Investigation of new techniques to improve quality and resource use efficiency in soilless protected horticulture

  • Salvatore Verdoliva

Student thesis: Doctoral ThesisDoctor of Philosophy


This study is focused on a specific sub-sector of agriculture which is the production of fruits and vegetables in controlled environments. This sector, called horticulture, is arguably one of the most technologically advanced in agriculture. However, due to the intensive use of inputs
such as energy and fertiliser, it is under constant pressure to improve its efficiency. Nowadays, a significant amount of fresh food is produced in greenhouses using hydroponic technologies that allows growing of plants without soil, saving water while controlling the climate. This
technology is now popular in the production of fruits and vegetables due to its reliability and capability of producing food offseason. Similarly, to other indoor growing technologies, hydroponics requires energy, synthetic fertilisers, and significant financial investments. Firstly, in this study, the validity of the benefits usually associated with hydroponic systems was assessed. These are usually referred to as year-round production, increased yields and fewer unpredictable variables related to weather. Additionally, in this study verification was made as to whether hydroponic produce can be of similar or better quality comparable to soil– grown produce. In this study it was shown that hydroponics can produce tomatoes that are not of a lower quality compared to soil-grown ones if the same nutrients are provided. Secondly, considering the high investment needs and the greater operations costs, the possibility of growing two crops in the same hydroponic system to optimise the production was assessed. This method called intercropping, is not new in agriculture and is often used in open field. However, it was never deeply tested in hydroponic systems as the industry is focussing almost completely on monoculture. The results showed that due to the concentrated nutrient solutions used in hydroponic systems, it is possible to cultivate two crops concurrently and create a mild competition that can enhance the growth of the companion crop. Thirdly, in order to operate properly, hydroponics needs a significant amount of fertilisers which are mainly sourced from mined material. Additionally, around 20-30% of the food we produce is wasted. Therefore, we evaluated the possibility to use in hydroponic food systems waste extracts as fertiliser to reduce the inputs costs and the carbon footprint of the industry, aiming to a more circular economy. Tomato and bananas are among the fruits and vegetables that are wasted the most and therefore were the focus of this study. Among the two, the banana extract provided the most promising results for a real-world use as a potassium-based supplement. This process needs to be scaled and stabilised, but it seems to be a valid solution towards the reduction of GHG emission and a circular economy.
Date of Award2021
Original languageEnglish
Awarding Institution
  • Aberystwyth University
SupervisorDylan Gwynn-Jones (Supervisor) & Paul Robson (Supervisor)


  • deep water culture
  • fertilization
  • hydroponic
  • lycopene
  • tomato
  • basil
  • water use efficiency

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