TEMPORAL TRENDS IN SOIL PRODUCTIVITY EVALUATIONS* |
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| Authors: | Bryan D Baker Philip J Gersmehl |
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| Institution: | 1. BRYAN D. BAKER (Ph.D. candidate, University of Minnesota) is Assistant Professor of Geography, Oklahoma State University, Stillwater, OK 74078. His research interests include biogeography, soils, and environmental planning.;2. PHILIP J. GERSMEHL is Professor of Geography at the University of Minnesota. His current interests include land evaluation, regional disinvestment, and geographic education. |
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| Abstract: | Studies of soil productivity must compensate for the effects of temporal trends in order to examine the pattern of crop yields along spatial gradients. An analysis of the published yield estimates for 30 soils in 233 counties, however, did not find consistent yield increases over the past three decades. On the contrary, the yield estimates for many soils were markedly uniform since 1972. The uniformity appears to have two causes: the acknowledged difficulty of making yield estimates in a time of increasing variability in soil and crop management, both within and between regions, and surveyors' awareness of data stored in a national soils data base. The effect is to cast doubt on soil productivity data reported in county soil surveys published between 1973 and 1988. |
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| Keywords: | crop yields geographic information systems soil productivity soil surveys SOILS-5 |
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