Effects of increasing salinity on fruit development and growth of tomato grown in soilless culture

There is likely to be increased use of soilless growing systems using recirculation in the greenhouse-based horticultural systems of coastal south-eastern (SE) Spain, because of social pressure to reduce nutrient loss to the environment and the higher efficiencies in water and fertiliser use. In this region, irrigation is conducted with groundwater with moderate salinity, which is further increased by the continuous application of nutrients using fertigation. For the adoption of soilless growing systems using re-circulation, it is essential that the effects of salinity on crops be understood, and that optimal management strategies be developed. The present study assessed the effects of salinity on flowering, fruit set and fruit growth of tomato grown in soilless culture with re-circulation under SE Spanish conditions. The experiment was carried out in Almeria, Spain. Tomatoes were grown from December to June in a greenhouse, in perlite containers with re-circulation. Five treatments of increasing salinity (2.5 - the control, 3, 4, 6 and 8 dS m(-1)) were applied. Increased salinity decreased the total number of flowers, but the total number of fruits did not show significant differences among treatments because the fruit set index increased with salinity except for the highest saline treatment. Fruit growth rate and fruit development period decreased with increasing salinity giving smaller fruits with lower fresh and dry weights. The percentage of dry matter in fruit increased linearly with salinity. This suggested that the flow of water into fruit was more sensitive to salinity stress than the transfer of assimilates.