Hotspur:
So before the "religious overtones" were introduced people were simply ploughing the fields and scattering the good seeds on the land and God's almighty hand had nothing to do with it.
Not quite.
Virtually every harvest festival had religious overtones. Whether you were thanking the Green Man while toasting with John Barleycorn or offering up praises to the Lord depends on what century the festival was happening.
Because a big part of farming is admitting that you're at the mercy of the weather and other elements that you can't control (vermin infestation, blights, etc) so when you get a harvest you thank whichever power you believe in that you'll have food in the coming winter. At least that's how it was traditionally - I'm not sure how atheist farmers do it.
Goodgulf