The Function of Manures and Fertilizers 27 



USE OF FERTILIZERS 



While manures in the ordinary sense, and even mate- 

 rials which are now included under the head of artificial 

 manures, such as ground bone and wood ashes, have been 

 used for a very long tune, the use of artificial products 

 in a true sense is of comparatively recent origin. The 

 first use of genuine artificial fertilizers dates from the pub- 

 lication of Baron von Liebig's book, "Organic Chemistry 

 in its Application to Agriculture and Physiology," in 

 1840 ; yet for a long time after this date the increase in 

 their use was very gradual. The very excellent, and at 

 that time surprising, results which were obtained from 

 the application of Peruvian guano, one of the first prod- 

 ucts to receive attention, manifestly increased the 

 interest in the subject also. These good results were 

 observed more particularly on the continent of Europe, 

 where the lands had been under cultivation for a long 

 tune. The use in America, previous to 1860, was quite 

 insignificant. Since the work of Liebig, a very great 

 amount of study has been given to the subject, both in 

 reference to the essential character of the various mate- 

 rials, and their influence upon the production of plants. 

 Perhaps no other single subject relating to agricultural 

 science has been studied more fully than the question of * 

 the use of artificial manures; and these studies have 

 resulted, not only in the discovery of new materials, but 

 in their better preparation for use as plant-food, which 

 greatly increased their effective use. There is no ques- 

 tion connected with agriculture which is of greater direct 

 and practical importance, particularly in those countries 

 which have been depleted of their active fertility by the 

 means mentioned, or in which the conditions are as pre- 



