56 T. Lyrrteron Lyon anp James A. [1zzELL 
The rainfall that percolated thru the soil was measured by monthly}! 
periods, and a record of each tank by months is therefore available. It}; 
is thus possible to ascertain the effect of certain treatments, such as liming}t 
and cropping, on the proportion of the rainfall passing thru the soil, and 
even to compare the relative permeability of the two soils. © 
QUANTITY AND RATE OF PERCOLATION 
The figures for the flow of drainage water from each of the lysimete 
tanks 13 to 16, expressed in liters for each month from May 1, 1913, t ) 
April 30, 1918, are given in table 2 of the appendix (pages 78 to 80). The 
flow calculated to acre inches annually for the same pericd is given in 
table 3 of the appendix (page 80). These tables furnish the data from 
which the average annual percolation in inches from the unplanted soil); 
may be found, and also that from the soil on which crops grew. This, |, 
together with the percentage percolation, is given in table 6. The rain-), 
fall during the five-years period averaged 32.97 inches annually. 
i 
I 
Percentage percolation of rainfall 
TABLE 6. AvpraGe ANNUAL PERCOLATION OF RAINFALL FROM UNPLANTED AND FROM) 
PLANTED SOIL DURING FIvE-YEARS PERIOD 
Average annual 
percolation | 
Tanks Crop treatment | 
Per cent | 
Inches of 
rainfall 
eh WOgedeoricosy ou Se sbiecca sex No plants allowed to grow...... ZiAS 82.) 
11S Foie Hts) Sees cape ae aie cr a ce a Plants raised every year........ 20.62 62.é 
Difference in percolation....... 6.51 19. 
On the basis of these figures, about four-fifths of the rainfall percolated 
thru the bare soil and three-fifths thru the cropped soil. Somewhat more 
than one-fifth of the rainfall may therefore be considered as being used 
by the crops, since the evaporation from the surface of the unplanted soil 
may be assumed to be greater than that from the surface of the planted 
soil. This, however, is only a small proportion of the total rainfall and 
would account for only about six and one-half to seven inches of the annual 
precipitation. 
