NITRATES - Reducing Water Pollution from Agriculture
Phosphorus
Phosphorus is an important plant nutrient which is added to soils in chemical fertilisers and organic manures. Unlike nitrate, it is relatively insoluble, and losses from agriculture tend to be associated with the loss of soil particles by soil erosion. This can occur by water and wind erosion or by the loss of very small particles in drainage waters. In some soils which have high levels of accumulated phosphorus, there can also be some loss of soluble 'phosphate' in drainage water.
Enrichment of waters by nutrients is called eutrophication. Whilst nitrate can cause eutrophication in saline water, phosphorus is the key nutrient in rivers and other freshwaters. It can cause algae and higher forms of plant life to grow too fast, disturbing the balance of organisms present in the water and affecting water quality.
The contribution to freshwater eutrophication from agriculture varies from catchment to catchment. In some catchments, wastewater from sewage treatment works can be the main source of phosphorus entering our waters, but in other catchments phosphorus inputs from agriculture can also be significant. To minimise the risks from phosphorus farmers are therefore encouraged to:
- Follow Defra's Code of Good Agricultural Practice for the Protection of Water (via this link) by careful management and spreading of animal manures to avoid surface run-off.
- Control soil erosion.
- Take care to follow published fertiliser recommendations.
- Apply only as much phosphorus as their crops require.
Page published 27 June
2002;
Page last modified
30 September, 2003