Long-term impact of no tillage in two intensified crop rotations on different soil organic matter fractions in Argentine Rolling Pampa

It is expected that the agricultural intensification occurred in recent decades in the Argentine Rolling Pampa significantly alters the SOM reserves. Therefore, it is necessary to identify soil organic carbon (C) and nitrogen (N) fractions to understand the functionality and stabilization of these reserves. Our objectives were to study the NT effect in two crop rotations, corn-double cropped wheat/soybean (MWS) and double cropped wheat/soybean (WS) on: 1) SOM and its particle size and biological fractions contents, 2) C and N stubble biomass and 3) some soil properties in order to explain the SOM differences found. The larger biomass residue remaining on the soil surface under NT promoted higher aggregate stability and lower soil temperature and pH. At 0-5 cm soil depth, NT exhibited higher C and N contents, for both uncomplexed and intimately associated to the mineral components fractions. However, the results indicated variations in the SOM protection according to the rotation: in MWS the high aggregate stability showed better physical protection, while in WS the greater cation exchange capacity and the lower value of N released by anaerobic incubation would indicate the presence of transformed SOM. At 5-20 cm soil depth, only in WS, C microbial biomass was higher with a low metabolic rate, indicating again the presence of highly decomposed SOM. The results obtained in WS under NT would indicate the possibility of achieving slower recycled of the SOM.Fil: Irizar, Alicia Beatriz. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Pergamino; ArgentinaFil: Andriulo, Adrian Enrique. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Pergamino; ArgentinaFil: Mary, Bruno. Institut National de la Recherche Agronomique; Franci

Mudanças na matéria orgânica edafica sob diferentes manejos de solo na província de misiones (Argentina)

Os solos altamente intemperizados dos trópicos perdem rapidamente matéria orgânica do solo (SOM) e podem ser afetados pela erosão hídrica e compactação depois de seu deflorestamento e agricultura contínua. O objetivo foi determinar a dinâmica da matéria orgânica do solo com capim-elefante (Pennisetum purpureum L.) em um Kandihumult da província de Misiones (Argentina) após desmatamento e cultivo contínuo de erva-mate (Ilex paraguaiensis Saint Hil.), utilizando a metodologia da abundância natural em carbono 13 (13C) e um modelo descritivo. O estudo foi conduzido em três parcelas contíguas de 50 x 100 m. As situações comparadas foram: (a) floresta nativa, e (b) local com 50 anos de monocultivo intensivo de erva- mate, e (c) erva-mate associada com capim-elefante como cultivo de cobertura sob plantio direto. Determinaram-se os conteúdos de carbono (C), de nitrogênio (N) e de 13C e a densidade aparente do solo (camadas 0 - 0,05 e 0.05 - 0,15 m) e a biomassa da gramínea. Depois de 50 anos de monocultivo de erva-mate, os conteúdos de C e N e a porosidade da camada 0 - 0,15 m da floresta nativa diminuíram em 42, 47 e 23%, respectivamente. Depois de 10 anos de associação erva-mate - capim-elefante, os conteúdos de C e N do solo e na mesma profundidade aumentaram em relação ao monocultivo de erva-mate em 19 e 12%, respectivamente, mas a porosidade não foi modificada. O aporte de C, o 13C e o C orgânico total do solo foram incorporados em um modelo de três compartimentos para avaliar a dinâmica do C proveniente do capim-elefante. A metodologia da abundância natural em 13C permitiu traçar a incorporação do C proveniente do capim-elefante e a perda do C "velho" no solo, e determinar sem ambigüidade os parâmetros do modelo: coeficiente de humificação (k1), coeficiente de mineralização da fração ativa de C (k) e o C estável (Cs). Os altos valores de k1 e k preditos pelo modelo foram atribuídos à alta contribuição do sistema radicular do capim-elefante sob plantio direto e ao clima subtropical úmido, respectivamente. No solo sob monocultivo de erva-mate, Cs representou 91% do C orgânico total do solo.Highly weathered tropical soils rapidly loose soil organic matter (SOM) and may be affected by water erosion and soil compaction after deforestation and intensive cultivation. With the main objective to estimate the SOM balances in a subtropical soil we determined the dynamics of SOM in a degraded yerba mate (Ilex paraguaiensis Saint Hil.) plantation introduced after deforestation and with elephant grass (Pennisetum purpureum L.) as a cover crop. The study site was in Misiones, Argentina, and we use the natural 13C abundance methodology and a descriptive model. The study was conducted on three contiguous 50 x 100 m plots of a typic Kandihumult soil with: (i) native forest, (ii) 50 years of continuous yerba mate monoculture with intensive tillage, and (iii) yerba mate associated with elephant grass as a cover crop and no tillage. We determined bulk density, carbon (C), nitrogen (N) and 13C content of the soil (0 - 0.05, 0.05 - 0.15 m layers) and the grass biomass. Yerba mate monoculture reduced soil C and N content as well as porosity at 0 - 0.15 m depth by 43 and 23%, respectively, as compared to the native forest. After ten years of yerba mate - elephant grass association soil C and N contents at the same depth increased by 19 and 12%, respectively, compared to the yerba mate monoculture, while soil porosity remained similar. Total C input,13C, and soil organic C were incorporated into a three compartment model to evaluate elephant grass C dynamics. Through the natural 13C abundance methodology we tracked the elephant grass C incorporation and the "old" soil C loss, and determined the model parameters - humification (k1) and mineralization (k) coefficients and stable C (Cs)- unambiguously. The high k1 and k predicted by the model are probably explained by elephant grass root system incorporation under no tillage and humid subtropical climate, respectively. In soil under yerba mate monoculture, Cs was counted as 91% of the total soil organic C

Phosphorus and nitrogen fractions during base flow conditions of a Pampean stream and their relationship with land use

During the last decades, population growth and the associated intensification of anthropogenic activities (agriculture, industrialization and urbanization) increased nutrient inputs to Pampean lotic waterbodies. However, few studies evaluated the influence of these changes on water quality. The objectives of this study were to determine nitrogen (N) and phosphorus (P) fractions, trophic status and nutrient limitation of a typical Pampean stream, and to compare nutrient contents and speciation with different land uses (urban/industrial versus agricultural). Stream water samples were obtained monthly between 2010 and 2012 from six locations along the Pergamino stream. The stream was highly productive (eutrophic/hypertrophic) and nutrient concentrations were greater than the environmental quality standards from different parts of the world as a result of point and diffuse source inputs in addition to the naturally high baseline nutrient concentrations. In the case of N, organic and particulate fractions predominated in sites surrounded by agriculture, while inorganic forms predominated in sites dominated by urban/industrial effluent discharges. Nutrients spatial variation along the Pergamino stream presented the lowest concentrations in the headwaters, the highest concentrations when crossing the city of Pergamino and intermediate values towards the mouth. In this basin, despite being located in the most important agricultural region of Argentina, urban and industrial point source discharges resulted in greater impairment of water quality than diffuse sources linked to agriculture. Between the city of Pergamino and the stream mouth, total N and P concentrations decreased by 50% as a result of dilution due to increased flow and other natural self-cleansing mechanisms. It is imperative to design a monitoring programme and to adopt management strategies designed to reduce nutrient input to avoid saturating the stream’s capacity to retain and process nutrient inputs.Durante las últimas décadas, la intensificación de las actividades antrópicas (agricultura, industrialización, urbanización) aumentó el ingreso de nutrientes a los sistemas lóticos pampeanos. Sin embargo, pocos estudios evaluaron cómo estos cambios afectaron la calidad del agua. Los objetivos de este estudio fueron determinar las fracciones de nitrógeno (N) y fósforo (P), el estado trófico y el nutriente limitante en un arroyo pampeano típico, y relacionar el contenido de nutrientes y su especiación con los diferentes usos del suelo (urbano/industrial versus agropecuario). Se colectaron muestras de agua del arroyo Pergamino mensualmente entre 2010 y 2012, en seis sitios a lo largo del curso. El arroyo resultó muy productivo (eutrófico/hipereutrófico) y la concentración de nutrientes fue superior a los estándares mundiales de calidad ambiental como resultado del aporte de fuentes puntuales y difusas sumado a concentraciones de base naturalmente elevadas. En el caso del N, las fracciones orgánicas y particuladas predominaron en los sitios con agricultura, mientras que las inorgánicas predominaron en los sitios con aportes urbano/industriales. En cuanto a la variación espacial, la concentración de nutrientes fue mínima en los sitios cercanos a la naciente, máxima luego de atravesar la ciudad de Pergamino e intermedia hacia la desembocadura. En esta cuenca, a pesar de encontrarse en la región productiva más importante de la Argentina, los aportes puntuales urbanos e industriales causaron mayor deterioro de la calidad del agua que los aportes difusos provenientes de las actividades agropecuarias. Desde su paso por la ciudad hasta la desembocadura, las concentraciones de N y P disminuyeron 50% como consecuencia de la dilución por aumento del caudal y de otros mecanismos naturales de autodepuración. Es imperativo el diseño de un programa de monitoreo y la adopción de estrategias de gestión orientadas a reducir los aportes de nutrientes para evitar superar la capacidad autodepuradora del sistema.EEA PergaminoFil: Torti, María Juliana. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Pergamino. Laboratorio de Calidad de Alimentos, Suelos y Agua; ArgentinaFil: Portela, Silvina Isabel. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Pergamino. Laboratorio de Suelos; ArgentinaFil: Andriulo, Adrián. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Pergamino. Departamento de Laboratorio de Suelo; Argentin

Estudio de caso sobre concepciones de evaluación por parte de profesores argentinos en matemáticas

Numerosos autores consideran que las creencias son elementos clave que influyen en la práctica educativa. Este artículo da cuenta de una investigación de campo referida a la exploración de creencias relativas a evaluación por parte de profesores en Matemática de nivel secundario de una ciudad bonaerense (Argentina). Se realiza un análisis estadístico de ponderación de respuestas a un cuestionario estructurado. Finalmente se caracterizan cinco grupos de creencias en función al nivel de consenso identificado

Developing a performance indicators lean-sigma framework for measuring aviation system’s safety performance

The paper introduces a conceptual framework that could improve aviation safety performance and the safety performance measurement process. The framework provides guidance on how organisations could design, implement and use a proactive, performance-based measurement tool for assessing and measuring Acceptable Levels of Safety (ALoS) performance at sigma (σ) level, a statistical measurement unit. Nevertheless, the framework provides a holistic view on how organisations could set leading performance indicators and monitor metrics on the top of identified root-causes that affect system's safety performance or how to set lagging indicators and feedback metrics on the top of safety outcomes. In fact, the framework adapts and combines classical Quality Management tools, a leading indicators programme and Lean-Six Sigma methodology to formally and continuously improve a stable and in-control safety management process. Finally, the paper underlines the necessity of a new way of thinking for the development of a robust, proactive process for measuring aviation safety performance and system performance variability

Avances en el desarrollo de una herramienta de soporte a la toma de decisiones : Índices de riesgo de contaminación por nutrientes (IRCONyP)

En la actualidad, el gran desafío para el sector agropecuario es incrementar la productividad y la competitividad, de una manera ecológicamente sustentable. La contaminación por nutrientes desde la actividad agrícola es de tipo difusa y por ello muy difícil de medir en forma directa. El impacto sobre las fuentes de agua, superficial o subterránea, puede ser estimado por diversos métodos, entre los que se encuentra el cálculo de índices. Se presenta aquí una herramienta electrónica, de apoyo a la toma de decisiones, basada en la valoración del riesgo de contaminación a través de índices. Está dirigida a los asesores técnicos, planificadores e investigadores, que deban evaluar sus sistemas productivos e implementar buenas prácticas en el manejo de la nutrición nitrogenada y fosfatada para minimizar los impactos al ambiente. Esta herramienta valoriza la vulnerabilidad de acuíferos y del agua superficial en relación a las cargas contaminantes de nitrógeno y fósforo, basada en factores geológicos, climáticos, edáficos, topográficos y de manejo de cultivos. Por combinación lineal de todos estos factores se obtienen los índices de riesgo de contaminación por Nitrógeno (IRCON) y por Fósforo (IRCOP). Cuando el valor de los índices resulte moderado a alto, se dan las recomendaciones de buenas prácticas para el caso analizado.Today, the challenge of agriculture is to increase productivity and competitiveness in an ecologically sustainable manner. Nutrient pollution of agricultural activity is diffuse and difficult to measure directly. The impact on surface or groundwater can be measured by various methods, such as the index calculation. An electronic tool based on the assessment of the contamination risk through an index is presented here. This tool is intended to be used for decision making by technical advisers, planners and researchers who must assess the risk of their production systems and implement good practices in Nitrogen and Phosphorus management. This tool takes into account the vulnerability of aquifers and surface water in relation to the Nitrogen and Phosphorus pollution loads based on geology of sediments, climate, soil, topography and crop management. The Nitrogen (IRCON) and Phosphorus (IRCOP) pollution risk indexes are obtained by linear combination of these factors. When the value of the index is moderate to high good practices are recommended.Sociedad Argentina de Informática e Investigación Operativ

La materia orgánica como indicador base de calidad del suelo

El incremento de gases de efecto invernadero (GEI) en la atmósfera, y el consecuente cambio climático tendrán efectos importantes (positivos y/o negativos) en el siglo XXI. Si se pretende reducir las emisiones de dichos gases e incrementar su captura en los suelos y en la vegetación, se deberá tomar un cierto número de medidas tecnológicas que estén acompañadas por el desarrollo de nuevas estrategias y políticas apropiadas para el manejo de la agricultura y los bosques.EEA PergaminoFil: Andriulo, Adrián Enrique. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Pergamino. Departamento Laboratorio de Suelo; Argentina.Fil: Irizar, Alicia Beatríz. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Pergamino. Departamento Laboratorio de Suelo; Argentina

Ecorregión Pampeana Norte de Buenos Aires : Sistema productivo

En la Ecorregión Pampeana, en el norte de la provincia de Buenos Aires, el sistema de producción predominante es agricultura continua bajo siembra directa (SD) con especies de ciclo primavero-estival, fundamentalmente soja y secundariamente maíz (ocupando aproximadamente 70% y 15% de la superficie agrícola, respectivamente). El 80% del cultivo de soja, el 61% del cultivo de trigo y el 72% del cultivo de maíz se hacen bajo SD en esta región (SAGPyA, 2006).EEA PergaminoFil: Irizar, Alicia Beatríz. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Pergamino. Departamento Laboratorio de Suelo; Argentina.Fil: Andriulo, Adrián Enrique. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Pergamino. Departamento Laboratorio de Suelo; Argentina