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A growing viticulture industry in Dodoma, Tanzania has sparked a need to establish best
management in irrigation practices for the improvement of quality of vine grapes and
wine. Drip irrigation is important in vines cultivation in tropical semi-arid areas as it
improves water productivity more than other irrigation systems. Fully irrigated grapes
have shown to have higher yield and lower grape quality when compared to rain fed
grapes which are coincidently under limited water availability. The use of deficit drip
irrigation in Marlborough New Zealand showed substantial improvement in grape
quality. However, the information of using deficit irrigation in vineyards in Dodoma is
inadequate. Farmers require information on deficit levels that will give optimum grape
yield and quality without detrimental effect to the vines.
A study was carried out in Dodoma Region in two seasons in 2014 and 2015 for the
determination of water requirement for Vitis vinifera L. cv. ‘Makutupora red’ (crop
evapontranspiration) by compensation heat pulse method. Sap flow sensors were used for
measuring transpiration and soil moisture probes were used for estimating surface
evaporation. The vines mean daily transpiration was 3.91 mm per day. The mean daily
evaporation was 0.38mm per day. Total seasonal evapotranspiration was 581mm.
Grapevine mean daily crop and basal coefficients for grapevine cv. ‘Makutupora red’
were0.31 (Kc) and 0.28 (Kb), respectively. The vine water consumption was high at fruit
set to veraison when the canopy was fully developed.
After the determination of vine crop water requirement, the vines were subjected to
deficit irrigation. Water was applied to the vines using different irrigation regimes at four
irrigation levels, which were 100%, 63.5%, 56.3% and 48.9% of crop evapotranspiration (ETc), interacting with three irrigation methods, which were conventional drip irrigation
(CDI), partial root zone drying (PRD) and root zone deficit rationing (RDR). The grape
yield and quality were optimum in conventional drip deficit irrigation method (CDI) at
63.5% and 56.3% of ETc. Moderate deficit irrigation proved to be the ideal irrigation
practice for improving grape quality with a little decrease in yield.
The improvement of water productivity by application of deficit irrigation and the
relationship between yield and quality components and the amount of water used by cv.
‘Makutupora red’ were investigated. Water productivity was higher in irrigation regimes
(treatments) CDI at 63.5% and 56.3% of ETc and in RDR at 63.5% which produced
optimum yields with good grape quality. In all full irrigated regimes (at 100% of ETc)
vines gave higher grape yields and low grape quality than regimes under deficit irrigation.
Pruned mass, leaf area index, berry diameter, berry weight and cluster weight (most of
yield components) decreased with water deficits. Total soluble solids, alcohol, phenols
and anthocyanins (most of quality components) were higher in vines under deficit
irrigation than in full irrigated vines. Malic acid and tartaric acid did not show significant
difference between full irrigated grapes and grapes subjected to deficit irrigation.
The finding in this study showed that the use of conventional drip irrigation method at
moderate water deficits is the best option because it produced optimum grape yield and
grapes of high quality. The relationship between water use, grape yield and quality
showed that moderate deficit irrigation improved grape quality and minimized the use of
water by vines. |
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