NFU Cymru is seeking an exemption that will allow farmers operating within Nitrate Vulnerable Zones to spread during the forthcoming closed period.
It has urged the Welsh government as the closed period commences next Tuesday (15th October).
The request comes as farmers operating within NVZs have contacted the union.
They have concerns that the prolonged wet weather has prevented them from spreading, with the result that they head into the closed period with their slurry storage near or close to full capacity.
The closed periods relate to the spreading of nitrogen fertilisers including manufactured nitrogen fertiliser, slurry and other organic manures.
It prevents spreading of organic manure with high readily available nitrogen between specific dates.
For grassland on all other soils this is 15 October to 31 January inclusive.
The issue was also raised by NFU Cymru members at Clwyd county meeting held on 9th October
Paul Williams, NFU Cymru Clwyd County Chair, said: “Rainfall in the second half of September easily exceeded average rainfall figures for the month.
“In fact, long-term Met Office data shows that September rainfall for Wales was higher in 2019 than in any other September this century.
“October has been no better in terms of rainfall and based on current weather forecasts, with rain predicted until Monday, it seems unlikely that farmers will be able to ease pressure on storage by spreading before the closed period.”
He added: “As a result, we have written to Welsh government to bring this matter to their attention and to seek flexibility and an exemption that will enable farmers to spread during the forthcoming closed period to prevent stores over-spilling.
“We very much hope Welsh government will be able to look favourably on this request and provide information to farmers within NVZs at the earliest opportunity.”