Effect of Mid-day Reduction of High Electrical Conductivity Treatment on the Yield and Quality of Greenhouse Cherry Tomato

Abstract

<jats:p>Cherry tomato (<jats:italic>Solanum lycopersicum</jats:italic> var. <jats:italic>cerasiforme</jats:italic>) plants were grown hydroponically with three different regimes of electrical conductivity (EC) of the nutrient solution to develop an effective EC management method to enhance the fruit quality. The EC treatments examined were 1) continuous high EC [4.7 dS·m<jats:sup>−1</jats:sup> (HE)], 2) continuous low EC [2.8 dS·m<jats:sup>−1</jats:sup> (LE)], and 3) high EC combined with midday (1030–1530 <jats:sc>hr</jats:sc>) low EC [midday reduction of high EC (MDR)]. The research was conducted to obtain preliminary information on the effect of EC treatments on the yield and fruit quality for 15 weeks of harvest under semiarid greenhouse conditions. Harvested fruit were sorted to several quality grades, including the “premium” grade based on fruit size, color, and total soluble solids. The number of fruit per truss was significantly higher in cultivar L308 than in cultivar L907 and in the LE treatment than in the HE or MDR treatment. The fruit size decreased over time regardless of EC treatment and cultivar. Cumulative yield of 15 weeks was greater in the LE treatment (26.3 kg·m<jats:sup>−2</jats:sup>) than in the HE treatment (22.1 kg·m<jats:sup>−2</jats:sup>) for ‘L907’, and there were no significant differences between the three EC treatments for ‘L308’ (24.1–28.1 kg·m<jats:sup>−2</jats:sup>). The cumulative yield in the MDR treatment was similar to that in the LE treatment regardless of cultivar. When quality attributes such as total soluble solids concentration measured for randomly sampled fruit were considered, cumulative premium-grade yield was the greatest for the HE treatment (12.9 or 17.6 kg·m<jats:sup>−2</jats:sup>) and was the smallest for the LE treatment (1.4 or 12.1 kg·m<jats:sup>−2</jats:sup>), regardless of cultivar. The cumulative yield of premium-grade cherry tomatoes in the MDR treatment was not significantly different from that in the HE treatment for ‘L308’ but was 11% less than that in the HE treatment for ‘L907’. Therefore, together with cultivar selection, the MDR treatment may be a potential alternative to a more commonly practiced continuously high EC treatment in semiarid greenhouses with limited environmental control capacity in which increasing the nutrient EC to increase quality is desired without significantly decreasing yield.</jats:p>

Effects of Nutrient Solution Management and Environment on Tomato in Small-scale Hydroponics

“…successfully grown under W/O for 8 weeks with a solution EC as high as 5.5 dSÁm -1 , results from this study using W/O confirmed the findings of others that show a reduction in yield and an increase in BER as a result of a high solution EC when growing tomato plants hydroponically (Table 1, Fig. 2A) (Adams, 1991;Buck et al, 2008;Heuvelink, 2018). The large differences in nutrient demand and susceptibility to high EC between fruiting crops such as tomato, and herbs such as basil, warrant different nutrient solution management strategies that must consider specific crop needs and plant responses to the production environment.…”

“…High solution EC lowers tomato fruit yield due to a reduction of water flux into the fruit (Adams, 1991;Adams and Ho, 1989;Adams and Holder, 1992;Buck et al, 2008;Johnson et al, 1992), which primarily affects yield by reducing fruit size rather than fruit number per se (Adams, 1991;Gormley and Maher, 1990; Nakano et al, 2010; Shalhevet and Yaron, 1973; Willumsen et al, 1996). This corresponds with the results observed in our study for total fruit number and total fruit fresh weight (Table 1).…”

“…In addition, high solution EC increases quality parameters such as lycopene, sugar, and total soluble solid concentration of tomato fruit, which could be particularly attractive for consumers aiming to produce nutritious fruit (Heuvelink, 2018;Wu and Kubota, 2008). High EC treatments are also more suitable for small-fruit-type tomatoes, as their yield is less affected by high solution EC than that of cultivars with larger fruit (Buck et al, 2008;Cuartero and Fern andez-Munoz, 1999). ENVIRONMENT.…”

Changes in Selected Quality Attributes of Greenhouse Tomato Fruit as Affected by Pre- and Postharvest Environmental Conditions in Year-round Production

“…The TSS was relatively higher during early spring than that during the rest of year, showing that TSS was affected not only by water potential in the root zone, but also by the greenhouse environment conditions. Similarly, increase in TSS by increasing nutrient concentration as well as salt concentrations was reported by Adams (1991), Buck et al (2008), Dorais et al (2001) and Krauss et al (2006). Buck et al (2008) also showed that seasonal changes in TSS were caused by the seasonal changes in greenhouse environments.…”

“…Total soluble solid concentration is affected by water content in fruit and can be increased by limiting water transport to the fruit by growing the plant under lower (more negative) water potential in the root zone. Based on this understanding, growing tomato plants hydroponically using nutrient solution with high EC has been commercially practiced worldwide, yet to a limited extent in North America (Buck et al, 2008).…”