Abstract

Outdoor-grown, containerized, Aronia melanocarpa (Michx.) Ell. and Rhododendron ‘Roseum Elegans’ were grown atop soil-filled boxes that had been recessed into a grassed field in separate studies. Aronia were fertilized with either a single application of controlled-release fertilizer (CRF) or a split application of CRF separated by 36 days. Rhododendron were supplied a single application of CRF and either a standard or excessive irrigation volume on each irrigation day. Soil samples were taken in 30 cm (12 in) layers to a depth of 90 cm (36 in) beneath containers at 14-day intervals and soil NO₃-N concentrations were determined. Accumulation of NO₃-N was immediate in the 0—30 cm (0–12 in) layer for both species with accumulation of NO₃-N in the deeper soil layers occurring later. Split application of a CRF was somewhat effective at reducing NO₃-N accumulation at specific times and in specific soil layers, but reductions were not as substantial as studies on NO₃-N concentrations in leachate have indicated. The large irrigation volumes used in the irrigation volume study resulted in NO₃-N moving rapidly through the soil profile beneath containers.