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Title:Predicting Crop Yields and Productivity Indices for Illinois Soils
Author(s):Garcia Paredes, J. Diego
Doctoral Committee Chair(s):Olson, Kenneth R.
Department / Program:Agronomy
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Agriculture, Agronomy
Abstract:Comparing established (Circular 1156) crop yields with predicted 1970s crop yields, generated from soil property models from base and benchmark soils, predicted high R2 values of 0.90 for corn, 0.90 for soybean, 0.81 for wheat, 0.81 for oat, and 0.88 for hay. These crop yield models were tested with 167 supplementary soils from nine selected counties representing the crop reporting and weather districts for Illinois. The equations explained 50% of the yield variation for corn, 47% for soybean, 41% for wheat, 33% for oat, and 47% for hay. Outliers (greater than +/-2 SD) were identified for further analysis. The relationship between crop yields, versus time (years) were established using regression analysis. Crop yield trends and magnitude of change were estimated for 66 countries in the northern region and for 36 counties in the southern region for the time period between 1976 and 1995. The magnitude of crop yield change by region was added to the 1970s predicted and established yields to generate the 1990s predicted and established yields. These yields were compared against 10-yr averages for the 1990s as reported in IAS for the nine test counties. As in the 1970s comparisons, predicted yields were closer to reported IAS yields than those established in Circular 1156 and projected to 1990s. There were no significant differences between the nine county predicted 1990s yields and the IAS 1990s yields for corn, soybean, and wheat.
Issue Date:1999
Description:122 p.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1999.
Other Identifier(s):(MiAaPQ)AAI9944859
Date Available in IDEALS:2015-09-28
Date Deposited:1999

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