32 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 49 



example, in the wheat variety test diagrammed in figure 1 the four 

 check plots which adjoined variety 1 (one in each series) were aver- 

 aged together, the four adjoining variety 2, the four adjoining variety 

 3, etc. The four check plots adjoining varieties 89, 90, 91, etc. were 

 similarly averaged. 



(3) The average yield of each border row for each variety was 

 converted to the percentage of the average yield of the same variety 

 in its interior rows. These yields of border rows in percentage will 

 be referred to as "relative border yields." The relative border yield 

 gives a rough indication of the effect of competition on the variety. 

 When it is above 100, the variety yielded more in border rows (subject 

 to competition) that in interior rows (protected from competition). 

 When it is below 100, the border yield was less than the interior yield, 

 in proportion. 



(4) An approximate measure of the competition between each 

 pair of adjacent varieties was obtained by dividing the higher relative 

 border yield by the lower, in the case of their adjacent border rows, 

 and substracting 100 from the result. When the variety on the left 

 has a higher relative border yield, this is given a positive sign; in the 

 reverse case a negative sign. This figure is simply the predominance 

 of the more strongly competing variety over the other in percentage of 

 relative border yield. It will be referred to, for convenience, as the 

 coefficient of competition. 



(5) This measure of competition was correlated with various 

 characteristics of the competing varieties, including the relative yields 

 in interior rows, the relative grain-straw ratios, the relative dates of 

 heading and of maturity, and the relative heights. In correlating com- 

 petition with the relative yield of the interior rows, the relative yield 

 was determined by dividing the higher yield by the lower, subtracting 

 100, and assigning a positive or negative sign, as before. The correla- 

 tion determined, therefore, is the correlation between the percentage 

 advantage of one variety over another in competition, and the differ- 

 ence in yield of the two varieties, expressed in percentage, when pro- 

 tected from competition. Relative grain-straw ratios were determined 

 similarly, the ratios being first obtained by dividing the yield of straw 

 by the yield of grain. Relative dates of heading and maturity and 

 relative heights were determined simply by subtracting the value for 

 one variety from the value for the other. In each case, of course, the 

 sign was determined in the same way. 



A simple example explained in detail may serve to make this 

 method clear. In the wheat variety test of 1921 the varieties Fultz 

 (Bayer), Michigan Amber, and Michigan Wonder No. 211 occurred 



