Evapotranspiración y balance energético de un cultivo de soja en la región semiárida de Buenos Aires (Argentina)

Cargnel, M. D. Universidad de Buenos Aires. Facultad de Agronomía. Buenos Aires, Argentina.Orchansky, A. L. Universidad Nacional del Sur. Departamento de Agronomía. Bahía Blanca, Buenos Aires, Argentina.Brevedan, R. E. Universidad Nacional del Sur. Departamento de Agronomía. Bahía Blanca, Buenos Aires, Argentina.Baioni, S. S. Universidad Nacional del Sur. Departamento de Agronomía. Bahía Blanca, Buenos Aires´, Argentina.Fioretti, M. N. Universidad Nacional del Sur. Departamento de Agronomía. Bahía Blanca, Buenos Aires, Argentina.181-189Two field experiments were carried out in a semiarid region of Argentina over a soybean (Glycine max L. Merrill) field. The sites of study were San Adolfo (39˚ 23’ S, 62˚ 22’ W, 22 m.a.s.l.) and Nueva Roma (38˚ 29’ S, 62˚ 39’ W, 70 m.a.s.l.). Soybeans were planted on Jan 4 (San Adolfo) and Nov 27 (Nueva Roma) in 0.75 m wide rows and at 400000 pl/ha during two consecutive growing seasons. Energy balance and evapotranspiration (ET) were estimated during the reproductive stages from full bloom (R2) to full maturity (R8). In Nueva Roma ET or latent heat flux (LE) was estimated using the Bowen ratio-energy balance (BREB) (LEb) and the Priestley -Taylor equation (LEPT) with αPT=1.26, 48 h after irrigation or rain. Both methods could be used to predict ET since the ratio LEb/LEPT ranged between 0.83 and 0.95. The observed Bowen ratio values were almost 0 during and after rain and increased to approximately 0.45 several days after rain. In San Adolfo LE was estimating using the Priestley -Taylor equation. For both sites the regression analysis for comparison available energy (Rn-G) and LE using BREB or LEPT indicated that, approximately 90% of the available energy was consumed by LE without detecting significative advective conditions

Evapotranspiración y balance energético de un cultivo de soja en la región semiárida de Buenos Aires (Argentina)

Cargnel, M. D. Universidad de Buenos Aires. Facultad de Agronomía. Buenos Aires, Argentina.Orchansky, A. L. Universidad Nacional del Sur. Departamento de Agronomía. Bahía Blanca, Buenos Aires, Argentina.Brevedan, R. E. Universidad Nacional del Sur. Departamento de Agronomía. Bahía Blanca, Buenos Aires, Argentina.Baioni, S. S. Universidad Nacional del Sur. Departamento de Agronomía. Bahía Blanca, Buenos Aires´, Argentina.Fioretti, M. N. Universidad Nacional del Sur. Departamento de Agronomía. Bahía Blanca, Buenos Aires, Argentina.181-189Two field experiments were carried out in a semiarid region of Argentina over a soybean (Glycine max L. Merrill) field. The sites of study were San Adolfo (39˚ 23’ S, 62˚ 22’ W, 22 m.a.s.l.) and Nueva Roma (38˚ 29’ S, 62˚ 39’ W, 70 m.a.s.l.). Soybeans were planted on Jan 4 (San Adolfo) and Nov 27 (Nueva Roma) in 0.75 m wide rows and at 400000 pl/ha during two consecutive growing seasons. Energy balance and evapotranspiration (ET) were estimated during the reproductive stages from full bloom (R2) to full maturity (R8). In Nueva Roma ET or latent heat flux (LE) was estimated using the Bowen ratio-energy balance (BREB) (LEb) and the Priestley -Taylor equation (LEPT) with αPT=1.26, 48 h after irrigation or rain. Both methods could be used to predict ET since the ratio LEb/LEPT ranged between 0.83 and 0.95. The observed Bowen ratio values were almost 0 during and after rain and increased to approximately 0.45 several days after rain. In San Adolfo LE was estimating using the Priestley -Taylor equation. For both sites the regression analysis for comparison available energy (Rn-G) and LE using BREB or LEPT indicated that, approximately 90% of the available energy was consumed by LE without detecting significative advective conditions

Plant growth and survival of five introduced and two native/naturalized perennial grass genotypes exposed to two defoliation managements in arid Argentina

The field performance of the native Pappophorum vaginatum, the naturalized Eragrostis curvula and various cultivars of the introduced Achnatherum hymenoides and Leymus cinereus was evaluated as potential forage resources in rangelands of arid Argentina during the warm seasons of 2007/2008 and 2008/2009. Plants of these grass species, obtained from seeds, were transplanted to the field in 2006, when they were 1 year old. During the study years, there were two defoliation managements: plants of all study genotypes either remained undefoliated (controls) or were defoliated twice a year during spring at 5 cm stubble height. Despite tiller number being lower (P 0·05) between defoliation managements by mid-spring, there were no differences (P > 0·05) in dry weight production between defoliated and undefoliated plants in all genotypes at the end of the second growing season. Plants of one or more of the introduced genotypes showed a similar (P > 0·05) or greater (P 0·05) or greater (P 70%) or naturalized (>39%) genotypes at the end of the first or second growing seasons.Facultad de Ciencias Agrarias y Forestale

La puesta en juego de la cultura física en programas socioeducativos del partido de Luján

Este escrito sintetiza algunos hallazgos de una investigación, realizada en el período 2008-2009 en el partido de Luján, que se propuso indagar algunas políticas públicas educativas, sociales y de salud en el ámbito del Estado. El objetivo general fue describir cómo son los programas y proyectos sociales, educativos y de salud implementados por el Estado (nacional, provincial y local), radicados en el Partido de Luján que incluyen contenidos de la cultura física; en tanto uno de los objetivos específicos del estudio se centró en conocer los perfiles del personal a cargo de las acciones; esto es ¿qué conocimientos y habilidades necesitan quienes intervienen en la planificación, implementación, desarrollo, conducción y evaluación de estas acciones?; ¿cómo es la formación, reconocimiento institucional y la supervisión de ese personal? y ¿qué significados otorgan a las acciones y prácticas que tienen a cargo? La presentación de este resumen en esta área y mesa de trabajo, es pertinente a la hora de compartir y/o reflexionar sobre las diferentes concepciones de ocio, tiempo libre y recreación que poseen quiénes practican la enseñanza en estos programas.Facultad de Humanidades y Ciencias de la Educació

Water stress and temperature effects on germination and early seedling growth of Digitaria eriantha

This study focused on the two major processes critical for plant establishment: Seed germination and seedling survival. We determined the effects of (1) water stress and temperature on the germination, and (2) water stress on early seedling growth of Digitaria eriantha cv ‘Irene’. Seeds harvested in 2007 were used for temperature studies, and those coming from 2006 and 2007 for water stress studies. In 2009, viability decreased by 65.4% from 2006 to 2007. During the first twenty-four hours, germination was more than 50% at constant (30 or 35°C) than alternating (10/30 or 10/35°C) temperatures, although total germination was about 80% for all temperature treatments. Polyethylene glycol 8000 was used to impose water stress conditions. Germination percentages and coefficients of velocity decreased with decreasing water potentials. Early seedling growth was smaller at lower water potentials. D. eriantha cv ‘Irene’ appeared to germinate within a wide range of temperatures, but it varied greatly in germination response to water potentials. Results suggest that this species could be planted in late spring-early summer, when seedbed temperatures are increasing and soil moisture might still be adequate.Fil: Brevedan, Roberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida(i); Argentina. Universidad Nacional del Sur. Departamento de Agronomía; ArgentinaFil: Busso, Carlos Alberto. Universidad Nacional del Sur. Departamento de Agronomía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida(i); ArgentinaFil: Fioretti, M. N.. Universidad Nacional del Sur. Departamento de Agronomía; ArgentinaFil: Toribio, M. B.. Universidad Nacional del Sur. Departamento de Agronomía; ArgentinaFil: Baioni, S. S.. Universidad Nacional del Sur. Departamento de Agronomía; ArgentinaFil: Torres, Yanina Alejandra. Universidad Nacional del Sur. Departamento de Agronomía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida(i); ArgentinaFil: Fernandez, Osvaldo Alberto. Universidad Nacional del Sur. Departamento de Agronomía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida(i); ArgentinaFil: Giorgetti, H. D.. Provincia de Buenos Aires. Ministerio de Asuntos Agrarios. Chacra Experimental de Patagones; ArgentinaFil: Bentivegna, Diego Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida(i); ArgentinaFil: Entío, J.. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales; ArgentinaFil: Ithurrart, Leticia Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida(i); Argentina. Universidad Nacional del Sur. Departamento de Agronomía; ArgentinaFil: Montenegro, O.. Provincia de Buenos Aires. Ministerio de Asuntos Agrarios. Chacra Experimental de Patagones; ArgentinaFil: Mujica, M. de las M.. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales; ArgentinaFil: Rodríguez, G.. Provincia de Buenos Aires. Ministerio de Asuntos Agrarios. Chacra Experimental de Patagones; ArgentinaFil: Tucat, Guillermo. Universidad Nacional del Sur. Departamento de Agronomía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida(i); Argentin

Root proliferation in native perennial grasses of arid Patagonia, Argentina

Pappophorum vaginatum is the most abundant C4 perennial grass desirable to livestock in rangelands of northeastern Patagonia, Argentina. We hypothesized that (1) defoliation reduce net primary productivity, and root length density and weight in the native species, and (2) root net primary productivity, and root length density and weight, are greater in P. vaginatum than in the other, less desirable, native species (i.e., Aristida spegazzinii, A. subulata and Sporobolus cryptandrus). Plants of all species were either exposed or not to a severe defoliation twice a year during two growing seasons. Root proliferation was measured using the cylinder method. Cylindrical, iron structures, wrapped up using nylon mesh, were buried diagonally from the periphery to the center on individual plants. These structures, initially filled with soil without any organic residue, were dug up from the soil on 25 April 2008, after two successive defoliations in mid-spring 2007. During the second growing season (2008–2009), cylinders were destructively harvested on 4 April 2009, after one or two defoliations in mid-and/or late-spring, respectively. Roots grown into the cylinders were obtained after washing the soil manually. Defoliation during two successive years did reduce the study variables only after plants of all species were defoliated twice, which supported the first hypothesis. The greater root net primary productivity, root length density and weight in P. vaginatum than in the other native species, in support of the second hypothesis, could help to explain its greater abundance in rangelands of Argentina.Facultad de Ciencias Agrarias y Forestale

Water stress and temperature effects on germination and early seedling growth of <i>Digitaria eriantha</i>

This study focused on the two major processes critical for plant establishment: Seed germination and seedling survival. We determined the effects of (1) water stress and temperature on the germination, and (2) water stress on early seedling growth of Digitaria eriantha cv ‘Irene’. Seeds harvested in 2007 were used for temperature studies, and those coming from 2006 and 2007 for water stress studies. In 2009, viability decreased by 65.4% from 2006 to 2007. During the first twenty-four hours, germination was more than 50% at constant (30 or 35°C) than alternating (10/30 or 10/35°C) temperatures, although total germination was about 80% for all temperature treatments. Polyethylene glycol 8000 was used to impose water stress conditions. Germination percentages and coefficients of velocity decreased with decreasing water potentials. Early seedling growth was smaller at lower water potentials. D. eriantha cv ‘Irene’ appeared to germinate within a wide range of temperatures, but it varied greatly in germination response to water potentials. Results suggest that this species could be planted in late spring-early summer, when seedbed temperatures are increasing and soil moisture might still be adequate.Facultad de Ciencias Agrarias y Forestale

Water stress and temperature effects on germination and early seedling growth of <i>Digitaria eriantha</i>

This study focused on the two major processes critical for plant establishment: Seed germination and seedling survival. We determined the effects of (1) water stress and temperature on the germination, and (2) water stress on early seedling growth of Digitaria eriantha cv ‘Irene’. Seeds harvested in 2007 were used for temperature studies, and those coming from 2006 and 2007 for water stress studies. In 2009, viability decreased by 65.4% from 2006 to 2007. During the first twenty-four hours, germination was more than 50% at constant (30 or 35°C) than alternating (10/30 or 10/35°C) temperatures, although total germination was about 80% for all temperature treatments. Polyethylene glycol 8000 was used to impose water stress conditions. Germination percentages and coefficients of velocity decreased with decreasing water potentials. Early seedling growth was smaller at lower water potentials. D. eriantha cv ‘Irene’ appeared to germinate within a wide range of temperatures, but it varied greatly in germination response to water potentials. Results suggest that this species could be planted in late spring-early summer, when seedbed temperatures are increasing and soil moisture might still be adequate.Facultad de Ciencias Agrarias y Forestale

Water stress and temperature effects on germination and early seedling growth of <i>Digitaria eriantha</i>

This study focused on the two major processes critical for plant establishment: Seed germination and seedling survival. We determined the effects of (1) water stress and temperature on the germination, and (2) water stress on early seedling growth of Digitaria eriantha cv ‘Irene’. Seeds harvested in 2007 were used for temperature studies, and those coming from 2006 and 2007 for water stress studies. In 2009, viability decreased by 65.4% from 2006 to 2007. During the first twenty-four hours, germination was more than 50% at constant (30 or 35°C) than alternating (10/30 or 10/35°C) temperatures, although total germination was about 80% for all temperature treatments. Polyethylene glycol 8000 was used to impose water stress conditions. Germination percentages and coefficients of velocity decreased with decreasing water potentials. Early seedling growth was smaller at lower water potentials. D. eriantha cv ‘Irene’ appeared to germinate within a wide range of temperatures, but it varied greatly in germination response to water potentials. Results suggest that this species could be planted in late spring-early summer, when seedbed temperatures are increasing and soil moisture might still be adequate.Facultad de Ciencias Agrarias y Forestale