26 THE AMERICAN FARMER. 



such analysis does not determine accurately its degree of fertility, since practical experience 

 proves that successful agriculture depends quite as much, if not more, upon its mechanical 

 condition, as its composition. Notwithstanding these facts, chemistry, as we have previously 

 stated, has been of great value to the .farmer, and the high standard attained in agriculture 

 at the present time is due largely to its instructions. 



Notwithstanding the inability of chemical analysis to furnish us all the knowledge 

 desired, sufficient information can be obtained through its teachings for all practical purposes. 

 Chemistry teaches that plant nutrition depends upon two great classes of matter organic 

 and inorganic ; and that no -plant can accomplish a perfect growth without being supplied 

 with both of these, in such proportions as it needs; and that if a plant has access to all the 

 requisite mineral elements in abundance, these mineral elements of nutrition are valueless in 

 the production of the plant, unless it can at the same time obtain in some way all it requires 

 of the inorganic elements of nutrition; also, that plants derive a large portion of their con 

 stituents from the atmosphere, either directly or indirectly, and the remainder from the soil, 

 and that the elements supplied by the one are as essential to plant growth as those of the 

 other. If there were even one of the requisite mineral elements wanting, though there were 

 an abundant supply of all the others, there would not be a perfect growth of the plant; neither 

 could an excess of one element make up the deficiency in the quantity of the others. For 

 instance, potash and phosphoric acid are both essential to plant growth, and this growth can 

 not be produced without the requisite quantity of each; now, if there should be a deficiency 

 in the quantity of potash in the soil, no surplus quantity of phosphoric acid, however great, 

 could counterbalance that deficiency in potash. We therefore see, that if any one of the 

 requisite elements of the soil becomes exhausted, or so diminished in quantity that it cannot 

 afford a necessary supply for the plant growth, the crop will be a small one until this neces 

 sary element is restored to the soil. Only a few of the elements of the soil are at all liable 

 to become exhausted. As a general rule, the principal mineral constituents that may become 

 so are phosphoric acid and potash; while nitrogen is the only organic element the farmer will 

 probably ever be required to supply. 



Prof. Stockbridge, of the Massachusetts Agricultural College, says that &quot;carbon, of 

 which plants in their dry state contain about fifty-five per cent., the farmer never need sup 

 ply, because in the soil and in the air there is an abundant supply for all the plants that 

 ever have grown or that ever will grow on the earth, and nature made the plant with the 

 capacity to gather it, so that without any aid from man the plant can gather all its carbon. 

 There is no need then that you feed a plant with carbon; it will take care of itself. So with 

 oxygen, and so with hydrogen. In the water and in the air, with which the plant is filled, 

 and by chemical action, the union of certain substances in the plant, carbon, oxygen, and 

 hydrogen, the plant can always supply itself with. No farmer need ever feed his plants 

 with these substances to promote their growth. If, however, we come to nitrogen, it has 

 been abundantly proved by scientists that there is here a deficiency. The plant takes large 

 quantities of nitrogen, especially in its seed ; it may gather some nitrogen naturally from the 

 air, perhaps in the form of carbonate of ammonia, and from the soil in the form of ammonia 

 taken in soil water. It can gather some, and yet the quantity of nitrogen available to the 

 plant is insufficient to supply its wants. Now, it is the fanner s clear duty, so far as these 

 four elements are concerned, to regard only the supply of nitrogen. Give your plant nitro 

 gen, and you may rely upon it as a natural law, that they themselves can take care of the supply 

 of the other organic elements. 



Turning now to the inorganic elements, the same law holds good. Take soda, for 

 instance; all our plants require soda, but so far as the farmer is concerned, he will find that 

 any of the soils that are made of micaceous rocks contain enough magnesia and soda to sup 

 ply all the plants probably that will ever be produced on that soil ; he will probably find enough 



