R.L. Perry, J. Hull, J.M. Clements
The training system that an apple (Malus × domestica) grower selects must be one that best maximizes all the resources in making the enterprise a profitable venture. There are many parts to the orchard system decision “puzzle” which must fit together in a complementary arrangement to gain maximum precision and profitability. The most immediate question that must be answered regarding the establishment of a new orchard is spacing. Extension agents and growers often need assistance in determining optimum tree density for sites. Trees planted too close cause excessive shading, and competition for resources results in inadequate light penetration, poor quality fruit, low cropping, excessive labor in pruning to reduce shading impact, etc. Excessive distance results in inefficient planting designs where the land surface is under utilized, and long-term profitability may be compromised. In 1989, we made an initial attempt at trying to simplify the decision making process by considering the most important variables and assigning them values (number codes in parentheses) in a formula. Assessments on vigor are derived from rootstock and cultivar trials and field observations. Our experience gained from working with the high-density orchards and with new cultivars and rootstocks has encouraged us to frequently update the model. The formula is available on the Michigan State University Depart¬ment of Horticulture web site for general use by the public, students and extension field agents in an interactive mode (spacing calculator) department/Perry/Spacing_Fruit/mispacingPC.htm. More revision in the future will be necessary as we learn more of the technical intricacies of new rootstocks, cultivars, marketing demands, and management constraints. The primary factors affecting spacing include scion vigor, rootstock vigor, soil type, irrigation, management system, and the interactions that take place between them. This spacing recommendation is only relevant to Michigan sites and for single row arrangement of trees.
Perry, R.L., Hull, J. and Clements, J.M. (2009). APPLE SCION AND ROOTSTOCK SELECTION AND PLANNING FOR MICHIGAN. Acta Hortic. 824, 313-318
DOI: 10.17660/ActaHortic.2009.824.37
Malus × domestica, decision support, rootstock, cultivars, soil, vigor, management, irrigation, tree spacing

Acta Horticulturae