Growth, Yield and Fruit Quality of Tomato as Affected by Root Zone Restriction in Combination with Solar-mediated Fertigation Regime

Plant growth and fruit development of tomato (Lycopersicon esculentum Mill. cv. House Momotaro) grown in different sized plastic pots (root zone volume, RZV, of 250, 500, 1,000 mL/plant) in combination with high or low rate of drip fertigation (HF and LF) were investigated. In the February-sown experiment, the plants were fertigated with standard to half strength of Ohtsuka-A solution in proportion to solar radiation keeping the ratio of drainage to supplied solution as 10 to 20ｵ, in 500mL- and 250mL-RZV for HF and LF, respectively. Stem and leaf growth decreased with decrease in RZV and the fertigation rate. The decreases were not significant in the distal plant part lower than the 4th inflorescence. The average fruit weight was greater in HF than LF and increased with increase in RZV only for HF. The incidence of blossom-end rot (BER) was more frequent in HF compared to LF and increased with increase in RZV only for LF. Consequently, fruit yield increased with increase in RZV for HF, but it decreased with increase in RZV for LF. Total soluble solid content (TSS) was significantly higher in LF than in HF and increased with decrease in RZV. Qualified fruits, called ‘fruit tomato’ having 8ｵ of TSS or higher, were obtained with 250 to 500mL of RZV in the successive October-sown experiment where the standard solution was supplied throughout. For ‘fruit tomato’ production with a substrate culture system, root zone restriction, in combination with solar-mediated fertigation control, can be a useful and stable stress factor, reducing shoot and fruit growth, but inducing fruit sugar accumulation and reducing BER incidence simultaneously