Nature works and has been working for a billion and a half years-ever since there were living things on earth. This is important. Before the prairies were settled, plowed and fenced, wild herds moved back and forth across them, never staying in one place after the grass was cropped too short. These moving herds distributed minerals from their droppings and remains, for it is well-known that wild animals usually maintain a good mineral balance by visiting salt-licks and varying their pasture-grounds. Here in a nutshell is the model for proper use of grasslands. (From the Introduction)