To judge tillage methods realistically, you need to know what the methods are ana to look at them in terms of the reasons for tillage. Then you can better judge how well the different methods work in getting the job done.
Schaller, F. W. and Amemiya, Minoru
"What Tillage for Corn?,"
Iowa Farm Science: Vol. 16
, Article 2.
Available at: https://lib.dr.iastate.edu/farmscience/vol16/iss10/2