152 



THE FIRST BOOK OF FARMING 



only when there is sufficient moisture in the soil to 

 permit breaking down and decomposition. 



The presence of moisture in the soil is necessary 

 for the process of nitrification to take place. 



Soil moisture is necessary to dissolve plant food. 

 Plant roots can absorb food from the soil only when 

 it is in solution, and it seems to be necessary that 

 a large quantity of water pass through the plant 

 tissues to furnish the supply of mineral elements 

 required by growth. 



Moisture is necessary to build plant tissues. The 

 quantity of water entering into the structure of 

 growing plants varies from sixty to as high as 

 ninety-five per cent, of their total weight. 



During the periods of active growth there is a 

 constant giving off of moisture by the foliage of 

 plants and this must be made good by water taken 

 from the soil by their roots. 



In a series of experiments at the University of 

 Wisconsin Agricultural Experiment Station, it was 

 found that in raising oats, every ton of dry matter 

 grown required 522.4 tons of water to produce it; 

 for every ton of dry matter of corn there were re- 

 quired 309.8 tons of water ; a ton of dry red clover 

 requires 452.8 tons of water to grow it. At the 

 Cornell University Agricultural Experiment Sta- 

 tion, a yield of potatoes at the rate of 450 bushels 

 per acre represented a water requirement of 1310.75 

 tons of water. 



