A SIMULATION STUDY OF FIELD TRIAL ANALYSIS

In variety trials, lattice designs are perhaps the most popular ones used by agriculture researchers. An eight by eight lattice design in which there were 56 test cultivars and a check cultivar in each of the eight blocks, was replicated four times. A simulation was performed in which the lattice design was superimposed on two soil fertility maps, one relatively uniform (map 1) and one more heterogeneous (map 2). Ratios of soil variation to total variation (soil + error ) ranging from .1 to 1.0 were studied. The results suggest that in the present setup blocking is more effective when soil variability is small but not very effective when soil variablility is large. The relative efficiency of lattice design over randomized block design increased from 101% to 136% as the ratio of soil to total variation varied from 0.1 to 1.0 in map 1 and ranged between 101% to 117% in map 2. The average within replication variance of the data from check plots was close to the intra-block error for map 1 but generally slightly larger for map 2. A 30-70% improvement in relative efficiency was found in the results after the data were adjusted for check cultivar in each block