The Composition and Use of Fertilizers. 19'.°> 



haustible store of the atmosphere; another part, however, is lost 

 forever if not replaced by man." 



3. " The fertility of the soil remains unchanged, if all the 

 ingredients of a crop are given back to the land. Such a restitu- 

 tion is effected by manure." 



4. " The manure produced in the course of husbandry is 

 not sufficient to maintain permanently the fertility of a farm; it 

 lacks the constituents which are annually exported in the shape 

 of grain, hay, milk and live stock." 



These four laws of Liebig contain a clear statement of the prin- 

 ciples underlying the use of fertilizers; but, to understand their 

 moaning with satisfactory clearness, we must know something 

 more in detail about such subjects as the following: The constitu- 

 ents of plants; the materials of plant food; the constituents of 

 soils; the relations of soils and plants; the sources and com- 

 position of different forms of plant food; what forms and quanti- 

 ties of plant food to use on different soils and crops, and other 

 similar questions. 



PART I. 



THE CHEMISTRY OF PLANTS, PLANT FOODS AND 



SOILS. 



1. The Constituents of Plants. 



Elementary Composition of Plants. — The number of different 

 kinds of plants growing on the earth is estimated at not less than 

 200,000; and these, with all their variation of stem, foliage, flower 

 and fruit, are made from about a dozen different chemical ele- 

 ments. Indeed, the greater proportion of the bulk of the vege- 

 table kingdom is made from only three different elements. 



By a chemical element, we mean any substance which cannot. 

 by any known means, be separated into two or more different kinds 

 of matter. Thus, oxygen is an element because it contains only 

 one thing, oxygen, so far as we now know. From pure gold, 

 nothing but gold can be obtained; hence, gold is an element. Sim- 

 ilarly, nitrogen, carbon, phosphorus, sulphur, iron, etc., are ele- 

 ments. 



At present about 70 different elements are known, and of 

 these 70 only 14 are used in the production of plants; while 

 of these 14, only 11 or 12 are really essential to plant 

 IS 



