Effect of Plant Density on the Yield of Hydroponically Grown Heat-Tolerant Tomato under Summer Temperature Conditions

Abstract

Producing enough tomato to meet market demand sustainably has not been feasible in the tropics like Ghana. Attempts to improve production using greenhouse facilities have not addressed the challenge because of high-temperature conditions in the greenhouse, which are difficult to manage. Heat stress, arising from high temperatures, hinder the performance of tomato in terms of fruit set and yield. Moreover, the impending climate change is expected to impose more unfavorable environmental conditions on crop production. An experiment was conducted in (greenhouse at Chiba University, Japan) summer period, which has similar high-temperature conditions like Ghana. This work sought to increase the yield of a heat-tolerant tomato using a state-of-the-art hydroponic system through high-density planting. The outcome of this work was intended for adoption and practice in Ghana. A Heat-tolerant tomato “Nkansah HT” along with Lebombo and Jaguar cultivars, were grown at high and low plant densities (4.1 and 2.7 plants m-2 respectively). Each plant was grown in a low substrate volume culture (0.5 L plant-1) in a recirculating nutrient film technique (NFT) hydroponic system. Parameters measured were plant growth and dry matter assimilation at 12 weeks after transplanting, and the generative components. Results showed that a high plant density increased plant height but reduced chlorophyll content by 9.6%. Under temperature stress conditions, the three cultivars recorded more than 95% fruit set, but plant density did not affect the fruit set and the incidence of blossom end rot (BER). The incidence of BER reduced the marketable yield of the Jaguar cultivar by 51% but, this physiological disorder was not recorded in the HT and the Lebombo cultivars. A high-density planting increased the yield per unit area increased by 38.9%. However, it is uneconomical to cultivate the Jaguar cultivar under a heat stress condition due to its high susceptibility to blossom end rot. To improve the yield of tomatoes under tropical heat stress with a threatening climate change condition, the HT is a better cultivar suited for high-density planting. This study shows that high-density cultivation of the HT cultivar in NFT hydroponic system has the potential to increase Ghana’s current tomato yield by 4.8 times.