286 SOILS: PROPEBTIES AND 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. 



PEG/OD OF O3SVAT/OM 



" \ 





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, 



