Yield and fruit quality of salinised tomato plants with enhanced Ca fertilization

Reduction in tomato yield and quality under saline growth conditions has been related, among other factors, to reduced Ca uptake by roots. The present study was developed to test whether increasing Ca concentration in the nutrient solution could alleviate the deleterious effects of salinity. Tomato plants, cv. Daniela, were treated with two concentrations of NaCl in combination with three concentrations of CaCl2, all of them supplied through the nutrient solution. The study was developed under unheated greenhouse conditions in two growing seasons: winter and spring-summer. NaCl in the irrigation water reduced tomato yield more in spring (70%) than in winter growing season (55%). In winter, enhanced Ca fertilisation did not affect yield of NaCl treated plants, however, in spring-summer, increasing Ca from 4 to 6 mM induced a 60% increase of yield in NaCl treated plants. This increase of yield was due to the larger size of fruits but not to higher fruit number. There was a significant increase of (o)Brix with NaCl treatments, the increase being higher in spring-summer (60%) than in winter (30%). No blossom-end rot (BER) symptoms were observed in winter, but a significant increase of BER was recorded on NaCl treated plants grown in spring-summer. Enhanced Ca fertilisation did not reduced BER in spring-summer crop season. We suggest that additional stress factors prevailing, such as low temperature during winter or very low ambient humidity during spring-summer, could have affected calcium uptake and/or calcium distribution within the plant. Those stresses would also have masked any beneficial effect of Ca on salinised plants.