198 



''Physics of the Soil. 



before and allowed to stand exposed under natural condi- 

 tions, and the surface kept free from weeds by shaving 

 them off close to the surface with a sharp hoe, it was found, 

 after an interval of 75 days from June until September, 

 that the water content of the soil stood as in the next table. 

 In this case the surface foot of subsoiled ground is dryer 

 than that not so treated, but the second, third and fourth 

 have gained in moisture, over and above that lost from the 

 other two feet, enough to represent a rainfall of 1.64 

 inches. 



229. Moisture Effects of Subsoiling The results which 

 have been given in the last section illustrate several very 

 distinct effects produced by subsoiling: 



(1) Subsoiling increases the percentage capacity of the 

 soils stirred for moisture. 



(2) Subsoiling decreases the capillary conducting power 

 of the soil stirred. 



(3) Subsoiling increases percolation through the soil 

 stirred or its gravitational conducting capacity. 



230. How Subsoiling Increases the Water Capacity of the 

 Soil Stirred. When a soil is broken into lumps lying loosely 

 together, and these become filled with water, each one 

 behaves in a measure much as if it were standing by it- 

 self and much as a lump of sugar would, plunged into 

 water and then withdrawn, coming forth with its pores 

 practically filled with water. In short columns of soil, 

 like the lumps, the surface films of water which span their 

 capillary pores are strong enough to maintain their whole 



