An Investigation into the Impact of Chitin Amendments on the Growth and Nutritional Properties of Greenhouse Lettuce and Tomato Crop Production

  • Edward Joseph Collins

Student thesis: Doctoral Thesis


This thesis investigated the impact of recycled waste chitin growing media amendments on the growth, yield, and antioxidant properties of lettuce and tomato crops. Chitin is a key component in the shells of all insects and shellfish and 6-8 million tonnes of waste crab, shrimp, and lobster shells are produced globally, as a result of the shellfish industry. This thesis aims to utilise recycled waste chitin as a growing media amendment in the cultivation of tomatoes and lettuce.
Two lettuce trials were carried out to assess the impact of chitin when added to growing media. The first trial tested cos lettuces and the second trial tested butterhead lettuces. Lettuces were treated with a range of crab and shrimp chitin dry weight percentages and their growth was monitored until harvest when yield data was collected. Antioxidant assays (Folin- Ciocalteu, FRAP, and DPPH) were utilised to assess the impact of chitin amendments on lettuce antioxidant capacity.
Three tomato trials were carried out. One trial mirrored commercial tomato trial conditions to assess the impact of chitin and biochar growing media amendments. Two further trials investigated the impact of a range of shrimp chitin amendments. Crop growth, yield, and fruit antioxidant capacity were all investigated. Growth was monitored throughout the tomato trials and fruit yield measurements were taken when fruit developed. Fruit antioxidant capacity was assessed using antioxidant assays (Folin-Ciocalteu, FRAP, DPPH, and Randox).
Cos and butterhead lettuce growth and yield were highest with chitin amendments 1%- 2%. Antioxidant capacity was highest for 3% chitin in cos lettuces and 1%-2% in butterhead lettuces. 1%-2% was concluded to be the optimum range of chitin required for lettuce cultivation.
In the multi-centre commercial tomato trial conducted as part of Horti-BlueC, chitin and biochar amended growing media had no beneficial or detrimental impacts to crop growth, fruit yield, or fruit antioxidant capacity. When tested as a range of chitin dry weight percentages, 3% chitin was concluded to result in the optimum crop growth, fruit yield, and fruit antioxidant capacity.
Finally, this thesis created engaging and novel platforms to disseminate research findings at public events and conferences.

This research was carried out as part of the Horti-BlueC project, a multi-partner UK and European project proposing new solutions and innovative growing media blends for sustainable greenhouse horticulture.

Date of Award20 Jan 2023
Original languageEnglish
Awarding Institution
  • University of Portsmouth
SupervisorCressida Bowyer (Supervisor), Mridula Chopra (Supervisor) & Matthew James Tallis (Supervisor)

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