WINNIPEG, 1909. 757 
against supply of nitrogen the curve begins by being concave instead of 
linear. (Curve 1.) 
There are a few exceptional years in which this relationship does not 
hold. 
(b) When further amounts of nitrogen are supplied other limiting 
factors come into play, the increase being smaller for the third and fourth 
Bushels 
ofgrain 
6000 38 
5000 32 
4000 26 
3000 20 
2000 14 
43 86 129 
Nitrogen supplied, lbs. per acre. 
CuRVE 1.—Effect of increasing supply of Nitrogen on the yield of Wheat. 
increments of nitrogen. The curve of production becomes convex, illustrat- 
ing the law of diminishing returns. There is an important practical appli- 
cation of this curve in districts where it is customary to manure for wheat. 
So long as the increased crop is more than proportional or is simply pro- 
portional to the supply of food, it may be profitable to go on adding manure. 
But when the yield falls off, a. point is reached where further additions of 
manure are unprofitable. 
Shillings 
250 Corn at...32/- 
Straw at..30/- 
_- Cost of Production. 
Returns, 
200 
Corn at...24/- 
RECUrNS, Straw gba 2O/ 
150 
100 
50 
43 66 129 172 
Lbs, Nitrogen supplied per acre. 
CuRVE 2.—Returns from plots receiving varying quantities of Nitrogen. 
