THE DRY ROUGHAGES 199 



are primarily those which lack lime. This element is supplied 

 naturally in certain soils as those containing limestone; to others 

 it must be supplied for growing crops which require it. The major- 

 ity of the cultivated soils of the eastern states are acid. This is 

 the principal explanation why so little alfalfa is grown in this 

 section. With conditions otherwise suitable this difficulty can 

 be overcome by liming. If the farmer does not know whether his 

 soil is acid or not the best thing for him to do is to take it up with 

 his Farm Bureau Agent and ask him to have the acidity deter- 

 mined. In this way he can learn just how much lime is needed per 

 acre. Probably the answer will be in terms of quicklime, also 

 called burnt lime. This is the most concentrated form. Where 

 ground limestone is used, twice as much is required as of the quick- 

 lime to get the same effect. Lime can be spread on the land any 

 time when there is no crop growing. 



335. Inoculation. — Supplying the soil with the bacteria which 

 enable legumes to take nitrogen out of the air is called inoculation. 

 We have mentioned that legumes are the only crops which can do 

 this, and how the soil is enriched in nitrogen in this way. However, 

 this cannot occur unless the right bacteria are present in the soil 

 and the chances are that they are not, unless the legume crop to be 

 sown has been grown recently on the land in question. Thus, the soil 

 must be inoculated. One way to do this is to send to your College 

 of Agriculture, telling them the number of acres to be grown and 

 asking for a " culture of the bacteria for alfalfa." The College 

 will either supply a sufficient amount of the culture for the acreage 

 in question at a nominal cost, or advise where it can be obtained. 

 Another method of inoculation is to take soil from an old alfalfa 

 field and apply it at the rate of 200 to 300 pounds per acre to the 

 new field. This assumes that the cultures were actually present 

 in the old field. If there is any doubt here the method should not 

 be used. One can tell whether the bacteria are present where 

 alfalfa is growing by noting whether there are any nodules on the 

 roots. Where soil from an old field is used, it should be taken at a 

 depth of two or three inches. It is best applied and harrowed in 

 immediately. Exposure to air, wind, and sun destroys the bacteria. 



