Partial rootzone drying is a feasible option for irrigating processing tomatoes

World water supplies are limited and water-saving irrigation practices, such as partial rootzone drying (PRD), should be explored. We studied the effects of PRD, applied through furrow and drip irrigation, on plant water relations, yield, and the fruit quality of processing tomato (Lycopersicon esculentum Mill. cv. 'Petopride'). There were four treatments. The first two were: full irrigation by hand on both sides of the root system which mimicked furrow irrigation (FuI), and half of irrigation water in FuI given alternately only to one side of the root system with each irrigation (PRDFuI). The next two treatments were: full drip irrigation (DrI) to both sides of the root system, and half of irrigation water in DrI given alternately only to one side of the root system with each irrigation (PRDDrI). Leaf water potential was the same among the treatments except for the PRDFuI plants, which had the lowest midday values only in one sampling out of four. Photosynthetic rate was the same among the treatments except for the drip-inigated plants having the lowest value in one sampling out of four. Number of fruit, mean fruit mass of fruit, total fresh and dry mass of fruit, and harvest index were the same among treatments, but PRD plants had increased irrigation use efficiency compared to fully irrigated plants. There was no incidence of blossom-end rot in any of the treatments. PRDDrI fruit had redder colour and higher total soluble solids concentration. Advancement in fruit maturity and enhancement of quality could be achieved without detrimental effect on fresh and dry mass of fruit by application of PRD. Independent of the irrigation method, PRD treatments improved irrigation use efficiency by ca. 70%. PRD has the potential for use in processing tomato especially in environments with limited water. (C) 2004 Elsevier B.V. All rights reserved.