328 PRINCIPLES OF AGRICULTURAL CHEMISTRY 



This experiment shows the great variation in the produce of 

 two crops grown under apparently the same conditions in a field 

 apparently uniform. It also shows that the error resulting from 

 variations may be reduced by using a sufficient number of check 

 plots, and by repeating the treatment on different plots. Great 

 care must, therefore, be exercised in planning and conducting field 

 experiments. 



A similar experiment is reported by Smith from the Illinois 

 Experiment Station, on 120 one-tenth acre plots of corn all treated 

 alike for three years. In 1895 the yield varied from 11.4 to 50.2 

 bushels per acre, in 1896 from 48.5 to 103.9, an d in 1897 from 

 44.2 to 80.2 bushels. The lowest yield in 1897 was on the plot 

 which gave the highest yield in 1896. The maximum variation in 

 adjoining plots was 18 bushels in 1895, n bushels in 1896, and 8 

 bushels in 1897. 



Precautions in Making Fertilizer Experiments. The following 

 are some of the precautions 1 to be used : 



(1) The greatest care should be taken to select land which is 

 as uniform as possible in fertility. Lack of uniformity will give 

 misleading results, and often render the experiments of little 

 value. 



(2) Level land should be selected if possible. If such cannot 

 be had, the plots should run up and down the slopes, so that the 

 washing by rain will not carry fertilizing materials from one plot 

 to another. 



(3) The experimental plots should be measured off carefully, 

 and each plot indicated by stakes or stones. 



(4) It is best to have the experimental plots long and narrow, 

 because thus they will average up for uneveness of soil. 



(5) It is best to separate plots by paths, to prevent roots of 

 plants in one plot from feeding on the fertilizer supplied to ad- 

 joining plots. 



(6) Avoid windy days in applying fertilizers, so that they may 

 not be blown and scattered unevenly over the plots. 



1 Thome, Circular 96, Ohio Exp. Sta. 



