Sedimentologische und mineralogische Merkmale von Lössen und Lößderivaten in Franken

Zur Charakterisierung der Anteile von Lössen und Verwitterungsprodukten der liegenden Keuper- und Liasgesteine innerhalb kolluvialer Mischsedimente und holozäner Terrassenkörper erweisen sich in Oberfranken neben Korngrößenverteilungen insbesondere Quarz-Feldspat- und Albit-Mikroklin-Quotienten als geeignete Indizes. Danach sind an den untersuchten bodenerosiv überprägten Flachhängen bevorzugte Abtragung von Löß und Liegendmaterial an den Oberhängen, vorherrschender Durchtransport an den Mittelhängen und Ablagerung von Mischsedimenten an den Unterhängen zu erkennen. In den holozänen Sedimenten der Vorfluter sind Lößderivate demgegenüber nur gering vertreten, woraus auf vorherrschenden Durchtransport dieses Materials in den untersuchten Talstrecken und — im Vergleich mit niedersächsischen Beispielen entsprechender Größenordnung — auf eine regionale Differenzierung der holozänen fluvialen Dynamik geschlossen wird, die möglicherweise auf Unterschiede des Regionalklimas zurückzuführen ist.researc

Clay sediments in a soil of the lower Colorado river valley (Argentina)

Se describe la presencia de capas sedimentarias ricas en minerales de arcilla en un subsuelo del valle inferior del río Colorado por su importancia para el régimen hídrico de suelos bajo riego. Difractogramas de rayos X efectuados sobre la fracción arcilla fina de estos sedimentos revelaron que está compuesta por smectitas con muy buena cristalización. La caracterización fisicoquímica del perfil de suelo mostró que el fuerte incremento de minerales de arcilla en el subsuelo estuvo vinculado con un aumento de pH y PSI y en consecuencia una marcada disminución en la conductividad hidráulica, motivo por el cual la eventual presencia de estas capas sedimentarias debe ser muy tenida en cuenta en la programación de las prácticas de riego para evitar el posible deterioro de los suelos.The presence of sedimentary clay layers in subsoils of the lower Colorado river valley are described due to their impact on the water balance of soils under irrigation. X-ray difractograms of the fine clay fraction of these sediments show that they are composed of smectites with a very good crystallization. The physicochemical characterization of the soil profile indicates that the abrupt increase of clay minerals was associated with high pH and ESP values as well as a sharp decrease in hydraulic conductivity. Therefore, the presence of sedimentary clay layers in soils has to be considered when planning irrigation practices to avoid soil degradation.Fil: Peinemann, Norman. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Agronomía; Argentin

Sedimentos arcillosos en un suelo del valle inferior del río Colorado (Argentina) Clay sediments in a soil of the lower Colorado river valley (Argentina)

Se describe la presencia de capas sedimentarias ricas en minerales de arcilla en un subsuelo del valle inferior del río Colorado por su importancia para el régimen hídrico de suelos bajo riego. Difractogramas de rayos X efectuados sobre la fracción arcilla fina de estos sedimentos revelaron que está compuesta por smectitas con muy buena cristalización. La caracterización fisicoquímica del perfil de suelo mostró que el fuerte incremento de minerales de arcilla en el subsuelo estuvo vinculado con un aumento de pH y PSI y en consecuencia una marcada disminución en la conductividad hidráulica, motivo por el cual la eventual presencia de estas capas sedimentarias debe ser muy tenida en cuenta en la programación de las prácticas de riego para evitar el posible deterioro de los suelos.<br>The presence of sedimentary clay layers in subsoils of the lower Colorado river valley are described due to their impact on the water balance of soils under irrigation. X-ray difractograms of the fine clay fraction of these sediments show that they are composed of smectites with a very good crystallization. The physicochemical characterization of the soil profile indicates that the abrupt increase of clay minerals was associated with high pH and ESP values as well as a sharp decrease in hydraulic conductivity. Therefore, the presence of sedimentary clay layers in soils has to be considered when planning irrigation practices to avoid soil degradation

Effect of landscape position on the acidification of loess-derived soils under Pinus radiata

Interactions between landscape position and the acidifying effect of trees planted into loess-derived grassland soils were studied in the Ventana region of Argentina. Forests of Pinus radiata planted at the end of 1940, were selected in two different positions from the landscape, plains and slopes. Samples of the soil surface mineral horizon were taken from landscape positions at four distances from the trees and compared with grassland soils. The values of the main soil chemical properties changed significantly with distance from trees, with a decrease in pH, base saturation, exchangeable Ca2+, Mg 2+ and K+, and increase in Na+, Al3+ and particularly H+ closer to the trees. This pattern confirms the prominent role of vegetation in bringing about changes in soil properties. Regression models showed high levels of explanation (r2 > 0.85) indicating that a high percentage of the spatial variability of soil chemical properties is systematic and predictable with distance from the trees. The pH in KCl proved an excellent tool for predicting the cationic composition of soils. Organic carbon and total nitrogen were significantly higher in the plains positions than in the slopes under the trees, whereas there was no difference under grassland. The slopes of the regression lines indicated that acidification is more intense in soils on the plains. Vegetation was the main factor influencing acidification of the studied soils. The landscape position regulates the bio-hydrological factor and thus the speed of acidification process.Fil: Amiotti, Nilda Mabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Agronomía; ArgentinaFil: Bravo, Oscar Abel. Universidad Nacional del Sur. Departamento de Agronomía; ArgentinaFil: Zalba, Pablo. Universidad Nacional del Sur. Departamento de Agronomía; ArgentinaFil: Peinemann, Norman. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Agronomía; Argentin

Disponibilidad de agua, nitrógeno y azufre en barbechos con y sin control de malezas en distintos niveles de residuos Water, nitrogen and sulphur availability in fallows with and without weed control and different residue levels

Con el fin de evaluar el efecto de los residuos vegetales sobre la eficiencia de almacenamiento de agua, la dinámica de nitrógeno y azufre disponible durante el barbecho con y sin presencia de malezas, se realizaron 10 ensayos con distintos niveles de residuos (A: 10.000 kg MS ha-1, M: 5.000 kg MS ha-1, B: menor a 2.000 kg MS ha-1) en Haplustoles de las regiones planicie con tosca y planicie medanosa de La Pampa y Sur de Córdoba. En cada tratamiento de residuos se dividieron las parcelas en dos subtratamientos de manejo de malezas: tratamiento con malezas (malezas) y sin malezas (barbecho). Se realizaron determinaciones de: textura, densidad aparente, punto de marchitez permanente, materia orgánica total. Al inicio y al final del barbecho se midió el contenido de agua en el suelo, nitratos (N), azufre de sulfatos solubles y adsorbidos (S) en 0-0,2 m de profundidad. Al comienzo del barbecho todos los sitios presentaron altos contenidos de agua útil (entre 51 y 100%). A pesar de ello, nuestros resultados mostraron que al finalizar el barbecho el nivel de residuos tuvo un efecto positivo en los contenidos de agua con una diferencia entre A y B de 33%. Con presencia de las malezas, no se pudo comprobar una ventaja por parte de los residuos y la diferencia entre A y B fue de 10%. El factor que más influyó en los contenidos de agua fue la presencia de malezas. Los contenidos de N y de S disponible no fueron influenciados por los distintos niveles de residuos, constatándose un mayor efecto de malezas. En el tratamiento con malezas se vería comprometida la siembra del cultivo de girasol por menor disponibilidad de agua y además se afectaría el rendimiento en 200 kg ha-1 por la menor disponibilidad de N y en 600 kg ha-1 por menor disponibilidad de S disponible en el nivel A de residuos.In order to study the effect of crop residues on the efficiency of water storage, available nitrogen and sulphate dynamics during fallow with and without weed presence, ten experiments with different levels of residue (A: 10,000 kg MS ha-1, M: 5,000 kg MS ha-1, B: less than 2,000 kg MS ha-1) were set up in Haplustolls of the tosca and dune plains in La Pampa and south of Córdoba. Each residue treatment was divided into sub-plots with different weed management: without weed control (malezas) and with control (barbecho). Soil texture, bulk density, permanent wilting pint, and organic matter were determined in each site. At the beginning and end of fallow soil water contents, nitrate (N) and soluble and adsorbed sulphates (S) were measured in samples from 0 -0.2m depth. At all sites the water content at the beginning of fallow was high (between 51 and 100% available water). Despite this, our results showed a positive effect of residue level on water contents at the end of fallow, with a mean difference between A and B of 33%. In weed treatments no effect of residue was observed, and the difference between A and B was 10%. Water contents were more strongly affected by the presence of weeds than by residue level. Available N and S contents showed no effect of residue level, but were strongly affected by weed presence. In weed treatments sunflower seeding would be severely limited by lower available water contents, and the expectable yields would be diminished by 200 kg ha-1 or 600 kg ha-1 due to the lower availability of N and S respectively

Factors affecting phosphorus sorption in loess soils of the semiarid Argentina

Previous results showed that phosphorus sorption strongly correlated with contents of active Al and Fe oxides and organic matter (OM) in soils of the-Semiarid Argentinean Pampas. Objective of this study was to determine the relative influence of these soil compounds on P sorption. It was hypothesized that contents of OM and Al and Fe oxides should decrease P sorption in the studied soils. With this purpose, sorption isotherms were carried out on non treated soils and on soils samples pre-treated with H2O2 (OM destruction), acid oxalate (AcOx, destruction of amorphous oxides) and boiled acid oxalate (BAcOx, destruction of crystalline oxides). Results showed that OM destruction did not affect none of the constants deduced from Freundlich isotherm (a, l/b and BCO.3). This was probably due to the variable effect of OM on these constants in each soil. On the other hand, constant a decreased 20 to 88% after elimination of crystalline oxides, and 17 to 48% after elimination of amorphous oxides, BCO.3 decreased 33 to 87% after elimination of crystalline oxides, and 21 to 44% after elimination of amorphous oxides, and 1/b remained unchanged. Such results indicate that P sorption (a), as well as the ability of the soil to liberate P to the soil solution (BCO.3), were highly influenced by the amount of amorphous and crystalline Al and Fe oxides and that the retention energy of P (1/b) remained unchanged.Fil: Hevia, Graciela Gloria. Universidad Nacional de La Pampa. Facultad de Agronomía; ArgentinaFil: Hepper, Estela Noemí. Universidad Nacional de La Pampa. Facultad de Agronomía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Buschiazzo, Daniel Eduardo. Universidad Nacional de La Pampa. Facultad de Agronomía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Peinemann, Norman. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentin

Moisture and temperature effect on soil phosphorus availability

The effect of desiccation temperature upon soil phosphorus availability was evaluated under laboratory conditions in soil samples of different texture. Soil samples of 1.4 g were weighed in 25 mL glass tubes and desiccated in an oven at 40, 60, 80 and 100o C using 2 different moisture levels: dry and wet. A total of 10 treatments were carried out with two replicates per treatment. Soil variables analyzed were: extractable phosphorus (Pe), organic phosphorus (Po), pH, organic carbon (OC), soil microbial activity (SMA), CaCO3 and texture (sand, silt and clay %). A marked increase in Pe was observed through the combined effect of moisture and temperature. Medium- and fine-textured soils showed higher Pe increments than coarser-textured soils. Whereas in medium-textured soils (loam) the increment in Pe varied between 4 mg kg-1 and 8 mg kg-1 as a result of the effect of temperature and temperature plus moisture, respectively, in the case of fine- and coarse-textured soils (clay loam and loamy sand) the increment was between 1 mg kg-1 and 6 mg kg-1. The soil variable analysis did not show any statistically significant relationships for Pe. However, high correlations were found between Po and SMA (r = 0.73, P <0.01) and between SMA and silt content (r = 0.86, P <0.01) . Thus, the results infer that soil microorganisms play an active role in the process of Po mineralization and the consequent increase in Pe.Fil: Zalba, Pablo. Universidad Nacional del Sur. Departamento de Agronomía; ArgentinaFil: Bravo, Oscar Abel. Universidad Nacional del Sur. Departamento de Agronomía; ArgentinaFil: Garay Schiebelbein, Maximiliano Miguel. Universidad Nacional del Sur. Departamento de Agronomía; ArgentinaFil: Peinemann, Norman. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Agronomía; Argentin

Water, nitrogen and sulphur availability in fallows with and without weed control and different residue levels

Con el fin de evaluar el efecto de los residuos vegetales sobre la eficiencia de almacenamiento de agua, la dinámica denitrógeno y azufre disponible durante el barbecho con y sin presencia de malezas, se realizaron 10 ensayos con distintosniveles de residuos (A: 10.000 kg MS ha-1, M: 5.000 kg MS ha-1, B: menor a 2.000 kg MS ha-1) en Haplustoles de lasregiones planicie con tosca y planicie medanosa de La Pampa y Sur de Córdoba. En cada tratamiento de residuos sedividieron las parcelas en dos subtratamientos de manejo de malezas: tratamiento con malezas (malezas) y sin malezas(barbecho). Se realizaron determinaciones de: textura, densidad aparente, punto de marchitez permanente, materiaorgánica total. Al inicio y al final del barbecho se midió el contenido de agua en el suelo, nitratos (N), azufre de sulfatossolubles y adsorbidos (S) en 0-0,2 m de profundidad. Al comienzo del barbecho todos los sitios presentaron altos con-tenidos de agua útil (entre 51 y 100%). A pesar de ello, nuestros resultados mostraron que al finalizar el barbecho el nivelde residuos tuvo un efecto positivo en los contenidos de agua con una diferencia entre A y B de 33%. Con presencia delas malezas, no se pudo comprobar una ventaja por parte de los residuos y la diferencia entre A y B fue de 10%. El factorque más influyó en los contenidos de agua fue la presencia de malezas. Los contenidos de N y de S disponible no fueroninfluenciados por los distintos niveles de residuos, constatándose un mayor efecto de malezas. En el tratamiento conmalezas se vería comprometida la siembra del cultivo de girasol por menor disponibilidad de agua y además se afectaríael rendimiento en 200 kg ha-1 por la menor disponibilidad de N y en 600 kg ha-1 por menor disponibilidad de S disponibleen el nivel A de residuosIn order to study the effect of crop residues on the efficiency of water storage, available nitrogen and sulphate dynamicsduring fallow with and without weed presence, ten experiments with different levels of residue (A: 10,000 kg MS ha-1,M: 5,000 kg MS ha-1, B: less than 2,000 kg MS ha-1) were set up in Haplustolls of the tosca and dune plains in La Pampaand south of Córdoba. Each residue treatment was divided into sub-plots with different weed management: withoutweed control (malezas) and with control (barbecho). Soil texture, bulk density, permanent wilting pint, and organicmatter were determined in each site. At the beginning and end of fallow soil water contents, nitrate (N) and soluble andadsorbed sulphates (S) were measured in samples from 0 -0.2m depth. At all sites the water content at the beginningof fallow was high (between 51 and 100% available water). Despite this, our results showed a positive effect of residuelevel on water contents at the end of fallow, with a mean difference between A and B of 33%. In weed treatments noeffect of residue was observed, and the difference between A and B was 10%. Water contents were more stronglyaffected by the presence of weeds than by residue level. Available N and S contents showed no effect of residue level,but were strongly affected by weed presence. In weed treatments sunflower seeding would be severely limited by loweravailable water contents, and the expectable yields would be diminished by 200 kg ha-1 or 600 kg ha-1 due to the loweravailability of N and S respectively.Fil: Fernandez, Romina Daiana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Pampa. Facultad de Agronomía; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional La Pampa-San Luis. Estación Experimental Agropecuaria Anguil; ArgentinaFil: Noellemeyer, Elke Johanna. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional de La Pampa. Facultad de Agronomía; ArgentinaFil: Funaro, Daniel. Instituto Nacional de Tecnología Agropecuaria. Centro Regional La Pampa-San Luis. Estación Experimental Agropecuaria Anguil; ArgentinaFil: Quiroga, Alberto Raul. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional La Pampa-San Luis. Estación Experimental Agropecuaria Anguil; Argentina. Universidad Nacional de La Pampa. Facultad de Agronomía; ArgentinaFil: Peinemann, Norman. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Agronomía; Argentin

A study of the effect of the interaction between site-specific conditions, residue cover and weed control on water storage during fallow

In the semiarid central region of Argentina the probability that rainfall meets crop requirements during growing season is less than 10%, therefore fallowing has been the most important practice to assure water availability during the growing season. Various site-specific and management factors have been identified as crucial for defining fallow efficiency (FE) and final available water contents (AW). The objective of the present study was to improve our knowledge about the interactions between residue cover, weed control, soil profile depth and water storage capacity (WSC) on FE. In 10 sites covering the environments of calcareous plains and sandy plains of the semiarid central region of Argentina and with different WSC, experiments with 3 different levels of residue cover (H, M, L) and with and without weed control (C and W respectively) during fallow were set up. A completely randomized block design with four repetitions and splits plots to consider weed control was used. Soil texture and organic matter were determined in samples of the A horizon (0.20 m). Bulk density, field capacity, permanent wilting point and soil water contents (monthly frequency) were measured at depth intervals of 0.20 m to the depth of the calcite layer or to 2.00 m depth. Soil temperature was taken in weekly intervals at 0.05 m depth and weed plants, separated by species, were counted at the end of fallow in 4 repetitions of 0.25 m2 in each treatment. An empirical model was developed to predict final AW under these experimental conditions. Model parameters were: Residue level, weed control, WSC, profile depth, and rainfall during fallow. Site-specific conditions (WSC and profile depth) affected water storage during fallow; soils with highest values for both parameters showed highest final AW. Weed density was the most important factor that controlled AW, with on average 35 mm less AW in W than in C treatments. Residue level had a positive effect on final AW in both C and W treatments, with a difference of 18.5 mm between H and L. An interaction between residue level and weed density was observed, indicating weed suppression in H treatments. This was also confirmed by correspondence analysis between residue level and weed species which revealed that different species were related to each level. High residue levels also decreased soil temperature, thus affecting germination of post-fallow crops. The empirical model had an overall average prediction error of 13.7% and the regression between measured and predicted values showed a determination coefficient of 0.77.