Potential use of produced water from oil and gas operations for irrigation during the rooting phase of Eucalyptus spp. mini-cuttings

In semi-arid regions, water scarcity restricts the expansion of industrial forestry, reinforcing the need for alternative and sustainable irrigation sources. This study evaluated the potential of treated produced water (PW), an effluent from onshore oil and gas extraction, as an irrigation source during the rooting phase of five hybrid Eucalyptus clones (13, 14, 30, 104, and 106) under controlled nursery conditions. The study evaluated five Eucalyptus clones separately within each irrigation system: treated produced water (PW) and urban water supply (UWS). Within each irrigation system, the experiment was arranged in a randomized block design with five replicates of eleven mini-cuttings each. Morphological traits, rooting percentage, survival, shoot height, stem diameter, root number and volume, and fresh and dry biomass were assessed along with water quality parameters [electrical conductivity (EC), sodium adsorption ratio (SAR), total oil and grease (TOG), metals, and nutrients]. The evaluated physicochemical parameters of PW, EC: 0.53 dS m− 1, SAR: 2.34, and TOG: 2.19 ppm, were below the thresholds established for effluent discharge by Brazilian environmental standards and consistent with internationally recognized criteria for irrigation water quality, and did not impair rooting (92.8%) during the evaluated period. Survival rates were numerically higher under PW (95.2%) than under UWS (87.3%), though this difference was not statistically confirmed. Clones 104 and 106 showed greater vigor and biomass under PW irrigation, whereas clone 30 responded more favorably to UWS, indicating genotype-dependent sensitivity to the ionic composition of the effluent. Exploratory multivariate analyses (PCA and k-means clustering) supported the existence of differential response patterns among the studied genotypes. These results suggest that treated PW may be compatible with the rooting phase of Eucalyptus mini-cuttings under controlled nursery conditions, for the evaluated genotypes and water source, although generalization requires validation across different PW batches, chamber-replicated trials, and assessment of subsequent growth stages. Produced water created a non-saline but ionically distinct environment for Eucalyptus rooting. Treated produced water (EC = 0.53 dS m-1; SAR = 2.34) maintained ≥ 92.8% rooting across five Eucalyptus clones, with numerically preserved survival rates. Rooting responses to produced water depended strongly on clone identity. Treated produced water showed preliminary compatibility for the rooting phase of Eucalyptus spp. mini-cuttings under controlled nursery conditions.