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MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 49 



Moreover, the Red Rustproof strains showed competitive effects 

 among themselves to some extent, though not so conspicuously as dif- 

 ferent varieties. For example the strains 0122 and 0123, which were 

 taxonomically identical, yielded as follows: 



Strain 0122 which was apparently 11 per cent inferior to strain 

 0123 in the yields of interior rows, appeared to be 12 per cent superior 

 to the same strain in the yields of their adjacent border rows. 



In the wheat mixture test of 1920 also the rows ran north and 

 south. An example of competition from this test is the following: 



In this case also differences in yield were increased by compe- 

 tition. 



The individual cases cited above will serve to show the existence 

 of competition as a source of error in these tests. As a result of 

 competition the differences Between varieties may be increased or de- 

 creased, and in some cases a material advantage in yield may be con- 

 verted to a material disadvantage. The phenomenon occurs, under 

 conditions at Columbia, whether the rows run north and south or 

 east and west. Of course it is not true that all of the difference in 

 yield between border rows and interior rows is necessarily caused 

 by varietal competition. Some variation in the yield of adjacent rod- 

 rows will occur regardless of competition. When the means of only 



