Not so long ago it would have been unthinkable that John Deere would have headed down the rotary route for harvesting cereal crops. In Europe, we were told, straw walkers were the way to go. Now, however, it’s all change, with the US giant topping off its harvesting line with no less than two rotary models – the twin-rotor 9780 CTS and the new single-rotor 9880 STS flagship. Earlier this year we tucked a prototype STS into winter wheat