6 ^ V MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 49 



THE PROBLEM. 



At present the type of plot most commonly used for the pre- 

 liminary testing of small grain varieties and strains is probably the 

 "rod-row." The methods of conducting rod-row tests described by 

 Love and Craig* may be considered typical. The varieties or strains 

 are sown by hand in rows one foot apart, usually opened and covered 

 with a wheel hoe or similar implement. The seed for each row is 

 weighed out in a quantity equivalent to ordinary rates of seeding in 

 field practice. In harvesting, six inches or a foot at the end of the 

 row is discarded, to prevent increase in yield by reason of the more 

 favorable space conditions at the ends of the rows. The list of va- 

 rieties is repeated in several series, and the results averaged to reduce 

 the error from plot variability. A check variety is grown in every 

 tenth row to indicate the variability of the field. 



The use of rod-row tests involves several errors, derived principally 

 from the modified conditions under which the plants are grown. The 

 object of the test is to discover the relative value of the strains under 

 field conditions, and therefore any modification of field conditions 

 which may favor some sorts more than others introduces error. The 

 wide spacing between rows, with consequently heavier seeding in the 

 row for any given rate of planting; the hand seeding and covering, re- 

 sulting usually in slightly ridged rather than slightly furrowed rows; 

 and the growing of different varieties in single rows, in competition 

 with other varieties rather than with their own kind, are examples of 

 typical conditions which may be expected to favor some varieties more 

 than others. Consequently the best varieties in the rod-row test are 

 not necessarily the best varieties under field culture, even when soil and 

 seasonal variability are reduced to the minimum by replication of plots 

 and repetition of the test through a series of seasons. 



Such sources of error as those mentioned do not necessarily affect 

 the variability of the yields of replicate plots, as Kiesselbach" has 

 pointed out, and are therefore more likely to escape notice. They are 

 systematic errors affecting the yields of replicate plots similarly. 

 Marked superiority of Turkey wheat over Fulcaster in a variety test 

 in Kansas does not indicate the superiority of Turkey over Fulcaster 

 in Illinois, no matter how low plot variability in the variety test may 

 be, because the growing conditions in Illinois are different from the 

 growing conditions in Kansas. Similarly the superiority of Turkey 

 wheat over Fulcaster in a rod-row test may not mean its superiority 

 under field conditions in the same locality, because here again growing 



