IV PREFACE. 



action and plant-growth is wonderfully complex ; and so 

 far from the old axiom being true, that any man can be 

 a farmer, we find that farming, in the problems it presents 

 for solution, is a calling that challenges the best ability 

 and the best culture to be found among men. To give a 

 history of the three principal elements which enter into 

 the composition of fertilizers, to discuss their relations to 

 plant-growth in the various forms in which they exist, to 

 tell in what form and where they may be obtained at the 

 lowest rates, to tell how they may be combined and 

 applied in the wisest way, brother farmers, is the object 

 of this treatise. Should it prove desirable to enlarge the 

 subject, I may take up barn and various other manures in 

 another work. 



To those who desire to study the subject of plants and 

 plant-growth more extensively, I would recommend such 

 excellent works as " How Crops Grow " and " How Crops 

 Feed," by Professor Johnson ; " Botanical Text-Book," by 

 Professor Grey ; and " Harris on Manures." 



