Improving tomato fruit quality by increasing salinity: Effects on ion uptake, growth and yield

Electrical conductivity (EC) of the nutrient solution is a key factor in the improvement of tomato fruit quality. The use of NaCl and KCl is associated with improved fruit quality and reduced BER, and is cheaper than using major nutrients for increasing the EC level of the nutrient solution. Four experiments were designed to compare the growth, yield, quality (firmness, color, soluble sugars, titrable acids, volatiles, shelf life) and mineral composition of greenhouse tomatoes grown under northeastern latitudes (eastern part of Canada). Tomato plants were grown in rockwool and the salinity of the nutrient solution was increased (1.8 to 5.6 mS cm(-1)), either with extra major nutrients or with NaCl or with NaCl/KCl. The effects of NaCl and NaCl/KCl on nutrient uptake of young tomato plants grown under different ECs (1.8 to 4.8 mS cm(-1)) were measured. Results from this study suggest that the yield salinity threshold is 1.45x of the control EC whereas the flavor salinity threshold is 1.6x of the control EC under Eastern Canadian growing conditions. Aroma volatile analyses have shown that both high EC and NaCl treatments improved tomato flavor. Bi-weekly cluster calcium application is a key factor in the reduction of BER. In the early stage of plant development, high Na and Cl concentrations in the nutrient solution (3 mS cm(-1)) did not affect adversely plant nutrition even if we observed Na accumulations. Detrimental long term effect of Na and Cl concentrations in the root environment were not observed.