CHEMICAL AND BACTERIOLOGICAL STUDY OF WHEAT SOIL. 107 
even down to 18 inches, and it is well seen to what limits 
a hot season can reduce soil moisture in soils under stubble 
or unprotected by a mulch. 
(3) Bacterial numbers are just average and tend to rise 
to a more or less uniform level for the hotter months and 
sink to lower figures in the colder wetter months. 
(4) In the table of nitrate content of the soil all the plots. 
show a rise to some extent for January determinations. 
January then has been a good period for the conditions. 
which assist the bacterial agencies in the soil. Further 
it seems that the hotter drier months favour the bacterial 
activities much more thansay spring weather. November 
and December were warm months averaging for maximum 
atmospheric temperatures 78° and 84 respectively; January 
followed with an average maximum of 87° and it is well 
known that optimum temperatures for the work of these 
bacteria are 82°— 87°. We may assume that the surface soil 
is well heated up and is vastly different to say September. 
It happened that at Christmas time 1921 there fell 168 
points of rain and high nitrate figures were obtained with 
the soils collected on 11th January, 1922. The favourable 
temperature and the addition of water caused the increase 
and the exceeding low limits of total moisture for February 
stopped the rise which was resumed in March. The increase 
shown in October—November might be considered as the 
skirmish which precedes the activity of the annual nitrifica- 
tion battle. There is no reason to doubt that if rain had 
fallen with the rise of temperature in November a different 
state of affairs would be seen in December, but the dessi- 
cating the soil received (only 10 points rain fell between 
October 22nd and December 21st) restricted bacterial 
activity. The amounts for August are inexplicable without 
more knowledge of the year’s cycle, but we may conclude 
that the greatest nitrifying activity occurs in the summer 
