VERTICAL FARMING 



PART II 



Fertilizers and the Chemical Properties 

 of the Soil 



HOW PLANTS FEED 



The fertility of a soil is its ability to produce crops. It is 

 not one condition, or two or three conditions, but the sum of all 

 conditions. It does not consist simply in hauling manures or 

 buying chemicals. It means that the water, air, temperature, 

 soil bacteria, tilth, and plant food or soil solution exist in the 

 right conditions and proper balance as well as in proper amount. 

 It is possible for seed to sprout, the crop to grow and ripen, and 

 the yield to be the best only when all these conditions are ful- 

 filled. Mere richness in mineral foods avails nothing if water 

 is lacking to maintain a large amount of soil solution for the 

 roots to absorb. The plant food may be there but may not be 

 soluble and cannot be absorbed. It may be soluble, but in a 

 form distasteful to and therefore rejected by the roots. 



All soils, even those considered poor, contain vast amounts 

 of plant food that is not naturally available, but which can be 

 converted into an available form. In such a case the problem 

 is one of condition and not one of total content. A worn out 

 soil is often only an unsanitary one and can be rebuilt to a high 

 state of productivity by proper cultural methods. 



Chemical Properties of the Soil. While hundreds of min- 

 erals are known to science, only a few are used in nature in 

 forming the common rock from which most soils are derived. 

 The more important of these to the farmer are potash, phos- 



THi 



