710 TRANSACTIONS OF SUB-SECTION K. 
Calculation shows that about one-third of this loss is to be accounted for 
by removal in grain and straw of the crops grown, the remaining two-thirds 
being dissipated by cultural operations. 
It is highly important that a system of crop rotation that will occasionally 
return humus-forming material and nitrogen should replace the present 
system of two grain crops, followed by a bare fallow. It will only be in the 
adoption of some such method that the present high fertility of the prairie 
soils can he maintained. 
6. The Nitrogen Problems of Dry Farming, 
By F. J. Auway, B.A., Ph.D. 
Fallowing, which in ‘ dry farming’ is necessary in order to accumulate 
water in the subsoil, facilitates the rapid loss of nitrogen, while the use 
of leguminous crops as green manures exhausts the moisture of the subsoil. 
The nitrogen problem will probably become acute much sooner in the 
central and southern portion of the semi-arid region than in Saskatchewan, 
as the original content of nitrogen is less. Six-inch samples of the heaviest 
types of soil, which are also those richest in nitrogen, were taken by the 
author from prairies in widely separated portions of the semi-arid region, 
viz., Indian Head, in Saskatchewan ; North Platte, in Nebraska; Solana, in 
northern New Mexico; and Douglas, in south-eastern Arizona. The per- 
centages of nitrogen were °384, ‘175, ‘161, and ‘087 respectively, and of 
organic carbon 4°19, 2°06, 1°29, and 0°58. 
The author reported the results of the determination of nitrogen, 
organic carbon, and soluble humus in over fifty samples of soil taken by 
him from different fields, plots, &c., of the Indian Head Experimental 
Farm, as well as from the adjacent prairie. The history of all the fields 
since the first prairie sod was turned is known. Continuous cropping with 
wheats, oats, and barley, with a fallow about every third year, has caused 
a loss of about one-third of the original content of nitrogen and carbon. 
Continuous bare cultivation for fifteen years has caused noticeably greater 
losses than cropping for the same length of time. Seeding down to grasses 
has checked the losses. In the case of a field of twenty-two rotation plots 
the average of the fifteen plots, on each of which during nine years a 
leguminous crop had been ploughed under every third year, was the same 
as that of the seven plots which had produced a cereal crop every year or 
had been fallowed every third year. 
That nitrogen has not yet become a limiting factor in the yield of wheat 
at Indian Head is shown by the annual reports of the Indian Head ‘farm. 
Applications of 100 and 200 Ibs. of NaNO, have caused no increase in yield 
of wheat. The yield after leguminous crops ploughed under has been less 
than on fallows, the difference in yield seeming to depend upon the extent 
of growth and the lateness of ploughing of the legumes, and accordingly 
upon the amount of water removed from the soil by the legumes. 
7. The Conservation of the Fertility of the Soil. 
By A. D. Hawn, M.A., F.R.S., and E. J. Russe, D.Sc. 
Nitrogen is the most important of the elements of fertility in the soil, 
and the one most subject to change through either the natural conditions 
prevailing or the form of cultivation the land receives. We may distinguish 
various factors affecting the amount of nitrogen in the soil :— 
(1) The growth of plants simply removes some of the nitrogen that has 
