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Nitrogen management effects on tuber initiation of selected potato cultivars
Dissertation (MScAgric (Plant Production and Soil Science))--University of Pretoria, 2015.
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| Format: | Thesis |
| Language: | English |
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2026
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| _version_ | 1867613521256120320 |
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| access_status_str | Open Access |
| author2 | Steyn, J.M. (Joachim Marthinus), 1963- |
| author_browse | Steyn, J.M. (Joachim Marthinus), 1963- |
| author_facet | Steyn, J.M. (Joachim Marthinus), 1963- |
| collection | Thesis |
| description | Dissertation (MScAgric (Plant Production and Soil Science))--University of Pretoria, 2015. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/110059 |
| institution | University of Pretoria (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:37:28.126Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2026 |
| publishDateRange | 2026 |
| publishDateSort | 2026 |
| record_format | dspace |
| source_str | UPSpace — University of Pretoria Institutional Repository |
| spelling | oai:repository.up.ac.za:2263/110059 Nitrogen management effects on tuber initiation of selected potato cultivars Steyn, J.M. (Joachim Marthinus), 1963- chantel.duraan@gmail.com Du Raan, Chantel Application timing nitrogen rate nitrogen top dressing tuber initiation tuber quality Dissertation (MScAgric (Plant Production and Soil Science))--University of Pretoria, 2015. Nitrogen (N) is an important plant nutrient that affects all aspects of potato growth, including tuber initiation. Tuber initiation (TI) is an important stage, as it affects crop growth and development, which can subsequently affect yield, size distribution and quality, and therefore also profitability. Potato producers are under immense input cost pressure and efficient nutrient management is therefore crucial. This study investigates the effect of N rate and timing on TI, final yield, size distribution and quality of selected potato cultivars. Field experiments (2013 and 2014) were conducted at the University of Pretoria’s Hatfield Experimental farm on a sandy clay loam soil (15-20% clay). The factorial experiment was laid out as a split-plot randomized complete block design (RCBD) with three replicates. Cultivars (BP1, Eos and Lanorma) were allocated to the main plots and three N levels (R1=160 kg/ha N, R2=240 kg/ha N and R3=320 kg/ha N), together with three N timing treatments (T1=30% at planting, 70% ±3 weeks after emergence; T2=50% at planting, 50% after emergence and T3=70% at planting, 30% after emergence), were allocated to the subplots. Weekly destructive harvests were conducted to conduct growth analyses and monitor TI status. At final harvest tuber yield, size distribution and quality were determined. Eos and Lanorma tended to initiate most tubers early in the season, whereas BP1 initiated tubers throughout the season. Timing also significantly affected TI early in the season, with treatments T2 and T3 initiating significantly more tubers than T1. Marketable yield (medium and large tubers) iv was significantly influenced by cultivar, N timing and N rate. Final total and marketable yields significantly increased from rate R1 to R3 when more N was applied at planting (T3). Timing of TI played a crucial role in Lanorma’s higher proportion of marketable yield, since this cultivar initiated most of its tubers early, which thereby extended the bulking period. R1 did not produce sufficient leaf canopy early in the season due to depleted soil N reserves, which resulted in insufficient bulking, whereas TI ceased due to stolon die-off. Although R3 produced a large and efficient canopy early, the lower harvest index suggests a stimulation of canopy growth at the expense of tuber development and bulking. The vegetative stage was also extended, delaying maturity and consequently reducing tuber quality as well as increasing residual soil N after harvest. T3 ensured sufficient canopy cover throughout the season to ensure optimum growth, tuber bulking and final yield. On the contrary, T1 resulted in an initial inadequate canopy but, due to a large amount of N later in the season, vegetative growth was extended, delaying maturity. Optimal N treatment combinations are R2 and T3 (current recommended guidelines) for all three cultivars, ensuring high yields, optimal tuber size distribution and acceptable tuber quality. Plant Production and Soil Science MScAgric (Plant Production and Soil Science) 2026-05-15T17:26:12Z 2026-05-15T17:26:12Z 16/06/28 2015 Dissertation http://hdl.handle.net/2263/110059 en application/pdf |
| spellingShingle | Application timing nitrogen rate nitrogen top dressing tuber initiation tuber quality Nitrogen management effects on tuber initiation of selected potato cultivars |
| title | Nitrogen management effects on tuber initiation of selected potato cultivars |
| title_full | Nitrogen management effects on tuber initiation of selected potato cultivars |
| title_fullStr | Nitrogen management effects on tuber initiation of selected potato cultivars |
| title_full_unstemmed | Nitrogen management effects on tuber initiation of selected potato cultivars |
| title_short | Nitrogen management effects on tuber initiation of selected potato cultivars |
| title_sort | nitrogen management effects on tuber initiation of selected potato cultivars |
| topic | Application timing nitrogen rate nitrogen top dressing tuber initiation tuber quality |
| url | http://hdl.handle.net/2263/110059 |