Improvement of Tomato Water Productivity by the Use of a Partial Rootzone Drying Irrigation Strategy

Water scarcity is becoming a major problem for agricultural development in the Mediterranean area. The Moroccan Massa region is a major supplier of tomato (Lycopersicum esculentum L.) both for export and for the domestic market. Current average water use for the tomato is 8,000 m(3)/ ha for an 8-9 month production cycle. This research aims to develop irrigation strategies with this goal water saving with no effect on yield or fruit characteristics. The objective of the work was to assess the effects of the partial root zone drying irrigation (PRD) on leaf stomatal conductance, relative leaf water content (RWC), stem maximum daily shrinkage (MDS), root development and water use efficiency (WUE) of tomato grown in a greenhouse on a sandy substrate. Three treatments were applied: a control that received 100% of the water requirement, PRD-70 and PRD-50 in which 70% and 50% of water requirements were applied. The root system was divided in two sides with alternation of irrigation every three days. When vapor pressure deficit rises, PRD treatments showed a decrease in leaf stomatal conductance with, respectively, 17% and 26% compared to control. PRD-50 had the highest leaf water content during the experimental period. During periods of low and moderate climatic demand, MDS of all treatments showed the same trend. Whereas when vapor pressure deficit rose, PRD-50 had lower signal intensity. Compared to the control, number of root hairs increased by 120% and 190% in PRD-70 and PRD-50, respectively. Water use efficiency (WUE) was the highest (P < 0.001) for PRD-50 with 43 kg of fresh fruit per m(3) of applied water.