Webinar: Clamp silage slippage – how to try and avoid slippage this season

Past Event

Wed, 15 April 2020

6:00 PM - 7:00 PM


Silage slippage decreases the nutritional and hygienic value of silage and causes significant wastage but each and every year the issue is seen on farms. The advice to reduce slippage has been in place for many decades and many small but important factors have changed over the years. The aim of the AHDB funded project was to identify underlying reasons and common factors behind the slippages. If you are a contractor involved in the silage making process or dealing with machinery join Dr Dave Davies to learn more about the findings. He will also give practical advice from chop length, compaction and filling angle to avoid slippage this season.

Dr Dave Davies is from a farming family, he worked as a research scientist at IGER Aberystwyth for 20 years before establishing his own company, Silage Solutions Ltd. He is passionate about getting independent evidence-based advice to farmers and to these ends continues to conduct silage trials and consults with farmers across Europe. He has links to many research establishments and is currently a visiting Professor at North Wyke, Rothamsted Research.

Questions and answers from the webinar

Q. Is there any difference using a forage wagon rather than a self propelled forage harvester?

A. In the survey one farm used both a forage wagon and a precision chop forage harvester,  All other farms used precision chop.  Whilst the chop length on the forage wagon will be longer there is a greater challenge, if the process is not carried out with greater attention to detail, of inconsistent density, because the chop length is more variable and the way the forage is dropped out of a forage wagon makes it more difficult to spread thinly, so potentially increasing differences in silage compaction and therefore density.   However good operators of forage wagons do an excellent job on chop length and compaction because they are very precise on following the rules. 

Q.I've been told enzymes (added as part of silage additives) can cause slippage, do you think that is true?

A. Enzymes have been shown in many silage trials to have little or no effect on digestibility or speed of fermentation.  A reason for this is that they are simply not added in sufficient quantity by the additive companies and the pH optima for them to work efficiently in the silo is very short in time duration.  So I think it is very unlikely they have any effect on slippage or silage quality.

Q. Given your comment about  acetic acid production, how many more tonnes of water could you expect to be produced in a clamp as a result of the poorer fermentation?

A. There are many fermentation pathways that produce acetic acid, but on average for every g of acetic acid produced 0.3 g of water result (with 0.7 g CO2).

So as an example if you have a silage analysis with 10g/kg DM acetic acid this will have had an additional 3 g water, therefore in 1 tonne of fresh silage at 30% DM this would equate to 300 kg of DM and 3 of of acetic acid which would result in 0. 9 kg extra water in 1 tonne of fresh silage.

The higher the acetic acid content the higher the water content.  These are all estimated values and can vary quite a lot for this value quoted.

Q. Does silage floor material i.e. concrete versus tarmac have an effect?

A. In this study that could not be looked at, However the silage seems to slip form mid way up a face and not the base so I suspect there is little effect of floor material on slippage risk.

Q. Can you explain why Ash and Oil is higher in earlier cut silage?

A. Ash is not just a factor of soil contamination but is first and foremost a measure of the mineral content in the growing plant.  As a plant grows it switches from a vegetative growth mode to a reproductive growth mode and in the last 10 days or so before a 6-7 week harvest regime there is a big increase in plant cell wall production and lignification.  This has the effect of diluting the relative amount of some plant components these include Minerals (hence the Ash) oil and protein. So in an early cut grass the concentration of all three of these will be higher than in a latter cut grass because they have been diluted less at that stage of growth. 

 Q. Maybe in the bench marking for your study you should ask how long its taken to fill the pits and how many acres, it does seem that pits are filled too quickly by forager gangs with shorter chop or as you said farmers filling their own getting distracted and not consolidating correctly.

A. Thanks for this comment I agree more information and notes on factors such as these taken by each farmer would add to the available information to assess the issue.  I have no doubt that the inconsistent compaction is the main cause of clamp slippage.

 Q. If different fields wilt at different rates is their an easy way to test DM content of grass in a field and is their an optimum?

A. The optimum for UK silage clamps is 28-32 % DM depending on your management.  However this should be achieved within 24 H other wise field losses out weigh the advantages of the higher DM content .  The hand test with practice is pretty accurate as a gauge, this is described very well in the AHDB good silage booklet and in Wales the HCC good silage booklet.   A microwave can be used but this is slightly more challenging and time consuming but more accurate.   Some on farm NIRS are accurate for grass DM some are not, but these are expensive.  There is no accurate quick method as a moisture meter in grain unfortunately.

 Q. Could the use of side sheets add to having less friction along the sides of the clamp (and so increase the risk of slippage).

A: An interesting suggesting.  However where there is a negative there is also a positive.  The side sheet will reduce losses in that vulnerable zone.  By reducing losses there will be a lower oil content.  So 6 of one half a dozen of the other.  Whilst I have no evidence that the side sheet makes things better or worse I would not change my advise which is to always use a side sheet.  One farm had earth walled banks with a side sheet and had slippage.  Even with a side sheet earth walled banks provide a significant amount of friction. 

Q.  Are indoor pits less prone to slippage as less likelihood of water ingress?

A. This I suspect is a very valid point. Is this due to water ingress or is it due to them being generally smaller.  Maybe a bit of both. However, one of the clamps I visited was indoors and had slipped.  And one farm that had slipped that I didn't manage to get to was also inside.

Q. Often I hear farmers say they put a second tractor on half way, is this a problem?

A.Yes two tractors should be used at the outset.  Adding a second tractor half way through improves density in the second part of the clamp but not that lower down, increasing the risks of differences in silage ty and increasing the risk of slippage.

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