Articles
DETERMINATION OF LOW-TEMPERATURE DEVELOPMENT THRESHOLD AND FORECASTING OF HARVESTING TIME BY DEGREE-DAY IN ‘OWHADI’ CULTIVAR
Article number
940_17
Pages
139 – 145
Language
English
Abstract
In order to the determine the low-temperature development threshold and forecasting of harvesting time by the degree-hour on Owhadi cultivar this research was done in Irans pistachio research institute.
First cuttings of Owhadi cultivar were taken in January and for overcoming chilling requirement they kept in 4C for 900 hours.
Then cuttings were divided in five groups, and each group was put in different incubators with 13, 16, 19, 22 and 25C, respectively.
Growth ratio was calculated by the time of swollen to bud opening (50%), then low-temperature devel-opment threshold was determined by regression analysis.
To determine fruit ripening time, sampling was done every two days from
5 August and ripening percentage (hull removing and percent of open shell) measured and determined best harvesting time when 50% of fruits ripped.
Based on the low-temperature development threshold, effective degree-hours were calculated from March.
Model of harvest time forecasting was determined by study on temperature of nine years (1992 to 1997 and 2006 to 2008) in Rafsanjan city and calculating of degree-hours based on the low-temperature development threshold.
Results showed the low-temperature development threshold in pistachio is 5.2C. Study on temperature data indicated in order to 50% fruit ripening; Owhadi cultivar needs 4280 degree-hours.
Based on calculating and analysis of data the following model resulted: Total degree-hours=1.01 (degree-hour of March) + 0.91 (degree-hour of April) + 5.06 (degree-hour of May) + 1.49 (mean temperature of March) 0.772 (mean temperature of April).
First cuttings of Owhadi cultivar were taken in January and for overcoming chilling requirement they kept in 4C for 900 hours.
Then cuttings were divided in five groups, and each group was put in different incubators with 13, 16, 19, 22 and 25C, respectively.
Growth ratio was calculated by the time of swollen to bud opening (50%), then low-temperature devel-opment threshold was determined by regression analysis.
To determine fruit ripening time, sampling was done every two days from
5 August and ripening percentage (hull removing and percent of open shell) measured and determined best harvesting time when 50% of fruits ripped.
Based on the low-temperature development threshold, effective degree-hours were calculated from March.
Model of harvest time forecasting was determined by study on temperature of nine years (1992 to 1997 and 2006 to 2008) in Rafsanjan city and calculating of degree-hours based on the low-temperature development threshold.
Results showed the low-temperature development threshold in pistachio is 5.2C. Study on temperature data indicated in order to 50% fruit ripening; Owhadi cultivar needs 4280 degree-hours.
Based on calculating and analysis of data the following model resulted: Total degree-hours=1.01 (degree-hour of March) + 0.91 (degree-hour of April) + 5.06 (degree-hour of May) + 1.49 (mean temperature of March) 0.772 (mean temperature of April).
Authors
A. Javanshah
Keywords
fruit ripening, degree-hour, modeling, harvesting
Online Articles (100)