Interactive effects of weeding regimes and seed shapes on growth, yield and nutrient compononents of SC701 green mealies during summer and winter planting seasons under rain-fed condition.
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Date
2013
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Abstract
Maize and weeds interfere with growth activities of each other to a varying degree. Weeds
compete for water, mineral nutrients, and light and hinder harvest operations. Maize plants are
susceptible to weed competition and yield losses are estimated at 30% to complete crop failure.
Seed shape and size can also be an important factor to consider for improving maize yield
because it influences seedling vigour. The aim of this study was to evaluate the interactive effect
of seed shape and size of SC701 maize hybrid on seed quality. Thereafter, the effect of seed
shape and weed competition on yield of SC701 was evaluated in field trials planted during
summer and winter, in KwaZulu-Natal.
Germination test was carried out on SC701 differentiated on the basis of seed shape, (round and
flat), and seed size (large and small). Seeds were germinated using four different temperature
regimes: constant 20°C and 30°C as well as two alternating temperature regimes, 15/20°C and
20/30°C (12/12 hrs.). The experiment was laid out as a split-plot design with temperature being
the main factor; variety was sub factor with four replications. Upon termination of the
experiment, germination rate (GR), mean germination time (MGT), germination velocity index
(GVI), vigour index (VI), seedling shoot and root lengths, seedling fresh and dry mass and
seedling shoot: root ratio were determined. Field trials were used to evaluate the interactive
effect of seed shape and weeding on SC701 harvested as green mealies during summer and
winter seasons under rainfed conditions at Ukulinga and Umbumbulu in KwaZulu-Natal. At
harvest, nutritional quality of the green mealies was determined.
Results of seed quality showed no significant differences in final germination and MGT among
seed sizes and shapes at different temperature regimes. Highly significant differences (P<0.001)
were observed for daily germination, GR, GVI and VI. Results of daily germination, GR, and
GVI showed that flat seeds germinated faster than round seeds at constant temperatures while in
terms of seed size, small seeds germinated faster than large seeds. A similar trend was observed
for VI. Alternating temperatures (20/30°C) produced higher VI when compared with constant
temperatures for all varieties.
Results from the field trials showed that emergence was faster during summer than during
winter season. Flat seeds emerged better by 1.4% than round seeds. Maize plants were taller
(P<0.001) in summer than in winter. Double weeding had the tallest (P<0.05) plants for both
seasons. Double weeding had the highest leaf number followed by single weeding while no
weeding had the lowest leaf number for both seasons. Weeding treatments had a significant
(P<0.05) effect on days to tasseling (DTT) during both seasons and at both sites. Days to
tasseling was faster by 29.1% during summer than winter while DTT in no weeding were
15.38% and 10.45% longer than DTT in double weeding during summer and winter respectively.
Stomatal conductance (SC) and chlorophyll content index (CCI) were significantly higher
(P<0.001) during the summer than winter season. Weeding frequencies had a significant
(P<0.05) effect on harvest index, total biomass, ear prolificacy, kernel rows per cob, kernels per
row and cob mass.
Weeding frequency was shown to have an effect on nutritional quality of green mealies as
indicated by results of total soluble sugars, starch and protein content; they were low with
decreasing weeding frequency. Proline accumulation was highest in the no weeding treatment
indicating the crop was stressed.
It is concluded that although, standard germination test values showed that flat small seeds
germinated faster at constant than alternating temperatures, this did not translate to better field
emergence. In the field, seed shape of SC701 had no influence on improving crop vigour and
ability to compete with weeds. Furthermore, the present study showed that season plays an
important role in growth and development of green mealies in that winter planting of maize
resulted in low yield production. Further research on the effect of weed competition on growth,
yield and nutritional value of SC701 conducted under irrigated conditions during winter planting
season for green mealies production is therefore recommended.
Description
M. Sc. Agric. University of KwaZulu-Natal, Pietermaritzburg 2013.
Keywords
Corn--KwaZulu-Natal--Growth., Corn--Weed control--KwaZulu-Natal., Corn--Seeds--KwaZulu-Natal., Corn--Yields--KwaZulu-Natal., Corn--Quality--KwaZulu-Natal., Germination--KwaZulu-Natal., Theses--Crop science.