New Zealand Journal of Crop and Horticultural Science abstracts
Using early-season measurements to estimate fruit volume
at harvest in kiwifruit
A. J. HALL1
H. G. McPHERSON2
R. A. CRAWFORD1
N. G. SEAGER1
1The Horticulture and Food Research
Institute of New Zealand
Private Bag 11 030
Palmerston North, New Zealand
2The Horticulture and Food Research
Institute of New Zealand
Private Bag 92 169
Auckland, New Zealand
Abstract The results of controlled environment experiments
and a field survey covering six major New Zealand kiwifruit (Actinidia
deliciosa) growing regions over 3 years showed, surprisingly, that the
effect of temperature on the rate of fruit growth is small, at least during the
second half of the fruit growth period. The considerable variation in the mean
and standard deviation of fruit volume at harvest observed in the field among
seasons and sites is therefore not attributable to temperature differences
during the fruit-growing season. This raises the possibility that most of the
factors affecting fruit growth rates may be established early in the season, so
harvest fruit volumes can be predicted from early-season measurements. Mean
fruit volumes observed in the field survey ranged from <85 ml (Kerikeri 1987
and Te Puke 1989) to >130 ml (Kerikeri 1988). However, the variation was not
consistent across years or sites. The standard deviation of fruit volume
differed significantly between one pair of sites but it is not known what
proportion of this should be attributed to management practices such as fruit
thinning. The fruit growth curves could be described by a two-phase curve, with
a reduction in slope 50-60 days after flowering. The initial phase, up to 50
days from flowering, produced growth rates of 1.55 ml/day. The second, slower
phase of growth, averaged 0.42 ml/day over the period to harvest. A simple
linear regression model was used to predict the mean fruit volume at harvest
from measurements of fruit volume made at a given time during the period from
50 to 110 days from flowering (typically mid January and mid March,
respectively). The percentage of the variation in mean fruit volume at harvest
accounted for by the regression was 75% when based on measurements made 50 days
from flowering and rose to nearly 98%, 110 days from flowering. A similar
approach was used to predict the standard deviation of fruit volume at harvest.
The observed standard deviation at harvest varied from 10 ml to just over 20
ml, which is within the range published by others. The regression of the
standard deviation of the fruit volume at harvest on the standard deviation of
fruit volume earlier in the season accounted for more than 80% of the observed
variation from 50 days after flowering onwards.
Keywords temperature; kiwifruit; Actinidia deliciosa;
prediction; forecasting; fruit growth; fruit size distribution
New Zealand Journal of Crop and Horticultural Science, 1996, Vol. 24:
379-391
0114-0671/96/2404-0379 $2.50/0 (c) The Royal Society of New Zealand
1996
PDF file of entire paper: medium quality (999K); (scanned from paper original: notes about this process)
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