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Fracciones de carbono y nitrógeno orgánicos y nitrógeno anaeróbico bajo agricultura continua con dos sistemas de labranza
Diovisalvi,Natalia Verónica; Studdert,Guillermo Alberto; Domínguez,Germán Franco; Eiza,Maximiliano Joaquín;
Ciencia del suelo , 2008,
Abstract: the organic carbon (co) is a key component that determines many soil properties, and it is composed of labile (particulate co, cop) and less labile fractions. particulate co is an early indicator of changes in co due to management practices. on the other hand, anaerobic n (nan) is an indicator of the soil capacity to mineralize n. the objective of this study was to evaluate the effect of no-tillage (sd), conventional tillage (lc) and n fertilization on total co (cot), cop, total organic n (not), particulate organic n (nop), and of nan contents, and on their relationship with corn yield. soil samples (0-5 and 5-20 cm-depths) were taken from two areas of a long term experiment started in 1997 on a mollisol in balcarce. there was greater concentration of cop, nop, cot and not under sd compared to lc, especially in the soil surface layer. in general, there were no differences in nan content between tillage systems. nitrogen fertilization did not affect either co and no fractions or nan contents. there were no significant relationships between the latter and corn yield or corn response to n fertilization. high co contents and c returns through crop residues in both tillage systems could have caused the lack of differences expected. the observed results and trends would indicate that significant differences between tillage systems could be manifested in the near future.
Individual biovolume of some dominant copepod species in coastal waters off Buenos Aires Province, Argentine Sea
María Delia Vi?as,Nadia Rosalía Diovisalvi,Georgina Daniela Cepeda
Brazilian Journal of Oceanography , 2010, DOI: 10.1590/s1679-87592010000200008
Abstract:
Fracciones de carbono y nitrógeno orgánicos y nitrógeno anaeróbico bajo agricultura continua con dos sistemas de labranza Effect of two tillage systems under continuous cropping on organic carbon and nitrogen fractions and on the anaerobic nitrogen indicator
Natalia Verónica Diovisalvi,Guillermo Alberto Studdert,Germán Franco Domínguez,Maximiliano Joaquín Eiza
Ciencia del Suelo , 2008,
Abstract: El carbono orgánico (CO), componente clave del cual dependen muchas de las propiedades del suelo, está compuesto por fracciones lábiles, CO particulado (COP), y menos lábiles. El COP es un indicador temprano de los cambios en el CO provocados por las prácticas de manejo. Por otro lado, el N anaeróbico (Nan) es un indicador de la capacidad del suelo de mineralizar N. El objetivo de este trabajo fue evaluar el efecto de la siembra directa (SD), de la labranza convencional (LC) y de la fertilización nitrogenada sobre los contenidos de CO total (COT), COP, N orgánico (NO) total (NOT), NO particulado (NOP) y Nan, y su relación con el rendimiento de maíz. Se analizaron muestras de suelo (0-5 y 5-20 cm) de dos sectores de un ensayo iniciado en 1997 sobre Molisoles de Balcarce. Bajo SD hubo mayor concentración de COP, NOP, COT y NOT que bajo LC, principalmente en los primeros centímetros del suelo. En general, no hubo diferencias en el Nan entre sistemas de labranza. La fertilización no afectó los contenidos de las fracciones de CO y NO ni el de Nan. Tampoco se observaron relaciones significativas entre ellos y los rendimientos y la respuesta del maíz a la fertilización. Los elevados contenidos de CO y los altos aportes de C por los residuos pudieron haber sido las causas de que no se manifestaran las diferencias esperadas. Los resultados y tendencias observadas estarían indicando que en el futuro, aquéllas podrían manifestarse. The organic carbon (CO) is a key component that determines many soil properties, and it is composed of labile (particulate CO, COP) and less labile fractions. Particulate CO is an early indicator of changes in CO due to management practices. On the other hand, anaerobic N (Nan) is an indicator of the soil capacity to mineralize N. The objective of this study was to evaluate the effect of no-tillage (SD), conventional tillage (LC) and N fertilization on total CO (COT), COP, total organic N (NOT), particulate organic N (NOP), and of Nan contents, and on their relationship with corn yield. Soil samples (0-5 and 5-20 cm-depths) were taken from two areas of a long term experiment started in 1997 on a Mollisol in Balcarce. There was greater concentration of COP, NOP, COT and NOT under SD compared to LC, especially in the soil surface layer. In general, there were no differences in Nan content between tillage systems. Nitrogen fertilization did not affect either CO and NO fractions or Nan contents. There were no significant relationships between the latter and corn yield or corn response to N fertilization. High CO contents and C returns throu
Chascomús: estructura y funcionamiento de una laguna pampeana turbia
Diovisalvi,Nadia; Berasain,Gustavo; Unrein,Fernando; Colautti,Darío; Fermani,Paulina; Llames,María E; Torremorell,Ana M; Lagomarsino,Leonardo; Pérez,Gonzalo; Escaray,Roberto; Bustingorry,José; Ferraro,Marcela; Zagarese,Horacio E;
Ecolog?-a austral , 2010,
Abstract: laguna chascomús is an eutrophic, turbid, shallow lake typical of the pampa region of argentina. this shallow lake is permanently mixed and displays a high degree of spatial homogeneity. the cyclical periods of excess and shortage of rain, characteristic of this area, result in periodic drying and flooding events. according to newspaper articles published during the first half of the xx century, the lake was originally turbid. the first patches of rooted vegetation appeared after the 1913 y 1914 floods. during most part of the xx century the lake remained in a "clear", vegetated state. during this period the dominant fish species was the silverside (pejerrey), odontesthes bonariensis, which accounted for over 60% of the total fish catches (in biomass). instead, by the end of the latest century the lake shifted to a turbid state that persisted until present. currently, the phytoplankton primary production is limited by light and its values are among the highest ones reported for natural aquatic systems. in light limited systems, the transparency may be expected to be controlled by the amount of incident light, through a negative feedback loop with primary production. these predictions have been confirmed, both in mesocosm experiments and "in situ". the phytoplankton biomass, dominated by nanoplanktonic cyanobacteria accounts for 75% of the total amount of carbon in the water column. the equilibrium predicted by the light limitation theory could not hold if the model assumptions were violated. this situation could happen if the phytoplankton biomass were controlled by herbivore zooplankton. however, such a control of primary producer by herbivores seems to be precluded due to the absence of large-sized zooplankton grazers, presumably due to the composition of the fish assemblage. in contrast to earlier reports of the 1960, the proportion of pejerrey biomass is presently quite low (0.04%) and the community is dominated by omnivore microphagous, such as the sabalito (cy
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