DRAINAGE AND VENTILATION 



Great injury is often done to the wheat crop by uncovering 

 the roots and leaving them exposed. The only method of pro- 

 tection against winds is to set out groves, rows of hedge, and fringes 

 of trees around every farm. In the Columbia River Valley the ex- 

 periments conducted along this line have been very satisfactory and 



Dunes. 



successful, and demonstrate beyond question the advisability of 

 providing suitable wind-breaks on open, exposed lands in windy 

 regions. 



In California and many other places drifting sands often ac- 

 cumulate and cover good soil and render it unfit for cultivation. 

 The sand drifts like snow and forms ridges and mounds called 

 dunes. The government has reclaimed some of these regions 

 from waste by setting out sedges and wind-breaks. 



EXERCISES 



1. In the bottom of a tomato can make twelve holes, in a second make 

 six holes, in the third make three holes ; leave the bottom of a fourth intact. 

 Fill the cans with warm, moist soil and plant the same kind of seed in each 

 one. Note results from week to week and explain. 



2. Repeat the experiment after driving holes into the side of each can. 

 Explain results. 



3. Repeat experiment one and place a layer of gravel or coarse sand in 

 the bottom of each can. Note results. 



4. Plant some seed in a glass vessel, an earthen jar, and a wooden box. 

 Is there any difference in the growths ? Why ? 



