HAZELNUT PRODUCTIVITY IN NORTHERN PORTUGAL: AN ECONOMETRIC APPROACH

Several commercial hazelnut cultivars located in northern Portugal were evaluated for growth and nut production from 1980 onwards. In a multistemmed trial containing eleven cultivars fruit production only became meaningful in the 6th year, when trees produced about 1.59 t/ha. Plant growth was very varied, the smallest bushes being ‘Daviana’ and ‘L. d'Espagne’, which can be cultivated at 6 x 4 m under local conditions. The most vigorous cultivars were ‘Segorbe’ and ‘F. Coutard’ which require larger spacings at around 8 x 6 m. In this paper, we apply the Hodrick-Prescott filter to decompose the annual production of the eleven cultivars into their trend (long-run yield) and cyclical (fluctuations around the trend) components for the 1985-2001 period. The results suggest that the eleven cultivars could be classed into four groups: a first group that clusters the 6 most productive cultivars: ‘Butler’, ‘F. de Coutard’, ‘Morell’, ‘Segorbe’, ‘Gunslebert’ and ‘R. Piemont’; a second that groups the medium-productive ‘Grossal’, ‘L. d’Espagn’ and ‘M. Bollwiller’; a third represented by the cultivar ‘Ennis’, evidencing a precocious decline in production, which may be a sign of lack of adaptation to local conditions; and a fourth, occupied by the pollinizer ‘Daviana’, which demonstrates a low rate of production and a marked cyclicity. The cyclical variation may have been due to variations in climatic conditions during pollination periods, which may also have caused different rates of blanks.