Irrigation Management of Greenhouse Tomato and Cucumber Using Tensiometer: Effects on Yield, Quality and Water Use

Irrigation is a crucial practice that operators often perform empirically, relying on their own experience, especially in productive areas characterized by low technology agriculture (i.e. several parts of Mediterranean countries). One of the possible approach for proper irrigation scheduling is measuring the soil water potential, simple and easy to manage. The purpose of this research was to examine the effects of two different irrigation regimes (obtained by the use of tensiometers connected to a relay controller) on yield, fruit quality and water consumption of greenhouse tomato (Solanum lycopersicum L. cv Naxos) and cucumber (Cucumis sativus L., cv Sarig, in the first cropping cycle, and the local landrace 'Mezzo lungo di Polignano', in the second one) grown on a silty-clay soil in Mediterranean conditions. For each species, two tests (August-February and February-July cycle) were carried out in a plastic greenhouse-tunnel. Drip irrigation was adopted, with automated schedule based on tensiometer readings. Two water potential irrigation set-points were compared: -100 and -400 hPa for tomato and -100 and -300 hPa for cucumber, in both cycles. Yield (marketable and unmarketable) and quality traits of fruits (soluble solids, dry matter and titratable acidity) were determined. Water consumption was calculated at the end of each crop cycle. In the first cycle, the two water regimes did not affect the yield of tomato and cucumber. The cucumber irrigated at the lowest soil water potential set-point produced fruits with 8% higher dry matter. In the second cycle, the tomato irrigated at the potential of -400 hPa showed a 40% lower yield (mainly due to the lower fruit size) compared to that of plants irrigated at -100 hPa. However, the fruits of tomato plants irrigated at -400 hPa showed total soluble solids, dry matter and titratable acidity, respectively 41, 45 and 59% higher than plants irrigated at 100 hPa. In both crop cycles, a water saving of 35% and 46%, on average, for tomato and cucumber, respectively, was obtained using the lowest potential as irrigation set-point. Proper use of tensiometer could allow a better use of water resource. Selection of proper water potential set-points according to the cultivation season is crucial for satisfactory results. The positive effects of a controlled and moderate water stress on fruit quality should be taken into account.