Half full or half empty?

Psychiatrists love to group people based on their intrinsic habits; so are you’re a half full or a half empty kind of person? Whilst the answer to this maybe interesting, what the hell has it got to do with making good silage?

Your fundamental approach to life probably has nothing to do with good silage to be honest, what we are looking at here is a half full, or half empty, silage clamp. In particular what decisions you can take if the intended crop is not going to fill all the clamp space available.

There can be many and varied reasons why the forage available is not going to require all the clamp space you have available. Whilst this might be at the least very disappointing, don’t dwell on what you are missing. There are some critical decisions you have to take to make sure you get the most out of what you do have. 

 Less than you wanted

Poor growing conditions have a massive impact on the crop volume as well as quality. Too dry, too wet, too cold – you know how this goes – but sometimes it’s not just all the fault of the weather. Poor establishment or untried varieties can produce yields that don’t live up to expectations. So if you’re faced with a taster sized portion of forage when you have clamp room for a banquet, what are your best options?

The options depend to some degree on where you are in the season. A lack of first cut silage may be compensated by a bumper second cut for example. For simplicity let’s consider a wholecrop or maize harvest that’s not going to fill the clamp. You could fill the clamp up from the back and leave room at the front for (maybe) a late “Indian Summer” cut of grass silage? That might be a half full approach from someone who is optimistic but it might not be your best choice. The problem comes from spoilage wasting once the clamp is opened and that will be determined by your feed out rate.

Working out the rations

You only get one chance to fill the clamp so you need to get it right months before you are actually going to be using it. With lower than anticipated tonnages of a certain crop you need to decide how you are going to use it. Are you going to feed it at the planned rate but for a shorter time – until it’s all gone – or are you going to reduce the rate to spin it out over the long period? This decision all comes down to your view on maintaining the bacterial populations in the rumen or the digester. With dairy cattle the lactation demand will be a factor but for other cattle and for an AD plant I would suggest that the better option is to maintain a consistent ration that will maintain a stable bacterial population. These are big decisions to make before the first load even arrives at the clamp but you need to be prepared with a plan.

Short and fat or long and thin?

If you pile all the forage up at the back of the clamp you use less plastic to cover it and less tyres to hold it down. You also have less spoiling on the surface as the rules of surface area and volume apply. So short and fat is better isn’t it?

Well no, not really, because the invisible losses are the most expensive in any silage clamp. Aerobic losses caused by micro-organisms on the face of the silage are eating up the forage nutrients and converting them into gas that blows away on the breeze. Your best defence against this is to work through the clamp at 2m per week in the winter and up to 3m per week in the summer. This keeps the forage fresh and uncovered for the least amount of time. So keep filling the clamp to half its height but using all the length would be a much better solution – the long and thin option.

Putting some numbers to this, let assume a 2500t maize silage clamp, roughly 55m long x 20m wide and 3m high and a 1250t crop to be stored. We can look at the two storage options and the possible losses.

Short and fat              

Surface losses 75mm deep – 4.4% = 55t

Aerobic losses – 25% = 312t

Total losses – 29.4% = 367t

Long and thin

Surface losses 75mm deep – 8.8% = 110t

Aerobic losses – 12% = 150t

Total losses – 20.8% = 260t

The taller heap has about 40% more losses!

Other options

An alternative could be to install a dividing wall into your clamp to keep the losses under control whilst keeping options open to use the rest of the space. In theory this might make sense but are you really going to be able to source a wall in the time available? Of course you could consider a temporary wall of big bales but you need to consider the safety and a whole host of other issues with this. In fact that’s enough for a whole blog of its own.

Chopping short and compacting really tightly can help you too, as can the choice of a silage additive that has a proven ability to reduce losses. But ultimately the very best thing you can do to reduce in-clamp losses is to work through the silage at the target rate. So before you start to think about how high you need to stack it, decide how long you need it to be…

If you need any further information or help planning the effective use of available clamp space, or for any of the other aspects of silage making covered in this series – contact Jeremy Nash @ jeremynash1@btinternet.com

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