Effect of Deficit Irrigation and Humic Acid on Growth, Yield and Blossom End Rot of Greenhouse Tomatoes

In order to investigate the effect of humic acid on growth characteristics of tomato under deficit irrigation conditions, a factorial experiment was conducted in a CRB design with three replications. Factors included irrigation at field capacity (FC), irrigation in half of the field capacity (1/2FC) and irrigation in two-thirds field capacity (2/3FC) and three levels of humic acid (0, 1000 and 2000 mg/L) was applied. The results showed that chlorophyll index, relative water content of leaf, shoot weight, root dry and fresh weight, photosynthesis, total fruit and fruit weight decreased with irrigation reduction. The level of ion leakage, fruit TSS and percentage of fruit rot in low irrigation treatments showed a significant increase compared to control.The lowest shoot loss was observed in the treatment of 2000 ppm × 2/3FC humic acid at 10% relative to control. Root weights in the 2000 ppm humic acid treatment decreased at all irrigation levels and dry weight without using humic acid decreased in both irrigation treatments. Fresh weight of fruits decreased by 1/2FC and 2000 ppm of humic acid, and the dry weight of fruit was decreased in 1/2FC and all humic acid levels. RWC of leaves decreased with reduction of irrigation in all humic acid treatments compared to FC and ion leakage increased. The number of green fruits decreased by 1/2FC with zero and 2000ppm humicacid.The number of fruit with the blossom end rot in 1/2FC treatment increased in all humic acid concentrations and was lower in other treatments.