Investigation on designing methods,spatial arrangements and data analysis in intercropping experiments

In recent days there is mounting interest in intercropping systems. Approaches of data analysis on intercropping experiments are very important in interpreting results. Intercropping advantages may be influenced by both plant density and relative frequency of the intercrop components as key factors .In this study by emphasize with this two factors ,methods of data analysis including, regression(reciprocal yield of individual plant) bivariate and simulated were investigated in three separate experiments .In two first experiment the experimental design was a randomized complete block in factorial arrangement with three replication and 15 treatments including 3 levels of plant populations and 5 levels of crops ratio in sorghum and sesame intercropped arrangement .The third experimental design also was a randomized complete block with 5 levels of crops ratio in bean and corn intercropped arrangement .Results showed that regression analysis(reciprocal yield approach )was the efficient and simplest method of analysis to measured quantitatively intera and interspecific competition and also interactions between density and proportion of sorghum and sesame species in the mixture .The method of bivariate analysis made it possible to analyzed two values obtained from one plot related to a specific treatment density, proportion or interaction of density and proportion simultaneously and the effect of density on grain yield of sesame and sorghum was significant ,and the yield of two crops showed a positive correlation. Light absorption and distribution in mixed canopies of corn/bean intercrops were simulated and compared with monocultures using the data obtained from a replacement design with different sowing ratios. Total absorbed radiation was significantly higher in all replacement ratios compared to sole crops. Calculated land equivalent ratios for absorbed light showed 22-24 benefits for intercrops over monocultures which was resulted to 32-36 yield advantage. Based on the results it was concluded that higher yield of intercrops is due to complementary effects of species in better light absorption as well as increased light use efficiency of species in intercrops.