The Journal of Soil and Water Conservation (Vol. 63, No. 3, Pages 112-119) has published research by Dana Sullivan et al. assessing use of conservation tillage by satellite.
As indicated in a USDA Agriculture Research Service news release (http://www.ars.usda.gov/is/pr/2008/080424.htm), "This satellite mapping technique shows promise for streamlining national efforts to monitor changes in conservation tillage adoption over time, evaluate the efficacy of conservation tillage placement, and reduce the need for time-consuming field surveys to ensure compliance with federal cost-sharing programs."
Image from the paper courtesy of the author (c) the Soil and Water Conservation Society.