Effect of irrigation regimes on yield and quality of grapes (Vitis vinifera L. cv. ‘Makutupora red’) in Dodoma, Tanzania

PhD. Thesis

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.