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Using the semi-dwarfing rootstock 'Controller 9' to develop a pedestrian orchard for Prunus persica

Day, K. R., Johnson, R. S., Phene, R. C., DeJong, T. M.
Acta horticulturae 2017 no.1177 pp. 117-120
Prunus persica, frost, nectarines, orchards, rootstocks, spring, trees, vigor, California
In 2008, a trial was initiated at the University of California Kearney Agricultural Center to compare a standard height nectarine orchard to a “ladderless” pedestrian orchard. Nemaguard and Controller 9 rootstock were planted in May 2008 and grafted in January 2009 to the early nectarine 'Zee Fire'. Nemaguard is the standard rootstock used in the California fresh-peach industry and Controller 9 provides about 90% the vigor of Nemaguard. Trees were grown in either a 6 leader Hex-V configuration spaced at 3.7×5.3 m with a density of 561 trees ha-1, or as a 4 leader Quad-V at 2.1×4.3 m with a density of 1100 trees ha-1, and were maintained at a conventional height of ~3.7 m or a pedestrian height of 1.8-2 m. Four systems were studied: 1) conventional Nemaguard/Hex-V; 2) pedestrian Nemaguard/Hex-V; 3) pedestrian Controller 9/Hex-V; and 4) pedestrian Controller 9/Quad-V. The trees produced commercial yields beginning in 2010. The pedestrian C-9/Quad trees had the greatest yield, crop load, and fruit size in the first three harvest years; significantly outperforming the tall, high-vigor, conventional treatment. The other two pedestrian height treatments performed similar to the conventional treatment. A spring frost occurred in 2013, reducing crop loads in all treatments but affecting short trees the most.