CONTENTS 
Page 
Summary 5 
Error due to competition between adjacent plats 14 
Illustration of principle of competition between adjacent rows 14 
Competition between adjacent rows of small grain 14 
Row competition in rate-of-planting tests with wheat and 
oats 15 
Relative stooling of two rates of planting when compared 
in alternating rows and alternating blocks 18 
Row competition between varieties of wheat and oats 19 
Evidence of plat competition in a wheat-breeding nursery 2 5 
Competition between individual plants 27 
Competition between corn test plats as a source of experi- 
mental error 2 9 
Row competition in rate-of-planting tests with corn 31 
Intra-hill and row competition in corn variety yield tests 3 3 
Summary of plat competition studies 41 
Variation of stand as a source of error in yield tests with corn 41 
Relation of stand to yield in single-row test plats 43 
Combination of rate planting with v ariety yield tests 45 
Effect of removing suckers with different varieties 47 
Reliability of estimating plat yields by means of fractional areas... 4 7 
Experimental errors caused by soil variation 51 
Use of check plats 53 
Reduction of error by replication 61 
Effect of size and shape of plat 64 
Significance of the probable error 65 
Probable error for 50 groups of four adjacent thirtieth-acre 
plats of Kherson oats 67 
Probable error of 50 groups of four systematically distrib- 
uted thirtieth-acre plats of Kherson oats 72 
Examples of limitation of the probable error 72 
Effect of change in methods on agronomic equipment 74 
Measuring improvement in yield thru breeding 75 
Soil limitation as a source of error in pot experiments 78 
Effect of the size of pot upon the growth of corn 80 
Effect of planting at different rates upon the growth of corn in 
pots 85 
Statement of methods in bulletins 89 
Bibliography 91 
