PAPERS ON BIOLOGY AND AGRICULTURE 143 



The recognition of the fact that a soil's response to tillage 

 and fertilizer treatments is never satisfactory when poor 

 drainage conditions exist led the Illinois Experiment Sta- 

 tion to lay out four series of four tenth-acre plots each in 

 Cumberland county in 1913 on an area tjT)ical of this type. 

 Ground limestone was applied to all plots in the fall of 1913 

 at the rate of 4 tons to the acre, and finely ground rock 

 phosphate was applied the following spring at the rate of 

 1 ton to the acre. The application of limestone is to be re- 

 peated every 4 years at the rate of 2 tons to the acre, and 

 rock phosphate at the rate of 1 ton to the acre. A rotation 

 of corn, soybeans, wheat, and sweet clover is used, and all 

 residues are returned. The series which is to go in corn is 

 plowed late in the fall, Plot one 5 inches deep. Plot two is 

 subsoiled 12 to 14 inches deep. Plot three is plowed 12 to 

 14 inches deep with a Spalding deep tillage machine, and 

 Plot four is djTiamited and afterwards plowed 5 inches 

 deep. The charges of d\Tiamite are placed in the imper- 

 vious stratum eight feet three inches apart each way on 

 the d>niamited plots of the first two series, and eleven feet 

 apart each way on the dynamited plots of series three and 

 four. 



The moisture conditions are such that the soil in this 

 section is supersaturated in the spring due to the imper- 

 vious nature of the tight clay substratum. It was thought 

 that if the tillage treatments or the dynamiting had reme- 

 died this condition, it should be reflected in a lower moisture 

 content of the surface and subsurface strata during this 

 period of supersaturation. Moisture equivalent determi- 

 nations had previously been made and the plots found to 

 be uniform in this regard. 



Early in the spring of 1919, a preliminary series ot ten 

 borings per plot were taken from Plots 4, 7, 10, and 13. 

 The samples were taken from systematically distributed 

 points in four depths, as follows : to 6, 7 to 12, 13 to 18, 

 and 19 to 24 inches. The percentages of moisture found 

 in the individual samples were averaged in groups of ten, 

 five and three, for the purpose of computing the probable 

 error of the averages as a means of determining the number 



