Experimental Precision and Variety Comparison Precision in Regional Crop Trials

According to the basic concepts of precision and the principles of analysis of variance (ANOVA), precision types for experiments and variety comparison in regional crop trials (RCT) were studied and developed; expected variety comparison precision (EVCP) and realized variety comparison precision (RVCP) and the corresponding statistical indexes of them were proposed. It was explained that experimental precision (EP) and variety comparison precision (VCP) are two kinds of precision of RCT; EP includes error precision and variety mean precision, which can be measured respectively by the coefficient of variation of single observation's error (CVe) and the coefficient of variation of variety mean's error (CVY); VCP includes EVCP and RVCP, which can be measured respectively by the detectable least relative difference (DLRD) and the relative least significant distance (RLSD); EP is an important factor of VCP but not identical to it; RVCP is the realization of EVCP. Besides error, experimental design and GE interaction and ANOVA model affect VCP. Several application examples for these precision indexes were presented, and the precision of regional cotton trials in the Yellow River Valley and the Changjiang Valley were investigated through the historical data of RCTs from 1980 to 1999.