166 FARMING ON FACTORY LINES 



The matter of the drying effect of a winter green 

 crop is of great importance, and serves as another 

 example of a very simple scientific fact being turned 

 to the greatest practical use. 



A LITTLE ELEMENTARY BOTANY 



The leaves of the plant are the lungs of the plant, 

 and perform functions in a plant similar to those 

 which the lungs perform in a human being or other 

 animal. One of the chief operations of the lungs in 

 a human being is the expulsion of moisture from the 

 system. If one breathes for a few seconds on to a 

 pane of glass, the glass becomes immediately damp. 

 Precisely the same effect may be obtained by placing 

 a cabbage under a glass globe for a few minutes in 

 the sunshine. 



A plant really obtains its nourishment from the 

 soil by absorbing through its roots plant food 

 dissolved in the soil water. The moisture is expelled 

 through the breathing pores of the tissues, leaving 

 behind the plant food for the building up of vegetable 

 tissue. 



Now, it has been found that for every pound of 

 dry matter in a plant, 250 lbs. of water are expelled 

 by the leaves. In rape, for instance, there is 14% of 

 dry matter. Hence, even in a 25-ton crop per statute 

 acre there will be 3^ tons of dry matter. 



Since 250 parts of water are required for the 

 elaboration of one part of dry matter, it follows that 

 for the production of 3J tons of dry matter 875 tons 

 of water are required. 



One inch of rainfall per acre is practically equal to 

 100 tons of water. Therefore, by growing during 

 the winter half-year 25 tons of rape we rid the land 

 by leaf evaporation of nearly 9 inches of rainfall. 



