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Inputs from precipitation and outputs of water and phosphorus were estimated for four catchments: one forested, two agricultural and one urban. Three showed net annual gains of phosphorus ranging from 6.0 to 10.8 kg/km² over 12 months, and only the urban catchment displayed a net annual loss (9.8 kg/km²). Results are compared with some from the Northern Hemisphere.
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IC Campbell (1978) studied this question.