Young Black Haired Girl At The Haystack

Early methods
Early farmers noticed that growing fields produced more fodder in the spring than the animals could consume, and that cutting the grass in the summer, allowing it to dry and storing it for the winter provided their domesticated animals with better quality nutrition than simply allowing them to dig through snow in the winter to find dried grass. Therefore, some fields were "shut up" for hay.
Up to the end the 19th century, grass and legumes were not ten grown together because crops were rotated. By the 20th century, however, good forage management techniques demonstrated that highly productive pastures were a mix grasses and legumes, so compromises were made when it was time to mow. Later still, some farmers grew crops, like straight alfalfa (lucerne), for special-purpose hay such as that fed to dairy cattle.