The OrganicA Project: A Six Year Summary of Research in Two Organic Apple Orchards

In 2006, the OrganicA Project, a multidisciplinary, multi-state research and outreach organic apple production project, was initiated at the University of Vermont.  The overall goal of this project is to holistically examine opportunities and challenges of organic production.  To accomplish this goal, two orchards were established utilizing two production systems growers use to change to new cultivars. Orchard 1:  a new orchard was planted with young trees purchased from a nursery and Orchard 2: an older orchard (established in 1986) was “top-grafted”.  The cultivars selected for this project were ‘Ginger Gold’, ‘Honeycrisp’, ‘Liberty’, ‘Macoun’, and Zestar!’.  Their selection was based on grower input of consumer preferences and ease of management.  The rootstocks are B.9 for Orchard 1 and M.26 for Orchard 2.  Orchard 2 has ‘Liberty’ and ‘McIntosh’ as interstocks (original scions).  Five year summary results indicate that the trees in Orchard 1 are not performing as well as in Orchard 2.  Tree size is smaller and yield is lower. In Orchard 1, the cultivars ‘Ginger Gold’ and ‘Honeycrisp’ are performing better than ‘Liberty’, ‘Macoun', and 'Zestar!’.  The number of bushels per acre in 2011 for ‘Ginger Gold’ and ‘Zestar!’ was 186 and 91, respectively.  For the same year, in Orchard 2, ‘Ginger Gold’ had the highest number of bushels per acre (505) and ‘Macoun’ had the lowest number (172).  For most horticultural parameters measured, there was no significant interstock effect.  In both orchards, ‘Liberty’ had significantly higher number of fruit drop than the other cultivars and ‘Liberty’ and ‘Macoun’ are not performing as well as the other cultivars. Results indicate that “top-grafting” appears to be an economical and sustainable technique to change existing apple cultivars.  However, the success of this technique is cultivar dependent and several years may be necessary to determine the success or limitations of “top-grafting”.