FERTILIZER METHOD AND CONTAINER SIZE EFFECTS ON SHADE TREES GROWN IN IN-GROUND CONTAINERS

Shade tree production in large, rigid, in-ground containers is a new n ursery practice for which scientific data is lacking. The objective of this research was to study the effects of fertilizer and container si ze on production and nutrient status of shade trees grown in this mann er. Whips of green ash (Fraxinus pennsylvanica Marsh.), European birch (Betula pendula Roth.), thornless honey locust (Gleditsia triacanthos L. var. inermis Willd.), and hybrid poplar (Populus angulata Ait, x n igra L. var. plantierenis (Simon-Louis) Schneid.) were grown for two s easons (1991-1992) with a blended medium in 38-L and 76-L containers. Each container was placed in another container of equal size previousl y sunken into the ground. Trees were trickle irrigated and fertilized with slow release (SR) or liquid (LIQ) fertilizer, or both (SR + LIQ). Poplar grew very rapidly, resulting in large roots escaping from the containers by September 1991, therefore, results for this species were excluded from the analysis. In both years, top dry weight and trunk d iameter of the other three species were significantly greater for SR-t reated than for LIQ or SR + LIQ-treated trees. Root dry weight was gre ater for SR-treated trees only in 1991. SR-treated trees also grew mor e than field-grown trees, planted within the experimental site as a ba seline comparison. Trees grew larger in the 76-L containers than in th e 38-L containers (1991 and 1992) or in the field(1991).