The majority of the UK maize is looking like it’s going to produce good yields and maybe you’re in the tricky position of not having enough clamp space following the bumper crop of grass earlier in the season. Traditionally it was easy to find a bit more space for some silage, just clear a corner of a field and build a heap before sheeting up. But with rules and regulations getting tighter and the threat of prosecution from SSAFO regulations it’s time to think again.
If you need to look at a temporary clamp for either Maize or some late Grass, then area to consider are:
- Choice of site
- How to construct it
- Plastic usage
- Financial costs
This Government site will give you the up-to-date guidelines required: Click here
Choice of site
- Without doubt the biggest factor when looking at the option to build a temporary clamp.
- The choice of site is dictated by a combination of legal, environmental, and operational constraints but most importantly you need to make sure the site is suitable and won’t cause pollution.
- Fundamentally you need to be able to get the crop to the place where it is to be stored and you need to be able to get it out again. This may sound obvious, but we’ve seen heaps where getting the laden feeder wagon out of the gate was almost impossible in wet weather.
- When selecting a site, the basic requirements are to ensure that the site is not under-drained, is at least 10m from a ditch or watercourse that any effluent could enter, and 50m from a spring well or borehole.
- You might also not get regulatory approval for a heap in a groundwater source protection zone 1 (SPZ) either.
How to form a field silage clamp
So, you have decided it’s the right decision to ensile your crop in a temporary clamp, you want to reduce your plastic use but also want to ensure you make good quality silage.
- Ideally the heap should be on level ground without too many stones and with a decent covering of turf. The key requirement of the regulatory guidance is that other than levelling minor ruts, you can’t do any site preparation – digging out or laying a hard surface for instance. The principle is that should any effluent be generated by the ensiled crop it should be absorbed by the soil underneath and broken down by soil micro-organisms. Putting a sheet underneath to keep the soil out of the silage is therefore not a good idea, but a layer of straw can be. The straw will help to absorb any effluent, protect the soil, and can be fed out if it is clean enough, or put to one side and treated as an organic manure if not.
- When making the heap try to keep wheels and therefore silage clean and uncontaminated – lay the straw layer (if being used) as you go, and tip the crop onto it, or lift and carry into position, spreading the crop and consolidating the wedge as normal. Care is needed to ensure heap edges / sides are safe and not too steep, and if you include a straw bale wall to keep things tidy, this should be used as a guide / absorbent and not subjected to significant lateral loading when rolling the clamp.
Plan and construct the clamp using the rule:
Every 1m of height = 3m width either side
This will give you slopes that are safe to drive over each way so enabling thorough compaction.
Clamp design: long and thin, with a relatively small face to reduce aerobic spoilage.
Well compacted field clamps with the correct 3;1 slope can achieve compaction levels comparable with bunkers.
Plastic usage
Covering a temporary clamp is the same process as covering your usual bunker. Good quality OB film on a well consolidated flat surface of the crop followed by a Protective Cover and lots of weight. The weight around the edges though is VERY important so pay attention to this area and ensure double rows of Gravel Bags are used.
Financial Costs
As Maize cannot be baled a Temporary Clamp is the only other option, however, for late season Grass Silage the bale is often to go to method.
We will be following up this article with a more detailed look are Bales versus Clamp silage soon but in general the cost of a temporary clamp compared to baling grass and the reduction in plastic is huge.
