For city folk who have never seen a round baler in action, try this video.
https://www.youtube.com/watch?v=RfhErSriDzw
Basically the machine consists of a pickup which lifts the windrow of hay into a chamber which has a number of spring loaded belts. As the hay enters, the hay is rolled. When the chamber is full, the operator stops, the machine applies string or webbing and the machine ejects the new bale out the back.
We still use small "square bales" for our horses. They weigh only 40 - 50 lbs, but my wife and 6 year old grand daughter can handle them.
Best
Les