SS4.10 Interdisciplinary Contributions to the Maintenance of the Integrity of Aquatic Ecosystems
Date: Tuesday, June 11, 2002
Time: 3:15:00 PM
Location: Colwood
 
FoyRH, Agricultural & Environmental Science Division, Belfast, United Kingdom, bob.foy@dardni.gov.uk
Gibson, C, E, Agricultural & Environmental Science Division, Belfast, United Kingdom, 
 
PHOSPHORUS ENRICHMENT OF SOILS AS THE MAIN DRIVER OF EUTROPHICATION IN LOUGH NEAGH
image
Monitoring of phosphorus (P) inputs to Lough Neagh since 1974 shows increasing losses of soluble reactive P from agriculture. The Lough is currently hypertrophic, but reconstructions of enrichment, based on diatom and chironomid sediment chronologies, suggest that it was mesotrophic in 1950. Increasing losses of P from agriculture have occurred despite minimal changes in either land-use, which is dominated by grassland, or the use of P by agriculture. Output of P in farm manures increased by only 9% from 1974 to 2000 compared to a 200% increase to 0.6 kgP/ha/yr in soluble P losses from agriculture over the same period. Agriculture has operated an average P surplus of 16 kgP/ha/yr since 1950, compared to 4 kgP/ha/yr before 1940. This surplus accumulates in the soil and is proposed as the likely source of increasing soluble P losses. The tendency for fertiliser and manure P to accumulate at the soil surface of grassland may make this type of agriculture particularly prone to high P losses even when P inputs are not increasing.