effect of humic acid growth and nutrient uptake of lettuce using nft system

abstract beneficial effects of humic substances on plant growth have been recognized by many researchers. a greenhouse experiment was conducted with humic acid (0, 20 and 50 mg/l) on lettuce cultivars ‘lollorossa’ and ‘javelina’ using completely randomized design at university of guilan. results showed that humic acid affected (p<5%) leaf number, height and nutrient uptake as well as ca, p and mg in both cultivars. no differences were found on ‘lollorossa’ in term of weight, leaf number and ascorbic acid. ‘javelina’ cultivar showed an increased width, diameter and total soluble solid. based on the results of this experiment an amount of 50 mg/l humic acid could be recommend for ‘lollorossa’ and ‘javelina’.