Análise de crescimento, interação biosfera-atmosfera e eficiência do uso de água da cana-de-açúcar irrigada no Submédio do Vale do São Francisco

• Autor(a) principal: Silva, Thieres George Freire da
• Data de Publicação: 2009
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1492
• topic: Balanço de energia; Biomassa; Evapotranspiração; Fator de desacoplamento; Irrigação; Energy balance; Biomass; Evapotranspiration; Decoupling factor; Irrigation; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::AGROMETEOROLOGIA

The objective of this work was to understand the growth patterns of the irrigated sugarcane, the variations of the crop control on water vapour exchange with the atmosphere and its water use efficiency under the climatic conditions of the Submedio of the São Francisco Valley. The experiment was carried in a commercial area of sugarcane of the Agroindústrias do Vale do São Francisco S.A., a Company located in the district of Juazeiro, in the semi-arid region of Bahia State. The variety RB 92579 during the ratoon cycle was used. The tower was installed for the accomplishment of micrometeorological measurements to every 60 seconds with storage of the medium values in intervals of 15 minutes. Additionally, biometrics and biomass measurements were obtained in intervals from two to five weeks, while yield data were quantified at the end of the crop cycle (to the 13 months), with the objective to determinate morphphysiological index and agrometeorological variables. The Bowen Ratio-Energy Balance (BREB) method was used to estimate the latent (LE) and sensible (H) heat fluxes. The decoupling factor was calculated to analyze the interaction for water vapour exchange between the sugarcane and the atmosphere. The LE values along of day were integrated to estimate the crop evapotranspiration (ETc) and the crop coefficient (Kc) of the sugarcane. Finally, analysis of the water use efficiency were carried out using indicators based an the water application performance in the production system as related to the requested water demand by the sugarcane and in function of the crop yield. As results, the growth and development patterns were defined for the irrigated sugarcane, as well as the radiation use efficiency (RUE) and the crop photosynthetic efficiency (PTE). The RUE and PTE values were of 1.29 g MJ-1 and 2.67 g MJ-1, respectively, when it was considered the production of aboveground dry biomass. The quality analysis of data obtained by the method BREB demonstrated that 65.7% of the measured values presented physical consistence, while 88% of the monitored days were considered valid for the calculations of the daily fluxes and during the crop cycle. The values of LE represented 81% of the radiation balance, while H and the soil heat flux corresponded to 16% and 3%, respectively. During the crop cycle, the parameter Ω was equal to 0.68 on average. This indicates that, there was a moderate to high decoupling between the crop and the atmosphere, where the process water exchange was controlled, especially, by the energy supply, instead of the stomata control of the sugarcane. However, this control was observed to be larger than in other cultivation areas under irrigation conditions, demonstrating a probable restriction of the soil-climate to the evapotranspiration process of the sugarcane. The medium ETc during the cycle was of 4.7 mm day-1, resulting in a total water requirement of 1710 mm. The Kc ranged from 0.65 to 1.10 between the sprouting and maximum growth phases, reducing to 0.85 in the crop maturation stage. The irrigated sugarcane presented a production efficiency of 9.49 kg of stalks, 1.22 kg of sugar and 875.23 ml of alcohol for cubic meter of consumed water by the crop (ETc) and of 5.36 kg of stalks, 0.69 kg of sugar and 494.14 ml of alcohol for each cubic meter of water that entered in the system as rain and irrigation (P+I).