LABOR REQUIREMENTS FOR 'EMPIRE' AND 'JONAGOLD' AFFECTED BY ROOTSTOCK AND THREE ORCHARD SYSTEMS IN THE MICHIGAN NC-140 TRIAL
A rootstock and orchard systems trial was established in 1990 at the Clarksville Horticultural Experiment Station in Michigan, USA. The experiment was established in a split plot randomized design with 4 replications and multiple plant plots for each of three orchard training systems and rootstock treatments. Orchard system treatments were separated by trees of the scion variety 'Gala' and established and evaluated on 8 rootstocks. The orchard system treatments consisted of the scions 'Jonagold' and 'Empire' trained to the central leader (CL) (1100 trees/ha) and tested on the rootstocks M.26 EMLA and Mark; the vertical axe (VA) (1502 trees/ha) tested on the rootstocks M.26 EMLA, Mark, P.1, M.9 EMLA, and Ottawa 3; and the slender spindle (SS) (2461 trees/ha) and tested on the rootstocks Mark, Bud.9, and M.9 EMLA. Since 1993, we have been monitoring the time (labor) it has taken us to prune (dormant and summer), train, hand thin and harvest trees. In all three systems, the rootstock has had a great impact on tree vigor, yield and labor efficiency. In 1993 cropping on M.9 EMLA trees was low and pruning was time consuming which appeared to lower the labor efficiency. Trees on weaker rootstocks require less pruning and training than trees on more vigorous rootstocks. In 1994 and 1995, both varieties required the most labor to manage with the most vigorous trees on P.1 rootstock in the VA. In contrast, trees on M.9 EMLA and Mark rootstocks were very efficient, especially for the more vigorous 'Jonagold' variety. In three years, both varieties have been most costly on M.9 EMLA in the SS system. In terms of labor spent per ton per hectare, trees in the SS have been the most costly, followed by CL and VA.
Perry, R., Swinton, S. and Schwallier, P. (1997). LABOR REQUIREMENTS FOR 'EMPIRE' AND 'JONAGOLD' AFFECTED BY ROOTSTOCK AND THREE ORCHARD SYSTEMS IN THE MICHIGAN NC-140 TRIAL. Acta Hortic. 451, 459-466