Abstract

Juniperus horizontalis Moench ‘Plumosa Compacta Youngstown’ (compact Andorra juniper) and Picea glauca Moench (Voss) ‘Conica’ (dwarf Alberta spruce) were grown for one season in 2.2 1 (#1) nursery containers in a potting medium containing composted hardwood bark, sphagnum peat moss and sand (1:1:1 by vol). The containers were placed over lysimeters permitting continuous collection and measurement of water passing through and around the containers. Slow release or soluble N was applied at an annual rate of 1.6 g of N per pot. Containers were irrigated by either trickle or overhead methods and water volumes were recorded. Subsamples of leachate were collected and analyzed for nitrate. Much less nitrate was leached by the trickle than by the overhead irrigation. Although slow release N sources lost considerably less nitrate in runoff water, there is still sufficient nitrate lost by these sources to pollute ground water unless annual fertilizer needs are supplied by split applications. Depending on sources, 58–80% of the N applied as slow release fertilizers was not recovered in either the plant or runoff water.