphate surface complexation constants, and a capacitance density parameter. The five surface equilibrium constants can be obtained from potentiometric titration data and o‐phosphate adsorption data. These constants are independent of pH but, in principle, can depend on the composition of the background electrolyte solution. The capacitance density parameter cannot be obtained directly from experiment. A working value can be chosen on the basis of previous applications of the Constant Capacitance model and other model parameters are not sensitive to this choice.
Joint Frequency Distributions for Use in Erosion Research
Authors: Istok J. D. , Boersma L. 
Published: July 2010

AbstractHighest rates of soil erosion are often associated with specific climatic and soil conditions, e.g., rainfall on a frozen soil surface or on a saturated soil. Development of methods for computing the frequency of occurrence of these conditions using historical precipitation and air temperature data is reported. The methods are based on dividing hourly precipitation and air temperature data into precipitation events, freezing events, and event clusters. Precipitation events are defined as “wet” hours separated by “dry” hours. Freezing events are defined as periods of consecutive “cold” hours (air temperatures <0°C) separated by periods of consecutive “warm” hours (air temperatures >0°C). Event clusters are defined as over‐lapping precipitation and freezing events. Sets of characteristics are defined for each type of event and for event clusters, e.g., duration and amount of precipitation for precipitation events, and freeze index and minimum temperature for freezing events. Joint frequency distributions for event and cluster characteristics are obtained, and examples show how to use these to predict frequency of occurrence of climatic conditions known to result in high rates of soil erosion. Application of joint frequency distributions to the Soil Conservation Service's curve number method for predicting watershed runoff is discussed, and it is shown how joint frequency distributions for precipitation amount and freeze index can be combined with the results of discriminant analysis for the occurrence of soil frost to compute the frequency of occurrence of rainfall on a frozen soil surface.
Calciustolls in Central Texas: I. Parent Material Uniformity and Hillslope Effects on Carbonate‐Enriched Horizons
Authors: West L. T. , Wilding L. P. , Stahnke C. R. , Hallmark C. T. 
Published: July 2010

AbstractMost soils associated with soft, Cretaceous limestones in Texas occupy moderately to strongly sloping erosional landforms and are underlain by interbedded weakly to strongly indurated limestone. Fourteen pedons from four hillslopes in these landscapes were sampled to evaluate soil parent materials and the effect of hillslope position on genesis of the soils and carbonate‐enriched horizons. Clay‐free, carbonate‐free particle size distribution and elemental analysis of the residue silt fraction indicate that the soils had developed from stratified parent materials. Calcareous microfossils observed in thin section and siliceous microfossils observed with scanning electron microscopy indicate the soil parent materials to be primarily limestone of composition similar to that underlying the soils. Dust is being added to the soil surface at a rate of 1 to 2 mm/100 yr but has not been an important parent material amendment. The primary effect of hillslope position on genesis of soils and carbonate‐enriched horizons is through site stability. No consistent relationships were observed between soils on backslope and summit positions, and expression of carbonate‐enriched horizons.
Cropping System and Nitrogen Effects on Mollisol Organic Carbon
Authors: Robinson C. A. , Cruse R. M. , Ghaffarzadeh M. 
Published: July 2010

AbstractTime, fertilizer, tillage, and cropping systems may alter soil organic carbon (SOC) levels. Our objective was to determine the effect of long‐term cropping systems and fertility treatments on SOC. Five rotations and two N fertility levels at three Iowa sites (Kanawha, Nashua, and Sutherland) maintained for 12 to 36 yr were evaluated. A 75‐yr continuous corn (Zea mays L.) site (Ames) with a 40‐yr N‐P‐K rate study also was evaluated. Soils were Typic and Aquic Hapludolls and Typic Haplaquolls. Four‐year rotations consisting of corn, oat (Avena sativa L.), and meadow (alfalfa [Medicago sativa L.], or alfalfa and red clover [Trifolium pratense L.]) had the highest SOC (Kanawha, 32.1 g/kg; Nashua, 21.9 g/kg; Sutherland, 27.9 g/kg). Corn silage treatments (Nashua, ≤ 18.9 g/kg; Sutherland, ≤23.2 g/kg) and no‐fertilizer treatments (Kanawha, 25.3 g/kg; Nashua, ≤20.9 g/kg; Sutherland, ≤23.5 g/kg) had the lowest SOC. A corn‐oat‐meadow‐meadow rotation maintained initial SOC (27.9 g/kg) after 34 yr at Sutherland. Continuous corn resulted in loss of 30% of SOC during 35 yr of manure and lime treatments. SOC increased 22% when N‐P‐K treatments were imposed. Fertilizer N, initial SOC levels, and previous management affected current SOC levels. Residue additions were linearly related to SOC (Ames, r2 = 0.40; Nashua, r2 = 0.82; Sutherland, r2 = 0.89). All systems had 22 to 49% less SOC than adjacent fence rows. Changing cropping systems to those that conserve SOC could sequester as much as 30% of C released since cropping began, thereby increasing SOC.
Rietveld Estimates of Mineral Percentages to Predict Phosphate Sorption by Selected Hawaiian Soils
Authors: Jackman J. M. , Jones R. C. , Yost R. S. , Babcock C. J. 
Published: July 2010

AbstractPredicting P sorption by weathered soils in order to manage soil, crop, and natural resources has been an important but elusive goal of soil science for decades. This study evaluated several soil properties, including mineralogy, of weathered Hawaiian soils in terms of their utility as predictors of P sorption. Chemical and physical properties associated with P sorption were measured and correlated. In addition, a theoretical quantity, potential P‐sorption sites, was estimated from the mineralogical characteristics of the clay fraction. Rietveld refinement was used to determine the quantity of soil minerals. Crystallite size was determined by curve‐fitting of selected x‐ray diffraction peaks. These parameters were then used to predict the soil P‐sorption potential by estimating the density of A‐hydroxyl sites per gram of soil. This estimate of potential P‐sorption sites provided the best correlation (R2 = 0.94) with measured P‐sorption capacity in 0.001 M CaCl2, which varied from 79 to 3280 mg P kg−1 soil at an equilibrium solution‐P concentration of 0.2 mg P L−1. Other bulk soil properties such as the moisture content at 1.5 MPa, specific surface area (glycerol retention), and the amount of amorphous (i.e., oxalate extractable) soil material, also correlated well with P sorption but yielded lower R2 values. Clay content and soil chemical properties alone were not good predictors of P‐sorption capacity across the full range of soils. Better estimates of the quantity of sorption sites, especially those contributed by amorphous oxides, would yield further improvements in this approach.
Delineation of Soil Variability Using Geostatistics and Fuzzy Clustering Analyses of Hyperspectral Data
Authors: Ahn C.‐W. , Baumgardner M. F. , Biehl L. L. 
Published: July 2010

AbstractA soil map is one of the key data layers for developing a robust global model and evaluating land quality and use. A current soil map produced by conventional soil survey is the major source of soil information. However, such a map may not provide the desired accuracy in terms of scale and cartographic quality as a digital format for geographic information system (GIS) modeling applications. This study was designed to introduce and test the procedures for improving the objectivity and accuracy in the delineation of soil patterns with the use of hyperspectral imagery. These hyperspectral data were analyzed through different models including the linear mixture model, block‐kriging interpolation, and fuzzy‐c‐means (FCM) algorithms. Hyperspectral remote sensing data, having very good spectral and spatial resolution, were used for quantifying soil patterns and conditions. A linear spectral mixing model was effectively used not only for reducing dimensionality but also for removing vegetation effects for studying soil patterns from a single soil map layer derived from hyperspectral remote sensing data. Block kriging interpolation based on a semivariogram fitted with the isotropic exponential model represented soil patterns very well beyond the limitation of the size of pixel. Fuzzy‐c‐means clustering analysis showed clear membership patterns and segmented soil patterns effectively, although this is not a soil map in the conventional sense.
Practical stabilizability of dyadic homogeneous bilinear systems
Authors: Tadi M. 
Published: July 2010

AbstractThis paper considers a class of homogeneous bilinear systems in which the rank of the B matrix is equal to one. It uses a transformation to convert the system into a form similar to the companion from. It then considers feedback control laws in the form of variable structure. Results indicate that it is possible to obtain practical stability for a class of dyadic systems. The results are particularly useful for low dimensional systems.Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society
An algorithm for direct identification of passive transfer matrices with positive real fractions via convex programming
Authors: De Tommasi L. , de Magistris M. , Deschrijver D. , Dhaene T. 
Published: July 2010

AbstractThe paper presents a new algorithm for the identification of a positive real rational transfer matrix of a multi‐input–multi‐output system from frequency domain data samples. It is based on the combination of least‐squares pole identification by the Vector Fitting algorithm and residue identification based on frequency‐independent passivity constraints by convex programming. Such an approach enables the identification ofa prioriguaranteed passive lumped models, so avoids the passivity check and subsequent (perturbative) passivity enforcement as required by most of the other available algorithms. As a case study, the algorithm is successfully applied to the macro‐modeling of a twisted cable pair, and the results compared with a passive identification performed with an algorithm based on quadratic programming (QPpassive), highlighting the advantages of the proposed formulation. Copyright © 2010 John Wiley & Sons, Ltd.
Midbrain SERT in degenerative parkinsonisms: A 123I‐FP‐CIT SPECT study
Authors: Roselli Francesco , Pisciotta Nicola M. , Pennelli Michele , Aniello Maria S. , Gigante Angelo , De Caro Maria F. , Ferrannini Ermanno , Tartaglione Bruno , Niccoli‐Asabella Artor , Defazio Giovanni , Livrea Paolo , Rubini Giuseppe 
Published: July 2010

AbstractSPECT imaging is widely used for the differential diagnosis of degenerative parkinsonisms by exploiting the high affinitiy of the radiotracer 123I‐FP‐CIT for the dopamine transporter. Reduced levels of DAT are found in Parkinson Disease (PD), Dementia with Lewy Bodies (DLB), and Progressive Supranuclear Palsy (PSP) compared to in Essential Tremor (ET) and Healthy Controls (HC). However, the extent of the neurodegenerative process may extend beyond nigrostriatal system. We have exploited the affinity of the same radiotracer 123I‐FP‐CIT for the serotonin transporter to investigate SERT levels in the midbrain of patients with PD, DLB, PSP, and ET compared to HC. Using MRI images as anatomical templates for midbrain uptake quantification, we found a mild decrease in SERT levels in PD compared to ET and HC, with marked inter‐individual variability; on the other side, PSP and DLB patients displayed markedly reduced to undetectable levels of SERT, respectively. These findings show that the neurodegenerative process affects serotoninergic neurons in parkinsonisms, with much more severe involvement in DLB than in PD patients, despite the comparable loss of striatal DAT. SERT‐dependent 123I‐FP‐CIT uptake may allow a more comprehensive assessment of neurochemical disturbances in degenerative parkinsonisms and may have a value for differential diagnosis. © 2010 Movement Disorder Society