EFFECTS OF DRAINING. 



141 



also deepens the arable soil and makes it more easy for 

 plants to extend their roots. 



439. The atmosphere is charged with fertilizing ele 

 ments as well as with moisture, and as it circulates freely 

 in the soil, these elements are taken up and retained to 

 serve as plant food. 



440. The soil having become more porous by the 

 removal of water and the admission of air among its 

 particles, its temperature is raised in consequence, that is 

 the soil is made warmer and warmed to a greafer depth. 



441. A higher temperature in the soil hastens forward 

 the growth of plants, and thus often makes the ripening 

 several days earlier. 



442. The texture or me 

 chanical condition of most 

 stiff soils is improved by 

 simply draining, and they 

 are thus made capable of 

 -being worked earlier in 

 spring and after long rains, 

 while the growth of plants 

 is stronger and more vigor- a ~ 

 ous. The difference may be 

 seen in figures 14 and 15, the 

 former showing the effect 



of draining and warming the surface soil, #, causing the 

 roots to penetrate even into the moisture below the drained 

 level at &, the latter, the same species of plant on an 

 undrained and unsuitable soil. 



448. After the land is properly cleared, it must next be 

 made ready for planting. In the first place the soil must 

 be mellowed or broken up fine to a proper depth. 



444. The spade, the plough, the harrow and the roller, 



