18 



Campbell's 1902 Soil Culture Ma>-ual. 



book should, by the way, be in the hands of every farmer. In treating 

 the question of the effect of rolling on soil moisture, he says: 



"When, however, the changes in the water contents of the surface 

 four feet of soil which follow the use of a heavy roller are studied, it is 

 found that we have here another case of the translocation of soil moisture: 

 a case where by destroying the many large non-capillary pores in the soil, 

 and bringing its grains more closely together, its water-lifting power is 

 increased and to such an extent that often within twenty-four hours after 

 rolling, the upper one or two feet beneath the firm ground have come to 

 contain more moisture than similar and immediately adjacent land does at 

 the same level, while the lower two feet have become dryer. Water has 

 been lifted from the lower into the upper soil. 



"In the table below will be seen the difference in the water con- 

 tents of the soils which have been rolled and the immediately adjacent 

 ones not so treated. These results are averages derived from 147 sets of 

 samples : 



"Surface 36 to 54 inches, unrolled, contained 19.43 per cent, of water. 

 Surface 36 to 54 inches, rolled, contained 18.72 per cent, of water. 



Difference, .71 per cent, of water. 



Surface 24 inches, unrolled, contained 19.85 per cent, of water. 

 Surface 24 inches. rolled, contained 19.49 per cent, of water. 



Difference. .36 



Surface 2 to 18 inches, unrolled, contained 15.64 per cent, of water. 

 Surface 2 to 18 inches, rolled, contained 15.85 per cent, of water. 



Difference, x .21 " 



It is here seen that when samples of soil are taken at a depth ex- 

 ceeding two feet, the rolled ground as a whole is dryer than that not 

 rolled, and that this difference is greater when the samples are taken at a 

 depth of from three to four or more feet. The data presented also shows 

 that the surface 2 to 18 inches of loose ground recently firmed contains 

 more water than that which has not been so treated. This presents an 

 important thought in regard to preparation of the soil. It is a matter 

 we have carefully studied, and in aU our experiment work we have 

 observed that the statements of Prof. King have been verified fully; thu^ 

 affording conclusive proof of the truth of all that we have said with refer- 

 ence to the sub-surface packing of the soil. When the extreme surface is 

 packed the effect is to draw the moisture to the surface where it is lost by 

 evaporation. By the sub-packing, as shown in cut Xo. 2, we have that 

 firm stratum at the point where the roots mainly grow, and with our loose 

 mulch on the surface we prevent the loss of our moisture by evaporation. 

 In our chapter on percolation we explained at some length how the water 



