The Irish Farmers' Association has appealed to land owners to take precautions during the silage season to prevent fish kills and the pollution of watercourses.
The organisation's national environmental committee chairman, Mr Francis Fanning, said farmers should to be extra vigilant in managing silage effluent during the current spell of very changeable weather.
He added: "Weather conditions always have a major impact on farming, and farmers need to be extra vigilant during the current silage season to ensure effluent is safely managed and poses no risk to water quality."
Because silage effluent was so rich in nutrients, it could be a major pollutant if it enters watercourses.
"Microorganisms present in water feed on the effluent which reduces the oxygen content of water. This can result in sudden fish kills."
He added: "Directly ensiled grass can produce peak effluent flows of up to 30 litres per tonne per day for the first few days after ensiling.
"Farmers need to be extra vigilant at silage time to ensure effluent collection tanks do not overflow, and for a number of days after ensiling grass to ensure collection channels and drains are working correctly."
Farmers, he said, should inspect watercourses in the vicinity of the farmyard so that emergency action can be taken if any contamination is suspected.