Impact of Deficit Irrigation on Yield and Fruit Quality of Orange Trees (Citrus Sinensis, L. Osbeck, CV. Meski Maltaise) in Southern Tunisia

An experiment on deficit irrigation of orange trees (Citrus sinensis, L. Osbeck, cv. Meski Maltaise) with saline water (1.5 g l‐1) was conducted in the arid region of Medenine, Tunisia. Four irrigation treatments were applied: full irrigation (FI), irrigated at 100% of the crop evapotranspiration; deficit irrigation (DI75) and (DI50), which received respectively 25 and 50% less water than FI; and the farmer's method (FM). Soil water content and salinity were monitored during the orange active period. Yield and fruit quality were measured at harvest and used to analyse water productivity (WP) and net income. Results show a decrease in soil salinity between the spring and winter seasons with maximum values observed for the DI50 treatment. Maximum yield levels were obtained under the FI treatment (26.6 t ha−1). Applying continuous deficit irrigation resulted in 24 and 45% yield reduction respectively for DI75 and DI50, compared to FI. Fruit‐quality parameters showed significant differences, with higher levels of total soluble solids for DI50 and better fruit weight for FI and FM. For total water supplies between 415 and 786 mm, WP was in the range 2.9–3.6 kg m‐3, with the highest values observed for the DI50 treatment and the lowest for FM. The soil water balance‐based irrigation method (FI) generated the greatest net income and the lowest soil salinization. Reduction in water supply produced an equivalent reduction in yield but a much stronger decrease in the economic return: using the DI75 strategy resulted in 25% water saving, 24% reduction in yield and 40% reduction in net income.