Abstract:

The increasing proportion of agricultural lands worldwide makes it necessary to intensify the research concerning the carbon exchange at agricultural sites. In order to determine the Net Ecosystem Exchange (NEE) in an agricultural landscape in the province of Buenos Aires, Argentina, we carried out eddy covariance measurements with a flux tower, which was placed between two agricultural fields. Therefore, the measured CO2 flux represents the accumulated flux from both areas, i.e., from different crop types. We here present an analysis method which attributes the flux to the two crop types. For this analysis, we applied the Hsieh footprint model to identify the contributing source area to the flux measurement. We then applied a multiple regression analysis to calculate the NEE in the growing season 2011/2012 for each field separately. The pronounced differences in the time courses of the CO2 fluxes in the two fields can be explained by the different sowing times and different growth stages of both cultivations. The time courses furthermore show that the CO2 uptake of the plants was strongly affected by the drought which lasted from December 2011 to January 2012. For the growth cycle of maize (216 days), the NEE was −240 g C m−2 and for the growth cycle of soybean (154 days) −231 g C m−2. In order to obtain the NEE of a complete agricultural cycle (from harvest to harvest), we also considered the NEE of autumn and winter 2011. Uncertainties of the spatially partitioned NEE are quantified and discussed.

Instituto de Clima y Agua

Author affiliation: Posse Beaulieu, Gabriela. INTA. Instituto de Clima y Agua; Argentina

Author affiliation: Richter, Klaus. INTA. Instituto de Clima y Agua; Argentina

Author affiliation: Lewczuk, Nuria Andrea. INTA. Instituto de Clima y Agua; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Cristiano, Maria Piedad. INTA. Instituto de Clima y Agua; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Gattinoni, Natalia Noemí. INTA. Instituto de Clima y Agua; Argentina

Author affiliation: Rebella, Cesar Manuel. INTA. Instituto de Clima y Agua; Argentina

Author affiliation: Achkar, Antonio. Universidad Católica de Santa Fe. Área Informática; Argentina

Abstract:

Tesis para obtener el grado de Doctor de la Universidad de Buenos Aires, Área Ciencias Agropecuarias en agosto de 2014

La deforestación en Sudamérica afecta principalmente a tres ecosistemas: El Cerrado en Brasil, la selva de Chiquitanos en Bolivia y el Gran Chaco en Bolivia, Paraguay y Argentina, siendo en estos dos últimos países en donde ocurren las mayores transformaciones del paisaje para la producción de commodities para exportación. En la presente tesis, para la porción Noroeste del Chaco Argentino, se analizó la dinámica de cambios de los últimos 30 años; se evaluó la ocurrencia del modelo cambio de uso del suelo denominado “Transición Forestal”; se estudió la influencia de factores locales que controlan la localización de desmontes; y se cuantificó el impacto de dicha transformación sobre el nivel de provisión de servicios ecosistémicos intermedios relativos a la dinámica del C. En el periodo 1977-2007 ocurrieron cambios que alcanzaron más del 26% del área de estudio. Los desmontes para actividad agropecuaria alcanzaron un total de 4,5 millones ha, de los cuales el 53% ocurrieron en el último período (1997-07), siendo los bosques secos y los pastizales las coberturas más afectadas. De continuar con esta tendencia, ocurrirá una inversión del paisaje en un periodo comprendido entre 40 y 100 años, en donde la actividad agropecuaria comenzaría a ser dominante en el paisaje chaqueño. No están ocurriendo ninguno de los modelos de cambios de uso del suelo de compatibilización de producción-conservación discutidos en esta tesis: (a) “Transición Forestal” (Forest Transition), (b) “separaciónterritorial” (land-sparing); o (c) “integración-territorial” (land-sharing). Se propone un nuevo modelo de cambio de uso de suelo que probablemente se verifica en otras regiones del Gran Chaco Americano, al que se denominó “modelo tipo Tsunami” por sus características de avance en forma de ola, que a su paso homogeniza el paisaje bajo el punto de vista estructural y funcional.

In South America deforestation is affecting three ecosystems: “El Cerrado” in Brazil, “Chiquitanos” jungle in Bolivia, and the “Gran Chaco” in Bolivia, Paraguay and Argentina. The biggest changes in the landscape are happening in the latter two countries due to agricultural expansion for soybean production and cattle ranching. For the Northwest Argentine Chaco was analyzed a) dynamics changes in the last 30 years; b) the incidence of "Forest Transition" model; c) the influence of local factors that control land clearing’s location; and, d) the impact of deforestation on the level of Intermediate Ecosystem Services provision associated with carbon gain dynamics. In the period 1977 -2007 changes reached more than 26% of the study area. Clearings for agriculture reached 4.5 million hectares, from which 53% occurred in the last period (1997-2007). Dry forests and grasslands were the most affected land covers. If this trend continues, a landscape reversion will occur within 40 and 100 years from now, where agricultural activities will predominate in Chaco landscape. There is no evidence of occurrence of none of the compatibilizing production-conservation models discussed in this thesis: a) Forest Transition; b) Land-Sparing; or c) Land-Sharing. As a contribution, a new model of land use change called "Tsunami model" is proposed. This name represents the way that land use changes are being produced: a wave shape change which homogenizes landscape from a structural and functional point of view. Probably it is happening in other regions of American Gran Chaco.

Author affiliation: Volante, Jose Norberto. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Salta; Argentina

Abstract:

Se evaluó el efecto de los polietilenos negros y bicapa sobre el comportamiento del cultivo de alcaucil en la zona de Rosario. Se utilizó el híbrido Madrigal y se evaluaron las variables Número de capítulos por planta, Peso de primer capítulo, Peso promedio de capítulos secundarios, Rendimiento total y por planta, Diámetro de primer capítulo y promedio de secundarios y Días a cosecha. No se encontraron diferencias signifi cativas entre los tratamientos. Ninguno de los acolchados demostró adelanto en la producción. El uso de coberturas plásticas en épocas de altas temperaturas en la zona evaluada, se recomienda utilizar no con el objetivo de obtener primicias sino para facilitar el control de malezas y dado que la cobertura con plástico negro genera desventajas, en el caso de ser necesaria por alta presencia de malezas, sería recomendable la utilización de polietileno bicapa.

The effect of black and bilayer polyethylenes on the behavior of the crop in Rosario area was evaluated. Madrigal hybrid was used and the evaluated variables were: Number of buds per plant, Weight fi rst buds, Average weight Secondary buds, Total yield and per plant, Diameter fi rst buds and average of secondary and Days to harvest. There were no signifi cant differences between treatments. None of the coverages showed an advance in production. The use of plastic coverages in times of high temperatures in the evaluated area, is recommended to use not with the objective of obtaining production in advance but to facilitate the control of weeds and since the coverage with black plastic generates disadvantages, in the case of being necessary because of high presence of weeds, it would be advisable to use bilayer polyethylene.

EEA Paraná

Author affiliation: Mondino, Maria Cristina. INTA. Estación Experimental Agropecuaria Oliveros. Agencia de Extensión Rural Arroyo Seco; Argentina. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias. Cátedra de Sistemas de Cultivos Intensivos; Argentina

Author affiliation: Balaban, David. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias. Cátedra de Sistemas de Cultivos Intensivos; Argentina

Author affiliation: Cavalieri, Ornela Yoana. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias. Cátedra de Sistemas de Cultivos Intensivos; Argentina

Author affiliation: García, Stella Maris. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias. Cátedra de Sistemas de Cultivos Intensivos; Argentina

Abstract:

Native desert plants have structural adaptations that maximize photosynthesis rates and minimize water loss. They can be successfully utilized as soil cover crops in drip-irrigated vineyards where water availability is low. The objective of this paper is to study seed germination conditions and to recommend which best species is most apt as soil cover crop in drip-irrigated vineyards. Seed weight (the higher the seed weight, the greater the success of mechanical seeding) and germination tests (at 15, 20, 25, 30, and 35 °C in light and dark conditions) were carried out for six species native to Mendoza, Argentina. Germination percentage (GP) and mean time germination (MTG) were calculated. Digitaria californica (C4) had the highest GP (97% in light condition), which is recommended as a cover crop because of its seed germination potential. Pappophorum phillippianum (C4) had a 70% GP in light conditions (regardless of temperature) and a high seed weight. Leptochloa dubia (C4) and Sporobolus cryptandrus (C4) reached the highest GP at the highest temperature, although S. cryptandrus had the lowest seed weight. Nassella tenuis (C3) averaged 54% GP at 25 °C in light conditions. The GP of Setaria leucopila (C4) was not affected by temperature (26% in light, and 16% in darkness). Based on the GP results, S. leucopila was the worst choice of the six species. Hence, during seeding, soil temperature should be high (>20 °C) to ensure a rapid plant establishment of all species.

EEA Mendoza

Author affiliation: Ferrari, Florencia Noemi. INTA. Estación Experimental Agropecuaria Mendoza; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Parera, Carlos Alberto. INTA. Centro Regional Mendoza-San Juan; Argentina

Abstract:

En San Genaro (Santa Fe, Argentina), la ordenanza 18/2008 prohíbe la aplicación de agroquímicos en la zona periurbana. Los afectados por la ordenanza son en su amplia mayoría productores familiares de leche, que demandan alternativas para el manejo del gramón (Cynodon dactylon) en sus verdeos de avena. Por ello, instituciones locales convocaron a la conformación de equipos de trabajo para analizar alternativas productivas en fincas de productores. Esto condujo a iniciar un proceso de investigación acción participativa (IAP) tendiente a aportar alternativas para el manejo agroecológico de malezas en áreas periurbanas. Con el objetivo de evaluar coberturas del suelo en intercultivos para obtener una combinación de especies que ofrezca mayor capacidad para el manejo del gramón, se implantó en finca de un productor avena consociada con distintas especies. El primer año se utilizó Vicia villosa, Lollium multiflorum, Trifolium repens y Trifolium pratense y un segundo año sólo V. villosa en comparación con avena pura. A partir de registros fotográficos se procedió al cálculo de los porcentajes de cobertura de suelo, mediante el programa informático Cobcal. Los resultados indican que la consociación de especies forrajeras en verdeos de avena se presenta como una posible estrategia para el manejo de gramón. La Vicia villosa se comportó como una muy buena especie acompañante, aumentando considerablemente la cobertura del suelo durante todo el ciclo.

The periurban area of San Genaro (Santa Fe, Argentina) is affected the Ordinance 18/2008 that prohibits the use of agrochemicals. Farmers within this area, mainly milking family dairy farms, are interested and in need of alternative management strategies of their oat forage with Bermudagrass (Cynodon dactylon).. Therefore, local institutions called for the assemblage of working teams to research on-farm productive alternatives. This led to a participatory action research (PAR) process to provide agroecological Bermudagrass management strategias for periurban areas. Therefore, a consociation of oat with different species was sowed together with one of the farmers, in order to evaluate intercropping soil covers and find out a combination of species with the capacity of managing Bermudagrass. The first year, oats forage was intercropped with Vicia villosa, Lollium multiflorum, Trifolium repens and Trifolium pratense while at second year oats forage was intercropped only with V. villosa. All intercroppings were compared with pure oat forage. The percentages of soil cover, were calculated useingCobcal software, based on photographic records. Results indicate that intercropping can be a possible strategy for Bermudagrass management. Vicia villosa behaved as a very good companion species, increasing considerablyground cover during all the production cycle.

IPAF Región Pampeana

Author affiliation: Perez, Raul Alberto. INTA. Instituto De Investigación Investigación y Desarrollo Tecnológico para la Agricultura Familiar Región Pampeana; Argentina

Author affiliation: Perez, Maximiliano. INTA. Instituto de Investigación Investigación y Desarrollo Tecnológico para la Agricultura Familiar. Región Pampeana; Argentina

Author affiliation: Lavarello Herbin, Agustina. INTA. Instituto de Investigación Investigación y Desarrollo Tecnológico para la Agricultura Familiar Región Pampeana; Argentina

Author affiliation: Pagani, Violeta. Centro Educativo Agropecuario N°5, San Genaro; Argentina

Author affiliation: Mangold, Daniel. Centro Educativo Agropecuario N°5, San Genaro; Argentina

Author affiliation: Galetto, Mauricio. Centro Educativo Agropecuario N°5, San Genaro; Argentina

Abstract:

The replacement of natural vegetation by pastures and extensive crops is generally driven by economic incentives and supported by technology improvements and multiple subsidies. However, towards areas of increasing aridity the productive performance of these replacements may decline from all perspectives – ecological to agronomic to economic – due to intrinsic differences in the structural and physiological adjustment of natural and cultivated vegetation to reduced and fluctuating water availability. We compare natural woody vegetation, perennial C4 pastures and annual crops (maize, soybean and wheat) along a gradient of decreasing precipitation (900–400 mm of annual mean) encompassing the current agricultural frontier of the Dry Chaco and Western Espinal ecoregions of South America. We assess (i) aboveground net primary productivity (ANPP) (ii) yields of product dry mass, edible energy and protein outputs and, (iii) economic gross profits and return of investment. We linked climatic with yield data from national statistics, field trials and empiric models, together with productive parameters and market prices obtained from local consultants and economic bulletins. Maize achieved the highest ANPP of all vegetation covers (+ 42% in average compared to the rest) along the entire precipitation gradient, while the rest of the crops were very similar to natural vegetation. Pastures approached the ANPP of natural vegetation in the humid range, but had the lowest performance below 700 mm (− 15%). Along the entire precipitation gradient, maize was outstanding in mass and edible energy yield while soybean was so in protein production. Soybean had the highest gross profit per hectare (+ 50%) and total capital return of investment (+ 70%). Pastures offered the highest functional capital return of investment (+ 98%; without fixed capital, infrastructure and land value costs), explaining their relevance at the onset of the deforestation process and the gradual prevalence of crops afterwards. While agronomic and economic incentives for natural vegetation replacement remain strong along the whole aridity gradient, crop choice rather than land use system seem to shape the key ecological process of net primary productivity.

EEA San Luis

Author affiliation: Murray, Francisco. INTA. Estación Experimental Agropecuaria San Luis. Agencia de Extensión Rural San Luis; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Luis. Instituto de Matemática Aplicada de San Luis; Argentina

Author affiliation: Baldi, Germán. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Luis. Instituto de Matemática Aplicada de San Luis. Grupo de Estudios Ambientales; Argentina. Universidad Nacional de San Luis; Argentina

Author affiliation: Bernard, Tamara von. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Luis. Instituto de Matemática Aplicada de San Luis. Grupo de Estudios Ambientales; Argentina. Universidad Nacional de San Luis; Argentina

Author affiliation: Viglizzo, Ernesto Francisco. INTA. Centro Regional La Pampa-San Luis; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Jobbagy Gampel, Esteban Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Luis. Instituto de Matemática Aplicada de San Luis. Grupo de Estudios Ambientales; Argentina. Universidad Nacional de San Luis; Argentina