While grass growth had been sluggish up until recently, crops will soon be rapidly bulking up and harvesting of first-cut crops will begin by the middle of the month. Repairs to silage pits are a bit like milking parlours: there are often only four to six weeks in which they are not in use and repairs can be carried out.

There are two factors to look at with regard to repairing pits: doing maintenance work to ensure the safety of both the contractor filling the pit and the farmer using it, as well as the environmental aspect, where silage effluent needs to be collected correctly and disposed of in an appropriate manner.

Silage effluent is highly polluting, can cause fish deaths in watercourses and contaminate wells, if not collected, stored and spread properly on land.

The volume of effluent can range from zero to 350l per tonne of grass. Silage effluent itself is extremely corrosive in nature and can degrade concrete and steel, which is a problem in itself.

Completing repairs and resurfacing

Clean the slab thoroughly through power washing to check if repairs are needed. Where there is existing silage still in the pit, complete the power washing prior to spreading this silage on the floor to allow for inspection of the floor surface for cracks.

Any repairs must be completed to Department of Agriculture, Food and the Marine (DAFM) specifications for Concrete Silage Bases S128 and Resurfacing of Silo Floors S128A.

Cracks can be sealed using bitumen or other suitable sealers. Where there is cracking due to subsidence underneath the pit floor, then this/these areas should be broken out and repaired using new concrete at a strength of 45N.

When this, or the resurfacing of the floor area using fresh concrete is complete, then the concrete needs to be cured for a minimum of 28 days before silage can be pitted in it, as use before proper curing can lead to failure of the concrete. Where there is a large amount of cracking due to subsistence, resurfacing using concrete or asphalt is not recommended. In these cases, complete removal of the old floor and replacement using fresh concrete or asphalt is recommended.

The benefit of asphalt for resurfacing is that the pit can be used almost immediately, provided concrete underneath it did not have to be broken out and replaced.

Storing safely

Store only the amount of silage that the slab or pit is capable of storing safely. Grass of a 25% dry matter has a density of approximately one tonne grass: 1.39 cubic metres (at settled capacity). To calculate capacity of the pit, several calculations and measurements need to be taken, with the pit width, length, height and angling from the side walls and the front of the pit all calculated. Pits should not exceed a settled height of 3.6m.

Where it is calculated that pit heights will exceed this with the volume of grass to be harvested, alternative arrangements, such as baling certain swards, may be necessary.

Problems with effluent arise if ensiled grass extends onto or over effluent channels. To prevent effluent flowing over pit walls, silage should not be pitted excessively high over the wall height and should be sloped back at 45° from the top of the walls. Effluent channels should be checked for blockages prior to silage harvesting, as well as to ensure they have been diverted to a suitable collection tank. This will be necessary for at least one month post silage harvesting.

While weather conditions are variable, and farmers and contractors may have a short working window, wilting silage for 24 hours before ensiling will aid in reducing silage effluent.

Where there is an issue with harvesting in wet conditions, additional drainage pipes on the pit floor can help to drain effluent, relieve pressure and reduce pit slippage.

Stacking bales

Baled silage is generally drier in nature, but effluent losses can still occur. Silage bales, including high dry matter silage or haylage, can only be stored a maximum of two bales high in the absence of adequate facilities for the collection and storage of any effluent that may arise.

Silage and haylage bales must be stored at least 20m from surface water or a drinking water abstraction point.