TRANSACTIONS OF SUB-SECTION K. 709 
During the past twenty years some 200 samples of soil collected from 
widely distant points over this immense area have been analysed, though all 
have not been subjected to a complete examination. Asa result of this work 
it can be unhesitatingly stated that the essential and distinguishing feature 
of the western prairie soils is their high organic matter and nitrogen content. 
It is to this fact unquestionably that they primarily owe their remarkable 
fertility and lasting quality. They contain for the most part fairly 
abundant stores of phosphoric acid, potash, and lime. We have. however, 
no evidence that the prairie soils, as a class, are exceptionally rich in these 
elements, though the presence of lime in liberal amounts indicates a condition 
of the soil particularly favourable to nitrification. The very intimate 
incorporation of this semi-decomposed vegetable matter with the clay and 
sund constitutes a very important and valuable feature and undoubtedly has 
an influence for good in many directions. The large percentage of this 
humus-forming material beneficially affects the soil from all three stand- 
points—chemical, physical, and biological. The relation between organic 
matter and nitrogen is a very close one; whatever destroys the former dissi- 
pates the latter. 
It is to be noted that in prairie districts the soil may be found of an 
extremely uniform character over very large areas, and that, as a rule, the 
decline in organic matter and nitrogen from above downwards is gradual, 
there frequently being no distinct line of demarcation between surface and 
subsoil. 
The nitrogen content of the Manitoban soils examined ranged from 2 to 
1:0 per cent., the larger number falling between ‘25 and ‘35 per cent. In 
Saskatchewan, the samples from eight or ten districts revealed a nitrogen 
content from ‘2 to 5 per cent. In Alberta many of the types analysed con- 
tained between ‘3 and ‘5 per cent., but the average was not quite so high as 
for the two provinces to the east. Asa rule, it was found that lower nitrogen 
percentages are obtained as we proceed westward across the plains, and un- 
doubtedly there is a direct relationship between the rainfall and the amount 
of nitrogen accumulated in the virgin prairie soil. 
The water-holding capacity of these soils rich in humus-forming material 
is very large, and it is to this fact that fallowing, now in vogue in grain- 
growing districts, largely owes its value. Moisture may be stored by this 
practice for the crop of the succeeding year, and from 200 to 300 tons of 
water per acre foot (over and above that otherwise present) thus supplied 
to the young crop at a time when the moisture can be used to the greatest 
advantage. 
The system of grain-growing now in practice leads to a large loss of 
nitrogen annually; probably twice as much loss of this important element 
being due to fallowing and other farming operations as to cropping. The 
following table presents the data from one set of experiments to illustrate 
this nitrogen depletion :— 
Indian Head, Sask. 
| Nitrogen. 
-_ To a depth of Aiea: | Ton depth of 8 inches. 
per cent. lbs. eee ve tie 
Virgin soil : : : = |) 0409 3284 | 0371 6936 
ieee agar 0-257 2402 0-253 4730 
| 
Lom duet removal in orops)}/ oss | em | oats | anos 
