Submitted to: American Society of Agricultural Engineers Meetings Papers
Publication Type: Abstract Only
Publication Acceptance Date: 7/21/1999
Publication Date: N/A
Technical Abstract: Seasonal runoff and sediment loss from three field-size watersheds in the highly erosive deep loess soil region of southwest Iowa were summarized from observed events during the 1974-1995 period of homogeneous cropping systems. One watershed (W-2) was managed in continuous corn cropping with conventional tillage on the general contour. Another watershed (W-3) was managed in continuous corn with a conservation tillage system of ridge-til on the general contour. The third watershed (W-4) was terraced with double-spaced, parallel, bench terraces with tile inlets and was also cropped in continuous corn with ridge tillage. Annual series of hydrologic and sediment loss observations from each watershed were analyzed by crop stage periods of rough fallow, seed bed, rapid growth, reproduction and maturation, and residue as defined by observed dates of spring tillage, planting, cultivation, and harvest. During the 90-da period from tillage to 30-da after the first cultivation, about 38% of annual precipitation, 3 to 50% of storm runoff, 90% of the annual sheet-rill sediment loss, and 40 to 75% of the gully sediment loss occurred from the watersheds. In this period, sheet-rill sediment loss from W-3 was about 1/8 that from W-2, and sheet-rill sediment loss from W-4 was about 1/2 that from W-3. In this period, gully sediment loss from W-3 was similar to that from W-4 and was only 1/25 of that from W-2. The ridge-till treatment on W-3 was very effective in reducing sheet-rill and gully sediment loss compared to the conventional tillage on W-2.