TRANSACTIONS OF SECTION B. 687 



nitrogen as nitric acid ; and in the experiments in question the deficiency of nitric 

 nitrogen in the soil and subsoil of the vicia sativa plots, compared with the amount 

 in those of the trifolium repent plot to the depth examined, was sufficient to 

 account for a large proportion of the nitrogen estimated to he contained in the 

 vicia crops. 



Other experiments were quoted which bore less directly on the point, the 

 results of which were, however, accordant ; and they at the same time afforded 

 illustrations of the loss of nitrogen that the land may sustain by fallow in a wet 

 season, and therefore of the benefits arising from the ground being covered with a 

 crop which takes up the nitric acid as it is produced. To conclude on this part of 

 the subject, it might be considered established that much, at any rate, of the 

 nitrogen of crops is derived from the stores within the soil, and that much, and 

 in some cases the whole, of the nitrogen so derived, is taken up as nitrates. 



This led to the consideration of the second part of their subject, namely, the 

 ^sources of fertility of some Manitoba Prairie soils. 



Soils from Portage la Prairie, from the Saskatchewan district, and from near 

 Fort Ellice, were first examined. They proved to be about twice as rich in nitrogen 

 as the average of arable soils in Great Britain, and perhaps about as rich as the 

 average of the surface soil of permanent pasture land. 



Four other Manitoba soils were examined in greater detail. One was from 

 jSiverville, forty-four miles west of Winnipeg, the second from Brandon, the third 

 from Selkirk, and the fourth from Winnipeg itself. These soils showed a very 

 high percentage of nitrogen ; that from Xiverville nearly twice as high a percentage 

 as in the first six or nine inches of ordinary arable land, and about as high as in 

 the surface soil of pasture land, in Great Britain. The soil from Brandon was not 

 so rich as that from Niverville; still the first twelve inches of depth was as rich as 

 the first six or nine inches of good old arable lands. The soil from Selkirk 

 showed an extremely high percentage of nitrogen in the first twelve inches, and in 

 the second twelve inches as high a percentage as in ordinary pasture surface soil. 

 Lastly, both the first and second twelve inches of the soil from Winnipeg were 

 shown to be very rich in nitrogen, richer than the average of old pasture surface 

 soil. 



The question arose — how far the nitrogen in these soils was susceptible of nitrifi- 

 cation, and so of becoming easily available to vegetation. The soils and subsoils 

 were placed in shallow dishes, covered with plates of glass, kept under proper 

 conditions of temperature and moisture for specified periods, extracted from time 

 to time, and the nitric acid determined in the extracts. 



The periods were never less than twenty-eight days, and sometimes more. The 

 rate of nitrification declined after the third and fourth periods. There was a verv 

 marked increase in the rate of nitrification in the subsoils during the eighth period 

 compared with the seventh, there having been only as much as a tenth°of a cram 

 of garden soil containing nitrifying organisms added. This result was of much 

 interest, affording confirmation of the view that the nitrogen of subsoils is subiect 

 to nitrification, if only under suitable conditions, and that the growth of deep-rooted 

 plants may favour nitrification in the lower layers, 



Records show that the rich prairie soils of the North-west are competent to 

 yield large crops; but under existing conditions they certainly do not, on the 

 average, yield amounts at all commensurate with their richness compared with the 

 soils of Great Britain which have been under arable cultivation for centuries That the 

 rich prairie soils do not yield more produce than they do, is due partly to climate, kit 

 largely to scarcity of iabour, and consequent imperfect cultivation, and too luxuriant 

 a growth of weeds ; and until mixed agriculture, with stock feeding, can be had 

 recourse to, and local demand arises, the burning of the straw, and° deficiency or 

 waste of manure, are more or less inevitable, but still exhausting practices. So 

 long as land is cheap and labour dear some sacrifice of fertility is unavoidable in the 

 process of bringing these virgin soils under profitable cultivation ; and the only 

 remedy is to be found in increase of population. Still the fact should not be lost 

 sight, of, that such practices of early settlement, however unavoidable, do involve 

 serious loss of fertility. 



