The presented study aimed to determine the effects of nano-selenium foliar application and types of irrigation water on growth traits of three citrus (C. aurantium, C. volkameriana, and C. aurantifolia) rootstocks. The research started in 2023 at the canopy of the Kerbala-certified citrus nursery, Holy Kerbala Governorate, Iraq. The experiment, laid out in a randomized complete block design, had a split-plot arrangement of three factors and three replications. The first factor was two types of water, i.e., river water and well water, placed in main plots. The second factor (subplot) was the seedlings grown from seeds of three types of Citrus rootstocks, i.e., sour orange, volkameriana, and lime. The third factor (sub-subplot) was the foliar application of nano-selenium with three concentrations (0, 1, and 2 mg L^-1). The results showed the river water was superior in the percentage of nitrogen (1.786%) and phosphorus (0.193%), while the well water was better in the content of CAT and POD enzymes (10.76 and 176.7 abs unit min g^-1, respectively). Notably also, the cultivar Volkameriana rootstock was superior in the percentage of nitrogen (2.083%) and phosphorus (0.213%). Moreover, the nano-selenium (2 mg L^-1) foliar application has a positive effect and exceeded all the doses for various traits.

Keywords: Citrus rootstock (C. aurantium, volkameriana, and aurantifolia), nano-selenium, water quality, growth and biochemical traits

Key findings: Citrus cultivar Volkameriana rootstock proved better with nano-selenium concentration (2 mg L^-1) than the other rootstocks and nano-selenium concentrations, providing superior results for various traits.