Effect of irrigation on processing tomato yield and antioxidant components

A 2-year (2007 and 2008) open-field experiment was conducted to study the effects of irrigation on the yield parameters and main antioxidant components (lycopene, phenolic compounds, and ascorbic acid) of processing tomato. Two different treatments were applied: some plants were regularly irrigated, and some had their irrigation cut off 30 days before harvest. Both groups were compared with a rainfed control. Daily irrigation volume was calculated from the average daily temperature to reach optimum water supply. Fruits were harvested at the red-ripe maturity stage. The irrigated plants gave a significantly higher yield, and rainfed plants showed a yield loss. Irrigation had a greater effect on the average fruit weight than on fruit number. A seasonal effect was also remarkable, but was not as strong as that of irrigation. A better water supply caused a lower Brix number than that of the rainfed control. In both years, the antioxidant concentrations in tomato fruit showed a decrease with irrigation, except for the ascorbic acid content.