For each grain production system, there is an optimum row spacing and plant density that
optimises the use of available resources, allowing the expression of maximum attainable
grain yield in that specific environment. Introduction of the ultra-fast maize hybrids raised
the question whether existing guidelines for row spacing and plant density were still
applicable. This necessitated the integration of optimum row spacing by plant density to
maintain productivity and sustainability the yields with the intention to increase water use
efficiency. Field experiments were conducted for two successive cropping seasons (2008/9
to 2009/10) at Kenilworth Experimental Station of the Department of Soil, Crop and Climate
Sciences, University of the Free State to evaluate the growth, agronomic performance,
phenological development and water use efficiency of an ultra-fast maize hybrid at varying
row spacing and plant densities under irrigation. The treatments involved in this study were
three row spacings (0.225, 0.45 and 0.90 m) and five plant densities (50 000, 75 000,
100 000, 125 000 and 150 000 plant ha-1). The treatments were arranged in a factorial
combination and laid out in a randomized complete block design (RCBD) with four
replications. The largest block was used for periodic destructive sampling for growth
analysis where a completely randomized design was adopted and replications consisted of
five (5) single plants randomly selected. Regarding soil water monitoring, twenty neutron
probe access tubes were installed prior to planting in the center of each plot in one of the
three blocks of the agronomic study. Soil water content was measured at 0.3 m intervals to
a depth of 1.8 m using a calibrated neutron probe. Measurements were made at weekly
intervals from planting to crop physiological maturity where the volumetric reading was
converted into depth of water per 1.8 m. Seasonal ET (water use) was determined by
solving the ET components of the water balance equation. From this water use efficiency
was computed as the ratio of total biomass/grain yield to seasonal ET. In each season crop
growth, agronomic, phenologic and water use efficiency parameters were measured and
the collected data were combined over seasons after carrying the homogeneity test of
variances. Growth parameters, agronomic traits, phenology and water use efficiency of
maize reacted differently to row spacing and plant density and the combination thereof.
In general a slow increase in growth parameters during establishment was followed by an
exponential increase during the vegetative phase. At the reproductive phase growth
ceased following the onset of flowering. Photosynthetic efficiency (NAR) and CGR,
averaged over row spacing, were highest at a plant density of 100 000 plants ha-1 at all
growth phases. Reducing row spacing from 0.45 to 0.225 m and a plant density below or above 100 000 plants ha-1 showed LAI outside the optimum with respect to NAR for
optimum seed yield.
Row spacing, plant density and its interaction affected yield and yield components of maize
significantly. Narrowing rows from 0.45 to 0.225 m and plant densities above
100 000 plants ha-1 as main or interaction effects led to the formation of smaller ears, a
shorter ear length and diameter, low seed mass, favored plant lodging and development of
barren plants with an obvious negative impact on grain yield. On other hand, plant densities
below 100 000 plants ha-1 were insufficient to utilise growth-influencing factors optimally.
Thus, growth analysis provided an opportunity to monitor the main effects and interaction
effects of row spacing and plant density on crop growth at different growth and
development phases.
Row spacing and plant density combinations affected the phenological development of
maize. Increasing row spacing from 0.225 to 0.90 m relatively prolonged the number of
days to anthesis and silking. Regarding anthesis-silking interval (ASI), the lowest plant
density had the shortest ASI while the higher plant densities had relatively longer ASI. Wide
row spacing coupled with low plant density increased the number of days to physiological
maturity and vice versa.
Row spacing and plant density and their interaction affected water use efficiency of maize.
Highest water use was observed at a plant density of 125 000 plants ha-1. Biomass WUE
was highest at a row spacing of 0.45 m with a plant density of 125 000 plants ha-1 while the
highest grain yield WUE recorded was at a row spacing of 0.45 m with a plant density of
100 000 plants ha-1.
The overall combined effect of row spacing and plant density revealed that a combination
of 0.45 or 0.90 m with 100 000 plants ha-1 to be the optimum for the selected ultra-fast
maize hybrid under irrigation.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-07182013-085742 |
| Date | 18 July 2013 |
| Creators | Yada, Gobeze Loha |
| Contributors | Prof LD van Rensburg, Dr GM Ceronio |
| 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-07182013-085742/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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