Characterization and management of flowering in walnut (Juglans regia) cv. Serr, for increased productivity in Central Chile

To determine the effects of pistillate flower abscision (PFA) on the productivity of 'Serr' walnut trees in central Chile, flowering behaviour was studied in the community of Hijuelas, in central Chile, during the 2001/2 and 200/3 growing seasons. Given the documented characteristics of this disorder (Polito et al, 1998), the trees response to pollen management was evaluated as a possible solution for PFA. The floral phenology of both male and female inflorescences was recorded. In addition PFA at different developmental stages was recorded, as well as from other causes, for catkins under agitation (mechanical shaking) treatments at 5, 15 and 50% of receptive female flowers (RFF). Fruit retention at harvest was also recorded. The statistics followed a completely randomized block design. From the first year to the second, there was a difference between the flowering period and the overlap between male and female flowering. The catkin shaking treatments reduced the abscission of flowers due to an excess of pollen, as compared with the control. The shaking treatment at 5% RFF (2002/03) was outstanding, showing the lowest percentage of PFA, which allowed a yield increase of 15%. Flowers that dropped due to poor fertilization were clearly distinguishable from those that dropped due to PFA, and no relationship was found between the treatments and subsequent drops. In both years an effect of the shaking treatments on fruit retention at harvest was seen, increasing the number of fruits that were retained.