The growth and productivity of hazelnut cultivars (Corylus avellana L.) in Australia

Abstract

During the 1990s, a question posed by new and intending growers of hazelnuts was “What is the best variety to plant when establishing a commercial orchard?” Although existing growers had a range of views on this matter, there had not been any scientific studies to evaluate the range of cultivars available in Australia. Although hazelnut cultivars were introduced to Australia in the mid-Nineteenth Century, there had been very limited industry development compared to other cool climate deciduous tree crops such as pome and stone fruits. In the 1970s many cultivars were imported from overseas, but there was no systematic evaluation of this material. In 1994, the author of this thesis obtained a grant from the Rural Industries Research and Development Corporation (RIRDC) to undertake an assessment of hazelnut cultivars and their potential for Australian conditions. The evaluation involved planting a range of cultivars at 5 field sites. Two were in New South Wales, 2 in Victoria, and 1 in Tasmania. There was variation between the sites in soil types and climate. A randomised block design was used with cultivars as treatments within blocks. Observations and measurements were recorded for tree growth, floral phenology, nut yields and the characteristics of both nuts and kernels. All sites had supplementary irrigation and common management practices. 1-year old hazelnut whips were planted at a spacing of 3 m x 5 m. Automatic weather stations were located at each site. There were major differences between cultivars, in terms of their vigour of growth, floral phenology, nut yields and kernel characteristics. In addition to the cultivar effects, soil type was a major factor influencing tree growth, as was rainfall. Cultivars with high vigour included ‘Barcelona’ and the Australian selection ‘Tokolyi/Brownfield Cosford’ (‘TBC’). Those of low vigour were ‘Tonda Gentile delle Langhe’ (‘TGDL’), ‘Negret’ and ‘Wanliss Pride’. There were significant interactions between cultivars and the sites in tree growth and nut yields. Timing of male and female anthesis was strongly influenced by cultivar and seasonal conditions. All cultivars were protandrous. The commencement of pollen shed ranged from late-May, for the cultivars ‘TGDL’ and ‘Barcelona’, to early August for ‘Hall’s Giant’. Chill hour requirements appeared to be the main factor influencing timing of pollen shed. Female anthesis was also spread over a period of several weeks with early cultivars being ‘Atlas’ and ‘Tonda di Giffoni’, late cultivars were ‘Ennis’, ‘Casina’ and ‘Hall’s Giant’. Studies with cut branches in controlled temperature environments indicated that catkins had a relatively high post-chill heat requirement compared to female inflorescences. The differences between cultivars in post-chill heat requirements for catkins were small. The relative dates of flowering across cultivars were found to be highly predictable. This, coupled with published data on genetic incompatibility, made it possible to recommend cultivars as pollinisers for the main nut-yielding cultivars. There were significant differences between cultivars in the date of bud break; ‘TGDL’ and ‘Tonda di Giffoni’ were early (late August) whereas ‘Hall’s Giant’ was late (late September). Nut yields were highly influenced by cultivar, vigour of growth, site and seasonal rainfall. Low rainfall in one season greatly reduced nut yields. High growth rates at one site lead to a closed canopy 7 years from planting with peak yields. Soil characteristics were a main factor influencing tree growth and nut yields. The best tree growth and highest levels of production were achieved on a deep, well drained, fertile loam soil. The characteristics of nuts and kernels were strongly influenced by cultivar, although seasonal conditions influenced nut and kernel size and the degree of kernel fill. An overall evaluation of cultivars was based on nut and kernel yields as well as kernel characteristics to meet market requirements. On average, ‘Ennis’ gave the highest yields of the in-shell cultivars. The cultivars ‘Barcelona’ and ‘TBC’ produced the highest average yields, although their relative performance varied between sites. These cultivars were considered best suited for snack foods and catering with 15-17 mm kernels. ‘Tonda di Giffoni’ produced moderately high yields, varying across sites, with kernels suitable for the confectionery market. Under favourable conditions ‘Barcelona’ achieved nut yields of 3 tonnes/ha within 6 years from planting. Potential areas in Australia for hazelnut production were identified, based on a set of recommended climatic parameters and soil characteristics.