VERTICAL FARMING 



35 



up a piece of cloth, one end of which is allowed to hang in water. 

 This capillary water is the water that supplies the immediate 

 demands of the plant. Some of the water collects on the surface 

 of each soil particle and sticks to it with a peculiar force, form- 

 ing a film over the soil grain. This " Film Water " is very 

 important, for the force that holds it so closely to the grains 

 enables it to dissolve the mineral plant foods in the particle and 

 prepare them for absorption by the roots. 



Air Must Circulate in the Soil. The air in the soil is as 

 essential to plant growth as the air above the soil. This soil 

 atmosphere below the surface is heavier than the air above, and 

 contains more carbon dioxide and similar compounds than our 

 atmosphere. These gases are absorbed into the soil water and 

 become a part of the attacking force that liberates the mineral 

 foods from the dense minerals. The nitrogen supply of the 



CYPRESS ROOTS THROW UP KNEES THROUGH WHICH TO 



BREATHE. FIELD CROPS CANNOT DO THIS SO THE 



EXCESS OF MOISTURE MUST BE DRAINED AWAY 



