14:0 



Physics of the Soil. 



From this table it is seen that the amount of water used 

 ranges from 270 tons of water with corn to 576 tons with 

 clover per ton of dry matter ; or when expressed in acre- 

 inches from 2.4 to 5.1 inches nearly, the average for the 

 six crops being nearly 450 tons or 4 acre-inches per ton of 

 dry matter. 



When the yields per acre are 2, 3 and 4 tons the num- 

 bers given above must be multiplied by the same factors. 



168. Amounts of Water Required for Different Yields of 

 Wheat. In order to express the data of the last section in 

 terms which it is more customary to use, there is given in 

 the next table the amount of water required by a crop of 

 wheat when the yields per acre range from 15 to 40 bushels. 



Observations made by Hellriegel in Germany show that 

 wheat uses about 453 tons or 3.998 acre-inches of water 

 for a ton of dry matter. Using this ratio and one pound 

 of grain to 1.5 pounds of straw the water required will 

 4and as below : 



Table showing the least amount of water required" to produce 

 different yields .of wheat per acre when the ratio of grain 

 to straw is I to 1.5. 



This table shows that 12 inches of effective rain during 

 the growing season of wheat, starting with the soil moisture 

 in good condition, should enable a yield of 40 bushels per 

 acre to be produced. 



