286 SOILS: PROPEBTIES ANB MANAGEMENT 



and during a good part of the time attained a difference 

 of 10 per cent. The effect of this was to reduce evapora- 

 tion by from 53 to 63 per cent on different days in July, 

 in spite of a higher temperature inside the tent. (3) The 

 direct effect of this was to increase the moisture content 

 in the soil in spite of a larger crop growth under the tent. 

 These differences are shown by the following curves (see 

 Fig. 45), which represent the percentage of water in the 

 soil to a depth of nine inches from June 13 to August 1. 





Cf 



3 



/O _ 



PE/2J0D or O3S£^VAT/0JV 



/S- 20 SJSr 30 3S 



^O 



-as- JZJYyS 



£/u 







































f 



X 



19 



fe 



-% 



.-JS, 



/ 



^ 





-JIK. 

























h 





I 





--"S 



■.-^'"' 







^ 



\ 



/" 



\ 





■^ 



'^ 



■J, 





, 





n/ 





Ji 



\ 



























r\ 



! 



1 













! 

























"v 



\ 



1 



V 





> 





> 



\ 







i 

































\ 

 \ 

 \ 



1 



1 



1 



. 1 



% 



\ 







































SJ 





■4 





C 























_ 



_ 







_ 



__ 









_ 



Fig. 45 — Curves showing the percentage of moisture in a sandy soil to 

 the depth of nine inches inside and outside of a loosely woven tent 

 over a period of about fifty days Heavy line, moisture inside of 

 tent ; broken line, moisture curve of soil outside of tent. 



Not only was the tent effective in preventing evapora- 

 tion and thereby increasing the average moisture content 

 of the soil, but the soil was able to maintain a more uni- 

 form content, due to the freer movement and adjustment 

 of the capillary water under the tent — conditions more 

 conducive to rapid crop growth. 



204. Level cultivation. — The velocity of the wind 

 next to the ground may be checked by ridging the soil. 

 It is doubtful whether this practice conserves moisture, 



