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Universidade Federal de Viçosa (2013)

Evapotranspiração e crescimento de clones de palma forrageira irrigada no Semiárido brasileiro

PEREIRA, Poliana de Caldas.

Titre : Evapotranspiração e crescimento de clones de palma forrageira irrigada no Semiárido brasileiro

Auteur : Pereira, Poliana de Caldas

Université de soutenance : Universidade Federal de Viçosa

Grade : Mestrado em Agrometeorologia ; Climatologia ; Micrometeorologia 2013

Résumé
The objective of this study was to quantify evapotranspiration and growth of clones of irrigated forage cactus during the first production year of the second crop cycle (March 2012 to February 2013). The experiment was carried out in Serra Talhada - PE, located in the Brazilian Semiarid region. A randomized block design with three replications was used in a factorial arrangement (3x3), in which the plots consisted of three conditions of soil water availability, determined by applying a fixed irrigation depth (L : 7.5 mm) with three frequencies (F : 7, 14 and 28 days), and subplots were three forage cactus clones (IPA : IPA Sertânia ; MIU : Tiny and, OEM : Mexican Elephant Ear). The soil water content was monitored from June 2012 to February 2013 with a capacitive probe (Diviner 2000 @ Sentek Pty Ltd, Australia.) using an average time interval of three days. Daily meteorological data were obtained from an automatic weather station and used to determine the reference evapotranspiration (ETo), according to the Penman-Monteith method, parameterized in the 56 FAO Bulletin. In addition to meteorological data, physical and hydraulic properties of the soil, a soil water budget (SWB) was performed every 14 days, and the components were accumulated subsequently in nine periods of 28 days. The actual crop evapotranspiration (ETr) was estimated as a residual of the SWB to determine the relationship ETr/ETo. After 150 days from the first cut, eight biometric campaigns were carried out in each thirty day time intervals for cladodes and plant morphological analysis. With these data, morphogenetic rates were determined over time for the three forage cactus clones. All data were compared by analysis of variance test and the Tukey test at the 5% level of significance. Evapotranspiration and other SWB components showed significant differences among clones and irrigation conditions over time. However, for values accumulate during the crop cycle, only the soil water flow for clone IPA, under the F14 condition (-66.5 mm), differed from the other two clones showing the highest flow value. The average ETr for irrigated forage cactus was 1.5 mm day-1 during the analysis period, based on an average atmospheric demand of 5.1 mm day-1. The ratio ETr / ETo for the clones showed low magnitude of the imposed conditions (ambient together with the irrigation), providing values of 0.27 ± 0.12, 0.30 ± 0.14 and 0.29 ± 0.12 for IPA, and OEM MIU, respectively. It was found that the evaluated conditions of water availability did not affect significantly (P> 0.05) most of the absolute and relative values of the growth variables of the three clones significantly. When different clones were compared, regardless of water availability conditions, it was observed that, in terms of absolute values, the OEM presented the highest means. Evaluations in the long run showed that there was a significant increase in the growth of clones in the last months of the first year of production. However, this occurred due to rainfall events which, together with the application of the irrigation treatments, provided greater growth increase for the OEM and IPA clones, in this order, reaching 70% and 60% of the total rate for height, and 37.0 % and 45.3% for plant width. Thus, it can be concluded that the different conditions of the soil water availability did not affect evapotranspiration and growth of forage cactus clones. Nevertheless, the OEM and IPA clones had the best growth performances when compared to the MIU clone, which was the one that showed the lowest

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