To Shut the Field for Silage or Not

Author: 
Dr D. Davies, IBERS

With the hard winter that hopefully is coming to an end, grass growth is currently very slow and I suspect many of you are wondering when there will be sufficient grass growth to turn stock out and how long your silage stocks will last.

It is worthy to remind ourselves that well managed grazed grass is the cheapest form of feed on grassland farms and when it comes to closing fields for silage production many of us forget this fact and only think of what fodder we require next autumn/winter.  

I would like to suggest that this year maybe it is worth considering a couple of things prior to shutting the usual acreage for silage production.

 

Consider your grazing requirements

Firstly, consider your grazing requirements and how you are going to maximise grazed grass quality in your system, be this rotational grazing, strip grazing or set stocking.  Of course, it is never easy to get this correct with the unpredictable UK weather conditions impacting grass growth.  However, the ability to remain flexible with your grazing land area will enable better grazed grass utilization, which can have a significant benefit on the economic benefits to your business.

Secondly, the last three spring/summers have provided some very challenging silage making conditions and with most dairy farms and many sheep and beef farms relying on contractors to make their silage, this provides an even greater challenge when trying to produce high quality silage.

 

Digestibility of forage fed is crucial

The most important factor for milk or meat production from both grazed grass and silage is the digestibility of the forage fed.  By closing all your silage fields at the same time this can lead to major challenges in maintaining both sufficient highly digestible grazed grass and also in producing high D value silage.

Forage digestibility affects dry matter intake with each unit increase in D value giving an increase in intake of 0.2kg and intake drives production response, so maintaining grazed grass digestibility and producing high D value silage is crucial in driving production.

So by closing fields as grass growth gets ahead of grazing requirements then the high quality of grazed grass can be maintained.  This approach also means that the silage fields will not all be ready for cutting at the same time and so can reduce the risks of bad weather at ensiling time resulting in delayed harvest and thus poorer D value silage.   

 

Consider more than one harvest window

Whilst many farms require one big cut of silage to fill their silage clamps, given the problems of the last three spring/summer harvests and the problems that has caused in producing high D-value silage, it is surely worth considering reducing these risks by having more than one harvest window, in an attempt to produce at least a proportion of your silage with good digestibility value.  After all the difference between 65 D and 70 D silage is worth 1.25 litres of milk/cow /d or 0.2 kg or 0.1 kg live weight gain in beef cattle and sheep respectively.

This approach may call for you to re-think your harvesting approach and whilst I understand that clamp silage is still the main way of preserving silage, baled silage can offer a flexible method that fits very well with maintaining grazed grass quality and making high quality silage from smaller land acreages.

If, however, you do decide to close all your fields at once:

  • Ensure that fields have no surplus grass, which is going to lead to dead material at the bottom of the sward at harvesting time which can then lead to contamination of the silo with large populations of undesirable micro organisms such as yeasts and moulds. 
  • Ensure that the fields are optimally fertilized (reducing the risks of residual nitrate nitrogen in the crop at harvesting) so that if the weather is good for ensiling one week before you would normally harvest, then you are in a position to cut rather than waiting one week longer when the weather may have turned sour and make the high quality silage that will be ideal for livestock production.
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