'Caution needed' as NI open slurry period commences 2 February 2021 | Slurrying should only be carried out if ground conditions are suitable, the UFU warns Northern Irish farmers have been told to act with extra caution after the open slurry period commenced on 1 February. The open period for spreading slurry started on Monday, and the Ulster Farmers’ Union (UFU) has warned farmers to ensure they are abiding by all guidelines. After snow and heavy rainfall last week, many areas across the region will not be suitable for slurry spreading, the union said. The introduction of the new Nutrients Action Programme (NAP) in 2020 brought with it various changes to spreading.