Propiedades edáficas de un suelo del caldenal pampeano en parches con diferente vegetación

The Caldenal soils receive residues that vary in quantity and quality, according to the dominant vegetation. The aim of this work was to analyze the influence of the vegetation on the edaphic properties of the soil. An Entic Haplustoll was sampled by patches with the predominance of forage species (F), non forage under Calden (NF) and shrub (A). Fractions of organic carbon, total nitrogen, available phosphorus, exchangeable cations and hydrophobicity and infiltration parameters were determined. The NF soil presented high contents of total organic carbon and its fractions and also a high level of total nitrogen and phosphorous availability. In the F soil was found that the apparent density was higher and the exchangeable calcium content was lower. The surface of the soil in the F patch was classified as slightly water repellent, while the other soils’ surfaces were strongly repellent. The medium infiltration rate was lower for the NF patch soil and higher for the A patch soil, which had the highest final infiltration rate. Soil studies in the Caldenal are recommended to be realized with an experimental design that allows controlling the variability that the dominant vegetation causes on the surface, due to the influence that vegetation has on the edaphic properties of the soil.Los suelos del bosque de Caldén reciben aportes de residuos variables en cantidad y calidad según la vegetación dominante. El objetivo fue analizar si ésta influye sobre algunas propiedades edáficas. Un Haplustol Éntico se muestreó en parches con predominio de especies forrajeras (F), no forrajeras bajo caldén (NF) y arbustivas (A). Se determinaron fracciones de carbono orgánico, nitrógeno total, fósforo disponible, cationes intercambiables, parámetros de hidrofobicidad e infiltración. El suelo de NF presentó mayor contenido de carbono orgánico total y de sus fracciones, de nitrógeno total y de fósforo disponible. En el suelo de F la densidad aparente fue mayor y el contenido de calcio intercambiable menor. La superficie del suelo del parche F se clasificó como ligeramente repelente al agua, mientras que la de los otros dos suelos como fuertemente repelente. La tasa de infiltración media fue menor en NF y mayor en A, este último presentó la mayor tasa de infiltración final. Estudios de suelos en el caldenal deberán realizarse con un diseño experimental que permita controlar la variabilidad ocasionada por la vegetación dominante sobre su superficie, ya que ésta influye sobre las propiedades edáficas

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

Propiedades edáficas de un suelo del caldenal pampeano en parches con diferente vegetación

Los suelos del bosque de Caldén reciben aportes de residuos variables en cantidad y calidad según la vegetación dominante. El objetivo fue analizar si ésta influye sobre algunas propiedades edáficas. Un Haplustol Éntico se muestreó en parches con predominio de especies forrajeras (F), no forrajeras bajo caldén (NF) y arbustivas (A). Se determinaron fracciones de carbono orgánico, nitrógeno total, fósforo disponible, cationes intercambiables, parámetros de hidrofobicidad e infiltración. El suelo de NF presentó mayor contenido de carbono orgánico total y de sus fracciones, de nitrógeno total y de fósforo disponible. En el suelo de F la densidad aparente fue mayor y el contenido de calcio intercambiable menor. La superficie del suelo del parche F se clasificó como ligeramente repelente al agua, mientras que la de los otros dos suelos como fuertemente repelente. La tasa de infiltración media fue menor en NF y mayor en A, este último presentó la mayor tasa de infiltración final. Estudios de suelos en el caldenal deberán realizarse con un diseño experimental que permita controlar la variabilidad ocasionada por la vegetación dominante sobre su superficie, ya que ésta influye sobre las propiedades edáficas

Fracciones de fósforo en suelos del Caldenal Pampeano expuestos a distintas temperaturas de quema Phosphorus fractions in soils of the Pampean Caldenal expose to different burn temperatures

RESUMEN En el Área del Caldenal donde la ganadería es una de las principales actividades productivas se utiliza el fuego para aumentar la producción de pasturas, sin embargo existen pocos antecedentes de los efectos de las quemas controladas sobre el contenido de las fracciones de fósforo del suelo. El objetivo de este trabajo fue evaluar el efecto de temperaturas de quema sobre fracciones orgánicas e inorgánicas de fósforo en un suelo franco arenoso y otro franco. Se tomaron muestras de los primeros 5 cm de cada uno de los suelos sin la cobertura vegetal, que fueron calentadas a 100, 200, 300, 400, 500 y 600 ºC dejando una muestra sin calcinar como testigo. A cada muestra se le determinó el contenido de P por extracción secuencial con los siguientes extractantes: carbonato ácido de sodio (Pi-HCO3), hidróxido de sodio (Pi-NaOH y Po-NaOH), ácido clorhídrico (Pi-HCl) y ácido sulfúrico (P-H2SO4). En general, el efecto de la temperatura de quema sobre los contenidos de las fracciones analizadas fue similar en ambos suelos. Por efecto del calentamiento a temperaturas de 300 ºC y superiores en ambos suelos, en general, aumentaron los contenidos de Pi-HCO3 y de Pi-NaOH mientras que disminuyeron los contenidos de P-H2SO4 como así también de la fracción Po-NaOH, atribuible a la descomposición de la materia orgánica a esas temperaturas con el consecuente aumento de las formas disponibles de fósforo inorgánico. Cuando los suelos fueron calentados a 300 °C, en el suelo franco arenoso se registraron aumentos de los contenidos de Pi-HCl y en el suelo franco disminuciones de dicha fracción. Al calentar ambos suelos a 600 °C se registraron aumentos de Pi-HCl los que estuvieron en relación con los aumentos de pH. Esto indica que disminuyó la solubilidad de los fosfatos de calcio predominantes en estos suelos. Quemas en las que la temperatura desarrollada en el suelo sea menor a los 300 °C no producirán cambios en los contenidos de las fracciones de fósforo. Sólo en el suelo franco el calentamiento a 300 ºC produjo una disminución neta de P posiblemente debido a la volatilización de compuestos orgánicos.<br>Cattle production is one of the main productive activities in the Caldenal area of La Pampa Province, and burning is used to increase forage production. However, there are very few reports in the literature on the effect of controlled burning on soil phosphorus fraction content. The aim of this work was to analyze the effect of burn temperatures on organic and inorganic phosphorus fractions of a sandy loam and a loam soil. Superficial soil samples (0-5 cm) without plant cover were air dried and heated at 100, 200, 300, 400, 500 and 600 ºC, and a non-heated sample was left as control. In every sample, the P content was determined by a sequential extraction procedure using the following extractants: sodium bicarbonate (Pi-HCO3), sodium hydroxide (Pi-NaOH and Po-NaOH) clorhidric acid (Pi-HCl) and sulfuric acid (P-H2SO4). In general, the effect of burn temperature on the analyzed fraction&#8217;s content was similar in both soils. In general, heating at 300 ºC or higher temperatures increased Pi-HCO3 and Pi-NaOH content and decreased P-H2SO4 and Po-NaOH content, possibly due to organic matter decomposition at these temperatures and the consequent increase in available inorganic phosphorus. When soils were heated at 300ºC, increases in Pi-HCl content were registered in the sandy loam soil, whereas this fraction decreased in loam soil. Heating both soils at 600 ºC caused an increase in Pi-HCl related to higher pH values, indicating a decrease in Ca-phosphates. Burns involving soil temperatures no higher than 300 ºC do not produce changes in phosphorus fraction content. Heating at 300ºC produced a net decrease in P only in the loam soil, possibly due to the volatilization of organic materials

Organic matter in size fractions of soils of the semiarid Argentina. Effects of climate, soil texture and management

Soil organic matter contents (SOM) of soils of the Semiarid Pampas of Argentina (SAP), mostly Entic Haplustolls, increase with the amount of silt+clay, but it is still not known how soil texture affects its qualitative composition in interaction with climatic and management conditions. Because of that the organic matter content of the following aggregate size fractions were determined: <2000 μm (SOM), 100-2000 μm (YOM), <100 μm (HOM), water floatable organic matter (FOM), and the E4/E6 quotient. These fractions were studied in the 20-cm topsoils of seven REFERENCE (virgin Caldenal savanna-like soils), and 10 CULTIVATED soils (under continuous conventional tillage since more than 50 years). Results showed that SOM of both REFERENCE and CULTIVATED soils was mainly composed by YOM (57%), and to a lesser extent by HOM (37%) and FOM (5%). Silt+clay conditioned positively the contents of SOM, YOM and HOM of both REFERENCE (R2=0.18, R2=0.21, R 2=0.21, respectively, n=21, p<0.05) and CULTIVATED soils (R 2=0.62, R2=0.44, R2=0.52, respectively, n=30, p<0.001). The positive relationship existing between silt+clay and both SOM and YOM seems to be not longer valid in sites with mean annual temperatures (MAT) higher than 17°C. YOM and HOM accumulation were positively affected by precipitation and negatively by temperature in combination with silt+clay. This effect was more pronounced for HOM. The slopes of the regressions between SOM, HOM and YOM with silt+clay were more pronounced for REFERENCE soils than for CULTIVATED soils, indicating the largest absolute losses of these organic matter fractions in fine- rather than in coarse-textured soils. E4/E6 quotients were lower than 5 in all studied soils indicating that humic rather than fulvic acids exist in the well humified organic fraction of the studied soils. Contents of FOM and E4/E6 values did not correlated with the climatic conditions nor with soil texture or management. Potential SOM losses can be larger in fine-textured soils (up to 54.3 Mg C ha-1) than in coarse-textured (up to 35.7 Mg C ha-1). Probable changes of soil texture by wind erosion will modify absolute contents of SOM, YOM and HOM, while modifications of temperature or rains regimes will affect HOM more.Fil: Hevia, Graciela Gloria. Universidad Nacional de La Pampa. Facultad de Agronomía; ArgentinaFil: Buschiazzo, Daniel Eduardo. Instituto Nacional de Tecnología Agropecuaria. Centro Regional La Pampa-San Luis. Estación Experimental Agropecuaria Anguil; Argentina. 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; ArgentinaFil: Hepper, Estela Noemí. Universidad Nacional de La Pampa. Facultad de Agronomía; ArgentinaFil: Ana María, Urioste. Universidad Nacional de La Pampa. Facultad de Agronomía; ArgentinaFil: Antón, E. L.. Universidad Nacional de La Pampa. Facultad de Agronomía; Argentin

Cultivation effects on the distribution of organic carbon, total nitrogen and phosphorus in soils of the semiarid region of Argentinian Pampas

Cultivation of native land can reduce the quality of soil by decreasing topsoil contents of organic carbon, total nitrogen, and phosphorus in the semiarid Pampas of Argentina. The objective of this study was to analyze the changes produced by cultivation on organic carbon (OC), total nitrogen (TN) and phosphate (inorganic and organic fractions) in two aggregate sizes of three different semiarid soils of Argentina as a function of soil depth. The study was carried out on three soils (loamy Hapludoll, loamy Haplustoll and sandy loam Haplustoll), with two uses compared at each site. Generally, the Caldenal savanna-like ecosystem (native soil) and a cultivated counterpart with annual crops for more than 60 years (cultivated soil) were compared. Results showed that all soils had similar distribution patterns with depth of OC, TN, total inorganic phosphorus (Pi), organic phosphorus (Po) and available phosphorus (Pa) in the 100-2000 μm and < 100 μm aggregates of both the native and cultivated soils. Contents of OC, TN and Pi in the whole soil (< 2000 μm) decreased sharply with depth in native soils (OC: 50%, TN: 45% and Pi: 23%), but they had a more homogeneous distribution in cultivated soils. These tendencies were attributed to the stratification occurring in non-disturbed native soils and the mixing of the upper 20 cm in cultivated soils. Cultivation produced losses of OC (73%) and Po (64%) from the 100-2000 μm aggregates at both depths in the sandy loam Haplustoll, while it produced losses of TN (52%) and Pi (42%) from the < 100 μm aggregates in the upper 10 cm of the loamy Hapludoll. OC and Po losses of the sandy loam Haplustoll were probably produced by the mineralization of organic compounds, whereas TN and Pi losses of the loamy Hapludoll were produced by wind erosion and plant uptake. Larger relative decreases of OC and Po than TN in coarse aggregates (100-2000 μm) and Pi in fine aggregates (< 100 μm) with cultivation indicate that coarse aggregates are less stable than fine aggregates (< 100 μm), and therefore more sensitive to changes in soil quality due to changes in land use. We concluded that management practices that tend to improve the formation of large aggregates as no-till or permanent pastures should be used in coarse textured Haplustolls in order to prevent large OC and Po losses. Management practices that include soil plowing will produce a breakdown of coarse aggregates and will moderately decrease OC, Po, TN, Pa and Pi contents in loamy Haplustolls and Hapludolls. Nevertheless, the destruction of coarse aggregates will increase the risk of losses of these elements by wind erosion.Fil: Ana María, Urioste. Universidad Nacional de La Pampa. Facultad de Agronomía; ArgentinaFil: Hevia, Graciela Gloria. Universidad Nacional de La Pampa. Facultad de Agronomía; ArgentinaFil: Hepper, Estela Noemí. Universidad Nacional de La Pampa. Facultad de Agronomía; ArgentinaFil: Anton, L. E.. Universidad Nacional de La Pampa. Facultad de Agronomía; ArgentinaFil: Bono, A. A.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional La Pampa-San Luis. Estación Experimental Agropecuaria Anguil; ArgentinaFil: Buschiazzo, Daniel Eduardo. Instituto Nacional de Tecnología Agropecuaria. Centro Regional La Pampa-San Luis. Estación Experimental Agropecuaria Anguil; Argentina. 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

Organic C, N and P in size fractions of virgin and cultivated soils of the semi-arid pampa of Argentina

Nutrient and organic carbon (OC) losses are important components of the soil degradation processes produced by continuous agriculture. It was hypothesized that coarse textured soils will be more affected by cultivation than tine textured ones. The purpose of this study was to evaluate the status of OC, total nitrogen (Nt), and three phosphorous fractions (total inorganic, Pi; organic, Po; and available, Pa) in different textured virgin (under Prosopis caldenia forest) and cultivated soils of the semi-arid pampa of Argentina. Three virgin and non-fertilized cultivated soil pairs, representative from soils of the region, were selected for this study: two tine sandy loam Entic Haplustolls and a sandy Typic Ustipsamment. The element content of each soil was analysed from the < 0.1-mm to 0.1-2-mm sized aggregates. Results indicated that cultivation decreased the OC, Po and Pi contents in tine aggregates of the tine textured soils, and in coarse aggregates of the coarse textured soil. Plant absorption and wind erosion were probably the main processes which decreased element contents in both textural soil types. It was speculated that in the sandy soil the elements lost from tine sized aggregates were restored by the break down of the weak coarse aggregates produced by tillage. The C/N ratios showed mostly small changes due to cultivation, indicating that no changes of organic matter quality occurred. Only the sandy soil showed C/N increases in the tine sized aggregates and decreases in the coarse sized aggregates. The C/Po quotients were not changed by cultivation, indicating that the qualitative composition of P organic compounds remained unchanged. Large OC decreases and Pa increases after cultivation detected in one of the tine textured soil were apparently linked to the occurrence of natural fires. © 2001 Academic Press.Fil: Buschiazzo, Daniel Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional La Pampa-San Luis. Estación Experimental Agropecuaria Anguil; ArgentinaFil: Hevia, Graciela Gloria. Universidad Nacional de La Pampa. Facultad de Agronomía; ArgentinaFil: Hepper, Estela Noemí. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Pampa. Facultad de Agronomía; ArgentinaFil: Ana María, Urioste. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Pampa. Facultad de Agronomía; ArgentinaFil: Bono, Alfredo A.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional La Pampa-San Luis. Estación Experimental Agropecuaria Anguil; ArgentinaFil: Babinec, Francisco José. Instituto Nacional de Tecnología Agropecuaria. Centro Regional La Pampa-San Luis. Estación Experimental Agropecuaria Anguil; Argentin

Decoupling of soil nutrients cycles as a function of aridity in global drylands

The biogeochemical cycles of carbon (C), nitrogen (N) and phosphorus (P) are interlinked by primary production, respiration and decomposition in terrestrial ecosystems. It has been suggested that the C, N and P cycles could become uncoupled under rapid climate change because of the different degrees of control exerted on the supply of these elements by biological and geochemical processes. Climatic controls on biogeochemical cycles are particularly relevant in arid, semi-arid and dry sub-humid ecosystems (drylands) because their biological activity is mainly driven by water availability. The increase in aridity predicted for the twenty-first century in many drylands worldwide may therefore threaten the balance between these cycles, differentially affecting the availability of essential nutrients. Here we evaluate how aridity affects the balance between C, N and P in soils collected from 224 dryland sites from all continents except Antarctica. Wefind a negative effect of aridity on the concentration of soil organic C and total N, but a positive effect on the concentration of inorganic P. Aridity is negatively related to plant cover, which may favour the dominance of physical processes such as rock weathering, a major source of P to ecosystems, over biological processes that provide more C and N, such as litter decomposition1. Our findings suggest that any predicted increase in aridity with climate change will probably reduce the concentrations of N and C in global drylands, but increase that of P. These changes would uncouple the C, N and P cycles in drylands and could negatively affect the provision of key services provided by these ecosystems.Fil: Delgado Baquerizo, Manuel. Universidad Pablo de Olavide; España. Universidad Rey Juan Carlos. Departamento de Biología y Geología. Área de Biodiversidad y Conservación; EspañaFil: Maestre, Fernando T.. Universidad Pablo de Olavide; España. Universidad Rey Juan Carlos. Departamento de Biología y Geología. Área de Biodiversidad y Conservación; EspañaFil: Gallardo, Antonio. Universidad Pablo de Olavide; EspañaFil: Bowker, Matthew A.. No especifíca;Fil: Wallenstein, Matthew D.. Northern Arizona University; Estados UnidosFil: Bran, Donaldo Eduardo. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche; Argentina. Universidad Rey Juan Carlos. Departamento de Biología y Geología. Área de Biodiversidad y Conservación; EspañaFil: Gatica, Mario Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales; ArgentinaFil: Hepper, Estela Noemí. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Pampa. Facultad de Agronomía; ArgentinaFil: Prina, Anibal Oscar. Universidad Nacional de La Pampa. Facultad de Agronomía; ArgentinaFil: Pucheta, Eduardo Raúl. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales; ArgentinaFil: Huber Sannwald, Elisabeth. Instituto Potosino de Investigación Científica y Tecnológica; MéxicoFil: Jankju, Mohammad. Ferdowsi University of Mashhad; IránFil: Liu, Jushan. Northeast Normal University. Institute of Grassland Science,; ChinaFil: Mau, Rebecca L.. Northern Arizona University; Estados UnidosFil: Miriti, Maria. Ohio State University; Estados UnidosFil: Monerris, Jorge. Université du Québec a Montreal; CanadáFil: Naseri, Kamal. Ferdowsi University of Mashhad; IránFil: Noumi, Zouhaier. Université de Sfax; TúnezFil: Polo, Vicente. Universidad Rey Juan Carlos. Departamento de Biología y Geología. Área de Biodiversidad y Conservación; EspañaFil: Ramírez Collantes, David A.. International Potato Center; PerúFil: Romão, Roberto. Universidade Estadual de Feira de Santana. Departamento de Ciencias Biológica, Herbario; BrasilFil: Tighe, Matthew. University of New England; AustraliaFil: Torres, Duilio. Universidad Centroccidental ‘‘Lisandro Alvarado’’; VenezuelaFil: Torres Díaz, Cristian. Universidad del Bio Bio. Facultad de Ciencias. Departamento de Ciencias Básicas. Laboratorio de Genómica y Biodiversidad; ChileFil: Ungar, Eugene D.. The Volcani Center. Agricultural Research Organization. Institute of Plant Sciences; IsraelFil: Val, James. Office of Environment and Heritage; AustraliaFil: Wamiti, Wanyoike. National Museums of Kenya. Zoology Department; KeniaFil: Wang, Deli. Northeast Normal University. Institute of Grassland Science; ChinaFil: Zaady, Eli. Gilat Research Center; Israe