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Response of kikuyu grass (Pennisetum clandestinum) to irrigation with saline, sodic wastes and nitrogenous, manganiferous effluent
The Manganese Metal Company (MMC) situated in Nelspruit, Eastern Transvaal, South Africa produces a manganiferous saline effluent from a manganese ore leaching process. The high NH₄ content of the waste has been identified as a possible nitrogen fertilizer source. Irrigation of the MMC waste over ne...
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Department of Geological Sciences
2017
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| _version_ | 1867613552493199360 |
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| access_status_str | Open Access |
| author | Mills, Anthony |
| author2 | Fey, Martin V |
| author_browse | Fey, Martin V Mills, Anthony |
| author_facet | Fey, Martin V Mills, Anthony |
| author_sort | Mills, Anthony |
| collection | Thesis |
| description | The Manganese Metal Company (MMC) situated in Nelspruit, Eastern Transvaal, South Africa produces a manganiferous saline effluent from a manganese ore leaching process. The high NH₄ content of the waste has been identified as a possible nitrogen fertilizer source. Irrigation of the MMC waste over nearby kikuyu ( Pennisetum clandestinum) pastures could thus potentially solve a waste disposal problem as well as provide fertilization of the pastures, although the high manganese content of the waste poses a risk of manganese toxicity or pollution. The kikuyu pastures are presently used as a land disposal system for a saline waste from a pulp bleaching process. Due to process changes, the dominant salt type in the waste is anticipated to change from KaCl to Na₂SO₄. Pot experiments with kikuyu were undertaken to investigate NaCl versus Na₂SO₄ salinity effects, Mn toxicity threshold levels and MMC waste versus a standard nitrogen fertilizer (NH₄NO₃) yield response. The results demonstrated that kikuyu grass is both salinity and Mn tolerant. Kikuyu salinity tolerance, using electrical conductivity as a salinity index, was significantly greater in NaCl than Na₂SO₄ salinity. This difference was attributed to the formation of SO₄ neutral ion pairs in Na₂SO₄ treatments which decreased cation uptake, increased osmotic stress relative to electrical conductivity and led to a possible SO₄-induced Ca deficiency. Cl adsorption in manganous sulphate and Na₂SO₄ treated soils was speculatively attributed to the formation of an undocumented ettringite-like mineral. Kikuyu exhibited both a fertilization effect and a Mn toxicity effect with manganous sulphate applications. An increase in yield occurred between Mn applications of 800 and 1600 mg/kg soil. This effect was attributed to increased nutrient availability as a result of nitrogen mineralisation and soil desorption processes. Mn applications of 3200 and 8000 mg/kg resulted in severe Mn toxicity symptoms and reductions in yield. Fertilization of kikuyu with NH₄NO₃ and MMC waste produced similar yield responses. Manganese toxicity did not manifest itself in MMC waste treated kikuyu, even at nitrogen loadings of 800 kgN/ha. Manganese attenuation in the soil by MnCO₃ precipitation, oxidation of Mn²⁺ and Mn adsorption are expected to prevent excess Mn²⁺ accumulation which would pose a Mn toxicity and water pollution risk. The disposal of untreated MMC waste as a nitrogen fertilizer substitute for kikuyu pastures is thus in principle a feasible operation in terms of maintaining pasture sustainability and preventing pollution of water resources. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/23082 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:37:57.985Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2017 |
| publishDateRange | 2017 |
| publishDateSort | 2017 |
| publisher | Department of Geological Sciences |
| publisherStr | Department of Geological Sciences |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/23082 Response of kikuyu grass (Pennisetum clandestinum) to irrigation with saline, sodic wastes and nitrogenous, manganiferous effluent Mills, Anthony Fey, Martin V Willis, James P Geological Sciences Environmental Geochemistry The Manganese Metal Company (MMC) situated in Nelspruit, Eastern Transvaal, South Africa produces a manganiferous saline effluent from a manganese ore leaching process. The high NH₄ content of the waste has been identified as a possible nitrogen fertilizer source. Irrigation of the MMC waste over nearby kikuyu ( Pennisetum clandestinum) pastures could thus potentially solve a waste disposal problem as well as provide fertilization of the pastures, although the high manganese content of the waste poses a risk of manganese toxicity or pollution. The kikuyu pastures are presently used as a land disposal system for a saline waste from a pulp bleaching process. Due to process changes, the dominant salt type in the waste is anticipated to change from KaCl to Na₂SO₄. Pot experiments with kikuyu were undertaken to investigate NaCl versus Na₂SO₄ salinity effects, Mn toxicity threshold levels and MMC waste versus a standard nitrogen fertilizer (NH₄NO₃) yield response. The results demonstrated that kikuyu grass is both salinity and Mn tolerant. Kikuyu salinity tolerance, using electrical conductivity as a salinity index, was significantly greater in NaCl than Na₂SO₄ salinity. This difference was attributed to the formation of SO₄ neutral ion pairs in Na₂SO₄ treatments which decreased cation uptake, increased osmotic stress relative to electrical conductivity and led to a possible SO₄-induced Ca deficiency. Cl adsorption in manganous sulphate and Na₂SO₄ treated soils was speculatively attributed to the formation of an undocumented ettringite-like mineral. Kikuyu exhibited both a fertilization effect and a Mn toxicity effect with manganous sulphate applications. An increase in yield occurred between Mn applications of 800 and 1600 mg/kg soil. This effect was attributed to increased nutrient availability as a result of nitrogen mineralisation and soil desorption processes. Mn applications of 3200 and 8000 mg/kg resulted in severe Mn toxicity symptoms and reductions in yield. Fertilization of kikuyu with NH₄NO₃ and MMC waste produced similar yield responses. Manganese toxicity did not manifest itself in MMC waste treated kikuyu, even at nitrogen loadings of 800 kgN/ha. Manganese attenuation in the soil by MnCO₃ precipitation, oxidation of Mn²⁺ and Mn adsorption are expected to prevent excess Mn²⁺ accumulation which would pose a Mn toxicity and water pollution risk. The disposal of untreated MMC waste as a nitrogen fertilizer substitute for kikuyu pastures is thus in principle a feasible operation in terms of maintaining pasture sustainability and preventing pollution of water resources. 2017-01-25T14:28:21Z 2017-01-25T14:28:21Z 1995 2016-11-22T08:41:27Z Master Thesis Masters MSc http://hdl.handle.net/11427/23082 eng application/pdf Department of Geological Sciences Faculty of Science University of Cape Town |
| spellingShingle | Geological Sciences Environmental Geochemistry Mills, Anthony Response of kikuyu grass (Pennisetum clandestinum) to irrigation with saline, sodic wastes and nitrogenous, manganiferous effluent |
| thesis_degree_str | Master's |
| title | Response of kikuyu grass (Pennisetum clandestinum) to irrigation with saline, sodic wastes and nitrogenous, manganiferous effluent |
| title_full | Response of kikuyu grass (Pennisetum clandestinum) to irrigation with saline, sodic wastes and nitrogenous, manganiferous effluent |
| title_fullStr | Response of kikuyu grass (Pennisetum clandestinum) to irrigation with saline, sodic wastes and nitrogenous, manganiferous effluent |
| title_full_unstemmed | Response of kikuyu grass (Pennisetum clandestinum) to irrigation with saline, sodic wastes and nitrogenous, manganiferous effluent |
| title_short | Response of kikuyu grass (Pennisetum clandestinum) to irrigation with saline, sodic wastes and nitrogenous, manganiferous effluent |
| title_sort | response of kikuyu grass pennisetum clandestinum to irrigation with saline sodic wastes and nitrogenous manganiferous effluent |
| topic | Geological Sciences Environmental Geochemistry |
| url | http://hdl.handle.net/11427/23082 |
| work_keys_str_mv | AT millsanthony responseofkikuyugrasspennisetumclandestinumtoirrigationwithsalinesodicwastesandnitrogenousmanganiferouseffluent |