impact of humic acid on growth properties and yield components of three tomato varieties (lycopersicon esculentum l.)

extra use of chemical fertilizers in recent decades had resulted in pollution of water, soil and other environmental recourses. to investigate the effects of humic acid as an organic fertilizer on some yield components of three tomato (lycopersicon esculentum l.) varieties, an experiment was conducted during 2010 growing season at khorasan-e-razavi, ahmadabad suburb of mashhad. experiment was arranged as split plots base on randomized complete block design with four levels of humic acid (0, 1, 1.5 and 2 kg.ha-1) and three tomato varieties (super ch, estern and super chief) with three replications. the main plots were allocated to three tomato varieties and the subplots consisted of four humic acid levels. the results revealed that the humic acid with 1.5 kg.ha-1 application had significant effect on biomass, brix index and fruit weight among three varieties. the highest single fruit weight per plant (93.85 g) was obtained by super chief variety in 1.5 kg.ha-1 humic acid application. it was observed that among three varieties, yield per plant and the total yield were belong to super chief variety. the highest amounts of leaf numbers per plant among the varieties was belonged to stern variety. the interaction between humic acid levels and varieties showed that application of 1.5 kg.ha-1 humic acid to super chief variety had the highest total fruit weight per plant (1.97 kg per plant).