MAN Mil 31 



claim as essential to successful vegetation, the existence in 

 the soil of but a part only of the food of plants. Thus, one 

 asserts that the salts alone will secure good crops ; others 

 maintain that the nitrogenous substances are the true source 

 of fertility ; while still another class refer to the presence of 

 humus or geine (the available product of vegetable and ani- 

 mal decay in the soil) as the only valuable foundation of vege- 

 table nutriment in all manures. Truth and sound practice 

 lie between, or rather in the combination of all these opinions. 



It has been shown in a preceding page, that all fertile soils 

 must have not less than 15, and more probably 16 different 

 simple or elementary substances, in various combinations 

 with each other. All of the ordinary cultivated plants con- 

 tain potash, soda, lime, magnesia, alumina, silica, oxide of 

 iron, oxide of manganese, sulphuric acid, phosphoric acid, 

 chlorine, and frequently iodine ; each of which, excepting the 

 two last, are in combination with oxygen. In addition to 

 these, they also have carbon, oxygen, nitrogen and hydrogen. 

 Other substances or ultimate principles may possibly exist in 

 plants, which analysis may hereafter delect, but hitherto they 

 have eluded the closest investigation. 



It is therefore obvious that such principles as all fertile soils 

 furnish to vegetables, must be contained in manures. It is 

 no satisfactory answer to this position to assert, that nume- 

 rous experiments have apparently been successful, of growing 

 plants in pure sand and water ; or with charcoal and the 

 salts added ; or even that there are some atmospheric plants, 

 that fulfil their zoophytic existence in air. Growth may con- 

 tinue for a long jtime under such circumstances ; but full ma- 

 turity never arrives, and probably never can, without the availa- 

 ble presence in tlie soil of every element which enters into the 

 composition of plants. 



Profitable farming requires that manures embodying all 

 these elements, should be added in sufficient quantities to the 

 soil, to develope fully and rapidly, such crops as are sought 

 from it. It becomes then, a matter of the highest consequence 

 to the farmer to understand, not only what substances may be 

 useful as manures ; but also how to apply them in the best 

 manner to his crops so far as they can be made profitable. 

 We shall first speak of the inorganic manures. 



ASHES. 



If any organic matter, whether animal or vegetable, be 

 burnt, an incombustible substance remains behind, called the 



