Effect of different amounts of organic humic acid on the quantity and quality of tomato varieties (Lycopersium esculantium)

In order to investigate the effects of humic acid on three tomato varieties, a field experiment was conducted as a split-plot design experiment based on randomized complete blocks design (RCBD) with 3 replications in Ahmad Abad, of (Mashhad), Khorasan Razavi, during 2009-2010. Two factorial combinations were four levels of humic acid (0, 1, 1.5 and 2 kg.ha-1) and three tomato varieties (Super CH, Estern, Super Chief). According to the results, all characteristics (except fruit pH) were significantly different (P<0.01). The level of 1.5 kg.ha-1 humic acid led to the highest increasing in fruit and leaf dry weight, final yield and Brix index in comparison with control. The effect of different humic acid levels and three tomato varieties interactions on most of characters, except Brix index and fruit dry weight, was significant (P<0.05). The highest yield (65.67 t.ha-1) and fruit dry weight (133 g) belonged to Super Chief variety in 1.5 kg.ha-1 humic acid level. Also, the highest Brix index was obtained in Super CH variety and 1.5 kg.ha-1 humic acid level.