Influence of salinity and greenhouse air CO2 enrichment on fruit quality in Raf type tomato (Delizia)

Growth of high sensorial quality tomato fruits requires a precise crop management as well as conditions of moderate salinity and thermal stress (low temperature) which in turn limit productivity. Greenhouse climate control modulates the negative effect of salinity on growth and development of the crop. On the other hand, studies on CO2 application in Mediterranean greenhouses have shown increases in yield between 15 and 20% for different horticultural species. The aim of this study is to evaluate the influence of carbon dioxide enrichment in a tomato crop grown in substrate and analyze its incidence on the mitigation of the toxic effect of salinity on fruit yield. The experiment was conducted in two similar greenhouses located at the IFAPA La Mojonera Institute equipped or the automatic control of climate and fertigation. A greenhouse was implemented to provide CO2 enrichment and the set-points established to control the concentration were defined to follow a strategy linked to ventilation (800 and 350 mu mol mol(-1), for vents closed and open respectively). Commercial yield and water use efficiency in greenhouses C (carbon dioxide enrichment) and T (reference) have been evaluated, applying in both two nutrient solutions of different electrical conductivity (EC) 4 and 7 dS m(-1). Results indicate that the supply of CO2 in greenhouse C avoided the 25% depletion observed in the reference greenhouse. Carbon dioxide enrichment increased commercial yield (19%) when the nutrient solution of higher osmotic potential (7 dS m(-1)) was applied allowing for a decrease of the adverse effect of salinity, partly for its positive effect on the number of fruits. The application of CO2 reduced water absorption and increased water use efficiency around 26%. These preliminary results show special interest on varieties appreciated for its quality and therefore economically valued by the market.