SALT CONCENTRATION OF THE NUTRIENT SOLUTION: EFFECTS ON TRANSPIRATION RATE OF SOILLESS CULTURE

          Main objective of the study was to verify the possibility of testing salt concentration effects on transpiration rate over an entire cycle of a crop, by using hydroponic lysimeters. The experiment was carried out in North - West of Sardinia (Italy). In 1996, nine hydroponic cropping units (CU) were used to measure transpired water and cotton (Gossypium hirsutum cv. ‘Ogosto’) was utilized as test crop. Three salt concentration levels were obtained adding seawater to the nutrient solution: control (0% of seawater, EC 3.0 mS cm^-1, pH 7.1), S8 (8% of seawater, EC 7.7 mS cm^-1, pH 6.7) and S16 (16% of seawater, EC 11.5 mS cm^-1, pH 6.4). Results indicate that cotton plants are able to develop and produce with 8% of added seawater without differences with control treatment, as previously assessed by other authors. High level of salt concentration reduced plant growth and productivity and increased TAF (transpiration per unit of leaf area, mm d^-1). The hydroponic lysimetric system proved to be an effective tool to study the effects of water salinity on water transpiration per unit of leaf area during the whole crop cycle and hence to distinguish the effects of salinity on plant development from the effects on leaf transpiration. (The abstract should be more concise. Both the rationale and the experimental set-up can be simplified).

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