Common and Alternating Long-Term Deficit Irrigations Improve Water Use Efficiency and Total Antioxidant Content in Tomato Fruits Under Glasshouse Conditions

Glasshouse experiments on long-term common deficit irrigation (DI) and alternating deficit irrigation causing partial root-zone drying (PRD) were performed on fresh tomato plants. The treatments started after the appearance of fruits on the first cluster and lasted about 100 days. Special split-root pots were used, enabling root growth of each plant into two halves of the pot. The root system of fully irrigated plants (FI) was irrigated at 100% of evapotranspiration (ET100); in PRD plants 50 or 60% of ET100 was irrigated to only one half of the pot and the irrigation was shifted every 6 days; DI plants were irrigated using the same amount of water as PRD plants but it was delivered to the whole pot. Both PRD and DI decreased leaf area and dry weight of shoots, size of fruits, and particularly yield of fresh fruits by 30% as compared to FI, but they increased water use efficiency, especially in PRD – by 9%. PRD and DI significantly (p ≤ 0.05) increased dry matter content and total acidity in fruits by 1.2% and 30%, respectively, as compared to FI. PRD and DI also significantly (p ≤ 0.05) increased total content of antioxidants in fresh fruit sap by 7 and 4%, respectively, as compared to FI. The results obtained in this study clearly suggest that both PRD and particularly the cheaper DI may be used in future sustainable horticultural production not only to save water but also to manipulate concentrations of key bioactive and health-promoting compounds in vegetables and fruits.