Articles
THE EFFECT OF REDUCED SOIL WATER STATUS ON ‘GOLDEN DELICIOUS’ APPLE TREES
Article number
1058_26
Pages
229 – 235
Language
English
Abstract
In the Western Cape, South Africa, uncertainty exists regarding effects of global warming-induced climatological changes on limited water resources, as well as the future incidence and extent of droughts.
A need to employ appropriate irrigation strategies timeously during drought periods, instigated research concerning the possibility to maintain optimum fruit yield and quality by means of deficit irrigation (DI) in the Koue Bokkeveld production region. Golden Delicious apple trees on M793 rootstock were subjected to 15 treatments, which consisted of irrigation at combinations of 50%, 75% or 90% plant available water (PAW) depletion or no irrigation during four phenological phases viz. vegetative growth and cell division (Phase 1), cell enlargement (Phase 2), fruit ripening (Phase 3) and postharvest (Phase 4). The vegetative growth, yield and fruit quality response of the trees to these treat-ments were evaluated during 2005/06, 2006/07 and 2007/08. Plant physiological data were collated in 2005/06 at the end of Phases 1, 2 and 3. In 2005/06, leaf (Ψl) and stem (Ψs) water potential correlated well at predawn and midday.
Cloudy conditions interfered with midday photosynthesis measurements of Phase 2. Water deficits during Phases 2 and 3 decreased predawn Ψs at the end thereof from ca. -0.43 MPa to ca. -1.67 MPa and ca. -1.41 MPa, respectively.
At the end of Phases 1, 2 and 3, midday Ψs decreased from ca. -1.1 MPa to ca. -1.8 MPa, -2.4 MPa and -2.2 MPa, respectively.
At the end of Phase 1, leaf photosynthesis, stomatal conductance and transpiration tended to decrease with decreased midday Ψs. During Phase 3, increased leaf temperatures tended to exacerbate water deficit effects on photosynthesis.
Under the prevailing conditions, DI during Phases 1 and 3, respectively, may be partially accountable for decreased shoot and/or fruit growth rates, and eventually lower yield and fruit quality.
A need to employ appropriate irrigation strategies timeously during drought periods, instigated research concerning the possibility to maintain optimum fruit yield and quality by means of deficit irrigation (DI) in the Koue Bokkeveld production region. Golden Delicious apple trees on M793 rootstock were subjected to 15 treatments, which consisted of irrigation at combinations of 50%, 75% or 90% plant available water (PAW) depletion or no irrigation during four phenological phases viz. vegetative growth and cell division (Phase 1), cell enlargement (Phase 2), fruit ripening (Phase 3) and postharvest (Phase 4). The vegetative growth, yield and fruit quality response of the trees to these treat-ments were evaluated during 2005/06, 2006/07 and 2007/08. Plant physiological data were collated in 2005/06 at the end of Phases 1, 2 and 3. In 2005/06, leaf (Ψl) and stem (Ψs) water potential correlated well at predawn and midday.
Cloudy conditions interfered with midday photosynthesis measurements of Phase 2. Water deficits during Phases 2 and 3 decreased predawn Ψs at the end thereof from ca. -0.43 MPa to ca. -1.67 MPa and ca. -1.41 MPa, respectively.
At the end of Phases 1, 2 and 3, midday Ψs decreased from ca. -1.1 MPa to ca. -1.8 MPa, -2.4 MPa and -2.2 MPa, respectively.
At the end of Phase 1, leaf photosynthesis, stomatal conductance and transpiration tended to decrease with decreased midday Ψs. During Phase 3, increased leaf temperatures tended to exacerbate water deficit effects on photosynthesis.
Under the prevailing conditions, DI during Phases 1 and 3, respectively, may be partially accountable for decreased shoot and/or fruit growth rates, and eventually lower yield and fruit quality.
Publication
Authors
T. Volschenk, J. Gindaba
Keywords
Malus × domestica, deficit irrigation, photosynthesis, stem water potential, stomatal conductance
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