Examining the targeting of conservation tillage practices to steep vs. flat landscapes in the Minnesota River Basin

Conservation tillage practices are being prescribed as a remedy to reduce soil erosion and phosphorus losses and to increase water-holding capacity of agricultural soils. This study evaluates the targeting of conservation tillage practices to steep vs. flat landscapes in the Minnesota River Basin. Tillage practices were identified using remote sensing techniques in nine subwatersheds of the Lower Minnesota River watershed and analyzed in relation to topography. A Landsat Thematic Mapper (TM) image acquired during the 1997 planting season was used to identify conventional and conservation tillage practices at a 30m (33 yd) resolution. Conservation tillage has been adopted on 32% to 54% of the cropland in the subwatersheds studied, while average cropland slope steepness ranges from 1.5% to 2.8%. A linear regression of percent adoption of conservation tillage vs. average slope steepness had a slope of 3.45 and an r² of o.o7. This shows that there was no significant targeting of conservation tillage to steeper topography across subwatersheds. Within a subwatershed, however, there was a slight tendency toward greater adoption of conservation tillage on steeper landscapes, up to slope steepnesses of 5%, then a significant decline in the adoption of conservation tillage. Overall, farmers in the Lower Minnesota River watershed seem to be adopting conservation tillage for reasons unrelated to soil conservation.