TT.-17\E7e REQUIRED BY CROPS 



135 



grams (one and one-half quarts) per day. Hunt observed 

 in Illinois that in one week in July the growth of corn 

 amounted to 1,300 pounds of dry matter per acre. As- 

 suming the requirement observed in Wisconsin, 272 

 pounds per pound of dry matter, this is equivalent 

 to 1.55 inches of water. 



Assuming the average production of dry matter 

 to be two tons per acre,, the amount of water required 



jz* 



Fig. 40. Solid, metal roller. The prevailing type of compacter. 



to produce such a yield of the staple crops, under the 

 best conditions of management, would amount, accord- 

 ing to the above figures, to from 427 tons to 1,820 tons 

 of water per acre, which is equivalent to a rainfall of 

 3.7 and 15 inches, respectively. 



II. AMOUNT OF WATER IN THE SOIL 



Soils exhibit great differences in moisture content 

 and in their ability to meet the needs of the plants for 

 water. In some of the southeastern states, where the 



