Preposition on and in

[diplomacy]

Why do we use the preposition "on" instead of "in"?

On his farm he had,we met each other.

[SoothingDave]

There isn't always logic behind each choice of prepositions. But "in" is used for enclosed things. The farm is thought of as the land, which things are on. The cows might be in the barn, but they are on the farm.

[Rover_KE]

A farm is an area of land.

'We met on his farm' would be a natural way to say this.

Rover