Influence of Salinity and Supplementary Calcium on Growth, Concentration of Some Nutrients and Quality of Tomato Fruit under Hydroponic Conditions

Soil salinity is one of the important stresses in agricultural production and plays an important role in reducing the growth of crops such as tomatoes. The proper concentration of calcium in salinity conditions is an important factor in controlling sodium and chlorine toxicity and increasing the yield of sensitive plants especially tomatoes. This research was carried out to study the effect of salinity and supplemental calcium on growth, concentration of some nutrients and fruit quality of tomato under hydroponic conditions.

For this purpose, a factorial experiment was conducted on the based on a completely randomized design with three replications in year 89-90 in the greenhouse of the Soil Science Department of Shiraz University.  The treatments consisted of three levels of salinity (0, 10 and 20 mM) from sodium chloride and three levels of calcium (0, 5 and 10 mM) from calcium nitrate source.

The results showed that the application of supplemental calcium in saline conditions to the nutrient solution reduced the negative effects of salinity and high sodium and chloride on tomato growth, although this supplemental calcium did not improve the growth and yield of the fruit, but could be considered as a competitive factor in the absorption of other cations by the plant.

The results showed that the sodium chloride had a negative effect on root and shoot dry weight, but this weight loss was significant only for the root (25.77% decrease compared to the control sample). Increasing salinity reduced the amount of nitrogen in the shoots. Changes in potassium were not significant in shoots, but in the root with increasing salinity and calcium, potassium absorption decreased. The lowest potassium uptake in the root was obtained from treatment with salinity of 20 mM and no supplemental calcium. Sodium chloride (salinity) treatment increased root and shoot sodium concentrations, and supplementation of calcium reduced the sodium concentration in them. The highest amount of magnesium absorption in shoots was in salinity treatment (20 mM) and without calcium, and the lowest magnesium adsorption was in non-saline treatments with 10 mM calcium. Salinity increased the concentration of manganese, zinc and copper in shoots and increased zinc in the root.