Some effects of environment, age and growth regulating compounds on the growth, yield and quality of sugarcane in southern Africa.
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Date
1974
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Abstract
An assessment has been made of the potential for
increasing yields of well grown irrigated sugarcane crops beyond
their present maxima. The effects of age at harvest and artificial
growth regulators on yield have also been investigated.
Measurement of the apparent maximum yield of cane
fresh weight (tc/ha) and total dry matter (t.dm/ha) of three
varieties grown on a specially prepared site, indicated that
actual cane yields were 63-70% of the estimated potential maximum.
Differences in morphology between two extreme varieties, NCo 376
and CB 36/14, were insufficient to affect growth and yield under
good growing conditions. The average productivity over a period
of one year of plant and first ratoon crops of three varieties
was 65 t.dm/ha and 150 tc/ha. This is a crop growth rate of
17,0 g/m(2)/dy, representing an average conversion into plant dry
matter of 1,9% of total incident radiation (ri.) or 4,3% of visible
ri. This level of productivity is equivalent to rates reported for
sugarcane growing in more favourable parts of the world and for
other highly productive crops.
In an experiment in which a series of crops were
ratooned at different times of the year and harvested at ages
ranging from 32 to 72 weeks, sugar yield and all measures of cane
quality were closely correlated with cane yield for crops of all
ages. Sugar yield varied with age at harvest, according to the
cycle of weather conditions experienced by the crop. Crops
ratooned in January and February produced the highest yields of
23 tons estimated recoverable sugar per hectare ( ters/ha) at
64-72 weeks of age. The average rate of sugar production at
this time ranged from 1,3-1,5 ters/ha/month. At 12 months of
age crops ratooned in July and September had the highest yields
of 17,2 ters/ha, but they then made little further growth. High
rates of sugar production of 1,4-1,6 ters/ha/month were obtained
from crops ratooned between June and September and harvested
between May and. August at 40-56 weeks of age. Considering data
for all crops, cane yield was correlated with weather conditions
only up to 40 weeks of age. After this, increments of cane yield
were correlated better with the amount of growth already made than
with either crop age or the average weather conditions experienced.
Artificial chemical ripening was successful on young
immature crops harvested in May at the beginning of the milling
season, but there was only a small response under less favourable
growing conditions and when the crop was older and more mature.
Ethrel and Polaris were the most successful of several ripeners
tested, Ethrel being more active than Polaris. Cane quality was
improved and sucrose storage was increased despite reductions in
rates of photosynthesis and sheath and lamina size. The ripening
response varied with variety, condition of the crop at the time of
spraying, rate of chemical application and the time interval between
spraying and harvesting.
From this work it is concluded that it will probably
be easier to raise the sugar yield of existing high yielding
varieties by altering the proportioning of photosynthate in
favour of sucrose storage, rather than by increasing cane yield.
Description
Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1974.
Keywords
Sugarcane--South Africa., Sugar growing--South Africa., Sugarcane--Yields--South Africa., Sugarcane--Growth., Plant regulators., Theses--Crop science.