High Tunnel and Grafting Effects on Organic Tomato Plant Growth and Yield in the Subtropics

Abstract

Although grower interest in high tunnel tomato (Solanum lycopersicum) production has increased in recent years, systematic high tunnel research conducted in humid, subtropical regions has been limited. The potential of tomato grafting to mitigate biotic and abiotic stresses makes it complementary to high-value production systems in high tunnels. In this 2-year study, grafted vs. nongrafted organic tomato production in high tunnels and open fields was investigated to determine possible synergistic effects of these two technologies. In 2016, high tunnels resulted in a significant increase of total and marketable yields, by 43% and 87%, respectively, over open field production. Grafting also significantly increased total and marketable yields over nongrafted plants by 34% and 42%, respectively. Cultivar effects demonstrated greater benefits with the implementation of high tunnel and grafting technologies for ‘Tribute’ (a beefsteak-type tomato) than for ‘Garden Gem’ (a plum-type tomato), as the increase in marketable yield was 33% greater for ‘Tribute’ in high tunnels and 45% greater for ‘Tribute’ with grafting. In 2017, a delayed effective transplanting date and the lack of high tunnel summer season extension produced results that were generally cultivar specific. While grafting increased the total yield of both cultivars (by 18%), marketable yield was increased by grafting only for ‘Tribute’ in high tunnels (by 42%). Additionally, high tunnels improved marketable yield of ‘Tribute’ by 129% but had no effect on ‘Garden Gem’. This demonstrated the consistent trend of the beefsteak-type tomato benefiting more from the combination of high tunnel and grafting technologies than the plum-type tomato. High tunnels reduced fruit decay and cracking by up to 71% compared with open field production. Stink bug (Pentatomidae) damage had the greatest impact on marketable yields each season, reaching 13% and 34% of total yields in 2016 and 2017, respectively, and was unaffected by high tunnel production or grafting. This study revealed the benefits of integrating high tunnel and grafting technologies for enhancing organic production of fresh-market tomato in the humid subtropics, and demonstrated more research is warranted to establish regional planting dates and further optimize this high-value cropping system.