Older machines without CE marking are used on our farm.
Are we obliged to provide these machines with a CE mark or is CE marking for an older machine not mandatory?
No, on older machines you do not affix a CE mark.
However, a risk analysis must be carried out and possible risks identified. If there are any risks, you should take appropriate measures. This can be a technical solution but also an organizational measure.
Keep in mind that your machines must also be periodically electrically tested.