The U.S. fresh-market tomato industry faces increasing competition from Mexico, which achieves greater productivity and quality due to the use of protected structures. Protected agriculture is limited in humid, subtropical regions of the United States. Although grower interest in high tunnel production has increased in recent years, systematic high tunnel research has not yet been conducted in subtropical Florida. Additionally, although tomato grafting has shown the potential to overcome biotic and abiotic stresses, research of high-tunnel, grafted tomato production in subtropical conditions is lacking. During this 2-year study (Citra, FL), a side-by-side comparison of open field and high tunnel organic tomato production was conducted using a split-split plot design. The most significant benefit of high tunnel production was season extension achieved through the reduction of foliar disease severity, which reduced the area under the disease progress curve by 64% across two seasons. This may be largely attributed to the pronounced reduction in the duration of leaf wetness during the wet months of the growing cycle. Grafting with ‘Multifort’ rootstock reduced the root-knot nematode soil population density by 88% as well as root galling severity, both of which demonstrated the potential for increased levels in the high tunnel production system compared with open field production. The more severe root-knot nematode infestation in high tunnels was likely due to the modification of soil temperatures, which were 2 °C greater during the early part of the season but were reduced after shadecloth application. Compared with the open field, solar radiation was reduced by 23% in the high tunnel before shadecloth application and by 51% after shadecloth application; however, due to the high radiation levels in subtropical Florida, daily light integral levels indicated that light was not limiting for high-quality tomato production. The average wind speed was reduced by 57% in the high tunnel and, together with the reduction in solar radiation, indicated the potential reduction in summer abiotic stress and evapotranspiration within high tunnels. These results revealed that the integrated use of high tunnel and grafting technologies may be important for enhancing fresh-market tomato production in the humid subtropics, especially in organic systems.
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.