Abstract

Cornus amomum and Rhododendron ‘Cary's Red’ were grown in #3 (10 1) containers outdoors and supplied with a controlled release fertilizer (CRF). At two week intervals, core samples were removed from the soil underlying the crop at 30 cm (12 in) increments to a depth of 90 cm (36 in). Soil samples and foliar samples were analyzed for nitrate nitrogen (NO₃-N) concentration. NO₃-N accumulated rapidly in the upper 30 cm (12 in) of soil underlying containerized crops. Accumulation in the 30–60 cm (12–24 in) layer occurred later in the growing season and NO₃-N buildup in the 60–90 cm (24–36 in) layer lagged behind both upper soil layers. Maximum NO₃-N concentrations exceeded 40 mg/kg (6.36 × 10⁻⁴ oz lb⁻¹) of soil and levels above 20 mg/kg (3.18 × 10⁻⁴ oz/lb) of soil were sustained throughout the 90 cm (36 in) soil profile for much of the growing season. Patterns of soil NO₃-N concentration suggest that, by the middle of the growing season, rapid-growing Cornus may better utilize released N fertilizer than slower growing Rhododendron. Foliar samples confirm significantly higher NO₃-N uptake by Cornus than by Rhododendron.