This research was conducted in the Department of Horticulture, University of Tehran to investigate the use of sawdust as a hydroponic medium for soilless culture in greenhouse tomato. Finding suitable nutrient solution was the other aim of the research. Two media, Mi containing a 3:1 mixture of coarse and fine perlite (control), and M2 sawdust as a new substrate plus two nutrient solutions (Si a commercial standard solution for soilless culture greenhouse grown tomato and S2 modified Coic solution) were compared during the experimental period (ten months from seed sowing). Plants grown in perlite produced better results than those grown in sawdust. Yield (number and weight of fruits per plant), fruit firmness and stem diameter were higher in perlite medium, while early yield, fruit VitC, titrable acidity, dry weight percentage, number of leaves and trusses per plant as well as plant stem length were the same in the two media. Stem diameter in plants fed by S2 solution was higher than in those fed by Si, while fruit titrable acidity in the latter was higher. No other significant differences were observed between the nutrient solutions.
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