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8 THE ROYAL SOCIETY OF CANADA 
I must refrain from further details of this interesting story, but 
I would impress upon you the important results that have accrued 
therefrom to our farmers. Our Canadian work has shown that from 
75 to 150 pounds of nitrogen may be stored up in a season, 
per acre, by the more commonly used legumes, and that, if the crop is 
nodule-bearing, a verp large part of this is from the atmosphere. This 
nitrogen, if the legume is ploughed under, or that part of it in the root 
system if the crop is removed, becomes available through nitrification 
for future crops of grain, etc. Out of all this has come the adoption 
of a rotation in which a legume forms a part and the practice of sowing 
clover with the cereal crop of the rotation, a plan now common, more 
especially in the older parts of the Dominion, one that is proving 
most economic and most valuable for the up-keep of the fertility of our 
soils. Our average acreage yields have been steadily improving in 
recent years, more especially in the cereals, and I attribute this fact 
in a large measure to the increased growing of clover and alfalfa 
throughout the Dominion, a natural result from our teachings and 
advice on this subject. 
Closely related to the above are the recent studies of the micro- 
scopic life of the soil and the relation of this life to soil fertility. This 
is perhaps the latest phase of agricultural research, but already most 
valuable results to practical farming have been obtained. Soil 
bacteriologists, aided by chemistry, have established that the prepara- 
tion of available food—and particularly of nitrogen—from the inert, 
insoluble stores of the soil is the life function of bacteria. Other 
things being equal, we may perhaps say that the number of these 
useful micro-organisms per unit of soil is a measure of the soil’s pro- 
ductiveness. It is obvious that the working out of the chemical and 
mechanical treatments of the soil, which will encourage the develop- 
ment of these organisms, is an important and valuable research. 
Further, it has been lately shown from a number of carefully 
conducted and most thorough investigations on the life of the soil, 
carried out at Rothamsted, that in addition to the nitrogen-fixing 
and other useful bacteria there are always present other forms of life, 
certain protozoa, that prey on these bacteria, checking their develop- 
ment and hence affecting soil fertility. The valuable part of this 
discovery, from the practical standpoint, has been the establishment of 
the fact that these predatory protozoa can be kept in check by pro- 
cesses of “‘partial sterilization” of the soil, as by moderately high tem- 
peratures or the use of live steam, toluene, formaldehyde or other 
chemicals and thus, without any addition of plant food, fertility of the 
soil increased. This is an eminently practical discovery. Though 
as yet methods of partial sterilization are not in use on the farms, 
