STUDIES CONCERNING THE ELIMINATION OF 
EXPERIMENTAL ERROR IN COMPARA- 
TIVE CROP TESTS 
By T. A. KlESSELBACH 
It is apparent that many sources of error have uncon- 
sciously entered into comparative crop yield tests. The very 
important matter of overcoming variation in soil conditions 
as a source of experimental error has been quite extensively 
studied and reported by various investigators during the past 
decade. The means suggested for reducing such error have 
been (1) repetition of plats and (2) correction of yields 
according to check plats planted to a uniform variety or 
treatment at stated intervals. Both methods have proved 
of value and a combination of both may often be used advan- 
tageously. Some danger always exists of error occurring in 
the check plats and that correcting according to them may 
introduce new errors in the yields of crops compared. The 
method should, for this reason, be used with caution. 
Studies in experimental error conducted at this Experi- 
ment Station prior to 1911 have been published by Prof. E. 
G. Montgomery, now of Cornell University, in Bulletin No. 
269, of the Bureau of Plant Industry, U. S. Department of 
Agriculture, and in the Twenty-sixth Annual Report of the 
Nebraska Agricultural Experiment Station. These pub- 
lished results concern primarily the general problems of repe- 
tition and size of nursery small grain plats, and the use of 
check plats. 
The object of the following investigations was to secure 
further information regarding the elimination of error in 
comparative yie\d tests. Shortage of facilities for carrying 
on this character of work in addition to the regular crop 
investigations of the Experiment Station has in some casei 
necessitated intermittent experiments. The duration of 
some of the tests has for the same reason been shorter than 
would have been desired. 
Acknowledtiment is gratefully made to Professor J. A. Ratcliff and Pro- 
fessor C. ^. Helm for valuable assistance in field supervision and in keeping- 
records during- much of the time these experiments were in progress. 
Messrs. H. G. Gould, E. R. PJwinu, K. E. Holland and H. B. Pier, have also 
rendered efficient assistance at various times. 
