THE GROWTH AND NUTRITION OF PLANTS. 117 



(4.) Definitions. — Plant food is any substance, which con- 

 tributes towards the nourishment of the plant — e. g. carbonic 

 acid, water, nitric acid, potash, etc. But a considerable part of 

 this food, nature provides in abundant quantities, free of cost. 



Deficient plant food is that part which becomes so diminished, 

 in an available form at least, that the crop producing power of 

 the soil is materiallj' reduced, e. g. nitrogen, phosphoric acid, 

 potash. 



A Fertilize^' is any substance which contains available deficient 

 plant food. 



A Commercial, or "prepared," fertilizer refers to any of the 

 goods mixed and put up in bags or barrels, and sold under a 

 guarantee of composition. 



Chemical fertilizers are those which are compounded from such 

 crude fertilizing chemicals, as bone black. South Carolina rock, 

 muriate of potash, kainit, nitrate of soda, sulphate of ammonia, 

 etc. 



Manures are the natural excrement of animals of all kinds, and 

 are as truly fertilizers as is any sacked or barrelled material, 

 though in common acceptance, manures are looked upon as being 

 unlike commercial goods in their action on crops. As a matter of 

 fact, they feed the plant on those things which it needs most, just 

 as the prepared fertilizers or chemicals do. Hence there is no 

 valid distinction between natural and artificial fertilizers. 



Farm-yard manure is, and always will be, a standard fertilizer 

 in all agricultural communities where live stock husbandry is 

 practised. Hence an intelligent and economical plan of storage 

 and use is imperative. But today I propose to consider more 

 especially the conditions that have led to an universal use, in all 

 old agricultural regions, of waste products as aids to manures. 



There are some who hold that there is no more need today of 

 commercial or chemical fertilizers than there was a half century 

 ago, if only the manures of tlie farm are saved and used rightly. 

 This cannot be well maintained. In any system of farming, there 

 must be some product sold, else there is no cash coming in, and if 

 crops or animals are sold, then to some extent nitrogen, phos- 

 phoric acid, and potash are sold, and the vast quantities of these 

 substances, which the sewers of Boston, New York, and the 

 multitude of cities and villages throughout our land daily pour 

 out into the ocean, represent just so much soil-fertility gone 



