CHAPTER III 



THE RELATION BETWEEN SOILS AND 

 FERTILIZING MATERIALS 



Exhaustible Elements and ' Non-exhaustible Elements 

 Preference Shown by Plant Life Separate Fertilizing 

 Ingredients Economy in Separate Ingredients. 



A MANURE is a substance designed to supply one 

 or more of the essential constituents of plant food, 

 and, where necessary, to improve the physical 

 condition of the soil to which it is applied. The 

 essential constituents of plant food must contain 

 the elements carbon, hydrogen, oxygen, nitrogen, 

 phosphorus, sulphur, potash, lime, magnesia, and 

 iron and probably silicon, chlorine and sodium. 

 Of these, carbon, hydrogen and oxygen, and some 

 of the nitrogen are derived from air and rain, 

 most of the nitrogen and the remaining elements 

 being obtained from the soil. Almost every soil 

 contains enough Ca, Mg, S, Fe, Si, Cl, and Na 

 for the growth of a full crop, but nitrogen, phos- 

 phorus and potash are often present in but small 

 quantity, and become exhausted by the removal 

 of farm produce. 



A general manure or fertilizer is usually under- 

 stood to be the agency which can supply these 

 three constituents, but inasmuch as some crops 



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