Papers by Roberto Raul Filgueira
Se determinaron experimentalmente la superficie específica (área superficial por unidad de masa),... more Se determinaron experimentalmente la superficie específica (área superficial por unidad de masa), la tasa fotosintética aparente máxima y la conductancia al vapor de agua de la hoja bandera de cuatro cultivares de Triticum aestivum, uno de Triticum spelta y otro de Triticum dicoccum, cultivados en invernáculo, con la finalidad de establecer la interacción entre estos parámetros, en condiciones de riego normal y de estrés hídrico. Los valores de superficie específica, medidos por adsorción de nitrógeno (temperatura 77,3 K), variaron entre 2,9 y 6,0 m2 g-1 lo que dio como resultado valores de superficie interna foliar mayores que los determinados por los métodos geométricos convencionales basados en microscopía óptica. Se atribuyeron estas diferencias a la capacidad de la técnica empleada para poner en evidencia una superficie interna extremadamente rugosa a nivel molecular, resultante de la intrincada estructura de la pared celular a través de la cual se realiza el intercambio gaseos...
Soil water diffusivity (D) is an important hydraulic property that is fundamental to characterize... more Soil water diffusivity (D) is an important hydraulic property that is fundamental to characterize unsaturated watertransport. Its determination is complex, time-consuming and requires expensive instruments. The objectives of this workwere: to propose a simple and low-cost laboratory methodology to determine D function; and to analyze the influence of soilmanagement systems on D and Sorptivity (S). The studied soil was classified as a vertic Paleudol. The first 10 cm of the soilunder three different management systems (T1: Natural grassland, T2: direct drilling, and T3: Polyphitic Pasture) was sampled.The samples were sieved and packed into horizontal columns. The columns were analyzed under horizontal infiltration and Dwas determined by variations of water content as a function of time for fixed positions, obtained from low-cost soil moisturecapacitance sensors. The results showed that the proposed methodology is valid in the studied soils. Soil management systemsignificantly affect...
La geometría fractal permite describir teóricamente estructuras de diversa naturaleza. De esta se... more La geometría fractal permite describir teóricamente estructuras de diversa naturaleza. De esta se obtiene, la dimensión fractal de fragmentación (D), la cual, está relacionada con el particionamiento y escalamiento que presentan las mismas, y que ha sido empleada en la caracterización y estudio de distribución de tamaño de partículas del suelo (DTP). Se planteó aplicar el modelo fractal e investigar sobre el proceso de microestructuración en seis suelos agrícolas de la pradera pampeana con DTP contrastantes. Las DTP y las D se obtuvieron bajo dos pretratamientos, uno sin materia orgánica (SMO), máxima dispersión, y otro con materia orgánica (CMO) conservando así la microestructura. El modelo fractal aplicado a la DTP con el pretratamiento SMO, en los suelos franco limosos, alcanzó a describir en promedio el 98% de la masa analizada; en el suelo franco arenoso ajustó hasta los 50 µm, describiendo el 38% de la masa, mientas que el suelo areno franco no ajustó al modelo fractal. Con lo...
Water Resources and Irrigation Management, Apr 1, 2016
Soil water diffusivity (D) is an important hydraulic property that is fundamental to characterize... more Soil water diffusivity (D) is an important hydraulic property that is fundamental to characterize unsaturated water transport. Its determination is complex, time-consuming and requires expensive instruments. The objectives of this work were: to propose a simple and low-cost laboratory methodology to determine D function; and to analyze the influence of soil management systems on D and Sorptivity (S). The studied soil was classified as a vertic Paleudol. The first 10 cm of the soil under three different management systems (T1: Natural grassland, T2: direct drilling, and T3: Polyphitic Pasture) was sampled. The samples were sieved and packed into horizontal columns. The columns were analyzed under horizontal infiltration and D was determined by variations of water content as a function of time for fixed positions, obtained from low-cost soil moisture capacitance sensors. The results showed that the proposed methodology is valid in the studied soils. Soil management system significantly affected D and S. They were greater for T2 compared with T1 and T3 (D varied between 0.00033 and 0.0321 cm 2 .s -1 ). This means that the soil under T2 can transmit water faster under non-saturated conditions as compared with the soil under grazing. In conclusion, the proposed methodology allowed to determine D in a simple and low-cost way, and to determine the influence of these properties on productive conditions.
La superficie específica de oxisoles y su relación con la retención hídrica Tomo 48 • N° 2 • 2016... more La superficie específica de oxisoles y su relación con la retención hídrica Tomo 48 • N° 2 • 2016 Rev. FCA UNCUYO. 48(2): 95-105. ISSN impreso 0370-4661. ISSN (en línea) 1853-8665. La superficie específica de oxisoles y su relación con la retención hídrica Resumen Se estimó la superficie específica (SE) de muestras de suelos mediante el método de adsorción de nitrógeno a 78 K, y se la relacionó con la capacidad de retención hídrica (RH), el contenido de arcilla, la capacidad de intercambio catiónico efectiva (CIC), y la cantidad de agua retenida sobre la superficie expuesta del suelo, en una aproximación de capas superpuestas. Se trabajó con veintisiete Oxisoles a potenciales hídricos equiva-lentes de-33,-500,-1000 y-1500 kPa. Se encontró una correlación positiva significativa entre la SE y RH, así como con el contenido de arcilla. No hubo una relación significativa de la dependencia entre la SE y la CIC. Entre la SE y el contenido de materia orgánica la correlación fue débil. La SE...
Revista De La Facultad De Ciencias Agrarias, 2016
The specific surface area of soil samples was estimated by the method of nitrogen adsorption at 7... more The specific surface area of soil samples was estimated by the method of nitrogen adsorption at 78 K, and it was related to the water retention cap...
Ciencia Del Suelo, Jun 1, 2009
La superficie bajo siembra directa continua se incrementa en forma sostenida. La maquinaria utili... more La superficie bajo siembra directa continua se incrementa en forma sostenida. La maquinaria utilizada en dichos sistemas posee gran peso y muchas veces se utiliza fuera de los rangos de humedad aconsejados. Todo lleva a un aumento generalizado del fenómeno de densificación de los suelos. Las variables hidráulicas serían las más afectadas por este fenómeno. Para mejorar esta situación se ha propuesto el uso de la descompactación mediante un subsolador. El efecto de descompactación favorecería la entrada de agua en el perfil del suelo. Existe una serie de modelos físico-matemáticos para estimar valores de variables hidráulicas a partir de experimentos de infiltración, con un infiltrómetro de disco. Los resultados obtenidos con estos modelos son a veces contradictorios. Los objetivos de este trabajo fueron evaluar el efecto de la tarea de descompactación sobre las variables hidráulicas en un suelo conducido en siembra directa con y sin tareas de descompactación y estudiar la sensibilidad de métodos físico-matemáticos para determinar el efecto sobre dichas variables. Las variables investigadas fueron Infiltración Básica (q ∞ ), Conductividad Hidráulica Saturada (Ksat) y Sortividad (S 0 ) a partir de ensayos con un infiltrómetro de disco. La descompactación produjo el aumento de la Ksat respecto del testigo. Luego del pasaje de la cosechadora no se verificaron cambios en dicha variable para el testigo, mientras que en el tratamiento con descompactación se registró una disminución significativa de Ksat. La S 0 no mostró una tendencia clara en su dependencia con el momento del muestreo, el sistema de labranza o el modelo utilizado, lo que indica la necesidad de seguir investigando en este tema. Adicionalmente, se concluyó que la Infiltración Básica (q ∞ ) obtenida con un infiltrómetro de disco no siempre es equivalente a Ksat.
Desde hace varios años, el modelo de fragmentación fractal ha atraido la atención de los investig... more Desde hace varios años, el modelo de fragmentación fractal ha atraido la atención de los investigadores, como un camino lógico para describir e interpretar distribuciones de partículas observadas. El análisis textural de un suelo ha mostrado ser muy importante, pues se utiliza para diagnosticar y predecir el funcionamiento y uso del mismo. Los métodos más populares para determinar la textura han sido los de sedimentación en agua utilizando el hidrómetro o la pipeta. Ambos tienen como objetivo encontrar la fracción de masa de partículas que se encuentran en suspensión a tiempos prefijados y relacionarla con los diámetros de las mismas. En este trabajo se ha desarrollado una nueva función potencial que relaciona la fracción de masa en suspensión con el tiempo de sedimentación. Utilizando la misma se puede determinar la dimensión fractal de fragmentación de una distribución de partículas en sedimentación. La nueva ecuación ha sido chequeada con datos propios obtenidos por el hidrómetro de Bouyoucos y otros publicados en la literatura, obtenidos mediante la pipeta de Robinson. El acuerdo logrado entre la teoría y los datos experimentales, mediante la técnica de regresión no lineal, ha sido excelente. Los valores de la dimensión fractal de fragmentación resultaron entre 2,
Ciencia Del Suelo, 2005
3) Investigador del CONICET.
Revista Brasileira de Ciência do Solo, 2016
The concept of soil physical quality (SPQ) is currently under discussion, and an agreement about ... more The concept of soil physical quality (SPQ) is currently under discussion, and an agreement about which soil physical properties should be included in the SPQ characterization has not been reached. The objectives of this study were to evaluate the ability of SPQ indicators based on static and dynamic soil properties to assess the effects of two loosening treatments (chisel plowing to 0.20 m [ChT] and subsoiling to 0.35 m [DL]) on a soil under NT and to compare the performance of static-and dynamic-based SPQ indicators to define soil proper soil conditions for soybean yield. Soil sampling and field determinations were carried out after crop harvest. Soil water retention curve was determined using a tension table, and field infiltration was measured using a tension disc infiltrometer. Most dynamic SPQ indicators (field saturated hydraulic conductivity, K 0 , effective macroporosity, ε ma , total connectivity and macroporosity indexes [C w TP and C w mac]) were affected by the studied treatments, and were greater for DL compared to NT and ChT (K 0 values were 2.17, 2.55, and 4.37 cm h -1 for NT, ChT, and DL, respectively). However, static SPQ indicators (calculated from the water retention curve) were not capable of distinguishing effects among treatments. Crop yield was significantly lower for the DL treatment (NT: 2,400 kg ha -1 ; ChT: 2,358 kg ha -1 ; and DL: 2,105 kg ha 1 ), in agreement with significantly higher values of the dynamic SPQ indicators, K 0 , ε ma , C w TP, and C w mac, in this treatment. The results support the idea that SPQ indicators based on static properties are not capable of distinguishing tillage effects and predicting crop yield, whereas dynamic SPQ indicators are useful for distinguishing tillage effects and can explain differences in crop yield when used together with information on weather conditions. However, future studies, monitoring years with different weather conditions, would be useful for increasing knowledge on this topic.
Revista De La Facultad De Ciencias Agrarias, 2010
Revista Brasileira de Ciência do Solo, 2015
Soil compaction has been recognized as a severe problem in mechanized agriculture and has an infl... more Soil compaction has been recognized as a severe problem in mechanized agriculture and has an influence on many soil properties and processes. Yet, there are few studies on the long-term effects of soil compaction, and the development of soil compaction has been shown through a limited number of soil parameters. The objectives of this study were to evaluate the persistence of soil compaction effects (three traffic treatments: T0, without traffic; T3, three tractor passes; and T5, five tractor passes) on pore system configuration, through static and dynamic determinations; and to determine changes in soil pore orientation due to soil compaction through measurement of hydraulic conductivity of saturated soil in samples taken vertically and horizontally. Traffic led to persistent changes in all the dynamic indicators studied (saturated hydraulic conductivity, K0; effective macro- and mesoporosity, εma and εme), with significantly lower values of K0, εma, and εme in the T5 treatment. The...
Zeitschrift für Naturforschung A, 1974
The centrifugal distortion constants for were calculated using Dowling and Watson’s formalisms. F... more The centrifugal distortion constants for were calculated using Dowling and Watson’s formalisms. From the fitting analysis and the deviation of predicted transitions it is concluded that the second formalism must be adopted. For the different parameters we have: A′ = 12406.012 ± 0.005 MHz; B′ = 5244.456 ± 0.002 MHz; C′ = 3869.191 ± 0.002 MHz; dJ = - 2.08 ± 0 .05 kHz; d J K = -23.63 ± 0.95 kHz; d K = - 33.43 ± 1.69 kHz; d W J = (0.56 ± 0.01) X 10-6; d WK = (5.08 ± 0.22) X 10-6.
Revista Brasileira de Ciência do Solo, 2014
The area under the no-tillage system (NT) has been increasing over the last few years. Some autho... more The area under the no-tillage system (NT) has been increasing over the last few years. Some authors indicate that stabilization of soil physical properties is reached after some years under NT while other authors debate this. The objective of this study was to determine the effect of the last crop in the rotation sequence (1st year: maize, 2nd year: soybean, 3rd year: wheat/soybean) on soil pore configuration and hydraulic properties in two different soils (site 1: loam, site 2: sandy loam) from the Argentinean Pampas region under long-term NT treatments in order to determine if stabilization of soil physical properties is reached apart from a specific time in the crop sequence. In addition, we compared two procedures for evaluating water-conducting macroporosities, and evaluated the efficiency of the pedotransfer function ROSETTA in estimating the parameters of the van Genuchten-Mualem (VGM) model in these soils. Soil pore configuration and hydraulic properties were not stable and ...
Soil and Tillage Research, 2010
Saturated Hydraulic Conductivity (Ks) is an important parameter for agriculture. Some authors hav... more Saturated Hydraulic Conductivity (Ks) is an important parameter for agriculture. Some authors have studied Ks anisotropy in soils with different results. Several methods have been developed and modified with time for the determination of Ks. The aim of this study was to determine ...
Revista Brasileira de Ciência do Solo, 2012
In view of the importance of the macroporosity for the water transport properties of soils, its q... more In view of the importance of the macroporosity for the water transport properties of soils, its quantitative assessment is a challenging task. Measurements of hydraulic conductivity (K) at different soil water tensions and the quantification of water-conducting macropores (θM) of a soil under different tillage systems could help understand the effects on the soil porous system and related hydraulic properties. The purpose of this study was to assess the effects of Conventional Tillage (CT), Chisel Plow (CP) and No Tillage (NT) on θM and on K; and to quantify the contribution of macroporosity to total water flux in a loam soil. A tension disc infiltrometer was used at two soil water pressure heads (-5 cm, and 0) to infer θM and K, during fallow. Macroporosity was determined based on the flow contribution between 0 and -5 cm water potentials (K0, K5, respectively), according to the Hagen-Poiseuille equation. The K0 values were statistically higher for CT than for NT and CP. The K5 val...
Zeitschrift für anorganische und allgemeine Chemie, 1981
Die Laser‐Raman‐Spektren der tetragonalen Orthovanadate der Seltenen Erden des Typs LnVO4 (Ln = P... more Die Laser‐Raman‐Spektren der tetragonalen Orthovanadate der Seltenen Erden des Typs LnVO4 (Ln = Pr bis Lu) sowie diejenigen von ScVO4 und YVO4 wurden aufgenommen und an Hand einer „Site‐Symmetrie”︁‐bzw. Faktorgruppenanalyse gedeutet. Auch Daten früher durchgeführter IR‐Messungen wurden herangezogen. Der Einfluß der Kationen auf die inneren Anionenschwingungen wurde eingehend diskutiert.
Soil Science Society of America Journal, 2001
size and density are identified as two of the most impor- tant properties of soil aggregates. Agg... more size and density are identified as two of the most impor- tant properties of soil aggregates. Aggregate density is DENSITY BY VOLUME DISPLACEMENT used to estimate inter-aggregate porosity, and, together with aggregate size, influence plant growth (De Freitas IN TWO NON-MIXING LIQUIDS et al., 1996). During the last decade, fractal models of soil structure have been developed that use variations in Guillermo O. Sarli, Roberto R. Filgueira, and Daniel Gime ´nez* aggregate density with aggregate size as a fundamental scaling property related to soil water retention and other Abstract soil properties (Rieu and Sposito, 1991). There is an interest in methods to determine density of soil aggre-Soil aggregate density is an important property influencing soil gates, and several methods have been proposed. biological, chemical, and physical processes. Current methods used Some methods use a group of aggregates to determine to estimate soil aggregate density are based on more or less restrictive assumptions or require specialized equipment. This study was con-an average aggregate density. In this group is the method ducted to develop an alternative method for measuring aggregate proposed by Chepil (1950), which was successfully used density of soil and other porous objects that is both simple and theoretto determine the density of aggregate size fractions sepaically sound. The proposed method solves the balance of forces rerated by sieving dry soil (Eghball et al., 1993; Filgueira sulting when a kerosene-saturated aggregate is immersed in a mix of et al., 1999a, 1999b). The method, however, assumes water and glycerin. We tested the accuracy of the method by measuring that aggregates and sand grains of similar size pack in the volume of 40 aggregates with diameters ranging from 4 to 20 mm the same way. This assumption is likely to introduce and with variable densities. Soil aggregates were saturated in kerosene, error in the determination of the density of irregularlydrained at a tension of Ϫ30 mm, and their volume estimated using a shaped aggregates. Voorhees et al. (1966) circumvented pycnometer. Upon resaturation, aggregates were suspended from a this problem by using a mixture of glass beads and thread and successively weighed in air, in kerosene, and in a mix of water and glycerin. Aggregate volumes and densities varied between aggregates packed to a known volume to determine 1.20 ϫ 10 Ϫ7 and 3.85 ϫ 10 Ϫ6 m 3 and between 1.05 to 1.86 Mg m Ϫ3 , reaggregate density. The same principle was applied by spectively. On average, aggregate volumes estimated with the pycno-
Journal of Molecular Spectroscopy, 1984
The rotational spectra of the normal and N-D isotopic species of pyrrolidine have been measured. ... more The rotational spectra of the normal and N-D isotopic species of pyrrolidine have been measured. The molecule exists in an envelope conformation, with the nitrogen atom out of the plane containing the carbon atoms and with the imino hydrogen in the axial position. The analysis of the rotational spectra of two and three vibrationally excited states for the normal and N-D isotopic species, respectively, indicates that both barriers to pseudorotation and to the imino hydrogen inversion are relatively high. Additionally, the N( ) quadrupole coupling constants have been determined. I The terms "twist" or "half-chair" (sometimes "chair") and "bent" or "envelope" are equally found in literature.
Journal of Molecular Spectroscopy, 1986
The microwave spectrum of thiane has been studied in the 8- to 18-GHz region. Thirty five new rot... more The microwave spectrum of thiane has been studied in the 8- to 18-GHz region. Thirty five new rotational lines of the ground vibrational state with J up to 41 have been measured and assigned. These lines and a previous set reported by R. W. Kitchin, T. B. Malloy, Jr., and R. L. Cook [J. Mol. Spectrosc.57, 179-188 (1975)] have been
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Papers by Roberto Raul Filgueira