Thesis (M. Sc. Agric.(Plant Production)) -- University of Limpopo, 2019 / Nightshade (Solanum retroflexum Dun.) is among the most important indigenous leafy
vegetables in Vhembe District, Limpopo Province, South Africa, due to its high values
of beta-carotene, vitamin E, folic acid, ascorbic acid, calcium, iron and protein.
Vhembe District occurs in the tropical regions of Limpopo Province and the production
of vegetables is dependent upon the availability of irrigation water. An Integrated Drip
Irrigation System (IDIS) and a 3S planter were developed to save water by planting
several plants/hole of drip irrigation system. The subsystems in IDIS allow for the
production of different crops with different water requirements, whereas the 3S planter
can be used for planting from one to nine plants/hole of drip irrigation system. Also,
the subsystems could be used in assessing irrigation interval for crops under various
planting densities. The interaction of irrigation interval and planting density of S.
retroflexum had not been documented. The objective of this study, therefore, was to
determine the interactive effects of irrigation interval and planting density on biomass
yield and chemical nutrient elements (summer harvest only) of S. retroflexum under
field conditions. The irrigation interval and planting density/hole were arranged in a
split-plot experimental design, with eight replications. The main plot was irrigation
interval and the subplot was the planting densities. Harvesting was done twice for both
summer and winter experiments. The first harvest (H1) was done at 6 weeks after
transplanting, with the second harvest (H2) being done at six weeks after the first
harvest. Fresh shoots were oven-dried at 60°C for 72 h for the determination of dry
matter. Mature leaves were powdered and analysed for mineral content (Ca, P, K, Mg,
Na, Fe, Zn, Mn and Cu) using the ICPE-9000. Data were subjected to analysis of
variance using SAS software. In the summer experiment, the interaction was
significant (P ≤ 0.05) for dry shoot mass at H1 and H2. However, the contribution of
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the interaction in the total treatment variation (TTV) of the variable was negligent and
therefore, only single factors were reported. Irrigation interval and planting density had
highly significant (P ≤ 0.01) effects on plant variables during H1 and H2 in summer
and winter. However, irrigation interval effects for dry shoot mass were not significant
for summer H2. Interaction effects were significant for Ca, P, K, Mg, Mn and Cu in leaf
tissues during summer H1, but were not significant for Na, Fe and Zn. Also, irrigation
interval was significant for Ca, Mg, P, K, Na, Fe, Zn, Mn and Cu during summer H1,
whereas planting density had no significant effects for all chemical nutrients except for
Ca, P and K during summer H1. Dry shoot mass of S. retroflexum increased linearly
with increasing irrigation interval and planting density. Results suggested that most
nutrient elements increased with deficit irrigation water and higher planting density,
whilst P decreased under high planting density. The study showed that there is a high
potential for saving water through longer irrigation intervals and produce good high
yields at a higher planting density. In conclusion, the use of IDIS and 3S planter to
promote growth and accumulation of essential nutrient elements on S. retroflexum
demonstrated that longer irrigation interval and higher plant density per drip irrigation
hole could be suitable for cultivation of this indigenous vegetable. The
recommendation of this study is that higher planting density and longer irrigation
intervals are key determinants of higher biomass yield and water saving strategies for
large-scale production of the crop. Further, the mineral composition of the crop was
under the influence of higher planting density and irrigation intervals.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ul/oai:ulspace.ul.ac.za:10386/2895 |
| Date | January 2019 |
| Creators | Mabotja, Thakgala Confidence |
| Contributors | Mashela, P. W. |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | xv, 109 leaves |
| Relation |
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