Precision ploughing

I had often wondered how fields could be so neatly ploughed with parallel lines and just the one track round the perimeter. Today I studied it in detail.

Here's how!

The tractor with ginormous plough attached and towing a harrow goes up and down the field, stops about 12 ft from the hedge, drops the harrow (automatically), lifts the plough, turns on a sixpence, drops the plough, hooks up the harrow (still automatic) and carries on with the parallel lines. 
Then one continuous circuit of the perimeter and job done! Easy peasy!