Great Plains Studies, Center for


Date of this Version

February 1994


Published in Great Plains Research 4:1 (February 1994). Copyright © 1994 The Center for Great Plains Studies, University of Nebraska–Lincoln. Used by permission.


The relative influences of interannual climate variability, technological development, and management strategies on crop yields are difficult to separate. Assessment of climate impacts and of an agricultural system s ability to protect crops from weather-related yield changes are important questions receiving considerable attention in view of the potential for climate change. Statistical and ecological crop-climate studies have assumed that the combined effects of technology and management have produced linear or exponential yield increases in most crops in recent years.

In this study, an empirical assessment of influences of management and technology on wheat yields in north-central Colorado was made using a control crop of unmanaged native shortgrass vegetation. A signal of climate variability was identified for the native grass, and was removed from the record of wheat yields, leaving departures termed the Management- Technology Index (MTI). The shape of the MTI curve was distinctly unlike the linear or exponential trend assumed in other models. The Index showed high variability from 1940 to 1963, but from 1963 to 1982 was characterized by step-functional increases. The step-functional behavior was interpreted to reflect the process of innovation diffusion.