Contour Cropping reduces erosion and is most effective on deep, permeable soils and on gentler slopes (2%–6%) that are less than 300 feet long. The effectiveness of contouring diminishes greatly on steeper or longer slopes because of frequent breakover of rows by runoff water. Contouring can reduce erosion losses up to 50% compared with up-and-down-hill tillage on slopes of 2%–6%. On steeper slopes (18%–24%), contour cropping without supplementary practices reduces erosion losses by only about 10%. Grass waterways are usually necessary to carry the runoff water safely from the contour rows.
Strip-Cropping, the practice of alternating contour strips of sod and row crops, is even more effective than contouring alone, reducing erosion to one-fourth of that resulting from up-and-down-hill tillage. Strip widths and sequencing should be determined using slope angle and length information.
Terraces are channels and ridges built across slopes to intercept and divert runoff water, shortening the effective length of a slope. They are generally more effective than either contouring or strip-cropping and are designed especially for longer slopes. Most terraces in Ohio are designed with gradual slopes to lead water safely into grass waterways or other suitable outlets. The number and spacing of terraces depend on the soil type, slope, and cropping practices. Terraces should be designed by qualified soil conservation technicians. Newer, improved designs allow easier farming with modern machinery and reduce the number of point rows.
Grass Waterways are natural or constructed outlets or waterways protected by grass cover. They serve as safe outlets for runoff water from contour rows, terraces, and diversions. Natural drainage areas are good sites for waterways and often require a minimum of shaping to produce a good channel. They should be designed to be wide and flat to accommodate farm machinery and be able to carry the runoff safely from the watershed above.