A Botanical and Economic Study. 175 



Miintz established by experiment the true nature of nitrifica- 

 tion. 1 Since these earlier trials additional proof has accumu- 

 lated, showing that nitrification in water and soils is due to 

 bacterial agents. Winogradsky 2 isolated by culture the 

 nitrifying organism. Frank, Wilfarth, Hellriegel and other 

 investigators have made many experiments which serve to 

 show that the nitrification of ammonia in the soil, and prob- 

 ably the nitrification of other nitrogenous matters, takes place 

 in two stages, and is performed by two distinct organisms. 

 One converts ammonia into nitrite, the other changes the 

 nitrite into nitrate. In the soil both organisms are present in 

 large numbers. The action of the two proceeds together- 

 The conditions favorable to their growth are alkalinity of soil, 

 oxygen, and a proper base with which the acid can combine- 

 Calcium carbonate usually plays this role in the ground. A 

 soil deficient in such a base is generally infertile and needs 

 dressings of chalk or lime. 



These discoveries, combined with the equally important 

 one that the utilization of free nitrogen by leguminous 

 plants is due to bacteria which form nodules on the roots, 

 will eventually revolutionize modern agricultural methods. 

 Mr. Mason, of Eynsham, Oxfordshire, England, commenced 

 some experiments in 1889, with a view of applying to 

 practical agriculture the knowledge accumulated concerning 

 the minute organisms. " His method is to grow nitro- 

 gen accumulating crops for home consumption, and after- 

 wards nitrogen consuming crops for sale." He grows mixed 

 crops of Leguminosce, liberally fertilized with basic slag and 

 kainit. He converts the first year's crop into silage, which 

 he feeds to his cattle, returning the manure to the soil, and 

 converts the second year's produce into hay. The land thus 

 produces highly nitrogenous crops without manure, and is 

 left in a high condition for potatoes or grain, which need 

 nitrogenous manuring. The fact that it is necessary, in order 

 to prevent "clover sickness," to grow in sucession a variety 

 of Leguminosce, will lead to radical and important changes in 

 our present system of rotation. 



1 Compt. Rend., lxxxiv, 301. 



- Winogradsky. Ann. de l'Inst. Pasteur, iv (1890-911. 213, etc. 



