Fluxos de massa e energia para a cultura de milho (Zea mays L.) no Rio Grande do Sul

• Ano de defesa: 2011
• Autor(a) principal: Aguiar, Leonardo José Gonçalves
• Orientador(a): Costa, José Maria Nogueira da
• Banca de defesa: Lima, Francisca Zenaide de , Malhado, Ana Cláudia Mendes , Silva, Marcos Antonio Vanderlei
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Doutorado em Meteorologia Agrícola
• Departamento: Agrometeorologia; Climatologia; Micrometeorologia
• País: BR
• Palavras-chave em Português: Micrometeorologia; Milho; Rio Grande do Sul; Fluxo de energia; Fluxo de massa
• Palavras-chave em Inglês: Micrometeorology; Maize; Rio Grande do Sul State; Energy flow; Mass flow
• Área do conhecimento CNPq: CNPQ::CIENCIAS EXATAS E DA TERRA::GEOCIENCIAS::METEOROLOGIA::MICROMETEOROLOGIA
• Link de acesso: http://locus.ufv.br/handle/123456789/1503

Maize (corn) plays an important role in Brazilian agriculture and is cultivated throughout the country. A better understanding of soil-maizeatmosphere interaction may result in increased crop productivity as well as assist in developing models that better represent this nteraction. Therefore, the aim of this work is to analyze the interaction of photosynthetically active radiation (PAR) and the crop canopy, to quantify the magnitude and variation of fluxes of CO2, sensible heat (H), latent heat (LE) and soil heat (G) during the phenological stages of maize, and to assess the influence of biophysical variables relevant to the magnitude of these flows. To achieve this, we carried out continuous measurements of incident (Sin) and reflected (Sout) global solar irradiance, incident photosynthetically active radiation (PARin), incident PAR at the base of the canopy (PARinb) and reflected PAR (PARout), net radiation (Rn), air temperature (T) and relative humidity (UR), soil temperature at 10 cm depth (TS), soil moisture in the layer from 0 to 30 cm depth (USOLO), rainfall and fluxes of CO2, H, LE and G in the period from November 11 2010 to February 19, 2011 on a maize crop grown in the experimental site belonging to the Network SULFLUX, located at the Foundation Center for Experimentation and Research (FUNDACEP) (28o36 'S, 53o40' W; 409 m altitude), located in Cruz Alta, in the State of Rio Grande do Sul, Brazil. Measurements were also made of leaf area during the crop cycle, with average periodicity of 15 days, in order to calculate the leaf area index (LAI). The fluxes of CO2, H and LE were measured by the Eddy Covariance micrometeorological technique. The decreased cloud cover in the afternoon resulted in higher amounts of Sin and PARin, thereby causing higher values of PARinb, PARabs and Rn. In the period P1 (VE-V11), the fraction of PARabs (FAPAR) tended to decrease as the solar elevation increased, while in periods P3 (R1-R2) and P4 (R3-R6) these was a slight upward trend throughout the day, probably caused by the high amount of PARinb combined with greater absorption by lower canopy leaves. Hourly variations of the diurnal flux of CO2 were better correlated with PARabs, while the nocturnal flux of CO2 presented an exponential relationship with soil temperature at 10 cm depth. The magnitude of CO2 fluxes showed dependence on cloudiness, with greater absorption of carbon at intermediate levels of cloud cover due to the higher amount of radiation that reaches the lower levels in the canopy as well as better quantum yield of the crop. Energy balance of the plants had good closure, with a slope of 0.82 and r2 of 0.96. The hourly values of H and LE fluxes were better correlated with Rn, while the daily measurements were strongly correlated with IAF. LE was responsible for most of the available energy use, especially during P2 (V12- VT) (75.88%) and P3 (73.07%) periods, during which the IAF of the culture was higher. During the periods P1 and P4, LE consumed about 46.62 and 52.26% of Rn, respectively. The flux of H was responsible for the use of 37.49, 11.56 and 11.77 and 39.75% of energy in the periods P1, P2, P3 and P4, respectively. In turn, the fraction of available energy used to heat the soil was 4.95, 3.83, 1.60 and 1.44% in the periods P1, P2, P3 and P4, respectively. The results presented in this study, when combined with modeling, can contribute to our understanding of how climate change may affect future production of maize in Brazil.