No. 4.] KEEPING UP FERTILITY. 85 



Nitrogen Gathering. 



We have heard a great deal of late concerning the impor- 

 tance to the farmer of the more extensive cultivation of crops 

 belonging to what the botanists know as the natural order 

 Leguminosm^ among the more important meml)ers of which 

 are clovers, peas, beans, vetches and lupines, because of the 

 ability they have to take most of the nitrogen they require 

 from the air. So far as we now know, none of our other 

 important field crops are able to do this. When we remem- 

 ber that nitrogen is the most costly of all the constituents of 

 fertilizers, — usually commanding from fourteen to eighteen 

 cents per pound, — and that the supply of this element in the 

 air, four-fifths of which is nitrogen, is exhaustless, we are 

 able to appreciate the importance of this peculiarity of the 

 members of the clover family. Time will not allow us to go 

 into details ; suffice it to say that, through the agency of 

 bacteria which develop in little nodules upon their roots, the 

 clovers and their relatives are undoubtedly able to assimilate 

 atmospheric nitrogen. How shall the farmer derive a benefit 

 from this knowledge ? Clearl}^ by the more extensive culture 

 of such crops as have this capacity. But this must be done 

 under appropriate conditions, or he will fail to reap the 

 expected advantages. Briefly, the more important of these 

 conditions are : first, well-drained and well-pulverized soil ; 

 second, a liberal supply of the mineral elements of plant 

 food, such as phosphoric acid, potash and lime ; third, the 

 presence of the germs of the proper bacteria ; and fourth, 

 only a small stock of available soil nitrogen. Only the third 

 and fourth of these, I think, require explanation. The 

 nodules on the roots are the result of the growth of certain 

 microscopic plants (bacteria) in the roots. In the absence 

 of these bacteria the plant is powerless to make use of atmos- 

 pheric nitrogen. The bacteria which develop on the roots 

 of different plants are distinct and different species, they 

 develop from germs or spores. Clover nodule bacteria come 

 from spores of that bacterium ; they can not come from the 

 bean nodule bacteria any more than clover seed can grow 

 from beans. Practicallv and fortunatelv, clover nodule bac- 

 teria are probably found in all soils, because clover has been 



