36 TheGakden. 



growth of plants than this, and if they gi'ow at all in snch soil 

 they will be gross, pungent, and unwholesome. The remedy is 

 trenching, underdraining, and the application of lime, gypsum, 

 ashes, etc. 

 Further means of improving soils will be treated of in the 



III.— MANURES. 



If your soil be either wholly or partially deficient in any of 

 the constituents of plants, these constituents must be supplied 

 by adding to it substances which contain them. The substances 

 thus added are called manures, which, in the broadest sense of 

 the word, embrace everything which, being added to the soil, 

 promotes directly or indirectly the growth of plants. 



Manures directly assist the growth of plants either by enter- 

 ing into their composition, or by absorbing moisture and nutri- 

 tive gases from the atmosphere, and holding them for their use. 

 Indirectly, manures assist the growth of jjlants by destroying 

 vermin or weeds, by decomposing the soil and rendering its 

 elements available, by protecting vegetation from sudden 

 changes of temperature, or by improving the texture of the 

 soil. They are divided into two classes^organic and inorganic. 

 The former embraces ordinai^y vegetable and animal substances, 

 and the latter mineral substances. 



Organic Manures.— ThQ principal organic manures are the 

 dung of animals, human excrements, urine, flesh, blood, fish, 

 swamp-muck, sea- weed, and decayed leaves, hay, straw, and 

 wood. Guano, though an animal product, contains so large a 

 proportion of salts, and is so deficient in the characteristics of 

 recent animal matter that it is generally classed with the inor- 

 ganic maniires. '■ 



InorganU Manures. — The principal inorganic manures are 

 ashes, lime, the marls, gypsum, bones, salt, charcoal, soo-t, and 

 guano. 



Theory of Manures. — The kind of manure which will prove 

 most useful in a given instance must be determined by refer- 



