Soil Test Experiment in 1918. 35 



test a soil and learn its fertilizer needs. And that is by grow- 

 ing the plants to be studied in the soil. 



After careful consideration of the difficulties and the ex- 

 pense involved the Station Council decided that all things con- 

 sidered there was no one thing that could be undertaken on 

 Aroostook Farm better calculated to add to the knowledge of 

 the permanent agriculture of the County than a long term ex- 

 periment with fertilizers. The crops and the soil type were, 

 easily decided upon. Potatoes, oats and clover are now and 

 are likely to be for many years to come the 3 standing staple 

 crops of the county. And Caribou loam is the best and most 

 common type of soil of the county. 



The Plan of the Experiment. 



The investment of time and money was to be so large that 

 2 years of time looking over literature, consulting with the best 

 soil experimenters by letter and by visits to their operations 

 were used before the final plans were adopted. As these plans 

 are necessarily a compromise and cannot include all that one 

 could wish and as it is hoped that this investigation may extend 

 over many years of time the considerations that led to the 

 adoption of the plan are here given in considerable detail. 



The soil can be studied by growing plants in pots and under 

 conditions where the growing conditions — moisture, shade, and 

 the like — are under control or by growing the plants in the 

 field. While there are many advantages in the greenhouse 

 method, if only one of these methods can be employed, the 

 advantages of growing the plants in the field offset its disad- 

 vantages. 



In soil test experiments as heretofore conducted in this 

 country and abroad the general plan has been to decide some- 

 what arbitrarily the amount of plant food to be used per acre 

 and then apply the ammonia, phosphoric acid and potash, each 

 by itself, in combinations of 2, and finally all 3 combined in 

 these fixed amounts upon the different plots. The great weak- 

 ness in this plan is that one assumes at the start that the 

 amounts of the ingredients decided upon are the amounts best 

 adapted to the crop. A more logical method would be to apply 

 each ingredient to different plots in varying amounts from none 



