Title

Nutrient balance case studies of agricultural activities in south west Western Australia

Document Type

Conference Proceeding

Publication Date

2004

Conference Title

Presented at the 7th International RiverSymposium, Brisbane Australia, Aug 31st – 3rd Sept 2004

Place of Publication

Brisbane

Keywords

Phosphorus, nutrient balance, agriculture, BMP, modelling

Abstract

The ecology of estuaries on the south coast of Western Australia has been disrupted because of increased nutrient and sediment discharge from predominantly rural catchments. Given the strong link between landuse and nutrient export, it is important to evaluate nutrient balances and flows so that opportunities for intervention can be better targeted. Specific data on the levels of nutrient export, and the nutrient inputs that give rise, are often limited. The case studies reported here developed nutrient balances for a broad range of land uses in the Peel Harvey catchment, in part to provide nutrient data for associated BMP modelling work. The studies indicate that inputs exceed outputs in most instances, suggesting nutrient accumulation (‘positive balance’). A range of nutrient balance and input:output signatures have emerged for different land uses, describing the general nutrient efficiency of each. Ratios vary significantly within land uses, possibly due to management practices, and environmental situation. The P input:output ratio provides some indicator of production P loss, but estimated levels of P loss to the environment are strongly correlated with farm P inputs. The selection and prioritisation of management practices needs to consider how each management action addresses the issue of “nutrient balance”.

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