CROP ROTATION DROPED AFTER WWII. “Today, Midwest farms often rotate between just corn and soybeans. But decades ago, oats, clover and alfalfa were a big part of the mix—and more farms also had livestock. The combination allowed for replenishment of nitrogen in the soil, both through the spreading of manure and by varying what types of crops went into the land. But after World War II, nitrogen fertilizer became widely available, and that made rotations and livestock less necessary.”
http://lnkd.in/dzg56Bq