TILLAGE EFFECTS ON WATER RUNOFF AND SOIL-EROSION AFTER SOD

Cultivated soils that have been put into sod experience an improvement in soil structural properties. This study was conducted to determine the effect of tillage systems on maintaining the infiltration characte ristics of sod sad and the effect of tillage systems on water runoff a nd soil erosion. An alfalfa (Medicago sativa L.)-smooth bromegrass (Br omus inermis Leyss.) sad established in 1984 was converted back to cro pland beginning in the spring of 1990. Tillage treatments established were moldboard plow, chisel plow, and no-till. Additional no-till trea tments were established in 1991, 1992, and 1993. A grass sod treatment was also maintained for comparison. After planting in 1993, two rainf all simulation runs with an average rainfall application rates of 70 m m hr(-1) were conducted on selected treatments. Time of each run was o ne hour; the second run was conducted a minimum of six hours after the first run but most commonly the next day. Water runoff from the moldb oard plowed treatments averaged 24 and 66% of the applied rainfall res ulting in soil loss levels of 6.7 and 18.2 t ha(-1) for the two runs, respectively. Maximum observed water runoff for the no-till treatments was 3% of the applied rainfall resulting in a soil loss of 0.2 t ha(- 1). No water runoff or soil loss was measured from the grass rod. Thes e results show that soil characteristics developed under sad that were beneficial to a reduction in water runoff and soil erosion rapidly di sappear with tillage, but can be maintained with no-till.