In order to keep Iowa soils from becoming less fertile and from being washed away, it is necessary that every farmer develop and carry out a program of soil and moisture conservation for his farm. This program need not be complicated. Any Iowa farmer can, by following practical methods, keep his soil fertile and in place.
Every acre of a farm should be planned to produce its maximum income in whatever crop it is adapted to produce. Soils on level areas can be kept fertile by proper crop rotation and necessary soil treatments. Rolling land should be handled the same way except that as it becomes steeper other practices must be adopted to keep the soil from washing away. Some lands must remain in pasture, while those less fertile areas which are becoming eroded should be planted to trees.
Van Vlack, C. H. and Clapp, L. E.
"Contour farming for soil and water conservation,"
Bulletin P: Vol. 1
, Article 1.
Available at: http://lib.dr.iastate.edu/bulletinp/vol1/iss11/1