IMPACT OF HARDY ORNAMENTAL NURSERY STOCK (HONS) SYSTEMS ON THE ENVIRONMENT - LOSSES OF NUTRIENTS AND AGROCHEMICALS

Hardy ornamental nursery stock (HONS) is container grown in systems em ploying frequent irrigation and considerable applications of nutrients and pesticides. These container systems are frequently isolated from the underlying soil by an impermeable membrane resulting in near-surfa ce drainage from the beds, An experiment was established to examine th e losses of nitrate, phosphorus and selected agrochemicals from a pest -based growing medium for HONS. Concentrations of nitrate-N in water d raining from the beds exceeded 200 mg l(-1) and phosphorus (P) exceede d 20 mg l(-1), which are considerably in excess of the EC limit for dr inking water and also represent a considerable eutrophication potentia l. Concentrations of pesticides in water draining from the beds were c onsiderably in excess of tile limit imposed by the EC Drinking Water D irective, of 0.1 mu g l(-1) for any one pesticide and 0.5 mu g l(-1) t otal. and could pose a threat to some aquatic environments, Peak conce ntrations observed were. oxadiazon 1500 mu g l(-1), fonofos 72 mu g l( -1), furalaxlyl 1500 mu g l(-1) and simazine 317 mu g l(-1). The use o f sand beds irrigated by a sub-surface system did not noticeably reduc e losses of either pesticides or nutrients, unless used in conjunction with a re-circulation system. (C) 1997 Elsevier Science B.V.