Effect of EC 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 or 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 er dS m-1) and an increased fraction of unmarketable harvest. At the LET0 treatments, yield loss was only 3.4 er dS m-1 in accordance with the reduction in fruit weight. Low transpiration did increase fruit fresh yield by 8 n 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 er 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.