108 ALFALFA FARMING IN AMERICA. 
tial things. AJl the rest that can be added will help; 
these two are indispensable. 
Other Functions of Lime—What other func- 
tions besides making the soil habitable for good and 
useful bacteria does the carbonate of lime have in 
the soil? 
It seems the very foundation of fertility itself. 
The presence of much carbonate of lime in the soil 
seems necessary to the formation of black humus. 
In nature soils rich in lime become black loams. 
Some good illustrations of this truth are seen in two 
instances. In Mississippi and Alabama are soils 
based on decaying limestone, the so-called ‘‘black- 
prairie’’ soils. They are exceedingly rich, strong, 
productive soils, among the best in the South. They 
grow any sort of crops well, and especially do they 
grow alfalfa luxuriantly. Most soils in the south are 
very deficient in humus and without the dark brown 
color. That is because most southern soils are lime- 
hungry. The vegetation that has fallen upon them 
and been buried in them has not changed to black 
humus, or to very little of it. Why not? Because of 
the absence of sufficient carbonate of lime. 
In Illinois one finds the northern end of the state 
a black, rich prairie soil, very full indeed of humus. 
The southern end of the state, on the other hand, 
has a soil of ight color, very deficient in humus. 
Think what story this tells! Glaciers ground up 
limestones in the northern end of the state and mixed . 
their detritus through the soil. Below the line where 
the limestones reached the light colored soils begin. 
