Phosphorus wastes causing river decline, says Teagasc

PHOSPHORUS wastes from farming sources are "leading to the slow but steady decline in the quality of Irish rivers and lakes", an agricultural research meeting was told yesterday.

The problem is causing pollution and a process of eutrophication in many freshwater locations and may have been responsible for the complete disappearance a fish species, the Arctic char, from Lough Conn in the west of Ireland.

The decline is caused by leakages of farmyard wastes, spreading slurry at the wrong rates or times, and the overland flow of water containing phosphorus from soils already overloaded with it, according to Dr Noel Culleton, a soils specialist with Teagasc.

A recent survey found that 20 per cent of Irish soils had phosphorus levels in excess of crop requirements.

Farmers were adding slurry or fertiliser, or both, when it was unnecessary. This was unsustainable and leading to "run offs" into water. High phosphorus was occurring even in farms participating in the EU Rural Environmental Protection Scheme, he told the annual Agricultural Research Forum in UCD.

In view of environmental concerns and the necessity to keep fertiliser costs to a minimum, Teagasc had adopted new, more focused recommendations which come into force this year.

The run off of phosphorus is believed have caused algal blooms along the shores of Lough Conn and damaged spawning areas of the Arctic char, according to Mr Martin McGarrigle, a senior research officer with the Environmental Protection Agency.

Intensification of farming had led to a dramatic increase in phosphorus occurring in water, he said. It was leading to eutrophication and organic pollution in the Conn catchment. With its sensitive salmonid rivers, a very low phosphorus level could cause problems.

Shortcomings in slurry spreading could soon lead to the introduction of a system of injecting it into soil, Dr J.J. Lenehan of Teagasc said. In the Netherlands, where there were problems with ammonia, contractors had been grant aided to adopt such a method, which was better from the smell and nutrient management point of view.