Using Incomplete Block Designs to Reduce Uncontrolled Variation in Field Experiments - Such as Variety Tests Fred Allen Department of Plant Sciences University of Tennessee SCC33 Annual Meeting, Feb. 8-10, 2012 New Orleans, LA

SOURCES OF UNCONTROLLED VARIATION IN FIELD EXPERIMENTS: * EXPERIMENTS WITH A LARGE NUMBER OF TRTS. (e.g. Large number of varieties) * LARGE AMOUNT OF VARIATION IN THE FIELD SITE (e.g., soil type changes, moisture, fertility) ONE WAY TO REDUCE THE UNCONTROLLED VARIATION IS TO USE AN INCOMPLETE BLOCK DESIGN * DIVIDE EACH REP INTO SMALLER BLOCKS * CAN BE IMPOSED EX POST FACTO PLANTING * BLOCK SIZES FROM 8-14 HAVE BEEN OUR BEST EXPERIENCE

TN WHEAT TEST 2011, EXAMPLE OF TWO LOCATION RANDOMIZATION 72 VARIETIES 3 REPS PER LOCATION 7 LOCATIONS

9 Range Field Layout

6 Range Field Layout

ANALYSIS OF HRREC USING REPS ANALYSIS OF HRREC USING BLOCKS

ANALYSIS OF ETREC USING REPS ANALYSIS OF ETREC USING BLOCKS

ANALYSIS ACROSS ALL 7 LOCS USING BLOCKS ANALYSIS ACROSS ALL 7 LOCS USING REPS

PARTIAL SUMMARY OF VARIETY MEANS ACROSS LOCS AND FOR THE TWO LOC EXAMPLES * CHANGE IN VALUE OF MEANS * CHANGE IN RANKS ANALYZED BY REPS ANALYZED BY BLOCKS

CORN EXAMPLE SHOWING DIFFERENT # ENTRIES PER BLOCK

14 ENTRIES PER BLOCK

ANALYSIS USING 8 VARIETIES PER BLOCK ANALYSIS USING 14 VARIETIES PER BLOCK