34 



SCfEN TIFIC A GRICUL TURE. 



not be in a condition to be readily used as food by the 

 plant. To remedy this condition, either mechan- 

 ical means must be used, such as repeated plow- 

 ing, deep and thorough, to bring about exposure to 

 air, and rain, and sunshine, and frost ; or chemical 

 means, as the application of lime and various salts 

 which supply food directly, or which exert a decom- 

 posing action, and thus prepare the food which al- 

 ready exists in the soil and render it suitable for use. 



68. Phosphorus and potassium, which are gen- 

 erally in minute quantities, as well as other elements 

 when deficient, must be supplied, or the vigorous 

 growth of plants whose structure requires these ele- 

 ments and thio includes all of our valuable crops is 

 an utter impossibility. As well might the carpen- 

 ter dispense with nails in the construction of a house? 

 or the tailor with thread in making a coat, as the 

 farmer dispense with these essential elements in the 

 growth of his crop. 



69. As soils are of great variety, their composition, 

 or character, should be determined, and the deficien- 

 cy pointed out, if any exists, before an attempt be 

 made to remedy the defect. While chemistry teaches 

 the farmer the cause of the exhaustion of his soil and 

 shows how this can be prevented, it must not be held 

 responsible for the failures resulting from the use of 

 the many mixtures which are sold under various 

 names as fertilizers. 



70. The means used for furnishing plants with 

 the elements necessary for their growth, that is, for 



