Section V, 1920 [71] Trans. R.S.C. 



Elevator Screenings ; Their Source and Composition and Certain Problems 

 Connected with their Disposal and Use 



By John R. Dymond, MA. 



Preseoted by R. B. Thomson, B.A., F. R.S.C. 



(Read May Meeting, 1920) 



Introductory 



Weed growth in farm crops constitutes an economic loss due to 

 the injury sustained by the growing crop on account of the com- 

 petition of the weeds for the Hght, moisture and plant food. 



As a result of estimates made in 1908 Pammel concluded that an 

 increase of twenty million bushels in the corn crop of Iowa should be 

 possible by better methods of cultivation. These conclusions were 

 based on the observation that good clean fields yield fifty to sixty 

 bushels per acre while the weedy fields only between twenty-five and 

 thirty. It is said that the farmers could easily increase their wealth 

 by eight million dollars, allowing a little expense for labour. 



In this connection it must be borne in mind that increased pro- 

 duction by means of more thorough tillage is not always economically 

 advantageous. Carver states that, 



"the aim of rational industrial management and statesmanship is, or always should 

 be, to secure as large a product per man as possible, and not necessarily as large a 

 product per acre as possible. In fact a large product per acre is desirable only when 

 it means a large product per man, and never otherwise." 



"Even assuming it to be possible to make one acre produce a hundred bushels 

 of wheat, it by no means follows that it would be economical to try to do so. In 

 fact, it most certainly would not be economical, for the reason that it would require 

 such a quantity of labor and care in the preparation of the soil, in the selection of the 

 seed, and in the nurture of the plants, as to amount to a great waste of time and 

 energy — a waste so great as to overbalance the economy of land. It would require 

 much less labor to produce a hundred bushels on two acres than on one, probably 

 less on three acres than on one, and quite possibly less on four than on one." 



In Western Canada, the area of cultivated land per man is very 

 large. This, together with the fact that a large proportion of the land 

 is sown continuously to cereals year after year, has allowed a great 

 variety of annual weeds to become widely established. Weed growth 

 in Western grain fields is therefore largely an economic question which 

 it is not proposed to deal with here. 



It was the object of the investigation reported herein to inquire 

 into (1) the extent to which Western grain is contaminated with weed 

 seeds, (2) the relative prevalence of the seeds of different species. 



