Impact of hardy ornamental nursery stock (HONS) systems on the environment: losses of nutrients and agrochemicals

Abstract

Hardy ornamental nursery stock (HONS) is container grown in systems employing 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-surface drainage from the beds. An experiment was established to examine the losses of nitrate, phosphorus and selected agrochemicals from a peat-based growing medium for HONS. Concentrations of nitrate-N in water draining from the beds exceeded 200 mg l −1 and phosphorus (P) exceeded 20 mg l −1, which are considerably in excess of the EC limit for drinking water and also represent a considerable eutrophication potential. Concentrations of pesticides in water draining from the beds were considerably in excess of the limit imposed by the EC Drinking Water Directive, of 0.1 μg l −1 for any one pesticide and 0.5 μg l −1 total, and could pose a threat to some aquatic environments. Peak concentrations observed were: oxadiazon 1500 μg l −1, fonofos 72 μg l −1, furalaxlyl 1500 μg l −1 and simazine 317 μg l −1. The use of sand beds irrigated by a sub-surface system did not noticeably reduce losses of either pesticides or nutrients, unless used in conjunction with a re-circulation system