"Rig" for "trick" is a longstanding English expression - it might even just be another way of saying the same word, though I can't think of any other cases where "tr" gets turned inro "r".

"Rigs of corn" is really the same word as "ricks of corn", and I dpoubt if its got any connection with the other meaning. The rig meaning a measure (of land etc) might I suppose be related to that.

Short little words like "rig" tend to be used in several unrelated ways - the same is true of "jig" for example, as any craftsman who also plays folk music will be well aware (particularly if they also indulge in the odd bit of criminality, of the sort which might provoke them - being old fashioned sorts - to exclaim "the jig is up", when it seems their plans have gone awry.)