A comparative study between actual and theoretical evapotranspiration of cucumber, cucumis sativus, grown in rockwool

Abstract

The current study compares the évapotranspiration of cucumber, Cucumis sativus L. cv. Figaro Fl, with the theoretical calculation using a modified Penman (ET) equation. Cucumber seeds, sown in 3.5 × 3.5 × 4.0 cm³ cones on August 10, 1994, were transplanted to 6 × 10 × 10 cm³ cuboides on August 18 and moved into 7.5 × 20 × 90 cm³ rockwool slabs on August 29. Four plants out of 408 plants, were placed in a self supported structure mounted on a one gram sensitivity digital balance. Balance readings, dry- and wet-bulb temperatures, solar irradiance level, and leaf and root zone temperature data were recorded in a data logger at 10 min. intervals for four months. Measures of plant vegetative development (i.e. leaf length and width, leaf area and plant height) data were also recorded. Leaf area index and leaf canopy index were calculated using plant height and plant age. The stomatal resistance was empirically estimated at 200 s m^-2. The ET equation was used to calculate the theoretical water loss given plant geometrical parameters, solar irradiance level and wet- and dry-bulb temperatures. The results compare the theoretical water loss calculation with the actual water loss readings.