Positions of lettuce seedling on polystyrene trays and effects on normality and homogeneity of the errors in the plant production

Abstract

The quality of an experiment can be described through statistics, being the experimental error one of the parameters of the evaluation of such quality. The objective of this study was to verify the interference of different positions of lettuce seedlings on polystyrene trays on the normality and homogeneity of the errors in experiments conducted in plastic greenhouse and field. Six experiments were carried out in the Federal University of Santa Maria, being three in the summer (2006-2007) and three in the autumn - winter (2007) with the lettuce crop, cultivar Vera. The treatments were defined by 12 different positions of the seedlings on the tray of production. The analyzed variables in the seedling production and after their transplant to the environments were the fresh and dry phytomass of leaves and roots and the fresh and dry phytomass of leaves, respectively. Presuppositions of errors normality and homogeneity were tested being compared to the averages of each treatment. The assumptions of homogeneity and normality of experimental errors were adequate for the leaves and root phytomass of lettuce in experiments with different positions in the tray seedling production, in different environments and cultivation seasons. For the dry phytomass of leaves trere was no adequacy of homogeneity and/or normality of experimental errors in the summer experiments, with seedlings and plants in plastic greenhouse. For the dry phytomass of root there was no adequacy of the assumption of normality of experimental error in the autumn-winter experiment with seedlings.