THE INFLUENCE OF INCREASING AIR TEMPERATURES ON BUD BREAK DATE IN COMMON WALNUT (JUGLANS REGIA L.)

We determined how increased winter and spring air temperatures could affect walnut (Juglans regia L.) bud break date (BBD) in the late- and medium bud-break cultivars ‘Franquette’ and ‘G-139’. The period 1984–1990 (P1) with a mean air temperature (Jan-Apr) of 3.7°C was compared to the period 2000–2006 (P2) with a 4.6°C mean air temperature.
Climatological data were collected by the Environmental Agency of Slovenia while the phenological data were recorded by the University of Ljubljana during long-term testing of foreign varieties.
In P1, the mean BBD was April 23^rd for ‘G-139’ and May 5^th for ‘Franquette’. In P2, BBD was advanced by 3 days for ‘G-139’ and 7 days for ‘Franquette’. During both periods, BBD was strongly correlated to the average monthly air temperature (T_Month). In P1, T_Feb and T_Mar had a stronger impact on BBD (r = between -0.53 and -0.75) than in P2, when BBD was more influenced by T_Jan (r = 0.75 for ‘G-139’ and 0.81 for ‘Franquette’). In’’Franquette’, BBD was also affected by T_Apr T (r = -0.84). Phenological models showed that the mean air temperature in the preceding one or two months (T_Mar and T_Apr) were important for predicting BBD. In the warmer time period (P2), T_Jan was also useful.

VIII International Symposium on Modelling in Fruit Research and Orchard Management

A. Solar, M. Solar, Z. Črepinsek, F. Stampar

Juglans regia, cultivars, onset of bud burst, spring frost, phenological models

https://doi.org/10.17660/ActaHortic.2008.803.18