The effect of supplementation of root zone dissolved inorganic carbon on fruit yield and quality of tomatoes (cv ‘Daniella’) grown with salinity

Abstract

The possibility that elevated root zone dissolved inorganic carbon (DIC) concentrations could increase yield and quality of Lycopersicon esculentum (L.) Mill. cv Daniella when combined with salinity in an agricultural production system was investigated. Root zone DIC was modified by supplying CO 2-enriched irrigation solutions (1 g l −1), NaHCO 3-enriched irrigation solutions (10 mM) or aerating the roots with ambient air or with air enriched with 5000 ppm CO 2. Plants were supplied with either low electrical conductivity ( EC=0.25 S m −1) nutrient solutions or with nutrient solutions supplemented with 55 mM NaCl to generate a high EC (0.7 S m −1). Plants were grown in plastic covered tunnel houses in two growing seasons to determine whether seasonal variations could alter the influence of root zone DIC on growth and yield. Although there were differences in vegetative and yield characteristics in the different seasons, no modification of the response to changes in root zone DIC was observed. With increased EC, growth and yield were decreased by 14 and 22%, respectively, relative to low EC treatments. High EC increased the total soluble solids (TSS) by ca. 18% and titratable acids by ca. 32% relative to low EC treatments. After storage for 2 weeks at 15°C, fruit of high EC treated plants was 12% less firm than that of low EC plants and no differences in TSS or acidity were found. At low EC, the HCO 3 − treatment decreased total yield and the yield of marketable fruit (>80 g) by ca. 22%, probably due to occlusion of drippers in this treatment. At high salinity levels, irrigation with DIC-enriched nutrient solutions had no significant effect on fruit yield or quality. Aeration of the roots with air containing 5000 ppm CO 2 increased the average marketable fruit weight by 7%, but had no significant effect on total yield or quality in comparison to controls. Aeration of the root zone with air containing 5000 ppm CO 2 also reduced the incidence of blossom-end rot by 57%. Overall, however, the influence of DIC enrichment of irrigation solutions and aeration of the root zone with air containing elevated CO 2 on fruit yield and quality is unlikely to be of commercial significance.