3Tebrugge F, Bohmsen A. Farmers and experts opinion on no-tillage in West-Europe and Nebraska[C]. Spain Madrid: World Congress on Conservation Agriculture, 2001.
4Kaspar T C, Radke J K, Laflen J M. Small grain cover crops and wheel traffic effects on infiltration, runoff, and erosion[J]. Journal of Soil and Water Conserva- tion, 2001,56(2) :160-164.