Soil Test Experiment in 1918. 37 



The extreme points of the angles represent ioo per cent 

 respectively of the ingredients ammonia (nitrogen) phosphoric 

 acid (phosphorus) and potash (potassium). Obviously each 

 side of the triangle can be divided into as many equal parts as 

 may be desired. Schreiner in his work in the greenhouse 

 with cultural solutions has been able to carry enough different 

 combinations so as to divide the sides into tenths. That, how- 

 ever, makes 66 different combinations which is a far larger 

 number than we could carry in this field test. Each side, there- 

 fore, is divided into fifths in the plan of the experiment here 

 begun. And as explained beyond for the purpose of making 

 the comparisons easier for the practical man familiar with usual 

 fertilizer formulas, the 5-8-7 formula, which makes a total of 

 20 per cent of ammonia, available phosphoric acid and potash 

 was used as a starting point. Hence, in the diagram here 

 shown the extreme points of the triangle represent 20 per cent 

 instead of 100 per cent as used by Schreiner. Although the 

 fertilizer mixtures are in reality based upon the percentages 

 expressed in terms of ammonia, phosphoric acid and potash 

 the symbols N, P, and K for the elements nitrogen, phosphorus 

 and potassium, which are the characteristic elements of these 3 

 constituents, are used in lettering. Wherever N is used in 

 diagrams or text it refers to ammonia in available form, P 

 refers to available phosphoric acid and K to water soluble 

 potash. 



The relation of the plots to each other is clearly seen by 

 following the lines on the triangle. The maximum phosphoric 

 acid (P) is at the left lower angle, the maximum potash (K) 

 at the right lower angle and the maximum ammonia (N) is 

 at the top of the triangle. From these points the different 

 ingredients diminish. On all of the horizontal lines the phos- 

 phoric acid diminishes from left to right and the potash from 

 right to left. On all of the lines inclined to the right the phos- 

 phoric acid decreases from bottom to top and the nitrogen 

 decreases from top to bottom. On all of the lines inclined to 

 the left the potash diminishes from the bottom to the top and 

 the ammonia diminishes from the top to the bottom. 



This plan calls for 21 plots. Obviously an indefinite num- 

 ber of plots could be introduced. To graduate on a scale of 

 tenths would give finer distinctions but would treble the plots 



