52 Nebraska Agricultural Exp. Station, Research Bid, 13 
of variation due to the soil or (b) correcting the results from 
the intervening test plats. (2) Replication of plats and bas- 
ing the conclusions upon the mean yield. (3) Use of long, 
narrow rather than short, wide plats. (4) Calculating the 
probable error for the mean results of replicated plats, to 
indicate the degree of confidence which may be placed in the 
results. 
The results from 207 thirtieth-acre Kherson oats plats, 
grown in 1916, illustrate each of the four p ;actices mentioned 
above. These plats were planted to a uniform crop upon a 
seemingly uniform field for the purpose of studying varia- 
tion in plat yields as a source of experimental error. The 
Fig. 14 — Two hundred and seven thirtieth-acre Kherson oats plats 
planted to a uniform crop for studj^ing experimental error in 1916 
entire field had been cropped uniformly to silage corn for a 
period of eight j^ears. It had been plowed each year and was 
also plowed in preparation for the oats in 1916. The oats 
were drilled during two successive days in plats 16 rods by 
66 inches, which equaled one drill width. 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 expo- 
sure. General views of this field are shown in Figures 13 
and 14. 
