Does a special trailer, designed only to be pulled by a tractor or a slow-moving vehicle, require registration?

According to Art. 71 para. 3 of the Road Traffic Act, a special trailer intended to be towed by an agricultural tractor or a slow-moving vehicle is not subject to registration requirements. Such a vehicle is admitted to traffic provided it meets relevant technical requirements and is in good working order. The vehicle visible in the photo is precisely such a special trailer (a manure spreader), which differs in legal status from a standard agricultural trailer.