Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 8, 1998
Publication Date: N/A
Interpretive Summary: The effects of previous cropping history (no-till versus conventional- till) on crop yields and on future soil losses from areas with shallow fragipan soils have not been established. Fifteen years of data from twelve pairs of continuous no-till and conventional-till plots were used to determine differences and trends in crop yields, runoff amounts, and soil losses. Simulated rainfall was applied to selected pairs in 1986, 1987, 1990, and 1997. For these rainfall simulation tests, the no-till history plots received cultivation in the same manner as the conventional-till plots prior to the rainfall. Results from the rainulator testing showed that no-till history greatly reduced runoff and soil loss as compared to conventional-till on plots that were lightly cultivated just before rain application. A major finding was that soybean yields for conventional-till were generally greater than those from no-till for the first few years after no-till establishment but increased to about 800 kg/ha less from no-till during the last 11 years of continuous no-till and conventional-till. Crop yield benefits for no-till as compared to conventional-till may be evident over many years but not in just a few years of study. These results will be useful to extension personnel, action agencies involved in conservation planning and soil loss prediction, and to farmers.
Technical Abstract: 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 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 15 years. Runoff and soil losses from no-till and conventional till were measured from selected pairs with a rainulator in 1986, 1987, 1990, and 1996. Rain was applied to the plots after a light cultivation used to provide a similar surface to both no-till and conventional till. Runoff from 60-minute initial runs at 65 mm/h on the no-till history plots was 11 to 35% less than from conventional-till history plots. During the 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. Soil loss measurements failed to show increasingly greater erodibility with continued erosion from conventional-till. 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 higher rates of soil loss with time for plots with conventional-till history.