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Macroalgal-derived alginate soil amendments for water retention, reduced nutrient release rate, and soil pH control
Thesis (MEng)
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| Format: | Thesis |
| Language: | en_ZA |
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Stellenbosch : Stellenbosch University
2022
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| _version_ | 1867613810171314176 |
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| access_status_str | Open Access |
| author | Van der Merwe, Roelof du Toit |
| author2 | Pott, Robert William M. |
| author_browse | Pott, Robert William M. Van der Merwe, Roelof du Toit |
| author_facet | Pott, Robert William M. Van der Merwe, Roelof du Toit |
| author_sort | Van der Merwe, Roelof du Toit |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MEng) |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/124848 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA |
| last_indexed | 2026-06-10T12:42:03.173Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2022 |
| publishDateRange | 2022 |
| publishDateSort | 2022 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/124848 Macroalgal-derived alginate soil amendments for water retention, reduced nutrient release rate, and soil pH control Van der Merwe, Roelof du Toit Pott, Robert William M. Goosen, Neill Jurgens Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering. Ecklonia maxima; macroalgal-derived alginate; hydrogels; slow-release fertilisers; water retention; reduce nutrient release rate; soil pH control Thesis (MEng) ENGLISH SUMMARY: There is a need to develop sustainably sourced products that can improve water retention, reduce release rates of fertiliser nutrients, and control the pH of soils for use in agriculture. This research investigates the use of alginate extracted from industrial solid kelp waste (IW) to produce soil amendments, potentially improving soil water retention, acting as slow-release fertilisers, and controlling soil pH levels. Analysing the guluronic to mannuronic acid (G/M) ratios within the IW alginate and pure (LG) alginate determined that the IW alginate has a higher G/M ratio (0.53) than the LG alginate (0.36). Hydrogels were produced using different concentrations of IW and LG alginate solutions, and the swelling capabilities of these hydrogels were investigated in deionised water. The results indicated that as the alginate concentration in the hydrogels increased, the hydrogels’ swelling capabilities decreased. Therefore, 1 wt% alginate solutions were selected to produce the hydrogels and soil amendments. The 1 wt% IW hydrogels achieved swelling ratios of 1.67, while the 1 wt% LG hydrogels only achieved 0.62, showing that the IW hydrogels had better swelling capabilities than their LG counterparts. Alginate-based hydrogels were loaded with NPK fertilisers and limestone to produce soil amendments. The swelling characteristics of the produced soil amendments were tested in deionised water, and it was determined that the addition of nutrients to the alginate-based hydrogels significantly decreased the swelling capabilities of the hydrogels. The 1 wt% IW hydrogels that were not washed before being dried achieved a swelling ratio of 0.92 at a steady-state, while the 1 wt% IW NPK+L soil amendments only achieved 0.35. Nutrient release tests were conducted in deionised water at room temperature to determine release rates of N, P, K, and Ca nutrients from the soil amendments and commercial 2:3:4 (30) NPK fertilisers. The results indicated that fertiliser nutrients could be encapsulated in the produced soil amendments. The produced 1 wt% IW NPK+L soil amendments achieved similar equilibrium nutrient release results as the commercial fertilisers but decreased the nutrient release rates of potassium and nitrogen nutrients in deionised water compared to commercial fertilisers. The water retention capabilities of the IW alginate-based soil amendments were investigated in soils, and 15% more water was retained in soils treated with 1 wt% IW hydrogels than untreated soils after 8 days. Plant growth trials were conducted planting Swiss chard in sandy loam soils with different soil treatments. The soils treated with 1 wt% IW NPK+L amendments achieved similar nutrient contents in the cultivated Swiss chard leaves and soils as those treated with commercial 2:3:4 (30) NPK fertiliser. The soils treated with 1 wt% IW NPK+L soil amendments resulted in a 0.33 higher pH in the soil than soils treated with commercial fertilisers. The soils treated with 1 wt% IW NPK+L soil amendments increased the cultivated Swiss chard leaf area by 133% compared to untreated soil. The results showed that IW alginate could be used as an alternative to pure LG alginate to produce alginate-based soil amendments. AFRIKAANS OPSOMMING: Daar is ʼn behoefte om volhoubare produkte te ontwikkel wat die waterretensievermoë van grond kan verbeter, die vrystellingstempo van kunsmis kan verminder en die pH van landbougrond kan beheer. Hierdie navorsing ondersoek die gebruik van alginaat wat uit industriële vaste kelpafval (IW) herwin word om landbouprodukte in die vorm van hidrogels te produseer wat die waterretensievermoë van grond kan verbeter, kunmisvrystellingstempo kan beheer en die pH-vlakke van grond kan aanpas. Die verhouding tussen die guluroon- en mannuronsuurkonsentrasies (G/M) binne die IW-alginaat en suiwer (LG) alginaat het getoon dat die IW-alginaat ’n hoër G/M-verhouding (0.53) het as die LG-alginaat (0.36). Hidrogels is vervaardig met behulp van verskillende konsentrasies IW- en LG-alginaatoplossings, en die swelvermoë van hierdie hidrogels is in gedeïoniseerde water ondersoek. Die resultate het aangedui dat namate die alginaatkonsentrasie in die hidrogels toeneem, die hidrogels se swelvermoë verminder. Daarom is 1 gew.% alginaatoplossing gekies as die konsentrasie om die hidrogels te produseer vir hierdie tesis. Die 1 gew.% IW-hidrogels het ewewig swelverhoudings van 1.67 behaal, terwyl die 1 gew.% LG-hidrogels slegs 0.62 behaal het. Die IW-hidrogels het dus beter swelvermoë as hul LG-eweknieë. Alginaat-gebaseerde hidrogels is met NPK-kunsmisvoedingstowwe en kalksteen verryk, waarna die swelvermoë in gedeïoniseerde water getoets is. Daar is gevind dat die toevoeging van voedingstowwe die swelvermoë van die hidrogels beduidend verminder het. Die 1 gew.% IW-hidrogels wat nie gewas is voor dit gedroog is nie, het swelverhoudings van 0.92 behaal by ewewigstoestande, terwyl die 1 gew.% IW-NPK+L-hidrogels swelverhoudings van slegs 0.35 kon behaal. Kunsmisvrystellingstoetse is in gedeïoniseerde water uitgevoer om die vrystellingstempo’s van N-, P-, K- en Ca-voedingstowwe uit die hidrogels te bepaal met en sonder toevoeging van kommersiële 2:3:4 (30) NPK-kunsmis. Die resultate het aangedui dat kunsmisvoedingstowwe vasgevang kan word in die geproduseerde hidrogels. Die geproduseerde 1 gew.% IW-NPK+L-hidrogels het soortgelyke ewewignutriëntvrystelling resultate as die kommersiële kunsmis behaal, terwyl dit die vrystellingstempo van K en N in gedeïoniseerde water verminder in vergelyking met kommersiële kunsmis. Die waterretensievermoë van die IW-hidrogels is in grond ondersoek, en 15% meer water is behou in grond wat behandel is met 1 gew.% IW-hidrogel as onbehandelde grond, na ‘n periode van 8 dae. Plantgroeiproewe is uitgevoer deur spinasie (Swiss chard) te plant in sanderige leemgrond met verskillende grondbehandelings. Die grond wat met 1 gew.% IW-NPK+L-wysigings behandel is, het soortgelyke voedingsinhoud in die gekweekte spinasieblare en grond tot gevolg gehad as dié wat met kommersiële 2:3:4 (30) NPK-kunsmis behandel was. Die grond wat met 1 gew.% IW-NPK+L-hidrogels behandel is, se pH was met 0.33 eenhede hoër as grond wat met kommersiële kunsmis behandel is na afloop van die proewe. Die gekweekte spinasie se blaaroppervlakte het met 133% vergroot in grond wat met 1 gew.% IW NPK+L-grondwysigings behandel is in vergelyking met spinasie wat in onbehandelde grond gegroei is. Die resultate toon dat IW-alginaat as 'n alternatief tot suiwer LG-alginaat gebruik kan word om alginaat-gebaseerde grondwysigings te produseer. Masters 2022-03-09T11:16:53Z 2022-04-29T09:36:43Z 2022-03-09T11:16:53Z 2022-04-29T09:36:43Z 2022-04 Thesis http://hdl.handle.net/10019.1/124848 en_ZA Stellenbosch University xvi, 161 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Ecklonia maxima; macroalgal-derived alginate; hydrogels; slow-release fertilisers; water retention; reduce nutrient release rate; soil pH control Van der Merwe, Roelof du Toit Macroalgal-derived alginate soil amendments for water retention, reduced nutrient release rate, and soil pH control |
| title | Macroalgal-derived alginate soil amendments for water retention, reduced nutrient release rate, and soil pH control |
| title_full | Macroalgal-derived alginate soil amendments for water retention, reduced nutrient release rate, and soil pH control |
| title_fullStr | Macroalgal-derived alginate soil amendments for water retention, reduced nutrient release rate, and soil pH control |
| title_full_unstemmed | Macroalgal-derived alginate soil amendments for water retention, reduced nutrient release rate, and soil pH control |
| title_short | Macroalgal-derived alginate soil amendments for water retention, reduced nutrient release rate, and soil pH control |
| title_sort | macroalgal derived alginate soil amendments for water retention reduced nutrient release rate and soil ph control |
| topic | Ecklonia maxima; macroalgal-derived alginate; hydrogels; slow-release fertilisers; water retention; reduce nutrient release rate; soil pH control |
| url | http://hdl.handle.net/10019.1/124848 |
| work_keys_str_mv | AT vandermerweroelofdutoit macroalgalderivedalginatesoilamendmentsforwaterretentionreducednutrientreleaserateandsoilphcontrol |