Effects of soil, climate and cultivation techniques on cotton yield inCentral Greece, using different statistical methods

摘要

This study aims to identify and quantify the relationship between the environmental and crop management variables and the cotton yield in the Thessaly plain in Central Greece. A total of 349 fields spread along the area were selected where cotton yield, soil and management data were measured for three consecutive growing seasons. A combination of statistical tools such as one-way and n-way analysis of variance (ANOVA), linear regression analysis and factor analysis was used for the identification and confirmation of the role of soil and management variables under different climatic conditions. ANOVA showed that soil order, topsoil and subsoil texture, carbonates, cultivar, previous uses of the sampling sites, defoliation and the spatial and temporal variation of the climate were significant for the yield (P < 0.001). Regression analysis confirmed the results of ANOVA and suggested that 50% of the yield variance is accounted for by soil variables, about the same percentage (47%) is accounted for by management variables, while soil and management variables together explain 65% of the yield variance. Factor analysis was applied on the data in two ways: (i) by including yield variable between the variables and (ii) by not including yield. Both analyses resulted in ten factors which were identified by the same groups of variables. Results from the first factor analysis suggested that 61% of the total yield variance is accounted for by the ten factors. Factors F1 and F2 explain about half of this variance while the factor F5 explains one third of it. Regression analysis on the factor scores calculated from the second factor analysis showed that factors F1, F2, F5 and F7 explain 41% of the total yield variance. In both analyses factor F1 is defined mainly from soil variables, while F2, F5 and F7 mainly from management variables.