Growth of Greenhouse-Grown Tomato Irrigated on the Basis of Plant or Soil Moisture Status

Abstract

Tomato plants under glasshouse culture frequently suffer from over-luxuriant vegetative growth, resulting in malformed fruits and delayed maturity. By imposing a mild water stress on the plants, a balance between vegetative and reproductive growths can be restored in favor of better fruit growth. To achieve this balance, an irrigation trial was conducted comparing method based on plant water status with that based on soil water status. Irrigated soil depth was 40 cm in both methods.
Vegetative growth was much poorer when plants were irrigated on leaf water potential (Ψ_L) than on soil moisture potential (Ψ_S) of pF 2.0. However, marketable yield and soluble solids contents of the fruits were significantly higher when Ψ_L rather than Ψ_S was used to time the irrigation.
From these results, it is concluded that soil water management based on Ψ_L, is preferable to that based on Ψ_S in the forcing cultivation of tomato in greenhouses. Ψ_L of -0.1MPa in the early growing stage (from planting to flowering on the third cluster) and -0.5 MPa thereafter are recommended as indicators for irrigation; a soil depth of 40 cm is recommended.