528 SOILS: PROPERTIES AND MANAGEMENT 



any system of soil management that does not include 

 one or more of these substances would probably, on some 

 soils at least, be improved by making provision for the 

 application of sulfur in some form. 



CATALYTIC FERTILIZERS 



The term catalytic fertilizers has been used rather 

 loosely to designate a class of substances that, when added 

 to a soil, increase plant growth by apparently accelerating 

 the processes that normally take place in soils. They 

 do not function as fertilizers because their value does not 

 lie in the nutrients that they possess, but they may 

 properly be classed as soil amendments. However, 

 substances not classed as catalyzers, such as t lime, have 

 such action, and in all probability most of the fertilizers 

 do also, so that it is difficult to draw any definite distinc- 

 tion and the term will doubtless be used only temporarily. 



446. Nature of catalytic action. — The term catalysis 

 is employed in a chemical sense to mean a change brought 

 about in a compound by an agent that itself remains 

 stable. As an example of this may be cited the part that 

 hydrochloric acid plays in the inversion of cane sugar, 

 the acid not entering into the reaction but by its presence 

 greatly accelerating it. When an attempt is made to 

 study these phenomena in soils, it becomes difficult, 

 owing to the multiplicity of factors and reactions, to 

 determine whether the agent is acting in a purely cata- 

 lytic manner. 



447. Catalytic action of soils. — Most soils themselves 

 act as catalyzers in so far as they hasten the decomposition 

 of hydrogen peroxide. Many substances, both organic 

 and inorganic, have this property, and it is not necessarily 



