Estimation of chilling and heat requirement of 'Chemlali' olive cultivar and its use to predict flowering date

Sahli, A.; Dakhlaoui, H.; Aounallah, M.K.; Hellali, R.; Aiachi Mezghani, M.; Bornaz, S.

Estimation of chilling and heat requirement of 'Chemlali' olive cultivar and its use to predict flowering date

2012

Temperature is recognized as being the main variable regulating the timing of recurring biological phases. Many studies on the prediction of olive flowering have been developed. Some consider only the action of forcing temperature and estimate the heat requirements from a fixed date until flowering, while other consider also the action of low temperature and estimate chilling requirements for breaking of dormancy and heat requirements for flowering. The aim of the present paper is firstly the comparison of the flowering dates between years and to calculate the chilling requirements (CR) for breaking of dormancy and threshold temperature (T(base)) and heat requirements (HR) for flowering of ‘Chemlali’ olive cultivar. Considering the high year-to-year variability of climate conditions, the observed flowering dates varied between 17 April and 7 May. For the same period, the simulated start day of chilling accumulation varied between 21 November and 10 January. The comparison of flowering dates observed in field conditions to those computed using identified parameters (CR, HR and T(base)) revealed that the difference is small considering the nine years studied. Both the Mean Absolute Error (MAE) and the Root Mean Square Error (RMSE) of the comparison were less than 4 days, reflecting the weak errors in the estimation of the flowering model parameters. Also, this work confirms recent research which documented that the winter conditions in the period after chilling accumulation are highly correlated with yearly differences in flowering date for a given fruit tree specie and cultivar.

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