APPENDIX. 



DESCRIPTION OF FERTILIZER MATERIALS. 



Broadly speaking, there are two kinds of fertilizers; 

 those which are in themselves a direct source of plant food, 

 and those which by their action tend to make plant food 

 fertilizers more available. While crops may be grown with- 

 out the use of fertilizers of the second class, no crops can 

 live without the fertilizers of the first class, even though 

 ample applications be made of the former. 



Fertilizers of the second class comprise lime, gypsum, 

 and common salt. They are all useful, but rarely indispens- 

 able. Lime, gypsum, (plaster), and common salt are some- 

 times called "stimulant fertilizers." They tend to make 

 rapidly available the stores of ammonia, potash and phos- 

 phoric acid naturally present in the soil. When stimulant 

 fertilizers are u-ed exclusively for a term of years, the soil 

 each year loses ammonia, potash and phosphoric acid, which 

 are not replaced. The inevitable result of such treatment 

 must naturally be the exhaustion of these important food 

 constituents from the soil. 



True fertilizers contain forms of plant food, which con- 

 tribute directly to the growth and substance of plants. 

 Such materials may contain either ammonia or potash, or 



