Comparing the relative efficiency of two experimental designs in wheat field trials

ABSTRACT:This investigation was conducted in 2010/11 and 2011/12 growing seasons at the experimental farm of the Faculty of Agriculture, Cairo University, Giza, Egypt. Twenty Egyptian bread wheat cultivars were evaluated in an alpha lattice design with three replications for nine characters. The aim was to compare the relative efficiency of two experimental designs based on error mean squares. In field trials, variation in soil fertility can result in substantial heterogeneity within blocks and thus, poor precision in treatment estimates resulted. For this purpose, two datasets were analyzed according to alpha lattice design and randomized complete blocks design (RCBD). For the two trials, alpha lattice design exhibited more efficient than randomized complete blocks design in reducing both the error mean squares and the coefficient of variation consequently, an efficient estimation of treatment differences, than RCBD. Average estimated relative efficiency (RE) was 9.5, 28.5, 30.0, 22.5, 40.0, 30.5, 35.0 and 28.5% for plant height, number of tillers plant-1, spike length, number of spikelets spike-1, number of grains spike-1, 1000-grain weight, grain yield plant-1 and grain yield feddan-1, respectively, indicating that the high precision to estimate treatment effects is gained significantly from using an alpha lattice design instead of RCBD. Whereas RE value of 0.98 for days to 50% heading indicated that the precision of both alpha lattice design and RCBD was similar. Mean rank comparisons for both RCBD and alpha lattice design were performed. The ranks were not constant across the experiments. The results showed that the traditional RCBD should be replaced by alpha lattice in the agricultural field trials when the number of treatments to be tested in an experiment increases to more than ten, where a homogeneous block is quite difficult to find in field experiments.