Effects of nitrate, chloride and sulfate ratios and concentration in the nutrient solution on yield, growth and mineral uptake characteristics of tomato plants grown in closed rockwool system

Tomatoes, cv. 'Momotaro T93', were grown in a recirculation rockwool system for 126 days after transplanting to study the effects of nitrate (NO3), chloride (Cl) and sulfate (SO4) concentrations in the nutrient solution on yield, growth and mineral uptake. The ratios of NO3, Cl and SO4 in the nutrient solution were 6.0:0.0:3.8 as control, 3.0:7.5:1.5, 6.0:7.5:1.0, and 6.0:7.5:3.8 in mmol/l. The EC of the recirculated solution was maintained around 1.6, 1.6, 1.8 and 2.3 dS/m, respectively. Plant height and total yield were not influenced by the treatments. Led and stem fresh weights were lower in treatment of lower NO3 (3.0:7.5:1.5) than in other treatments. Marketable yield was lower at treatment 6.0:7.5:3.8, due to higher incidence of blossom-end rot and more malformed fruits. Total uptake amount of NO3-N during the experiment was lowest at treatment 3.0:7.5:1.5, but the uptake concentration was higher than the concentration of recirculating solution. The Cl uptake during the experiment was about 4.0 mmol/l at the treatment containing 7.5 mmol/l Cl in the recirculating solution. It was demonstrated that the yield of tomato was not affected by the concentration of Cl up to 7.5 mmol/l, when EC in the root environment was kept at the same level as control.