140 ALFALFA FARMING IN AMERICA. 



All the region east of the Mississippi Eiver will 

 be helped by use of ground limestone, with the ex- 

 ception of some favored spots where glaciers have 

 already ground the rocks to powder and mixed it 

 through the land. Anywhere that alfalfa fails to 

 thrive after the land has been made; dry and fairly 

 rich one may know that carbonate of lime is de- 

 ficient. Especially may one be sure that all soils 

 along the Atlantic seaboard are deficient in car- 

 bonate of lime, and by supplying this lack their 

 capacity for crop production may be immensely 

 increased. 



The Chemistry of Lime. — In "The Breeder's Ga- 

 zette" of July 14, 1909, Dr. Cyril G. Hopkins, agron- 

 omist of the College of Agriculture, University of 

 Illinois, sets forth clearly the chemistry of lime in 

 its relation to soil improvement. I quote his state- 

 ment complete : 



The use of lime for soil improvement is a subject ■which is dis- 

 cussed with a great deal of misconception and confusion, due In 

 large part to the erroneous practice of referring to lime as though 

 it were a chemical element. 



Lime is not an element and consequently is not an element of 

 plant food. It Is an alkaline substance and is known in three 

 forms: the carbonate, the oxide and the hydroxide. The carbonate 

 is the natural form found in rocks and soils and it consists of 

 either calcium carbonate, magnesium carbonate or a double com- 

 pound of calcium magnesium carbonate known as magnesian 

 limestone or dolomite. When highly heated these carbonates lose 

 their carbon dioxide as a volatile gas and the oxide or quicklime 

 remains. This substance takes up water either from direct appli- 

 cation or from the moisture of the atmosphere and changes into ' 

 the form of hydroxide or water-slaked lime. On long exposure 

 to the air the hydroxide will absorb carbon dioxide from the air 

 and give off water, thus reforming the carbonate compound. Thus 

 we may say that calcium carbonate (CaCOs), calcium oxide (CaO) 



