Pitting your wits: Best effluent management and silage pit advice for Limerick farmers

Pitting your wits: Best effluent management and silage pit advice for Limerick farmers

SILAGE season is beginning and Limerick farmers need to ensure that silage storage facilities are fit for purpose.

Unfortunately in 2019 a number of incidents occurred in County Limerick where silage effluent entered into rivers and streams resulting in fish kills in some rivers.

With water quality coming under increased pressure in County Limerick it’s all the more important that the silage pit and silage effluent collection and storage facilities on farms meet the standards required by the Department of Agriculture and Food (DAFM).

Under Covid-19 restrictions the DAFM considers that some limited projects that are essential for animal welfare should continue. Examples considered critical include work on silage pits (storage of fodder) or urgent calf housing.

Silage pits – slabs and walls, need to be structurally sound to ensure ensiling is completed is a safe environment. Silage effluent collection channels and tank storage must be capable of managing the volume of effluent generated. The effluent is a highly polluting liquid and can cause fish kills in watercourses/rivers and contaminate wells if not collected, stored and land spread properly.

While silage pits are empty now is the time to examine the slab and channels to see what maintenance and repairs are needed before the pit is used again.

Inspect and 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 for Concrete Silage Bases S128 and Resurfacing of Silo Floors S128A. These can be obtained at www.agriculture.gov.ie

The silage pit in photo 1 is in need of repair. The base has cracks and effluent is not collected correctly. This silage pit is not suitable for use until cracks are repaired and effluent channel is cleaned.

Silage effluent is escaping in Photo 2. The effluent channel is either cracked or blocked or the grass was filled out over the effluent channel

Making silage

It is important that you know how much silage your slab is capable of storing. If your pit is designed to store 50 acres of silage at normal yield then that is all that should be stored in the pit. 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. This will 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.

Where a suitable wilt is not possible due to wet weather 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 silage

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.


nEnsure that effluent tanks, channels, silo floors, walls and wall floor joints are inspected annually.

nRepairs are to be carried out well in advance of the start of silage making.

nKnow how much silage you can store in your silage pit and store excess silage in another pit or as round bales.

nWhere possible, wilt the crop that is to be ensiled in order to keep effluent production to a minimum.

nKeep all effluent collection channels and drains clear of blockages.

nCheck effluent tank levels on a daily basis when effluent is being produced. Land spread as necessary (dilute 1:1 with slurry or water).

nDo 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.

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