Performance evaluation of hydroponic system for co-cultivation of microalgae and tomato plant

Conventional hydroponic units producing disease free plants with 30-40% faster growth rate are regarded as a promising agricultural alternative in case of unfertile/metal contaminated soil. However, most nutrients in hydroponics medium remain unused and are drained off creating environmental pollution. To reduce the nutrient load and eutrophication effects, cocultivation of plant and microalgae in the hydroponic units has attracted the attention of researchers over the past few years. The present study aims to explore the influence of initial inoculum concentration of a native algal consortium over the performance of hydroponic system. Cocultivation of tomato plant with varying initial inoculum algal concentration of 0.2-0.8 mg/ml, showed that 0.8 mg/ml concentration resulted in positive interactions between microalgae and plant, with algal and plant productivity of 0.149 +/- 0.024 and 0.328 +/- 0.087 g/m(2)/d respectively after 42 days. Higher chlorophyll accumulation, along with nutritionally rich algal and plant biomass revealed lack of unwanted competition during cocultivation. Increase in dissolved oxygen during cocultivation was corroborated with efficient root respiration. Highly developed roots also provided adequate metabolic energy thus significantly increasing the nutrient uptake and accumulation, thereby reducing the nutrient load during drainage. The supernatant after algal harvesting (recycled media) supported plant growth for 24 days due to limited nutrients. Such system with microalgae symbiotically favouring plant productivity and simultaneous nutrient load reduction would ultimately support in attaining sustainable agriculture. (C) 2020 Elsevier Ltd. All rights reserved.