EXPERIMENTS IN FIELD PLOT TECHNIC 25 



test. Kiesselbach has therefore adopted the practice of testing such 

 strains in 5-row blocks replicated ten times instead of in single-row 

 plots. 



Love 8 has criticized these results because in some cases at least 

 the rows ran east and west rather than north and south. He states 

 that in experiments at Ithaca, New York, there is little competition be- 

 tween varieties grown in single rows, when the rows run north and 

 south. "In order to obviate any criticism of this method," he adds, "it 

 might be well to follow the plan of arranging varieties so that late 

 sorts are grown together and the earlier ones together. In other words, 

 the different sorts could be so arranged that they grade into one another 

 as regards yield, earliness, and the like." To this Kiesselbach 6 replies 

 that in some of his competition studies the rows ran north and south 

 and in others east and west, and that striking competition occurred in 

 both cases. He adds that although error resulting from row compe- 

 tition would undoubtedly be reduced by grouping varieties of sim- 

 ilar growth habits together, it appears that varieties fairly similar 

 in growth habit may vary for some reason in relative competitive qual- 

 ity. 



Experimental Results. Some further evidence on competition 

 as a source of error in plot experiments is afforded by a study of the 

 relative yields of border rows and interior rows in the 5-row blocks used 

 in these preliminary tests. It should be remembered, of course, that the 

 effect on yield would be decidedly greater in single rows exposed to com- 

 petition on both sides than in these border rows, which compete with 

 another sort on only one side. The extent of the error from compe- 

 tition in such border rows is of interest in determining whether it is 

 necessary to discard the border rows of small blocks. When 5-row 

 blocks are used, even if the border rows are not discarded, the relative 

 effect of competition is greatly reduced, since only two of the five 

 rows are subject to varietal competition and these are exposed only 

 on one side. If this results in reducing the error from competition to 

 a low point, or if varieties can be so arranged as to give this result, 

 it may be advisable in practice to harvest 5-row blocks entire, thus 

 avoiding the principal objection to the use of border rows the loss of 

 a considerable portion of the experimental area. 



Competition is particularly important as a source of error because 

 of the fact that it tends to affect replicate plots similarly, and conse- 

 quently does not necessarily increase plot variability. For this reason 

 it is likely to escape detection, and, when it is involved in an experi- 

 ment, its effect cannot be measured. There is no 'great objection to a 

 considerable experimental error from plot variability in field experi- 



