11 research outputs found
Water relations and gas exchange in olive trees under regulated deficit irrigation and partial rootzone drying
19 páginas, 9 figuras, 2 tablas, 58 referencias.It is widely believed that partial root
drying (PRD) reduces water losses by transpiration
without affecting yield. However, experimental work
carried out to date does not always support this
hypothesis. In many cases a PRD treatment has been
compared to a full irrigated treatment, so doubt remains
on whether the observed benefits correspond to
the switching of irrigation or just to PRD being a
deficit irrigation treatment. In addition, not always a
PRD treatment has been found advantageous as
compared to a companion regulated deficit irrigation
(RDI) treatment. In this work we have compared the
response of mature ‘Manzanilla’ olive trees to a PRD
and an RDI treatment in which about 50%of the crop
evapotranspiration (ETc) was supplied daily by
localised irrigation. We alternated irrigation in the PRD treatment every 2 weeks in 2003 and every
3 weeks in 2004. Measurements of stem water
potential (Ystem), stomatal conductance (gs) and net
CO2 assimilation rate (A) were made in trees of both
treatments, as well as in trees irrigated to 100% of
ETc (Control trees) and in Rain-fed trees. Sap flow
was also measured in different conductive organs of
trees under both PRD and RDI treatments, to evaluate
the influence of alternating irrigation on root water
uptake and tree water consumption. We found small
and random differences in Ystem, gs and A, which gave
no evidence of PRD causing a positive effect on the
olive tree performance, as compared to RDI. Stomatal
conductance decreased in PRD trees as compared to
Control trees, but a similar decrease in gs was also
recorded in the RDI trees. Sap flow measurements,
which reflected water use throughout the irrigation
period, also showed no evidence of gs being more
reduced in PRD than in RDI trees. Daily water consumption
was also similar in the trees of the deficit
irrigation treatments, for most days, throughout the
irrigation period. Alternating irrigation in PRD trees
did not cause a change in either water taken up by
main roots at each side of the trees, or in the sap flow
of both trunk locations and main branches of each
side. Results from this work, and from previous work
conducted in this orchard, suggest that transpiration is
restricted in trees under deficit irrigation, in which
roots are left in drying soil when water is applied by
localised irrigation, and that there is no need to
alternate irrigation for achieving this effect.This work was funded by the Dirección
General de Investigación of the Spanish Ministerio de Ciencia
y Tecnología (research project AGL2002-04048-CO3-01).Peer reviewe