Thesis (MScAgric (Viticulture and Oenology))--University of Stellenbosch, 2007. / The South African and international table grape industries are growing rapidly, which
necessitates the production of high quality export fruit at competitive production costs.
For this reason, alternative irrigation methods are required to utilise water optimally
while still attaining good quality table grapes. An increase in agricultural productivity
may be dependent on either the availability of more water for irrigation or an increase in
the efficiency of water use.
The first aim of this study was to evaluate the effectiveness of the Partial Rootzone
Drying (PRD) irrigation strategy in Crimson Seedless and Dauphine table grape
production. This irrigation system is based on the drying of half of the vine roots,
thereby allowing the plant to produce hormones like abscisic acid (ABA) in reaction to
water stress. The hormone production in turn results in stomatal closure and the
reduction of water loss via transpiration. The drying cycle is then repeated after 10 to 15
days on the other side of the vine, irrigating the previously dried roots. PRD will
encourage a consistent production of the stress hormone abscisic acid (ABA), without
actual water stress. This strategy reduces the amount of water used for irrigation,
without an accompanying loss in fruit yield, as compared to conventional techniques. In
this study, conventionally treated vines were irrigated according to historical block data
and PRD-treated vines were irrigated at the same times.
The second aim of this study was to monitor the efficacy of a foliar nutrient, Croplife.
This foliar nutrient allegedly improves the uptake of foliar applied nutrients, assists with
transport of all minerals through the leaves and enables the plant to attain higher pest
and disease resistance thresholds. Conventionally treated vines that did not receive
foliar nutrient treatment were compared to vines that received foliar nutrients as
prescribed by the manufacturer.
Vine cultivars Crimson Seedless and Dauphine, were grown under open hydroponic
principles with drip and drip irrigation respectively in this experiment. For the hydroponic
vines (Crimson Seedless), all vines were situated in the same row and 72 vines were
divided into mini-plots of three vines. Treatments were then assigned to an equal
number of plots at random. The same procedure was followed for the drip irrigated
vines (Dauphine) but the vines were situated in two rows of equal length. Treatment effects were followed from budburst until harvest, where after post-harvest analyses
were conducted.
The first aim, namely to show that PRD is an effective irrigation strategy for table grape
production in Crimson Seedless and Dauphine cultivars , has shown that vines did not
exhibit signs of stress even though they received only half the conventional amount of
water. This study was conducted over only one growth season and therefore no definite
conclusions could be drawn about the long term effectiveness of PRD on table grapes.
It did, however, confirm numerous results obtained from different studies on the use of
PRD in wine grape production.
The results obtained in the second part of the study were inconclusive and could not
show that Croplife is effective in improving the uptake and transport of applied foliar
nutrients. Because Crimson Seedless is cultivated under open hydroponic principles,
nutrients can be absorbed by the roots via the soil and micronutrients are also available
from chemical sprays during the season. There was no evidence to indicate that the use
of Croplife increased nutrient absorption and transport, neither did it supplement or
detract form the observed effect of PRD.
Despite the limitations experienced during this study, it has shown that the use of PRD
for table grape production may be a useful tool for improving water utilisation efficiency
in future. The strategy will have to be developed systematically through experimentation
to fully unlock the potential of the PRD management system for table grape production.
This study provides a good starting point for future research required to elucidate
numerous aspects of the PRD system and has clearly shown that established vineyards
can be switched to a PRD system without a loss in table grape quality. It is envisaged
that the advantages of this system could have a positive effect on the production of high
quality fruit for the international market.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/1506 |
| Date | 12 1900 |
| Creators | Van Zyl, Tinake |
| Contributors | Du Toit, P. G., Strever, A. E., Raath, P. J., University of Stellenbosch. Faculty of Agrisciences. Dept. of Viticulture and Oenology. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Rights | University of Stellenbosch |
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