Effects of wastewater applied with discrete irrigation techniques on strawberry plants’ productivity and the safety, quality characteristics and antioxidant capacity of fruits

Abstract

Water scarcity renders wastewater (WW) reuse for irrigation an increasingly common practice worldwide. Comprehensive guidelines and criteria have been established to secure the safety of WW irrigation, especially for food crops or crops that are eaten raw. The aim of this short-term study was to assess the impacts of strawberry crop irrigation with tertiary treated wastewater (WW) using common irrigation techniques (Drip, sprinkler, drip under plastic mulch), as compared to potable water (PW) irrigation, on strawberry fruits' quality and safety, and on crops' productivity. The impacts on fruits' weight and marketability, as well as on fruits' taste (soluble solids, titratable acidity and soluble solids/titratable acidity ratio), antioxidant capacity (ascorbic acid concentration, FRAP, total phenolics and total anthocyanin content), heavy metal content (Cu, Zn, Mn, Co, Ni) and microbial contamination (total coliform, E. coli, Salmonella spp., Listeria spp), were evaluated. The results revealed that WW irrigation did not significantly affect the fruits' marketability, taste and antioxidant capacity, as well as the heavy metal content, in comparison to controlled irrigation, regardless of the irrigation technique applied. Fruits heavy metal content was found to be below the maximum permissible levels (MPLs) set for fruit safety, whereas no microbiological contamination (total coliform, E. coli, Salmonella spp., Listeria spp.) of fruits was found in all irrigation water treatments. Overall, the results obtained with regard to the parameters examined highlight the potential for the reuse of the advanced tertiary treated effluent of good quality as a valid alternative for the irrigation of strawberry crops, even with sprinklers. However, further long-term studies are needed in order for such a practice to be regulated.

Productivity and nutritional and nutraceutical value of strawberry fruits (Fragaria x ananassa Duch.) cultivated under irrigation with treated wastewaters

“…The treatments exhibited quite similar TSP concentrations, with the highest variation (approximately 10%) being observed between TWW 1 (2521 mg catechin/100 g DW) and control (2807 mg catechin/100 g DW). This trend was also found elsewhere on Camarosa strawberries irrigated with a tertiary TWW characterized by conductivity and concentrations of BOD 5 , COD, N tot and P tot similar to those of the TWWs tested in the present study 13 . The comparison between TWW 1 (the most salty TWW) and TW was the only one providing a statistically significant difference ( P < 0.05).…”

“…In more detail, plants irrigated with TWWs showed a reduced fruit production compared to controls, from 10% with TWW 4 to 26% with TWW 1 , with the latter exhibiting the highest level of salinity by far, as measured by electrical conductivity (2428 μS cm –1 in TWW 1 versus 1322–1647 μS cm –1 in the other TWWs and 872 μS cm –1 in TW). Interestingly, a similar reduction in productivity (12–24% depending on the kind of irrigation system) was previously reported for Camarosa strawberry 13 irrigated with a TWW, which displayed a conductivity comparable to TWWs used in the present study. A stronger yield reduction (38–63%) was highlighted in various Fragaria x ananassa varieties in response to increasing conductivity levels (from 700 to 2500 μS cm –1 ) of irrigation water 30 .…”

“…In more detail, the irrigation with TWWs gave rise in all cases to statistically significant decreases of this parameter compared to the control. It is remarkable, however, that the TSP and TMA concentrations of strawberries produced with TWWs were included in the range of values reported in the literature for Camarosa fruits purchased in the market or produced in research orchards 1, 13, 41, 42 . Therefore, fruits irrigated with TWWs demonstrated a nutraceutical quality in line with their marketability.…”

“…Conversely, the impact of crop irrigation by TWWs on nutritional and nutraceutical value is poorly described in the literature. In more detail, irrigation with TWWs of short‐term crops, such as strawberries, does not appear to promote significant variations of the principal nutritional and nutraceutical values, 13 whereas, for long‐term crops, such as olive trees, the effect of an extended TWW irrigation increased the level of β‐carotene and total tocopherols of olive oil 3 …”

Heavy Metals in Food Crops: Ideal Sources and Roles of Urban Agriculture in Facilitating Their Consumption- A Review

“…The global water supply is decreasing due to population growth and climate change, thus, wastewater becomes the cheapest source of water for irrigation worldwide (Christou et al, 2016;Mkhinini et al, 2020). The practice of wastewater irrigation is more common in developing countries where water scarcity is more severe (Nzediegwu et al, 2019).…”