Tackling water scarcity through treated wastewater in Patagonian steppe: Carbon assimilation, water use and fruit traits in olive trees

One of the most important environmental factors affecting plant development and productivity is water availability. Recently, olive crops have been cultivated in the coastal area of the Patagonian steppe where drier and cold conditions could limit olive production. However, all over the world, irrigation practices using alternative water sources like urban treated wastewater are constantly increasing. Consequently, this study aimed to investigate the impact of using wastewater on the physiological performance and fruit characteristics in olives trees in southeast Patagonia. A field experiment with two irrigation treatments (FW: freshwater, WW: wastewater) was conducted in well irrigated young olives trees growing outdoors in individual pots (cvs. Arbosana, Arbequina, Barnea and Hojiblanca). At a physiological level, net carbon exchange and transpiration rates were higher in olive plants under WW, without significant differences in water use efficiency. In terms of growth and fruit traits, WW promotes the height growth and biomass in several cultivars and led to a significant increase in fruit number per plant, especially in Arbequina and Hojiblanca. Overall, our findings indicate that despite increasing transpiration, the high nutrient load of WW enhances carbon assimilation, suggesting that olive orchards could function as an effective carbon sinks. This study demonstrated for the first time in the Patagonian steppe, that urban treated wastewater represents a sustainable and viable alternative for irrigation in the Patagonian steppe where water scarcity and nutrient poor soils are the major limiting factors for agricultural development.