A County Tyrone farmer has been fined £950 at Dungannon Magistrates Court to polluting discharge to a waterway.
David John Allen, from Claggan Lane, Cookstown, pleaded guilty for causing the entry of nitrogen fertilizer into a waterway, namely a tributary of the Lissan Water.
The court was told it was an "important salmon waterway".
He was also ordered to pay £28 in court costs.
On 21 May 2009, a water quality inspector, acting on behalf of the Northern Ireland Environment Agency (NIEA), inspected the farmyard owned by Mr Allen.
They found a manhole adjacent to cattle sheds which contained a diverter which appeared to be sending slurry, overflowing from the tank, in the direction of the river to the rear of the site.
The NIEA said is was a "serious polluting incident" that allowed an "extremely polluting farm effluent" to discharge into a tributary which is an important salmon waterway.
A sample taken at the time of the incident confirmed that the discharge contained poisonous, noxious and polluting matter which was potentially harmful to fish life in the area.