294 Journal of Agricultural Research voi. xix.no. 7 



clear that the innate differences in different parts of the field do not 

 in some seasons exert their full influence upon crop yield because of the 

 weight of other factors. The practical conclusion to be drawn from this 

 result is that an experimental field which might be demonstrated to be 

 sensibly uniform for one crop plant or for one season might not prove to 

 be so for another crop or in a different season. 



7. KHERSON oaTs 



Kiesselbach {10, 11) has given records of yield for 207 i/30-acre plots 

 of Kherson oats. He says: 



These plats were planted upon a seemingly uniform field for the ptirpose 



of studying variation in plat yield as a source of experimental error. The entire 

 field had been cropped uniformly to silage com for a period of eight years. It had 

 been plowed each year and was also plowed in preparation for the oats in 1916. The 

 oats were drilled diaring two successive days in plats 16 rods by 66 inches . 

 The plats were separated by a space of 16 inches between outside drill rows. A wide 

 discard border of oats was grown around the outer edge of the field, so that all plats 

 should have a similar exposure. 



lyove {13) has shown the existence of heterogeneity in this field. 

 Grouping the entries of Kiesselbach 's Table 27 in a 3 by i fold manner 

 the heterogeneity coefficient is found to be 



^ = 0-495 ±0-035, ?'/Er=i4- 



For data on a second test of the influence of heterogeneity on the 

 yields of experimental plantings of oats we turn to a small experiment 

 by Montgomery (77), who has given the yields of thrashed grain in 

 grams from 100 consecutive rows of Kherson oats {17, p. 35, Table XIII) 

 each 12.5 feet in length. 



The plat chosen for this test was quite uniform and the appearance of the plat at 

 harvest was very satisfactory. 



Combining by twos, we find for the correlation between adjacent rows 

 ^=0-339±0-o6o, r/E^=5.65. 



8. GRAIN AND NITROGEN CONTENT IN WHEAT 



Montgomery {17, p. 37, fig. 10) has given the yield of grain in grams 

 on 224 blocks each 5.5 feet square. Combining in a 2 by 2 fold manner 

 we deduce 



r= 0.391 ±0.038, rlEj.= 10.2. 



Again, Montgomery {17, p. 21-22, fig. 7) has given the values of 

 nitrogen content from 224 Turkey wheat plots of the same size. These 

 values are quoted in figure i of this paper. The correlation between the 

 plots is found to be 



r = 0.020 ± 0.045 » ^l^r = 0-44- 



