Our Organisation Search
Quick Links
Toggle: Topics

Silage Pits & Effluent Management

Before silage season starts farmers need to ensure that silage storage facilities are fit for purpose.  When silage pits are empty thats the time to examine the slab and channels to see what maintenance and repairs are needed before the pit is used again.

Inspect / Repair slab

Clean slab thoroughly, power wash to identify any problems. Defects or problems should be remedied before silage making commences. Slab and channels must be leak proof and all silage effluent must be collected and safely stored.  If the pit is not fit for purpose, cease using until all repairs are completed.  Repair works must be completed to DAFM specifications. These can be obtained at www.agriculture.gov.ie  

Making silage

It is important that you know how much silage your slab is capable of storing. A lot of the problems with effluent arise from farmers attempting to ensile more silage than the slab is designed to hold. Additional silage should be stored on another slab or made into round bales.


When cutting silage aim to wilt for 24 hours before ensiling to reduce the volume of silage effluent produced.   All effluent should enter the channels under the cover of the silage polythene and the edge of the ensiled grass should not extend onto or over any channel. The open space is maintained by placing a plastic drainage pipe in the channel.  Ensure effluent is diverted to the effluent tank. Depending on how wet the grass is at ensiling, the volume of effluent generated can range from 0 – 350 litres of effluent per tonne of grass.

Where a suitable wilt is not possible, it is advisable to provide additional drainage pipes to help get the liquid away. For example, additional pipes could be laid at the butt of clamp walls or for long clamps; additional pipes could be laid across the pit. These will help relieve the pressure build up from the effluent and reduce the possibility of the pit slipping.

To prevent effluent from flowing out over silage walls in the first few days it is important not to pile the grass too high over the walls and to slope the grass back at 45˚ from the top of the walls.

Land spreading of silage effluent

When land spreading silage effluent, dilute the silage effluent with one part water / slurry to one part effluent.  Do not spread if rain is forecast in the next 24 hours.  Do not spread within 5m of any watercourse, 10m where field slope exceeds 10%, 20m from lake/main river, 25 – 200m well/public water supply.  

Round Bale storage

Generally round bales have higher dry matter content than pit silage and do not generate any effluent. However where round bales are made in wet conditions then these bales can generate silage effluent. The effluent from round bales is treated the same as from silage pits and must be collected and stored in same way. It is recommended not to store bales greater than 3 bales high as this will lead to more effluent being generated and also for farm safety reasons.


  • Ensure that effluent tanks, channels, silo floors, walls and wall floor joints are inspected annually.
  • Repairs are to be carried out well in advance of the start of silage making.
  • Know how much silage you can store in your silage pit and store excess silage in another pit or as round bales.
  • Where possible, wilt the crop that is to be ensiled in order to keep effluent production to a minimum.
  • Keep all effluent collection channels and drains clear of blockages.
  • Check effluent tank levels on a daily basis when effluent is being produced. Land spread as necessary (dilute 1:1 with slurry or water).
  • Do not land spread near watercourses or any water body. Keep 5m buffer margin.  These buffers are increased depending on water body type e.g. well, lake, river etc.