Effect of electrical conductivity and transpiration on production of greenhouse tomato (Lycopersicon esculentum L.)

We investigated the hypothesis that manipulating water out-flow of a plant through the shoot environment (potential transpiration, ET₀) in a glasshouse could modulate the effect of salinity/osmotic potential in the root environment upon yield of tomatoes. Contrasting root-zone salinity treatments were combined with two climate treatments — a reference (high transpiration, HET₀) and a “depressed” transpiration (low transpiration, LET₀). The salinity treatments, characterised by their electrical conductivity (EC) were 6.5, 8 and 9.5 dS m^?1, were always coupled with a reference treatment of EC=2 dS m^?1. In another experiment, concentrated nutrients (Nutrients) and nutrients with sodium chloride (NaCl) at the same EC of 9 dS m^?1 were compared.Marketable fresh-yield production efficiency decreased by 5.1% for each dS m^?1 in excess of 2 dS m^?1. The number of harvested fruits was not affected; yield loss resulted from reduced fruit weight (3.8% per dS m^?1) and an increased fraction of unmarketable harvest. At the LET₀ treatments, yield loss was only 3.4% per dS m^?1 in accordance with the reduction in fruit weight. Low transpiration did increase fruit fresh yield by 8% in both NaCl and Nutrients treatments at an EC=9 dS m^?1. Neither EC nor ET₀ affected individual fruit dry weight. Accordingly, fruit dry matter content was significantly higher at high EC than in the reference (4% per each EC unit in excess of 2 dS m^?1) and responded to ET₀ to a minor extent. Control of the shoot environment in a greenhouse to manipulate the fresh weight of the product may mitigate the effects of poor quality irrigation water without affecting product quality.