The optimal size for tractors is more a function of the topology of the land and the soil type than $/acre spent on the equipment. In theory, the minimum feasi

The optimal size for tractors is more a function of the topology of the land and the soil type than $/acre spent on the equipment. In theory, the minimum feasible unit of equipment should be a lot smaller for sand than dirt (less weight is required to break up the sand), and beaches tend to be curved and bumpy, so that favors a swarm of small robots. However, the cost of maintaining the swarm is linear in swarm size, but the cost of maintaining one tractor is sublinear in tractor size. I'd guess it's roughly as difficult (within a factor of 2-10x) to unclog up the sand sifter on a beach combing tractor as it is to unclog the analogous component on a single swarm robot. At 10x, that suggests a swarm of over ~ ten robots is infeasible (unless they are self-repairing and self-maintaining). The article mentions places where wheeled devices can't reach (stairs, steep beaches). I'm guessing that'll be the main use case for these things. As for precision herbicides + planting, I suspect that's better done with special tractor attachments that have fine grained control over each row's implement. Most stuff is grown in large fields and GPS guided tractors are getting more common.