NITROGEN, NITRIFICATION, NITROGENOUS MANURES 143 



acids then act upon the soil bases and produce humates 

 or organic salts. In many fermentation changes there 

 is first the production of some chemical compound, and 

 then the action of this compound upon other bodies. In 

 rendering plant food available, as in humification and 

 nitrification, it is the final and not the first product of 

 the organism, which is of value as plant food. 



160. Inoculating Soils with Organisms. In growing 

 leguminous crops on soils where they have never before 

 been produced, it has been proposed to supply the 

 essential organisms which assist the crops to obtain 

 their nitrogen; For example, if clover is grown on new 

 land, the soil may not contain the organisms which 

 assist in the assimilation of nitrogen and which are 

 present in the root nodules of the plant. If these 

 organisms are supplied, better conditions for growth 

 exist. Some soils are benefited by inoculation, while 

 others are not. Frequently the failure successfully to 

 grow legumes is due to other causes, as poor seed, poor 

 physical condition of the soil, lack of mineral plant 

 food, and adverse climatic conditions rather than to a 

 lack of the necessary nitrogen fixing-bacteria. 68 



In old soils where the process of nitrification is 

 feeble, it has been proposed to inoculate the soils with 

 more active forms of bacteria so as to make the inert 

 humus nitrogen more available as plant food. In order 

 to secure the best results from inoculation, suitable 

 food must be supplied for the organisms, and any ad- 



