Articles
Evapotranspiration measured in a traditional rainfed and an irrigated intensive olive orchard during a year of hydrological drought
Article number
1150_39
Pages
281 – 288
Language
English
Abstract
Quantifying water use in ecosystems is important for irrigation and for planning of related infrastructures but also for the management of rainfed ecosystems, either natural or agricultural.
Understanding how plants cope with highly variable available water in soil, as a function of inter- and intra-annual precipitation variability provides an insight on how to manage deficit irrigation.
An experiment was performed from 2011 to 2013 on two olive orchards, one rainfed and another drip irrigated (Olea europaea ‘Cobrançosa’ and ‘Arbequina’, respectively) few km away from each other, in South Portugal, with the aim of understanding survival strategies and providing parameters for irrigation planning and scheduling.
In the frame of this general study, sap flow was measured in stems and roots.
The hydrological year 2011/2012, classified as dry to extremely dry, in almost all regions of Portugal, being the driest winter since 1931, provided a special opportunity to observe water stress impacts in the rainfed orchard.
Different biometric and water status variables, namely leaf water potential at pre-dawn (PLWP) and soil moisture (0 to 1.3 m, with a neutron probe) were monitored.
Between May and July 2012, direct measurements of actual evapotranspiration (ETa) using the eddy covariance micrometeorological method, were performed at the rainfed orchard.
The latent (LE) and sensible (H) heat fluxes data were selected according to the footprint analysis (Schuepp et al., 1990) and to the energy balance closure error.
Between July 2 and 10, average ETa was 1.5 mm day-1. For a period of two months of LE and H measurements (May 15-July 15), PLWP decreased from -0.4 to -1.1 MPa.
During the same period, the ratio H/LE increased from near one to three, while the relationship between ETa and reference evapotranspiration decreased from around 0.5 to 0.2. The decrease in available water in the observed soil layers was strong until mid-July, and decreased slowly until the total depletion that occurred in mid-September (before the first rains). These values are compared with those found for the irrigated orchard, as a reference.
On the other side, they are interpreted using the outcomes from the parallel study of sap flow in roots.
Understanding how plants cope with highly variable available water in soil, as a function of inter- and intra-annual precipitation variability provides an insight on how to manage deficit irrigation.
An experiment was performed from 2011 to 2013 on two olive orchards, one rainfed and another drip irrigated (Olea europaea ‘Cobrançosa’ and ‘Arbequina’, respectively) few km away from each other, in South Portugal, with the aim of understanding survival strategies and providing parameters for irrigation planning and scheduling.
In the frame of this general study, sap flow was measured in stems and roots.
The hydrological year 2011/2012, classified as dry to extremely dry, in almost all regions of Portugal, being the driest winter since 1931, provided a special opportunity to observe water stress impacts in the rainfed orchard.
Different biometric and water status variables, namely leaf water potential at pre-dawn (PLWP) and soil moisture (0 to 1.3 m, with a neutron probe) were monitored.
Between May and July 2012, direct measurements of actual evapotranspiration (ETa) using the eddy covariance micrometeorological method, were performed at the rainfed orchard.
The latent (LE) and sensible (H) heat fluxes data were selected according to the footprint analysis (Schuepp et al., 1990) and to the energy balance closure error.
Between July 2 and 10, average ETa was 1.5 mm day-1. For a period of two months of LE and H measurements (May 15-July 15), PLWP decreased from -0.4 to -1.1 MPa.
During the same period, the ratio H/LE increased from near one to three, while the relationship between ETa and reference evapotranspiration decreased from around 0.5 to 0.2. The decrease in available water in the observed soil layers was strong until mid-July, and decreased slowly until the total depletion that occurred in mid-September (before the first rains). These values are compared with those found for the irrigated orchard, as a reference.
On the other side, they are interpreted using the outcomes from the parallel study of sap flow in roots.
Authors
N. Conceição, M. Häusler, S. Lourenço, C. Pacheco, L. Tezza, M.I. Ferreira
Keywords
Olea europaea, evapotranspiration, water use, drought, survival strategies
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