76 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 49 



5. Competing quality was correlated fairly consistently with 

 yield and with earliness of heading and maturity. No relation to 

 grain-straw ratio was found in the one season in which this charac- 

 ter was determined. A significant correlation between competition 

 and height was found in the wheat variety test of 1921, but the rela- 

 tion of competition to height was not determined in the other tests. 



6. In the oats tests competition was most closely related to earli- 

 ness of heading and maturity, but was also related to yield. In the 

 wheat, competition was related fairly closely to both yield and earliness. 

 In the barley it was not significantly correlated with any of the char- 

 acteristics studied, though the relation to yield was considerably closer 

 than the relation to any of the other characteristics. 



7. In the wheat and oats tests in which earliness and yield were 

 correlated with competition, earliness and yield were correlated quite 

 closely with one another. 



8. Single-row plots, protected from competition by border rows 

 discarded at harvesting, were somewhat more variable in yield than 

 3-row plots similarly protected, but the difference was not great 

 enough to outweigh their advantage in size. The mean yield of five 

 replicate protected single-row plots is therefore more reliable, under 

 the conditions of these tests, than the mean yield of three replicate 

 protected 3-row plots, which would occupy the same area and require 

 considerably more labor in harvesting and threshing. 



9. There was no consistent difference in variability between 3- 

 row and 5-row plots. 



. 10. Plot variability was increased with increase in the size of the 

 experiment field. The number of replications required for a given 

 degree of precision, as measured by the variability of plot yields, is 

 therefore increased somewhat when border rows are added for the 

 control of competition. 



11. The variability of 120 distributed check plots of Kherson oats 

 differed widely from that of 120 distributed plots of Red Rustproof 

 oats, adjacent to them. If the variability of the check yields were con- 

 sidered a measure of the precision of the test, entirely different con- 

 clusions would be drawn on the basis of the yields of these two check 

 varieties. 



12. Adjustment of plot yields on the basis of the yields of check 

 plots resulted in a decrease in plot variability in three tests and in an 

 increase in five tests. In general the practice was effective on fields of 

 high plot variability, and was ineffective on fields of low plot varia- 

 bility. 



