Five key lessons from your open grass silage clamp

Having results of a silage analysis is one thing. But often, it’s only when you get stuck into seeing what’s inside, and feeding it, that you get a full picture of what you’ve produced.  

And how good it is.
silage clamp

The quality (and quantity) of your silage can have a major impact on the financial health of your business for six months or more. So, it’s worth checking it now, to see if any improvements can be made next year.

The key is to commit to noting down your clamp observations. Better still, take photos.

That way, you’ll have a handy memory jogger when next year’s silage season comes around.

How does the clamp look?

Ask yourself, is this a clamp I’d be proud to show off? Is the face tidy? Or is it non-uniform, and allowing air to penetrate and cause waste? Correcting an untidy face can make a big difference. Deeper waste, on the other hand, may mean your clamp consolidation and sealing techniques need improving, to help fermentation and help in other ways. A common problem nowadays is trailers arriving at the clamp with fresh grass before the previous load has been fully compacted. Trailers may need to wait. If you’re seeing darker, black layers in the silage, it can mean excess nitrogen was present in the grass at harvest. You may need to leave it longer after applying for all the nitrogen to be used up.

Temperature – how cool is it?

Is the silage warm to the touch? If so, it’s a sign of aerobic spoilage. This is caused by yeasts and moulds in the presence of air, effectively burning up the silage’s nutrients. So again, consolidation and sealing may need improving. Also, if it is heating in the clamp, it’s not likely to get any better when exposed to more air at feedout. So, you may need to consider an additive at feedout designed to reduce heating in the feed trough.

Smell – what does it smell like?

Does it smell sweet? Or unpleasant? If unpleasant, it could be signs of a poor fermentation or the wrong type of fermentation caused by undesirable microbes. Just as with aerobic spoilage, this means some of its feed value could already be lost. You may have done all the other ensiling steps well, but if the fermentation hasn’t been dominated by good bacteria, your other efforts could be undermined. To find out more about the importance of fermentation, watch our video here.

Feel – how does it feel?

Has the silage gone slimy? Slimy silage can also be due to excess nitrogen at harvest, and to low sugars and a poor fermentation allowing undesirable microbes to take hold. These start to break down what’s in the clamp. Also, is the silage as leafy as you were expecting? Or is it more fibrous? If it’s more fibrous, you may have cut it too late – for example if you delayed cutting to achieve extra bulk. Optimum cutting time for yield and quality is just before heading. After heading, the digestibility of grass falls by about 0.5% a day.

Moisture – how wet or dry is it?

Does the moisture level match what you thought it was going to be when you made it? Or is it wetter or drier? If it is, your wilting technique may need re-checking. The aim should be to wilt as rapidly as possible to a target dry matter of 28-32%, but no longer. This is the optimum DM for both minimising in-field losses during drying and minimising effluent risk in the clamp.

To find out more about improving silage-making, visit the Cut to Clamp website at While you’re there, why not sign up for one of our limited number of Cut to Clamp grass silage consultations? They’re FREE!

Visit our YouTube Channel for more video's showing you how to assess your silage clamp.