CHAPTER I. 
MAKING THE SOIL RICH. 
Everybody understands that the soil becomes impover- 
ished by continued cropping, if no return be made in the 
form of manure or fertilizer. This impoverishment is some- 
times real, while sometimes it is more apparent than real, 
owing to the exhaustion of only one or two elements of 
fertility. 
Farmers have learned a great deal about agricultural 
chemistry since the introduction of artificial fertilizers. They 
know that while plants demand many things for their growth, 
there are but three elements which are in danger of being 
exhausted in ordinary cropping. These three things are 
nitrogen, phosphoric acid and potash. 
Lime. — Lime is used on the land not for its direct results 
as a fertilizer, but because it has the ability to break up com- 
binations already existing in the soil and set free the plant 
food that previously was in an insoluble form. Lime some- 
times produces almost marvelous results; at other times no 
visible effects whatever. Hence, it is not a fertilizer, though 
in actual practice it is sometimes a fertilizing agent of great 
value. Land that has been much manured or long in sod is 
likely to be benefited by lime. 
Artificial manures, on the other hand, furnish real plant 
food in soluble form, and may be expected to produce crops 
invariably, year after year, if the soil be sufficiently moist. 
When a fertilizer contains nitrogen, phosphoric acid and pot- 
ash it is said to be complete. When any element is missing 
the fertilizer is said to be incomplete. Ground bone, wood 
