The no-till methods really got going in the plains states during the last 25-30 years. One factor was fear that the topsoil layer was disappearing at an alarming rate due to wind and water erosion from repeated conventional tillage. No-till seems to be pretty standard practice throughout the Midwest today, with extensive ag-science research, specialized equipment, etc.
Those three sentences about exhaust my knowledge on the subject. If you want to know more, well maybe the real farmers will jump in for the rest of the story /forums/images/graemlins/crazy.gif