SOIL BUILDING 



141 



The most efficient method of building up the 

 storage capacity of the soil is to drain it from be- 

 neath. All other material for that purpose has 

 given way to tiles, that being the cheapest and most 

 .efficient. Sub-drainage will lower the level of 

 gravitational water to the bottom of the tile bed, 

 the depth of capillary water increasing the same 

 distance. If soil is "water-logged" eight inches be- 

 low the surface there can be neither aeration, nitri- 

 fication nor ordinary root growth below that point, 

 vegetation penetrating such subsoil with great diffi- 

 culty. By putting tiles two feet underground the 

 water table descends to that depth, giving three 

 times as much — three times the ground in the farm. 



After drainage the most practical and efficient 

 aid in soil building is growing leguminous crops. 

 Even among established trees they condition sub- 

 soil cheaply, for nitrogen gathered by legumes from 

 atmosphere is deposited below the strata of ordi- 

 nary fertility where most needed; and after the 

 legumes die each rootlet readily decays, leaving a 

 porous thread for water and air to continually cir- 

 culate downward. The most beneficial rains come 

 in show x ers during growing seasons, and such de- 

 cayed roots provide organic matter to retain much 

 moisture where it falls. 



Mulching is receiving unusual attention at the 

 present time, and is described in another chapter; 

 it promises at no distant day to modify some of 



