This is going to be messy. One camp are going to get angry and start kicking off, because so many people have fixed opinions on this one. If that’s you, might I suggest you read something else instead? But for those with a more open-minded position the question remains; when it comes to good silage, which is best, forage wagon or forage harvester?

That question is a bit unfair because, as with just about everything in life, there are the costs to consider. I think it would be fair to say that the question most people really want to answer is:

Are forage harvesters worth the extra costs?

It seems to be widely accepted that precision chop forage harvesters, if set up and operated properly, can set the standard for consistent chop length and (if you’re using it) additive application. So they can do a good job, but “they aint cheap” – not by any measure. Second-hand price, list price, monthly finance quotes they are all equally scary, and that’s before you add in the fuel bill.

So the forage wagon deserves some attention because it can offer so much of what the chopper delivers but at a fraction of the price and fuel usage. But there are other advantages over forage harvesters that we should consider. In particular, one of the key advantages is the output of the wagon.

As we have previously discussed, the matching of the forage kit output is critical in achieving your target dry matter in wilted forage. It’s almost impossible to get a uniform dry matter if the harvester covers twice as many acres per day as the mower. At the other end of the project, a buckrake that’s drowning in tipped loads is never going to do the best job in filling and consolidating the clamp. So a forage wagon clearing 50 to 60 acres per day is a whole lot less demanding than a hungry Jaguar with an appetite for over 150 acres per day.

Forage Wagon flexibility

The scalability of forage wagons is also an additional flexibility. If the clamp is a bit far from the crop or the farm is a bigger operation, it’s so easy to add in an additional wagon or two to balance up the output. For a contractor running a couple of wagons, this flexibility means you can maximise the output of the kit whilst keeping the operations efficient for the customer. This is good for making consistent, cost effective silage.

For a farmer the wagon also provides the option to take the silage process in-house on a smaller scale. This can offer some timeliness benefits as well as possible cost advantages.

What are the Forage Wagon downsides?

So we can’t avoid the elephant in the clamp any longer, it’s chop length. Forage wagons have been renowned for some pretty variable chop lengths, although newer models are much better. Auto knife sharpening and better quality materials have led to more consistent chop length. Even so, the manufacturers will openly admit that maybe only half the material will be chopped down at the theoretical length. And whilst wagons continue to improve, even that theoretical chop length is on the long side for clamp silage.

The ideal chop length has been looked at elsewhere but in summary, the higher the dry matter the shorter the chop length needs to be. This is for a couple of reasons. Firstly we need to expose the contents of the crop to the actions of fermentation. Secondly the higher the dry matter the more difficult it is to compact the clamp so the shorter the crop should be chopped. This clamp consolidation is super critical for aerobic stability of the silage. Some producers request slightly longer chop lengths to increase intakes, digestibility and butter fats but the aerobic stability will need some very careful management.

The best solution to control the stability would be to work through the silage very quickly and minimise the exposure of the silage to oxygen. Practically this is much easier for the producer with a larger herd number as the usage will be higher. In the UK it’s the smaller producers that are more likely to be working with a forage wagon.

The forage wagon costs saving

So it’s clear that the wagon is a compromise in terms of silage quality, but it might still be worth the potential savings so lets do some maths.

The costs of running a wagon are in the region of £100-£120 per hour so you’re likely to be around £2.77-£4.30 per tonne (assuming 16t per acre per year) depending on how much time the wagon is loading. Let’s assume £3.70 average. At the same time the forage team working close to the clamp is around £5 to £6 per tonne for the chopping and carting to the clamp element. Using a mid value £5.50, that’s a potential saving of £1.80 per tonne.

That’s a substantial saving but let’s look at the reasonable costs for the increased losses. We can predict that the aerobic losses for wagon chopped silage will be at least 50% more than a precision chopped clamp, and maybe as much as double the value. The (current) value of a tonne of silage is around £30 to £35 per tonne, so we will assume £32.50. Normal aerobic face losses are around 10%, or £3.25 per tonne. Increasing the losses with a forage wagon will therefore cost an additional £1.62 - £3.25 per tonne. 

To get the costs to work for the wagon filled clamp you have to control the losses to 150% of the forager filled pit. Now that is not impossible, but you need to be aware that to really benefit from the savings a forage wagon can offer, you need to get everything else right. The dry matter, clamp consolidation, feed face progression all have to be optimised or the savings will be lost.

I recently overheard someone claiming that using a forage wagon produced his silage for far less. He might be correct, but that statement is not really the important one. What REALLY matters is what it costs to feed the cows, not what it costs to put the grass in the clamp. 

If you want any further information or help calculating the costs of producing your forage, or to discuss any of the other aspects covered in this series – contact Jeremy Nash at jeremy@silageconsultant.co.uk

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