Deposition of ammonia to a Irish forestry Norway spruce (Picea abies (L.) Karst.) stand at Ballyhooly, Co. Cork.

Abstract

Emission of ammonia from manure spreading influences the nitrogen input and acidity of forest ecosystems in agricultural areas. This is mainly due to the interaction between ammonia in ambient air and the forest canopy. The foliage canopy effect can be considered as the difference between precipitation and throughfall fluxes, i.e. net throughfall, and is the result of leaching, dry deposition, uptake and emission. Net throughfall calculated after a heavy shower preceded by a relatively dry period results in total wash-off, which is equivalent to total deposition when no canopy exchange occurs. Precipitation and forest through fall fluxes in an agricultural area (Ballyhooly, Co. Cork) have been monitored since 1989. This provides information on dry deposition of ammonia in relation to throughfall composition. Net throughfall fluxes for ammonia at Ballyhooly show a strong seasonal effect. The flux is clearly greater during the summer, which is probably the result of increased dry deposition of ammonia due to manure spreading. Negative net throughfall fluxes during spring indicate an uptake effect. Throughfall fluxes for certain ions can be used as an estimate of total deposition. Due to canopy uptake, however, total deposition of ammonia at Ballyhooly is higher than the throughfaU flux.