Fruit nutritional quality under deficit irrigation: the case of table grapes in California

Authors: CENTOFANTI, TIZIANA - California State University; Banuelos, Gary; Ayars, James

Submitted to: Journal of the Science of Food and Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/15/2018
Publication Date: 11/28/2018
Citation: Centofanti, T., Banuelos, G.S., Ayars, J.E. 2018. Fruit nutritional quality under deficit irrigation: the case of table grapes in California. Journal of the Science of Food and Agriculture. 99:2215-2225. https://doi.org/10.1002/jsfa.9415.
DOI: https://doi.org/10.1002/jsfa.9415

Interpretive Summary: Sustainable agricultural practices are needed to face current threats to agricultural production in areas where water scarcity, recurrent droughts, and decreases in soil quality are endangering productivity and food security. To survive increasing drought conditions, deficit irrigation (DI) practices (reducing irrigation water applied below full crop evapotranspiration losses) are being considered for use throughout a crop's growing season or at specific phenological stages of a crop. Does DI have any effect on nutritional quality of a given crop? In this 4-year study, we studied the effects of DI irrigation on nutritional characteristics in berries of two different types of seedless grapes grown at two different locations in California. Different DI treatments were developed as a reduced percentage of water applied compared to the grower's irrigation practice of fully irrigating to replenish all evapotranspiration losses. Each year, berries were randomly picked from various clusters within the vines for each DI treatment at each site and were analyzed for mineral elements, berry weight, diameter and firmness, carbon and nitrogen content, pH, soluble solids, and total phenolic compounds. Results showed that DI treatments did not significantly increase or decrease nutraceutical compounds in grape berries, nor were there any significant decreases in size of either berry type. This study showed that DI practices can be safely used in drought susceptible areas like Central California for at least four years without affecting the quality of grape berry in ‘Crimson seedless’ and ‘Sugraone’ table grapes.

Technical Abstract: Conservative estimates of the water required for grape production in California are in the range of 2.3 billion cubic meters. Drought conditions will likely play a more significant role in determining which crops will be grown and fully irrigated in California. Utilizing alternative water management strategies will become a new reality for growing irrigated crops, and more sustainable approaches are needed to manage perennial crops that require a large amount of irrigation. One approach is the use of deficit irrigation (DI) (applying water below full crop evapotranspiration losses throughout the growing season), which has been successfully adapted for large crop water consumers like tree crop orchards and vineyards. In this study, we investigated responses in 'Crimson seedless’ and ‘Sugraone’ table grapes to reduction of water applied (known as DI) during specific phenological stages. We evaluated the effect of DI strategies on fruit nutritional quality such as total phenolic compounds, total nitrogen and carbon, soluble solids, pH, berry diameter, weight and firmness, and macro- and micro-nutrient concentrations for four consecutive years. Results showed berry size and firmness varied with time for both table grapes, but these characteristics were not affected with DI treatments. The DI treatments also did not significantly increase or decrease nutraceutical compounds in grape berry. In general, mineral element and total phenolic concentrations were not strongly affected by deficit irrigation. In this regard, DI may have a greater impact on specific phenolic compounds rather than on total phenolic concentration. Moreover, there were also no significant DI effects on total soluble solids or pH in the berries. Our results indicate that DI practices can be safely used for at least 4 years without affecting the quality of grape berry in ‘Crimson seedless’ and ‘Sugraone’ in central California. Deficit irrigation practices appear to be a safe water saving practice at times of drought, however, more studies are needed to see what the consequences are (if any), when DI becomes a more permanent method of irrigation.