Submitted to: Fruits
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/1/2017
Publication Date: 1/31/2017
Citation: Centofanti, T., Banuelos, G.S., Wallis, C.M., Ayars, J.E. 2017. Deficit irrigation strategies and their impact on yield and nutritional quality of pomegranate fruit. Fruits. 72(1):46-53. doi: 10.17660/th.2017/72.1.5.
Interpretive Summary: Deficit irrigation (DI) is often conducted as a response to water shortage, inconsistent water supply, and recurrent droughts. The cultivation of drought tolerant crops and the application of DI strategies are necessary agronomic measures for sustainable agriculture in arid regions of the world and in areas that are experiencing recurrent water shortages (i.e., Central California). Pomegranate is a drought tolerant fruit tree and is extensively cultivated in arid and semi-arid regions of the world. In this study, pomegranate trees grown in Central California were treated with four different DI treatments [35%, 50%, 75% and 100% of evapotranspiration (ETlys)]. Tree physiological responses were evaluated relative to fruit yield and nutritional quality including pH, soluble solids, total phenolic compounds, anthocyanin and non-anthocyanin compounds, and mineral elements). Results of this 2-year study showed that DI strategies, as low as 35% of ETlys, did not affect yield, fruit color, pH, concentration of soluble solids, total phenolic compounds, anthocyanin and non- anthocyanin compounds, and mineral elements. The application of deficit irrigation may be a strategy to reduce water usage and increase agricultural sustainability on arid and drought-stricken regions. Longer-term studies are needed to better predict physiological responses to water deficit in crops and trees relative to nutritional quality and productivity.
Technical Abstract: In arid regions of the world, farmers use deficit irrigation (DI) strategies to supply water at levels below full crop evapotranspiration throughout the growing season or at specific phenological stages. In water-sensitive regions, growing crops that are water stress-resistant and tolerant of arid environments lend themselves well for DI strategies. One such crop is pomegranate (Punica granatum L.). Very little is known about effects of reduced irrigation on pomegranate fruit yield, as well as on nutritional characteristics. Hence, the goal of this study was to evaluate the physiological response of pomegranate trees subject to DI strategies for two years relative to fruit yield and quality. Pomegranate trees were fully irrigated for the first 2 years after planting to insure stand establishment and reasonably uniform tree size prior to beginning the deficit irrigation treatments. We used sustained deficit irrigation that applied a fixed amount of water throughout the growing season. Deficit irrigation treatments began in 2012. Four treatments were applied: 35%, 50%, 75% and 100% of evapotranspiration (ETlys) based on pomegranates grown in a lysimeter located in an adjacent field. Fruits were harvested in 2012 and 2013 by manually picking 10 fruits from 5 trees in the center row of the plot. Fruit juice was analyzed for pH, soluble solids, concentration of total phenolics, anthocyanin and non-anthocyanin compounds, and mineral elements. We did not observe any significant differences in fruit yield among DI treatments. Fruit juice pH was significantly higher in 2012 for all treatments, except for 75% of ETlys. Total phenolics were significantly higher in 2013 than 2012. No significant differences were observed among DI treatments for total phenolics and all anthocyanin and non-anthocyanin compounds in 2012 and in 2013. Lastly, there were no differences among treatments for all elements analyzed, except Na; Na concentration increased with time. Our two-year study has shown that application of DI strategies did not affect yield and fruit nutritional quality of pomegranate, and may be a strategy to sustain production in drought-stricken Central California.