INFLUENCE OF MOISTURE 



229 



slightly with the physical properties of a soil. Twenty-two soils 

 varying widely in physical properties yielded maximum nitrification 

 when the soil contained from 50 to 60 per cent, of their water- 

 holding capacity, as indicated in Fig. 30. Furthermore, the opti- 

 mum moisture content for maximum nitrification is correlated 



FIG. 32. Average percentages of nitric nitrogen produced in soil receiving various 

 quantities of water. The quantity produced at 60 per cent, is taken as 100; on the 

 ordinate is given the per cent of nitric nitrogen formed, whereas on the abscissa is 

 given water applied as per cent, of water-holding capacity. 



with the other soil constants with a set of equations similar to 

 those given for ammonification, page 201. Thus, 



Mn = .55 C 



Mn = .8525E + 11.55 



Mn = 1.472 W + 11.55 



Mn = 2.163 H + 11.55 



