Long-term management effects on runoff, erosion, and crop production

Twelve pairs of no-till and conventional-till soybean plots were used to evaluate the effects of erosion on erodibility and soil productivity Crop yield data were collected from 1983 to 1997 and an initial report published in 1992 on results from the first eight years of data. No-till annual crop yields varied widely due to weather but appeared to slightly decrease with time. A definitive trend line was derived for declining conventional-till soybean yields with time. In the first several years after establishment of no-till, conventional-till yields exceeded no-till yields. However no-till yields exceeded those from conventional-till by about 800 kg/ha after 14 years. Runoff and soil losses from no-till and conventional till were measured from selected pairs of plots with a rainulator in 1986, 1987, 1990, and 1996. Rain was applied to each pair after a light cultivation used to provide a similar surface to both no-till and conventional till. Runoff from 60-min initial runs at 65 mm/h on the no-till history plots was 11 to 35% less than from conventional-till history plots. During these runs, soil loss amounts from no-till history were 23 to 77% less than from the conventional-till history. Soil losses from no-till decreased slightly with time. Except for 1990, soil losses from conventional-till changed little with time from initiation of the test. Little support was given for earlier indications of a trend for increasing erodibility with time for plots with conventional-till history.