Title

Nitrogen and phosphorus budgets for the sub-tropical Richmond River catchment, Australia

Document Type

Article

Publication details

McKee, LJ & Eyre, BD 2000, 'Nitrogen and phosphorus budgets for the sub-tropical Richmond River catchment, Australia', Biogeochemistry, vol. 50, no. 3, pp. 207-239.

The original publication is available at www.springerlink.com, http://dx.doi.org/10.1023/A:1006391927371

Abstract

Nitrogen and phosphorus budgets were developed for four sub-catchments in the Richmond River catchment for two study years. The catchment is used for a variety of farming pursuits including dairying, beef,cropping, fruit, nuts, forestry, and sugar cane. Each sub-catchment varies in hydrology, the proportion ofeach land use, and the population density which enabled a unique opportunity to study fluxes and storage associated with a variety of environmental factors. Total loadings entering each sub-catchment varied from 12 to 57 kg ha–1yr–1 for nitrogen and 0.25 to 6.6 kg ha–1yr–1 for phosphorus with little inter-annual variation. Averaged across the whole catchment, nitrogen fixation (47%) dominated the inputs; fertiliser (26%) and rainfall (21%) made up the next largest inputs. Fertiliser inputs dominated the phosphorus budget(65.5%); rainfall and manures making up 13% and 12%respectively. Produce dominated the outputs of both nitrogen and phosphorus from the four sub-catchments being greater than the riverine export. The delivery of nitrogen to catchment streams ranged from <1>to24% of the total inputs and the delivery of phosphorus to catchment streams ranged from <1 to>39%. Storage of phosphorus in catchment soils varied between –0.32 and 4.46 kg ha–1yr–1. When denitrification and volatilisation were estimated using data from other studies, storage of nitrogen ranged from 1 to 24 kg ha–1yr–1. Despite the episodic nature of run off in the sub-tropical Richmond River catchment, the magnitude of nutrient fluxes and storage appear similar to other catchments of the world which have mixed land use and relatively low catchment nutrient loadings.