Keywords: phosphorus, best practice, soil, depletion, water, recommendations, efficiency, effectiveness.
Phosphorus (P) is recognised as a common controlling factor in algal and plant growth in surface waters. Concentrations as low as 0.1 mg total P/L can be associated with excessive algal growth. Industry, sewage treatment and agriculture are the main sources of phosphorus to waters and, as improvements are made to other sources, the share of agricultural inputs to the total load of P in water has increased. Improvements remain possible in sewage treatment and these probably offer the most immediate opportunity for reducing phosphorus concentration in waters. However, there must be efforts to ensure the contribution of phosphorus from agriculture is minimised. Agriculture, as practised in the EU, inevitably will involve some enhanced transfer of phosphorus from soils to water. Good management of manures, fertilisers, cultivations and livestock can minimise, but not eliminate, this enhanced loss. There is scope for improving agronomic practices to minimise the risk of phosphorus transfer from soils but the value to the farmer of the phosphorus conserved is small. Improvements therefore need to be part of wider agri-environment schemes that can offer adequate incentives. If further regulatory control of phosphorus is considered, account should be taken of the inevitability that agricultural activity will affect phosphorus concentration in surface waters.
Dr Ian R Richards, Ecopt, Dewells Farm House, Ufford Road, Bredfield, Suffolk IP13 6AR, UK.
19 pages, 2 figures, 4 tables, 21 references.