Effects of a Split-Root Hydroponic System on Salinity Tolerance of Tomatoes

Abstract

Tomatoes are the most produced greenhouse crop globally and are loved due to their nutritional and health benefits. Meanwhile, the production of saltwater fish is on the rise, with consumers willing to pay premium prices for these species. Given the profitability and market demand for both saltwater fish and tomatoes, combining their production systems could significantly enhance overall profitability. One viable option is brackish water aquaponics, which integrates the cultivation of saltwater fish with high-value plants such as tomatoes. The primary challenge is that saltwater fish require different salinity levels than tomatoes, which can significantly reduce the yield and productivity of the tomatoes. Two studies were conducted using the split-root system to explore the feasibility of integrating these two systems. The first study used the split-root system to investigate the salinity threshold of ‘Washington’ cherry tomatoes under three salinity levels 0 parts per thousand (ppt), 4.5 ppt, and 9 ppt, under two root conditions: homogeneous (Homo) and heterogeneous (Hete) in a randomized complete block design. Results showed that 9 ppt treatment reduced the fruit weight by 78% and the fruit number by 60% indicating that it's too high for the Washington tomatoes. No significant differences were observed in the shoot dry weight, fruit weight, and fruit number between the Homo and Hete treatments at 4.5 ppt and 9 ppt. The second study used ‘Favorita’ cherry tomatoes to investigate salinity stress in a heterogeneous split-root system. Four treatments were evaluated: a control (0 ppt Homo), and heterogeneous treatments with salinity levels of 0 ppt (0 ppt Hete), 4 ppt (4 ppt Hete), and 6 ppt (6 ppt Hete). The sensory analysis showed consumer preference for either the 0 ppt Hete or 6 ppt Hete treatment and that heterogenous split-root improved the fruit sweetness. Future studies will use shrimp aquaculture effluent, study the feasibility of the split-root system for commercial production, and use electronic nose to further understand consumer preferences.