The standout machinery debut at the Royal Highland Show 2026 was the new Stewart Tetrad, a massive quad-axle silage trailer developed for high-output forage operations. Built by Scottish manufacturer Stewart Trailers, the Tetrad offers a 70 m³ capacity and a 35-tonne payload, making it the largest agricultural trailer ever produced by the company and one of the largest silage trailers currently available on the market.
Designed primarily for large-scale farming operations outside the UK, particularly in markets such as Australia, the Tetrad significantly exceeds the capacity of Stewart’s previous flagship models. The trailer rides on four BPW axles, with passive steering on the front and rear axles to improve maneuverability despite its size. Heavy-duty chassis construction, reinforced structural sections and a massive hydraulic tipping system underline the machine’s focus on maximum throughput rather than road transport practicality. According to Stewart, the trailer requires a tractor weighing at least 18 tonnes for optimal operation.
Strategically, the launch highlights an important trend in agricultural logistics: while tractor horsepower growth is slowing in some markets, transport capacity continues to increase. Larger forage harvesters, wider headers and higher-output harvesting systems are creating demand for larger support equipment capable of moving more material per trip. The Tetrad is a clear example of manufacturers responding to the productivity requirements of very large farming businesses and contractors.
Bottom Line
The Stewart Tetrad is more than an oversized trailer. It reflects the continuing industrialization of agricultural logistics, where the objective is increasingly to maximize tonnes moved per hour across the entire harvesting chain. As farm scale grows in several global regions, support equipment is becoming just as critical to productivity as the harvesting machines themselves.
