126 AGRICULTURAL EXPERIMENT STATION. [Jan. 



B. Observations with Scabby Potatoes. 

 The experiments were inaugurated in 1886 for the pur- 

 pose of inquiring into the circumstances which control the 

 development and the propagation of the scab on potatoes. 



IS 86. — The first year's work in this connection has been 

 confined to the task of observing the behavior of scabby 

 potatoes as seed potatoes, under some definite i)revious 

 treatment. To prevent a possible propagation of scab in the 

 new crop by infected seed potatoes, the following course was 

 adopted : Thoroughly scabby potatoes, obtained from the 

 previously described experimental plats, were treated with 

 some substances known to be destructive to various forms of 

 parasitic growth. This operation was carried out with the 

 intention of destroying the propagating power of adherent 

 germs of an objectionable character before planting the seed. 



The field for the experiment was distinctly separate from 

 other experimental plats for the cultivation of potatoes. It 

 had been used for many years previous for the raising of 

 grass, and had since been planted but once, — the preceding 

 year ( 1885) , — with corn. The land was prepared by plough- 

 ing and harrowing in the same way as other potato fields. It 

 was fertilized broadcast, at the rate of 600 pounds of ground 

 rendered bones and 290 pounds of potash-magnesia sulphate. 



The field was subdivided into five plats of equal size, 

 eighty feet long and fifty feet wide, and the potatoes subse- 

 quently planted in rows, three feet three inches apart, with 

 hills three feet from each other in the rows. Three feet of 

 space was left between the plats unoccupied. The scabby 

 seed potatoes selected for the trial were, as far as practi- 

 cable, of a uniformly medium size. Each lot was immersed 

 in the particular solution prepared for the different plats ; 

 after being kept there for twenty-four hours they were 

 removed and directly planted. 



Plat 1 was planted with healthy and smooth potatoes, 

 without any previous treatment. This course was adopted 

 to learn whether soil, fertilizer, or atmospheric agencies of 

 the season would favor the appearance of scab in the crop. 



