To study the quality response of beetroot to nitrogen fertilizers, a pot trial was conducted in
the glasshouse facility of the Department of Soil, Crop and Climate Sciences, Faculty of
Natural and Agricultural Sciences, University of the Free State, during the 2011 season. The
effect of five nitrogen sources (limestone ammonium nitrate, ammonium nitrate, urea,
ammonium sulphate and urea ammonium nitrate) at five nitrogen levels (0, 50, 100, 150 and
200 kg N ha-1) on beetroot (Detroit Dark Red) on a Bainsvlei soil type was investigated. The
data collected was analyzed using Tukeyâs Least Significant Difference test, at 5% level of
significance to determine statistically significant differences between means.
The results showed that all fertilizers used resulted in a reduction in plant height for the first
six weeks of growth. Nitrogen application only increased plant height significantly from week
8 where the height of plants that received nitrogen, irrespective of the fertilizer used, were
significantly taller than control plants. At week 8 no significant differences in height were
noted between various nitrogen application rates, but by week 10 significant differences in
plant height were noted between the 50 kg N ha-1 and 150 kg N ha-1 or 200 kg N ha-1
application rates. The findings showed that beet plants reacted better to N-fertilization using
ammonium sulphate nitrate and urea ammonium nitrate than other nitrogen sources,
although limestone ammonium nitrate and ammonium nitrate also produced improvements
in plant growth, whereas plants that received urea showed no improvements.
Nitrogen at 100 kg ha-1 resulted in more leaves per plant than its application at other levels.
Urea ammonium nitrate as a nitrogen source significantly improved plant leaf area, leaf fresh
mass, total fresh mass and root diameter. Application of nitrogen at 200 kg ha-1 also
increased leaf area, leaf fresh mass, total fresh mass, beet diameter and beet volume. Urea
ammonium nitrate increased leaf dry mass by an average of 397% while the lowest leaf dry
mass by (139.42% of control) was observed with the use of limestone ammonium nitrate as
a nitrogen source. The greatest leaf dry mass was obtained at the highest rate of nitrogen
application (200 kg ha-1) and the lowest leaf dry mass was observed at the control level.
Beet yields were found to increase as the nitrogen application rate increased, from 2.99 t ha-
1 in the control treatments to 14.37 t ha-1 in the treatments that received 200 kg N ha-1.
Fertilizing with urea ammonium nitrate gave the highest yields (12.17 t ha-1), while using
limestone ammonium nitrate gave the lowest yields (9.00 t ha-1). Application of nitrogen at 50 kg ha-1 resulted in firmer beets than nitrogen application at other
levels. Beets from plants that did not receive any nitrogen were significantly softer than those
that received nitrogen at higher levels. The darkening of beet colour (decrease of L*) was
experienced at the control level while the highest changes of colour (increase of L*) was
obtained at the highest nitrogen level. Nitrogen at 100 kg ha-1 influenced the lowest change
of coefficient a from red to green while the control level resulted in more intensive change.
The results showed that nitrogen at the control level led to more intensive changes of
coefficient b colours from yellow to blue and its application at the highest level resulted in
less intensive changes of coefficient b colours from yellow to blue.
Neither nitrogen source nor nitrogen level had any effect on the pH, sucrose or fructose
contents of the roots. Application of nitrogen at 150 kg ha-1 resulted in greater total soluble
solids content in the roots, while the starch content of plants that received no nitrogen was
significantly greater than that of plants receiving nitrogen. Nitrogen application at 100 kg ha-1
and at the control level influenced the glucose content, which was significantly higher in
these plants than in those that received 50, 150 and 200 kg N ha-1, however, the highest
glucose content of the roots was observed at the control level.
Nitrogen application at 200 kg ha-1 resulted in higher nitrogen content in the leaves as
compared to application of other nitrogen sources at different levels. Limestone ammonium
nitrate influenced potassium content of the leaves more than other nitrogen sources.
Nitrogen application at 200 kg ha-1 resulted in a greater calcium content in the leaves than
other nitrogen sources. The highest sodium content of the leaves was observed at 150 kg N
ha-1 while the lowest sodium content was observed at 50 kg N ha-1. Urea ammonium nitrate
had a greater positive influence on the manganese content of the leaves than other nitrogen
sources. Plants that received no nitrogen had significantly greater levels of iron in the leaves
than at all nitrogen levels. Ammonium nitrate as a nitrogen source influenced the calcium
content of the beets more than other nitrogen sources. Other root minerals such as
phosphorus, potassium, sodium, magnesium, manganese, copper, iron and zinc were not
significantly influenced by nitrogen source or nitrogen level, or the interaction between these
factors.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-04102014-155348 |
| Date | 10 April 2014 |
| Creators | Rantao, Gabriel |
| Contributors | Dr M de Wit, Dr J Allemann |
| Publisher | University of the Free State |
| Source Sets | South African National ETD Portal |
| Language | en-uk |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.uovs.ac.za//theses/available/etd-04102014-155348/restricted/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University Free State or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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