22 



Maine Agricultural Experiment Station. 1918. 



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 carries 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 dress- 

 ing on mowing fields. Obviously a 5-8-7 fertilizer carries 20 

 per cent of plant food. This amount of 240 pounds is absurdly 

 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 nitrate 

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

 phoric 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 1917 it was in the form of sul- 

 phate. 



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. 



Application of Fertilisers Per Acre for Potatoes. 



Treatment No. 



Phosphoric Acid 



1 







240 







2 







192 



48 



3 



48 



192 







4 







144 



96 



5 



48 



144 



48 



6 



96 



144 







7 







96 



144 



8 



48 



96 



96 



9 



96 



96 



48 



10 



144 



96 







11 







48 



192 



12 



48 



48 



144 



13 



96 



48 



96 



14 



144 



48 



48 



15 



192 



48 







16 











240 



17 



48 







192 



18 



96 







144 



19 



144 







96 



20 



192 







48 



21 



240 











