Role of Topography in Water and Crop Management Decisions.

Crop yields are consistently related to local topography, in both rain-fed and irrigated fields, in flat and rolling fields, and in all geographies.  This relationship is largely due to the impact of topography on soil moisture patterns, and the central role of topography suggests that re-distribution of precipitation, both rainfall and irrigation, may play a greater role to determine soil moisture patterns than we have previously considered.  Analysis of data across the Corn Belt has shown that yields are most often limited in extreme topography zones, either summits or toeslopes, and that the extent of yield variability is related to annual weather patterns.  The dominance of topographical patterns has pointed toward greater attention to water management (drainage, irrigation, land shaping, and residue management) as a means to significantly increase crop yields.  It also suggests that technologies to characterize soil moisture levels should play a more central role in framing other agronomic decisions.