[defrost]

The data layer most grain farmers rely upon is often ground based radar showing rain bearing clouds ..

eg, this: http://www.bom.gov.au/products/IDR581.loop.shtml#skip

is a "composite radar loop" that stitches together several ground based radars tuned to detect water.

Grain farmers in the wheat belt here, and elsewhere, can generally get by fine w/out sat data as long as they can have their cloud data.

What most (large) farmers heavily rely on today though is GPS - sat based positioning. That'll often be projected onto high res local imagery .. which can often come from an air photo survey or sat photography AND | OR high res vector data showing fence lines and boundaries but no actual image data (they can see out the window of the tractor after all).