Thesis (MSc)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: The effects of regulated deficit irrigation on the production and fruit quality of peaches were
investigated. A field trial was carried out in a twelve-year-old Neethling peach orchard at Robertson
Experiment Farm. Treatments consisted of five different soil water depletion levels applied during five
different growth stages. Irrigation was applied at the five soil water depletion levels of which T1 was
regarded as relatively wet (irrigation was applied when the average soil matric potential reached
ca. -50 kPa). T2 was regarded as normal (irrigation applied at ca. -100 kPa) and three different
deficit irrigation regimes T3, T4 and T5, irrigated at soil matric potentials of ca. -200, -400 and -800
kPa respectively. The five growth stages were Stage 1 (cell growth), Stage 2 (slow fruit growth),
Stage 3 (rapid fruit growth), Stage 4 (ripening) and Stage 5 (post-harvest). The soil water content was
monitored and irrigation was scheduled by means of a neutron probe. Vegetative and fruit growth,
fruit mass and production were measured. Fruit were examined for bruises and firmness.
Fruit size, fruit mass, fruit quality, as well as production, were not sensitive to water deficits during the
different growth stages with a normal crop load. However, a tendency to reduced shoot growth with
decreasing soil matric potentials was observed during the slow fruit growth, rapid fruit growth as well
as the ripening stages. The application of deficit irrigation during the slow fruit growth or post-harvest
stages can save substantial amounts of water with a normal crop load, provided that normal irrigation
is applied during the other growth stages.
A combination of water deficits during the ripening stage and high crop load resulted in smaller fruit
and lower production. Fruit size, fruit mass, fruit quality, as well as production, were not sensitive to
water deficits during either the cell growth, slow fruit growth or post harvest growth stages, provided
that normal irrigation is applied in the other growth stages. Irrespective of crop load, soil matric
potentials up to -200 kPa can be applied during anyone of the growth stages without seriously
affecting the final fruit size, fruit mass, fruit quality or production. However, this soil water deficit may
then only be applied in one of the growth stages and normal irrigation must be applied in the other four
stages.
Although deficit irrigation reduced seasonal water consumption, it could not be justified as water
saving with a heavy crop load. / AFRIKAANSE OPSOMMING: Die effekte van gereguleerde tekort besproeiing op die produksie en vrugkwaliteit van perskes is
ondersoek. 'n Veldproef is in 'n twaalf-jaar-oue Neethling perskeboord te Robertson Proefplaas
uitgevoer. Die behandelings het bestaan uit vyf grondwater-ontrekkingspeile wat gedurende vyf
verskillende groeistadiums toegepas is. Besproeing is toegedien by vyf verskillende
grondwaterontrekkingsvlakke waar T1 beskou is as redelik nat (besproeiing is toegedien wanneer
gemiddelde grondmatrikspotensiale ca. -50 kPa bereik het). Behandeling T2 is as normaal beskou
(besproeiing toegedien by ca. -100 kPa en drie verskillende regimes van tekort besproeiing naamlik
T3, T4 en T5 wat onderskeidelik by ca. -200, -400 en -800 kPa besproei is. Die vyf groeistadiums
was onderskeidelik Stadium 1 (selgroei), Stadium 2 (stadige vruggroei), Stadium 3 (vinnige vruggroei),
Stadium 4 (rypwording) en Stadium 5 (na-oes). Die grondwaterinhoud is gemonitor en die besproeiing
is met behulp van 'n neutronpeiler geskeduleer. Vegetatiewe groei, vruggroei, vrugmassa en
produksie is gemonitor. Vrugte is ook ondersoek vir kneusbaarheid en fermheid.
Geen negatiewe effek as gevolg van watertekorte is ten opsigte van vruggrootte, -massa, -kwaliteit
sowel as produksie waargeneem gedurende die verskillende groeistadiums waar 'n normale
vruglading gehandhaaf is nie. 'n Afnemende tendens in lootgroei met afnames in
grondwatermatrikspotensiale is egter gedurende die stadige- en vinnige vruggroei-stadiums, asook in
die vrugrypwordingstadium, waargeneem. 'n Aansienlike hoeveelheid water kan bespaar word deur
gereguleerde tekort besproeiing gedurende die stadige vruggroei- of na-oes-stadiums toe te pas, mits
'n normale vruglading gehandhaaf word en normale besproeiing in die ander groeifases toegedien
word.
'n Kombinasie van watertekorte en 'n hoë vruglading gedurende die rypwordingstadium het tot kleiner
vrugte en laer produksies gelei. Vruggrootte, -massa, -kwaliteit en produksie is egter nie gevoelig vir
watertekorte gedurende die selgroei-, stadige vruggroei- en na-oes-stadiums nie.
Tekort besproeiing by 'n grondwatermatrikspotensiaal van tot -200 kPa kan egter met 'n normale en
hoë vruglading in enige van die fases toegepas word, sonder om die finale vruggrootte, -massa, -
kwaliteit of produksie nadelig te beïnvloed. Hierdie tekort besproeiingsregime mag egter slegs in een van die groeistadiums toegedien word en normale besproeiings moet in die ander groeistadiums
toegedien word.
Alhoewel tekort besproeiing die seisoenale waterverbruik verminder het, kan dit nie geregverdig word
as 'n waterbesparende praktyk indien 'n hoë vruglading gehandhaaf word nie.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/53107 |
| Date | 04 1900 |
| Creators | Beukes, Odette |
| Contributors | Watts, J. E., Karsten, J. H. M., Stellenbosch University. Faculty of Sciences. Dept. of Botany and Zoology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 1 v. (various pagings) : ill. |
| Rights | Stellenbosch University |
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