Several techniques are used to alleviate salinity stress. Rootstock and fertilization receive special attention among these techniques. For this reason, a trial was established with Satsuma mandarin (cv. Owari) nursery trees budded onto Trifoliate Orange (P. trifoliata) and Troyer Citrange. Irrigation was applied at five levels of saline water and at three levels of potassium. Response measurement included photosynthesis, transpiration and water use efficiency. Water use efficiency was determined as the ratio of photosynthesis/transpiration per unit leaf area. Canopy growth modelling and leaf area index (LAI) of the plants were measured and whole plant gas exchange capacity was investigated. Irrigation with saline water ranging between 0.65 to 6.5 dS/m reduce the photosynthetic capacity per unit area as well as further limiting vegetative growth of the whole tree. LAI increases with 100 g K2O application but high levels of K2O (200 g per tree) caused decreases with an exception of non-saline control treatments on both rootstocks.