SOIL Test Experiment in 1918. 39 



center of the figure contain all 3 of the ingredients and the .; 

 plots in the dotted triangle have them somewhat more nearly 

 to ordinary percentages than do the others. While the 3 

 lowest plots in the heavy triangle have the ammonia in the 

 amount that is fairly common in many high grade fertilizers. 

 As noted in the figure for convenience of reference in the text, 

 these groups are called N5, N3, P5, P3, K5, K3, Comp 6, Comp 

 3 and A1T14. This plan and diagramatic arrangement makes 

 comparative studies of the different combinations easier and 

 more clearly shown than, by any other method that has come 

 to the attention of the writer. 



THE FERTILIZING MATERIALS. 



In the field experiments at Aroostook Farm with potatoes 

 a 5-8-7 fertilizer or one that carrier 5 per cent of ammonia, 8 

 per cent of available phosphoric acid and 7 per cent of potash 

 has been used at the rate of 1200 pounds per acre. The same 

 formula at the rate of 300 pounds per acre is used when seed- 

 ing to oats and at the rate of 150 pounds per acre as a top 

 dressing on mowing fields. Obviously a 5-8-7 fertilizer carries 

 20 per cent of plant food. This amount of 240 pounds is ab- 

 surdly high and it was, therefore, taken as a maximum in the 

 scale so that on the diagram where ammonia is shown as 20 

 per cent it represents 240 pounds of ammonia. This amount 

 of ammonia would be furnished by 4800 pounds of a 5-8-7 

 fertilizer. 



The ammonia is one-third in the form of ammonium ni- 

 trate and two-thirds in the form of sulphate of ammonia. The 

 phosphoric acid is in the form of acid phosphate. The potash 

 is all water soluble and is being applied during the war in the 

 form that can be obtained. In 191 7 and in 1918 it was in the 

 form of sulphate. 



The weights of ammonia, phosphoric acid and potash ap- 

 plied to each plot when the crop is potatoes is shown in the 

 table that follows. 



For the 1-40 acre plots these amounts are divided by 40. 

 These amounts are further reduced for application to oats by 

 dividing by 120 and for application to grass by dividing by 240. 



