SOIL MOISTURE AND PREPARATION OF SOIL. 65 



(fi) At regular intervals say, every two or three days 

 apply equal quantities of water to each of these pots. 



(/') In about five or six weeks remove the soil plant and 

 all (see "Propagation of Plants") and note the depths 

 to which the roots have penetrated. In which have they 

 gone the deeper, the drained or undrained soil ? If these 

 conditions of soil moisture existed in the open field in 

 early spring, and were followed by a drought, how 

 would these root systems compare in aiding the plant 

 to withstand it ? In nature, when these root systems 

 die, how would they compare in affecting the porosity 

 of the soil ? How would such soils affect the nitrogen- 

 fixing bacteria (Chapter I.) ? How would the work of 

 earth-worms, grubs, and other burrowing animals com- 

 pare in these two soils? 



Soils having a loose and open subsoil are nat- 

 urally underdrained, and do not need to be arti- 

 ficially drained. Soils of fine texture, or those 

 having a clay or hard subsoil, do not allow the 

 free water to percolate through them, and it 

 stands very near the surface, unless artificially 

 drained. It is not as the water passes down 

 through the soil that it is carried away by drains, 

 but as it rises again in saturating the soil above 

 the impervious layer of hard-pan or bed-rock. 

 The deeper the drain the greater the area drain- 

 ed, hence the wider apart the drains may be. 



EXPERIMNT 12. (a) Procure a keg, or barrel, which 

 does not leak, and in its side bore two or three holes, one 

 above the other, about twelve inches apart, the first hole 

 being six inches from the bottom. 



(fr) Nearly fill this keg, or barrel, with soil. Shake it 

 down firmly. 



