EXPERIMENTS IN FIELD PLOT TECH NIC 23 



COMPETITION AS A SOURCE OF ERROR IN PRELIMINARY 



TESTS. 



Previous Investigation. The possibility of error from competi- 

 tion in single-row tests was noted by Montgomery" in 1913, in the 

 following passage : 



"In 1908 it was observed that a certain strain of early wheat in a series 

 of row plats made a very poor appearance at harvest time, while the same 

 strain planted in centgeners made a much better comparative showing. Ap- 

 parently the larger and faster growing strains on each side, the rows being 

 only 8 inches apart, exercised some competitive effect. This effect of com- 

 petition has been noted for two years since. Also in certain variety tests 

 of oats, grown in row plats 10 inches apart, the same effect was noted. 

 Exact data cannot be given on this point, as the results from the series of 

 plats planted in 1909 and in 1910 for this purpose were seriously impaired 

 by unfavorable conditions; but Table XVIII, giving results from adjacent 

 row plats sown at different rates H shows that the 800-seed rate made a marked 

 increase over the 700-seed rate, while in a similar series of blocks (Table 

 XIX), sown at the same rate, this marked increase was not noted. Since the 

 800-seed row was always adjacent to the 400-seed row, it may have had some 

 advantage on this account. Danger from this source can probably be avoided 

 if care is taken to plant only similar varieties in adjacent rows. Where the 

 block plat is used this source of error is eliminated." 



Hayes & Arny 4 found considerable competition between rod-rows 

 grown one foot apart. Three-row plots were used in variety tests of 

 winter wheat, spring wheat, barley, and oats, and the yields of each 

 row determined separately, in 1916. The comparative yield of the 

 border rows in each plot was then correlated with the comparative 

 height and yield of the adjacent rows. There was some effect on the 

 yield of border rows due to the height of adjacent rows in the case 

 of barley and winter wheat. The results were variable in different 

 plots. In the case of oats the effect of height was rather obscure, and 

 in the case of spring wheat it was not apparent. The yield of adjacent 

 rows appeared to be of some importance in the barley tests and in 

 some of the spring wheat tests. These results led to the adoption of 

 3-row plots with discarded border rows for preliminary testing at 

 the Minnesota Station. 



Love and Craig* in describing the methods used in cereal investiga- 

 tions at the Cornell Station describe the single-row test and add : "In 

 order to prevent any effect which may be caused by two unlike sorts 

 growing together the different strains are arranged according to 

 earliness and other characters so as to reduce this source of error to a 



