DECOMPOSITION OF ORGANIC MATTER IN THE SOIL. 253 



nitrogen. Older humus has, therefore, a narrower carbon-nitrogen 

 ratio than humus of recent origin. It is likewise more resistant to decay 

 than new humus. Hence under any given climatic conditions and in 

 any given soil type, the carbon-nitrogen ratio may give important indi- 

 cations as to the availability of the humus nitrogen. Lawes and Gilbert, 

 as quoted by Hall, found the following carbon-nitrogen ratio in the 

 organic matter of different soils: 



Cereal Roots and stubble 43 



Leguminous stubble 23 



Dung 1 8 



Very old grass land 13 7 



Manitoba prairie soils 13 



Pasture recently laid down 11.7 



Arable soil 10. i 



Clay subsoil 6 



Hall concludes, therefore, that humus with a wide carbon-nitrogen 

 ratio is more valuable than humus with a narrow carbon-nitrogen ratio, 

 since it will be attacked more easily by the soil bacteria. 



THE TRANSFORMATION OF NITROGEN COMPOUNDS. 



AMMONIFICATION. Experimental Study. By ammonification is meant 

 the production of ammonia by bacteria out of protein substances or 

 their cleavage products. That ammonia production in the soil is a 

 biological process was first demonstrated by Miintz and Coudon in 1893. 

 These investigators showed that no ammpnia is formed in sterile soils. 

 They also showed that ammonia may be produced out of nitrogenous 

 organic matter by molds as well as by bacteria. Marchal not only 

 confirmed these observations, but proved that various microogranisms 

 differ markedly in their ability to produce ammonia. Of the several 

 species of bacteria tested by him, B. mycoides (one of the common 

 soil bacteria) proved itself particularly efficient in the breaking down of 

 nitrogenous materials and the prodution of ammonia. 



Since the publication of these experiments a large number of investi- 

 gators, both in Europe and America, have studied ammonia production 

 in culture solutions as well as in the soil itself. It has been shown that 

 under favorable conditions the breaking down of protein compounds and 

 the formation of ammonia may be very rapid; for instance, in some ex- 

 periments carried out by Lipman and his associates the following 



