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COMPARISON OF EXPERIMENTAL DESIGNS USED TO DETECT CHANGES IN YIELDS OF CROPS EXPOSED TO ACIDIC PRECIPITATION
Citation:
Evans, L. AND K. Thompson. COMPARISON OF EXPERIMENTAL DESIGNS USED TO DETECT CHANGES IN YIELDS OF CROPS EXPOSED TO ACIDIC PRECIPITATION. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-84/338.
Description:
A comparison of experimental designs used to detect changes in yield of crops exposed to simulated acidic rain was performed. Seed yields were determined from field-grown soybeans(Glycine max) exposed to simulated rainfalls in which all ambient rainfalls were excluded by automatically moveable rainfall exclusion shelters. When all eight, 4 x 4, latin squares were used, simulated rainfalls of pH 4.1, 3.3, and 2.7 exhibited yields 10.6, 16.8, and 23.9%, respectively, below yields of plants exposed to pH 5.6. The linear component of pH treatment differences showed a highly significant decrease in yield (p<0.001). The eight latin squares analyzed as individual experiments yielded erratic conclusions. However, when all eight latin squares were combined a satisfactory evaluation can be made. The low probability value for differences among latin squares (p<0.005) indicates that field locations are a legitimate source of stratification.