Articles
PREDICTING KIWIFRUIT MATURITY IN ORCHARD BY THE USE OF DAILY MEAN AIR TEMPERATURE ACCUMULATION
Article number
498_27
Pages
239 – 246
Language
Abstract
Soluble solids concentration (SSC) during maturation of kiwifruit (Actinidia deliciosa) in the orchard was followed during 1995 and 1996 in an experiment where air temperature was increased using relocatable greenhouses.
Three treatments were compared to a control having normal orchard temperatures.
The change in SSC for each treatment was estimated as an exponential function of thermal time (degree-day accumulation from September 1 onwards, base 0°C). For the two years, the higher temperatures obtained under the greenhouses, even temporarily, significantly decreased SSC values in fruits.
According to these results, we decided to weight (from 0 to 1) each daily temperature on a sigmoidal pattern.
Various points of inflection and slopes were tested until the difference between the curves of SSC change was minimum.
A single sigmoidal curve for the two years (slope =1.9 and inflection point =13°C) was obtained.
When fitting the curves of SSC evolution to the transformed thermal time using this curve, we obtained two equations, one for each year, when a single one was expected.
However, when compared to either the curves of SSC evolution or the observed SSC values, these equations were considered to be good estimates particularly on the 1996 data set.
The fact that we could not get a single equation can be due to highly different potential SSC levels between the two years.
This could mean that, in order to predict SSC change and thus harvest time, weighting temperature is a useful tool but needs to be supplemented with an estimate of potential final SSC value.
Three treatments were compared to a control having normal orchard temperatures.
The change in SSC for each treatment was estimated as an exponential function of thermal time (degree-day accumulation from September 1 onwards, base 0°C). For the two years, the higher temperatures obtained under the greenhouses, even temporarily, significantly decreased SSC values in fruits.
According to these results, we decided to weight (from 0 to 1) each daily temperature on a sigmoidal pattern.
Various points of inflection and slopes were tested until the difference between the curves of SSC change was minimum.
A single sigmoidal curve for the two years (slope =1.9 and inflection point =13°C) was obtained.
When fitting the curves of SSC evolution to the transformed thermal time using this curve, we obtained two equations, one for each year, when a single one was expected.
However, when compared to either the curves of SSC evolution or the observed SSC values, these equations were considered to be good estimates particularly on the 1996 data set.
The fact that we could not get a single equation can be due to highly different potential SSC levels between the two years.
This could mean that, in order to predict SSC change and thus harvest time, weighting temperature is a useful tool but needs to be supplemented with an estimate of potential final SSC value.
Publication
Authors
O. Pailly, M. Battini, J.J. Polidori
Keywords
Actinidia deliciosa, fruit maturity, soluble solids concentration
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