The effect of partial rootzone drying and foliar nutrition on water use efficiency and quality of table grape cultivars Crimson seedless and Dauphine

[摘要] The South African and international table grape industries are growing rapidly, whichnecessitates the production of high quality export fruit at competitive production costs.For this reason, alternative irrigation methods are required to utilise water optimallywhile still attaining good quality table grapes. An increase in agricultural productivitymay be dependent on either the availability of more water for irrigation or an increase inthe efficiency of water use.The first aim of this study was to evaluate the effectiveness of the Partial RootzoneDrying (PRD) irrigation strategy in Crimson Seedless and Dauphine table grapeproduction. 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 towater stress. The hormone production in turn results in stomatal closure and thereduction of water loss via transpiration. The drying cycle is then repeated after 10 to 15days on the other side of the vine, irrigating the previously dried roots. PRD willencourage a consistent production of the stress hormone abscisic acid (ABA), withoutactual water stress. This strategy reduces the amount of water used for irrigation,without an accompanying loss in fruit yield, as compared to conventional techniques. Inthis study, conventionally treated vines were irrigated according to historical block dataand 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 withtransport of all minerals through the leaves and enables the plant to attain higher pestand disease resistance thresholds. Conventionally treated vines that did not receivefoliar nutrient treatment were compared to vines that received foliar nutrients asprescribed by the manufacturer.Vine cultivars Crimson Seedless and Dauphine, were grown under open hydroponicprinciples with drip and drip irrigation respectively in this experiment. For the hydroponicvines (Crimson Seedless), all vines were situated in the same row and 72 vines weredivided into mini-plots of three vines. Treatments were then assigned to an equalnumber of plots at random. The same procedure was followed for the drip irrigatedvines (Dauphine) but the vines were situated in two rows of equal length. Treatment effects were followed from budburst until harvest, where after post-harvest analyseswere conducted.The first aim, namely to show that PRD is an effective irrigation strategy for table grapeproduction in Crimson Seedless and Dauphine cultivars , has shown that vines did notexhibit signs of stress even though they received only half the conventional amount ofwater. This study was conducted over only one growth season and therefore no definiteconclusions 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 ofPRD in wine grape production.The results obtained in the second part of the study were inconclusive and could notshow that Croplife is effective in improving the uptake and transport of applied foliarnutrients. Because Crimson Seedless is cultivated under open hydroponic principles,nutrients can be absorbed by the roots via the soil and micronutrients are also availablefrom chemical sprays during the season. There was no evidence to indicate that the useof Croplife increased nutrient absorption and transport, neither did it supplement ordetract form the observed effect of PRD.Despite the limitations experienced during this study, it has shown that the use of PRDfor table grape production may be a useful tool for improving water utilisation efficiencyin future. The strategy will have to be developed systematically through experimentationto 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 elucidatenumerous aspects of the PRD system and has clearly shown that established vineyardscan be switched to a PRD system without a loss in table grape quality. It is envisagedthat the advantages of this system could have a positive effect on the production of highquality fruit for the international market.

[发布机构] Stellenbosch University