CONTENTS 



Page 



The Problem 6 



Plan and Method of Investigation 9 



Terminology 9 



Procedure 11 



Work of 1919 12 



Work of 1920 16 



Work of 1921 18 



Competition as a Source of Error in Preliminary Tests 23 



Previous Investigation 23 



Experimental Results 25 



Illustrations of Effects of Competition 26 



Relation of Competition to Various Characteristics of the Com- 

 peting Varieties 31 



Discussion 40 



Size and Replication of Plots 43 



Previous Investigation 43 



Experimental Results 44 



Size of Plots 44 



Replication of Plots SO 



Adjustment of Yields by Means of Check Plots 54 



Previous Investigation 54 



Experimental Results 56 



Method Used in Adjusting Yields 58 



Relative Variability of Actual and Adjusted Yields 60 



Difference in Results Obtained by Adjustment with Different Check 



Varieties 63 



Value and Limitations of Adjusting Yields by Means of Check Plots 71 



Concluding Remarks 73 



Summary 75 



Acknowledgment 77 



References Cited 78 



TABLES 



Table 



Number Table Page 



1 Yields of Barley Varieties 1919 13 



2 Yields of Oats Varieties 1919 14 



3 Yields of Oats Strains 1919 15 



4 Yields of Wheat Varieties 1920 16 



5 Yields of Wheat Varieties 1921 17 



6 Yields of Wheat Varieties and Mixtures 1921 18 



7 Yields of Oats Varieties 1921 21 



8 Yields of Oats Strains 1921 22 



9 Relative Yields of Two Small Grain Varieties When Compared in Al- 



ternate Rows and in Blocks (Kiesselbach) 24 



10 Correlation of Competition with Various Characteristics in Barley Va- 



riety Test 1919 35 



11 Correlation of Competition with Various Characteristics in Oats Va- 



riety Test 1919 .35 



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