EFFECTS OF VARYING SULFATE CONCENTRATIONS ON GROWTH, PHYSIOLOGY AND YIELD OF THE GREENHOUSE TOMATO

In soilless culture systems, recycling the nutrient solution causes an accumulation of sulphate ions, which can generate nutrient imbalances affecting crop yield. This study determined the effects of four sulph ate concentrations in the nutrient solution on growth, foliar mineral composition, physiology and yield of greenhouse tomatoes. Ten days aft er transplanting, young tomato plants (Lycopersicon esculentum Mill. c ultivar 'Trust') grown in rockwool were subjected to four sulphate con centrations (S-0 = 0, S-1 = 5.2 (control), S-2 = 10.4 and S-4 = 20.8 m mol L(-1)) in the nutrient solution. The S-0 reduced plant dry weight, photosynthetic rate, chlorophyll content, and the total number of fru its. The S-0 treatment was associated with high concentrations of P, C a and Mg, but low levels of S in the leaves. The highest concentration of sulphates in the nutrient solution did not reduce shoot dry weight , photosynthesis, crop yield and fruit quality, although it decreased Mg, Ca and P content in the leaves. Consequently, tomato plants appear ed prone to sulphate deficiency but tolerated sulphate concentrations up to 20.8 mmol l(-1) in the nutrient solution with no apparent detrim ental effects on yield and fruit quality over a short cropping period.