1574 The Cornell Reading-Courses 



gained and as experiment indicates the best method of procedure. On 

 the hardpan soils of southern New York, alfalfa culture should be tried 

 only on the most favorable land at present. 



Form of lime 



There are three forms of lime. When loo pounds of raw lime rock is 

 burned it is reduced to 56 pounds, because of certain gases being driven 

 off. When this burnt lime, or "quicklime," is water-slaked it takes up 

 18 pounds of water, giving a weight of 74 pounds. Therefore, the amount 

 of each form of lime to give equivalent results is expressed as follows: 



Burnt lime, or quicklime 56 pounds 



Hydrated lime 74 pounds 



Ground limestone 100 pounds 



U. S. DEPT. AGS.. BUR. PLANT INDUS. 



Fig. 238. — Root nodules of alfalfa 

 , INOCULATION FOR ALFALFA 



Alfalfa requires large amounts of nitrogen. If the soil is very rich in 

 easily available nitrogen, the alfalfa plants will acquire a sufficient amount 

 for good growth. In ordinary soils, however, alfalfa is not able to obtain 

 its nitrogen from the soil, but must have the aid of certain bacteria that 

 fix free nitrogen from the air in such form that it can be utilized by the 

 plant. 



Root nodules are found abundantly on the roots during most of the 

 growing season. These nodules are the home of the nitrogen-fixing 

 bacteria, which have the power of assimilating free nitrogen from the 

 air and fixing it in the nodule, the latter decaying and leaving it in the soil. 



Where alfalfa has never been grown the bacteria are probably not 

 present, unless sweet clover is found growing. In the absence of sweet 

 clover, bacteria must be introduced artificially. The best method of 



