Conserving Soil Moisture. 199 



interior nearly full of water, drainage being largely con 

 fined to those passageways and cavities which have largei 

 than capillary dimensions. 



If a dozen strands of candle-wicking, two feet long, are 

 twisted loosely together, saturated in a basin of water, and 

 then held horizontally from the two ends to drain, more 

 water will be retained than if it is allowed to sag into a 

 loop and drainage from it will be still more complete when 

 hanging from one end. So it is with long continuous col 

 umns of soil; from them the drainage is more complete 

 than from shorter ones. 



231. How Subsoiling Decreases the Capillary Conducting 

 Power. When large open spaces have been formed in a 

 soil, by any means, as is the case in subsoiling, every such 

 cavity cuts off the capillary connection with the unstirred 

 soil below and above and in this way reduces the number 

 of capillary passageways by which water may rise to the 

 surface. This being true, when rains fall upon subsoiled 

 ground, water travels downward quite slowly until after it 

 has become- capillarity saturated and, if the rain is not 

 enough to over-saturate the layer, the whole will be retained. 



On the other hand, when the subsoiled layer has once 

 become dry, the poor connection with the firmer ground 

 below and its open texture makes it impossible for the 

 moisture to rise through it to the surface as rapidly as it 

 could through a more compact layer. 



It is clear, from these relations, that when the root 

 system of a crop once develops through the subsoiled layer 

 it may then act as a mulch of great thickness and increase 

 the yield ; but should a -crop fail to get its roots below the 

 subsoiled layer before the moisture becomes too scanty 

 then a diminished yield might be the result even with an 

 abundance of water below. 



232. How Subsoiling Favors Percolation. When rain 

 enough has fallen upon an earth mulch or upon subsoiled 

 ground to completely saturate the soil the balance of the 



