Co-application of kaolin and superabsorbent polymer mitigate water stress and improves yield and water use efficiency in tomato plant

•Water stress at 50 % ETc decreased fruit yield and WUE on tomato plant.•Using a combination of Kaolin and SAP improved yield and WUE on tomato plant.•Using Kaolin and SAP alleviated harmful effects of drought on tomato plant. Water stress is one of the factors that remarkably constrain agricultural productivity in Iran. This experiment aimed to evaluate the effect of Kaolin (KL) and Superabsorbent polymer (SAP) separately or in combination on alleviating harmful effects of water stress on tomato. A factorial experiment was designed with two main factors: irrigation regimes (100, 75 and 50 % of the crop evapotranspiration (ETc)) and drought-alleviating treatments (control, KL, SAP, and KL+SAP) under field condition. Results showed that water deficit (exclusively at 50 % ETc) significantly decreased total fruit yield, water use efficiency (WUE), relative water content (RWC), and chlorophyll content, whereas it increased the rate of osmolyte accumulation, malondialdehyde, and antioxidant enzymes activities. As compared to the other treatments, the interaction of KL+SAP at different irrigation regimes (at 50, 75, and 100 % ETc) raised total fruit yield by 172, 111, and 103 %, respectively. Furthermore, the highest WUE, RWC, and chlorophyll content and conversely the lowest osmolyte accumulation, MDA, and H2O2 content were obtained by KL+SAP treatment at different irrigations. This indicates that co-application of KL and SAP could alleviate the harmful effect of water stress on tomato plant; therefore, it can be used to improve tomato's yield and WUE in areas with drought stress.