172 THE KOYAL SOCIETY OE CANADA 



2. Choice of materials for fertilizer. 



Perhaps the first consideration would be the choice of the most 

 favorable materials for fertilizer. For this, the element to be tested 

 is tried in various proportions, the other elements always being present 

 in excess of requirements. We thus find the respective merits of nitro- 

 gen in its various forms or mixtures of forms, similarly the best forms 

 of phosphorus and potassium. To approximate these values we 

 need not apply each in more than 3 or 4 amounts (see table I). 



3. The use of the diagram in practice. 



Without having recourse to the greenhouse and also restricting 

 the number of plots in the field, we can divide up the plane 3 dimension 

 diagram by choosing not more than 18 points and form it into various 

 triangles by joining up these points (see diagram IV). The mixtures 

 of elements designated by these 18 points need not be tried in more 

 than 3 or 4 amounts. In this way we find the maximum possibilities 

 for each point by having regard to the law of minimum. If this work 

 is sufficiently exhaustive the correct "formula" is located with a fair 

 degree of exactness. This may be at one of the points or within a cer- 

 tain triangle. By using perpendiculars, as mentioned before, a conical 

 surface might be formed, the apex of which is found by interpolation. 

 On the other hand we could simply enter on the diagram the maximum 

 profit (in $) possible for each point and perhaps also make use of this as 

 a 4th dimension. 



A few other plots might be added to round out the experiment. 

 Point 17 is chosen, representing the "formula" 4-8-10 (N-P 2 5 -K 2 0) 

 and it is tried in combination with manure and with subsequent treat- 

 ments in the second and third years, (see table II). 



POINTS ILLUSTRATED BY THE DIAGRAM. 



The plan of procedure is of very general application and by it 

 each of the many farm practices can be studied — from field crops to 

 orchards and garden truck. 



It is interesting to study the diagram (IV) and locate on it many of 

 the commercial brands of fertilizer. It will be found that by far the 

 greater number of the brands on the market, and of those in general use, 

 are located inside the triangle formed by joining the points 8, 9 and 10. 

 The chief logic in this that is apparent off-hand is the fact that they are 

 farthest removed from the N and K corners — the most expensive — 

 and are closer to the P corner — the cheapest. Of late years, however, 

 the use of others higher in potassium (as 4-8-10 or point 17) is becom- 

 ing more general. 



Most commercial fertilizers are richer in phosphorus than in 

 nitrogen or potassium and yet the products of agriculture and manure, 



