Effect of Spacing and Topping on the Performance of Hydroponically Grown Tomato Under Tropical Conditions

Production of tomato in the tropics especially in Ghana is beset with lots of setbacks thereby causing low yields per hectare. Greenhouse cultivation systems are promising yet yields of tropical tomato cultivars are hampered by adverse temperature conditions. In order to mitigate this, an experiment was conducted during the extreme summer temperature conditions in the greenhouse at Kashiwanoha Campus of Chiba University, Japan. The study was conducted between May 23, 2018 and September20, 2018. The low substrate volume production system of 500mL in closed recirculated hydroponics (sub-irrigation) method was employed. Three tropical tomato cultivars (Jaguar, Lebombo and Lindo) were evaluated for yields. Plants were spaced at 20cm (4.2 plants m-2) and 30cm (2.8 plants m-2). At 7 and 9WAT, plants were topped at 2nd and 4th nodes respectively. The 3x2x2 factorial in Randomised Complete Block design in three replications was adopted. Some parameter collected were; 1. Morphometrics such as plant height, girth, leaf number and chlorophyll content, days to 50% flowering and fruit set 2. Yield components and fruit quality such as fruit number, marketable yield, yield per area, yield per hectare, percent blossom end rot, fruit TSS, TA, TSS/TA ratio and 3. Dry matter partitioning at last harvest, 11WAT. Results showed that blossom end rot reduced the yields of Jaguar and Lindo almost by 50% while Lebombo recorded less than 1%. Lebombo produced significantly the highest plant dry mass of 125g of which 57.7% was converted to vegetative growth compared to the Jaguar. For Jaguar however, 53.7% of total plant dry mass was allocated to fruits. This in effect was translated to the highest yield of 93tons ha-1 year-1 for Jaguar plants that were pinched at 4th truss in high density planting of 4.2 plant m-2.