CHAPTER VI. 



HOW SOILS LOSE THEIR NITROGEN TABLE OF PROPORTIONS 



NECESSITY OF SOIL ANALYSIS TABLE OF PHYSICAL 



ELEMENTS AND CHEMICAL CONSTITUENTS. 



We have now reviewed the nature of the principal elements 

 essential to vegetation, and have described the parts they severally 

 play and the places they probably occupy in the organisms of plants. 

 While admitting that, in some insignificant instances, we are still 

 unable to completely unravel the mysteries connected with vegeta- 

 ble inner organisms, we may claim to be no worse off in this respect 

 than the science of Pathology, to whose professors many secrets re- 

 lating to the blood have still to be revealed. We have nevertheless 

 been able to place on record a series of facts which support our theo- 

 ries and confirm our deductions ; and facts, as we are all aware, are 

 "very stubborn things." 



Thus, with man, it is not enough to give him food : his diet must 

 contain a mixture of substances, the absorption of which is the con- 

 dition of his existence, and whose composition is found to be iden- 

 tical with the materials constituting his bodily frame and tissues. 



In plants the same phenomenon presents itself : deprived of cer- 

 tain elements they pine, droop, and die ; supplied with them they 

 nourish and are vigorous ; and, upon analyzing their organism, we 

 prove them to contain an abundance of the very elements without 

 which they were unable to exist. 



It will be interesting here to examine some figures showing 

 us in what proportion the soil is regularly deprived by the different 

 crops of its nitrogen, phosphoric acid, and potash. 



