Section III, 1918 [83] Trans. R.S.C. 



The ''Alkali' Content of Soils as Related to Crop Growth 



By Frank T. Shutt, M.A., D.Sc, and E. A. Smith, M.A. 



(Summary) . 



(Read May Meeting, 1918) 



Introduction, 



The nature, concentration and distribution of "alkali" as occur- 

 ring in soils of certain semi-arid districts of Western Canada have 

 been studied during the past five years in the laboratories of the 

 Experimental Farm system. This work has included the analysis of 

 several hundreds of soil groups collected chiefly in tracts about to be 

 placed under irrigation in Southern Alberta. The data so obtained 

 have materially assisted the Government in the classification of the 

 areas in question into irrigable and non-irrigable lands. For the 

 purpose of applying these data American standards as regards safe 

 limits of alkali have largely been used. The results presented in 

 this paper are a contribution towards the establishment of standards 

 more particularly adapted to Canadian conditions. 



The Nature and Formation of Soils in General. 



Arable soils are made up of two great classes of constituents: 

 (1) mineral, as derived from the disintegration and partial decom- 

 position of rock material ; and (2) vegetable matter, the semi-decom- 

 posed remains of past ^generations of plant life, commonly known as 

 humus. It is from the former that the stores of lime, phosphoric 

 acid, potash, etc., present in the soil are furnished, while the latter 

 supplies the nitrogen required for crop growth and at the same time 

 acts as an important factor in supporting bacterial life and in regulating 

 the temperature, the moisture-content and the aeration of the soil. 



Soil formation is not merely a matter of the past; it is now going 

 on. Under natural conditions, as in the forests, our soils are being 

 constantly enriched in humus from decaying roots, fallen leaves — 

 from the death and decay of vegetation generally, and, further, by 

 physical changes and chemical reactions favored by warmth, moisture, 

 carbonic acid of the atmosphere, &c., the rock elements of the soil 

 are being continually, though slowly, disintegrated and decomposed, 

 giving rise to soluble mineral compounds, some of which may be 

 useful and others injurious to plant life. 



