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Optimal hydroponic growth of Brassica Oleracea at low nitrogen concentrations using a novel ph-based control strategy
Dissertation (MEng)--University of Pretoria, 2021.
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| Format: | Thesis |
| Language: | English |
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University of Pretoria
2021
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| _version_ | 1867613520734978048 |
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| access_status_str | Open Access |
| author2 | Nicol, Willie |
| author_browse | Nicol, Willie |
| author_facet | Nicol, Willie |
| collection | Thesis |
| dc_rights_str_mv | © 2019 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. |
| description | Dissertation (MEng)--University of Pretoria, 2021. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/80979 |
| institution | University of Pretoria (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:37:27.661Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2021 |
| publishDateRange | 2021 |
| publishDateSort | 2021 |
| publisher | University of Pretoria |
| publisherStr | University of Pretoria |
| record_format | dspace |
| source_str | UPSpace — University of Pretoria Institutional Repository |
| spelling | oai:repository.up.ac.za:2263/80979 Optimal hydroponic growth of Brassica Oleracea at low nitrogen concentrations using a novel ph-based control strategy Nicol, Willie ignatiuslvr@gmail.com Van Rooyen, Ignatius Leopoldus UCTD Proton to nitrate ratio Nitrate concentration control Nitrogen spillage Soilless agriculture Engineering, built environment and information technology theses SDG-02 Engineering, built environment and information technology theses SDG-06 Engineering, built environment and information technology theses SDG-12 Engineering, built environment and information technology theses SDG-15 Dissertation (MEng)--University of Pretoria, 2021. Aquatic nitrogen pollution from conventional agriculture contributes severely to the degradation of numerous ecosystems and is considered one of the main contributors to earth's alarming rate of biodiversity loss. Soilless agriculture, in contrast to conventional agriculture, has the advantage of discharge control since the nutrient solution is contained. However, periodic replacement of the nutrient solution is dictated by inert build-up over time resulting from transpiration. As the spent solution is usually discharged, the nutrient concentrations are proportional to the load of nutrient spillage to the environment. This study investigates a novel pH-based control strategy to minimise the nitrate concentration while maintaining optimal plant growth and nutrition. Experiments were performed where the nitrate concentration was controlled at 11 mM (representing standard protocol), 1 mM, 0.5 mM, and 0.1 mM. This was accomplished by controlling the pH with a mixture of HNO3 and NaNO3. A molar ratio of 3:2 (HNO3:NaNO3) resulted in relatively stable nitrate profiles with slow depletion of nitrate in solution, owing to a near-constant ratio between proton dosing required for pH homoeostasis and nitrate absorption. Small manual corrections were made for the 1 mM and 0.5 mM runs, accounting for 8% of the total nitrate absorbed. For the 0.1 mM run, instead of manual correction, an automatic nitrate addition strategy was incorporated, in which nitrate extinction was inferred from a reduction in the rate of change of pH. Zero reduction in plant growth rate and leaf chlorophyll content was detected when comparing the 11 mM run with the other runs, indicating optimal hydroponic performance. A novel nitrate control algorithm is presented that uses pH measurement as the sole input. The experimental results and the control algorithm provide encouraging alternatives for reducing nitrogen spillage from soilless agriculture. mi2026 Chemical Engineering MEng Unrestricted SDG-02: Zero hunger SDG-06: Clean water and sanitation SDG-12: Responsible consumption and production SDG-15: Life on land 2021-07-26T08:32:01Z 2021-07-26T08:32:01Z 2021-04-30 2021 Dissertation * S2021 http://hdl.handle.net/2263/80979 en © 2019 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. application/pdf University of Pretoria |
| spellingShingle | UCTD Proton to nitrate ratio Nitrate concentration control Nitrogen spillage Soilless agriculture Engineering, built environment and information technology theses SDG-02 Engineering, built environment and information technology theses SDG-06 Engineering, built environment and information technology theses SDG-12 Engineering, built environment and information technology theses SDG-15 Optimal hydroponic growth of Brassica Oleracea at low nitrogen concentrations using a novel ph-based control strategy |
| title | Optimal hydroponic growth of Brassica Oleracea at low nitrogen concentrations using a novel ph-based control strategy |
| title_full | Optimal hydroponic growth of Brassica Oleracea at low nitrogen concentrations using a novel ph-based control strategy |
| title_fullStr | Optimal hydroponic growth of Brassica Oleracea at low nitrogen concentrations using a novel ph-based control strategy |
| title_full_unstemmed | Optimal hydroponic growth of Brassica Oleracea at low nitrogen concentrations using a novel ph-based control strategy |
| title_short | Optimal hydroponic growth of Brassica Oleracea at low nitrogen concentrations using a novel ph-based control strategy |
| title_sort | optimal hydroponic growth of brassica oleracea at low nitrogen concentrations using a novel ph based control strategy |
| topic | UCTD Proton to nitrate ratio Nitrate concentration control Nitrogen spillage Soilless agriculture Engineering, built environment and information technology theses SDG-02 Engineering, built environment and information technology theses SDG-06 Engineering, built environment and information technology theses SDG-12 Engineering, built environment and information technology theses SDG-15 |
| url | http://hdl.handle.net/2263/80979 |