Tomato root distribution, yield and fruit quality under different subsurface drip irrigation regimes and depths

Abstract

Rui M. A. Machado1 and Maria do Rosàrio G. Oliveira1

(1) Instituto de Ciências Agrárias Mediterrânicas, Universidade de Évora, Apartado 94, 7002-554 Évora, Portugal

Received: 3 November 2004 Accepted: 9 May 2005 Published online: 2 August 2005

Communicated by A. Kassam Abstract Tomato rooting patterns, yield and fruit quality were evaluated in a field trial where three irrigation regimes [0.6 (DI), 0.9 (DII) and 1.2 ETc (DIII)] and three drip irrigation depths [surface (R0), subsurface at 20 cm depth (RI) and subsurface at 40 cm depth (RII)] were imposed following a split-plot experimental design, with four replications. The behaviour of the root system in response to the irrigation treatments was evaluated using minirhizotrons installed between two plants, near the plant row. Root-length intensity (L a)—length of the root per unit of minirhizotron surface area (cm cm−2)—was measured at four crop stages. For all sampling dates, none of the factors studied were found to influence L a or rooting depth significantly or the interaction between treatments. For all treatments most of the root system was concentrated in the top 40 cm of the soil profile, where the root-length density ranged from 0.5 cm cm−3 to 1.4 cm cm−3 . The response of tomato fruits to an increase in the water applied was similar in quantitative and qualitative terms for the different drip irrigation depths. Water applied by drip irrigation had the opposite effect on commercial yield (t ha−1) and soluble solids (°Brix) (r=−0.82, P<0.001), however, yield in terms of total soluble solids (t ha−1) was the same for the 0.9 and 1.2 ETc. The increase in commercial yield can be described by the equation