146 ILLINOIS STATE ACADEMY OF SCIENCE 



proximately 5 months elapsed between the tillage and dy- 

 namite treatments of 1918 and the taking of the first 

 regular set of samples on April 11, 1919. 



The plots of Series 400 had been given the tillage and 

 dynamite treatments in the fall of 1917 and had received 

 but one such treatment. Tables 3, 4, and 5 contain the data 

 obtained in this first season's work. 



The probable error of the seasonal average (average of 

 averages) is computed by means of the formula: 



P.E. = (-)l|.f.J,-, „2e2 . . . „2.2 



In which N = total number of borings entering the average 

 n = number of borings in each average 

 e = probable error of average. 



It will be noted that there is no significant difference in the 

 moisture content of the differently treated plots of either se- 

 ries. The moisture content of Plots 2, 3, and 4 is higher in 

 each case than that of the corresponding stratum in Plot 1. It 

 seems apparent, however, that this fact must be attributed 

 to soil heterogeneity rather than to treatment, for corres- 

 ponding behavior is not found in Plots 14, 15, and 16 com- 

 pared to Plot 13. 



During the spring of 1920 this work was continued by 

 taking four sets of samples from Plots 5, 6, 7, and 8. These 

 plots had received the tillage treatment in the fall of 1915 

 and again in the fall of 1919. Fourteen systematically dis- 

 tributed borings per plot instead of five were taken dur- 

 ing this season's work in order to increase the reliability 

 of the average. The strata sampled were the same as in 

 1919. Table 6 contains the data obtained during this sea- 

 son's work. 



It will be noted again that there are no significant dif- 

 ferences in the moisture content of these plots in 1920 which 

 had received a tillage treatment the previous fall and one 

 in the fall of 1915. 



It seems apparent that neither the subsoiling, deep til- 

 ling, or dynamiting have had any effect which is reflected 

 in the moisture content of this poorly drained prairie soil. 



