Controlling factors of ‘Caatinga’ and sugarcane evapotranspiration in the Sub-middle São Francisco Valley

• Published in: Revista brasileira de engenharia agrícola e ambiental 2018-04, Vol.22 (4), p.225-230
• Main Authors: Carvalho, Herica F. de S., Moura, Magna S. B. de, Silva, Thieres G. F. da, Rodrigues, Carlos T. A.
• Format: Article
• Language: English
• Subjects: AGRICULTURAL ENGINEERING; ENVIRONMENTAL SCIENCES
• ISSN: 1415-4366; 1807-1929; 1807-1929
• DOI: 10.1590/1807-1929/agriambi.v22n4p225-230

ABSTRACT In the Sub-middle São Francisco Valley, the main controlling factors of ‘Caatinga’ and irrigated sugarcane ETr were investigated in this study. Between 2015 and 2016, environmental variables were measured by sensors coupled to two micrometeorological towers, one in the preserved ‘Caatinga’ and the other in an irrigated sugarcane crop. Soil moisture and vegetation cover index were also evaluated and biometric data were obtained only in the sugarcane. Actual evapotranspiration was determined based on the latent heat flux, by the energy balance method. Therefore, the ratio between actual and reference evapotranspiration was calculated. Response variables were formed by the actual evapotranspiration and by its ratio with the reference evapotranspiration. Explanatory variables included growth and environmental data. Multicollinearity, canonical and track analyses were applied. It was verified that only the environmental variables exhibited correlation with the actual evapotranspiration and its ratio with the reference evapotranspiration. In the ‘Caatinga’, soil moisture directly and indirectly influenced ETr, as the global solar radiation altered the response of actual evapotranspiration to the atmospheric demand. In sugarcane, ETr was directly and indirectly controlled by the intercepted photosynthetically active radiation and soil temperature, and the latter one also affected the ratio between actual and reference evapotranspiration. RESUMO No Submédio do Vale São Francisco, os principais fatores controladores da evapotranspiração real da Caatinga e da cana-de-açúcar irrigada foram investigados neste estudo. Entre os anos 2015 e 2016, variáveis ambientais foram medidas por sensores acoplados a duas torres micrometeorológicas, uma na Caatinga preservada e outra em um cultivo de cana-de-açúcar irrigada. A umidade do solo e o índice de cobertura vegetal também foram avaliados, e dados biométricos obtidos apenas na cana-de-açúcar. A evapotranspiração real foi determinada com base no fluxo de calor latente, pelo método do balanço de energia. Logo, calculou-se a razão entre a evapotranspiração real e de referência. As variáveis respostas foram compostas pela evapotranspiração real e por sua razão com a evapotranspiração de referência; já as variáveis explicativas incluíram os dados de crescimento e ambientais. Análises de multicolinearidade, canônica e de trilha foram aplicadas. Verificou-se que apenas as variáveis ambientais exibiram correlação com a evap