CHAPTER V 



MANURES 



FOB proper growth every plant requires the following 

 ten foods, viz. : 



Oxygen, hydrogen, carbon, nitrogen, potash, phos- 

 phoric acid, lime, magnesia, iron, and sulphuric acid. 

 (Three additional foods may be mentioned, but they 

 possess little interest for those who grow on allotments 

 and in vegetable gardens ; they are silica, chlorine, 

 and sodium.) 



Of these ten ingredients, the first three are derived 

 by the plant from the air and from the water drawn in 

 by the root system. 



The fourth, nitrogen, is obtained partly from tlie air 

 and partly from the soil. 



The fifth, sixth, and seventh, i.e., potash, phosphoric 

 acid, and lime, are taken from the soil, but are generally 

 found there in insufficient quantities for producing 

 abundant crops. 



The last three, magnesia, iron and sulphuric acid, also 

 come from the soil, but they occur abundantly. 



From this summary, it will be noted that the first 

 and last group of foods need not trouble the vegetable 

 grower as they are always obtainable under natural 

 conditions. With the two middle classes, however, that 

 is to say, nitrogen, potash, phosphoric acid, and lime, 



