DAIRY AND SEED IMPROVEMENT MEETINGS. 379 



The work of the agricultural experiment station in Rhode 

 Island, covering a period of four years, showed most conclu- 

 sively that if the microscopic organisms which cause the com- 

 mon potato scab are present in the soil already or are on the 

 "seed" tubers which are planted, the presence of carbonate of 

 lime in the soil is a most powerful factor in promoting the devel- 

 opment of scab. It was further shown by using various salts 

 of sodium and potassium that this result was due to the creation 

 of a more nearly neutral or alkaline condition of the soil and the 

 scab organisms were found to be particularly active in such 

 cases, regardless of whether the neutrality or alkalinity was 

 caused by soda, potash, or lime. 



It is also true that when soil becomes excessively acid, this 

 condition lessens to some extent the total yield of potatoes, and 

 in a striking degree the percentage of tubers of ordinary mar- 

 ketable size. 



From what has been said it will be obvious that one should 

 always avoid the use of excessive and unnecessary amounts of 

 lime on land where potatoes are to be grown in later years. If 

 potato lands are limed, the application should be made follow- 

 ing the crop so as to allow as much time as possible to elapse in 

 the rotation before the next crop is grown. 



In all cases where potatoes are raised on land which is known 

 to be ideally adapted to the crop at the outset, it is to be assumed 

 that the soil is no more than slightly or moderately acid or that 

 it may be even alkaline. Such being the case, one should never 

 omit treating the "seed" tubers with formalin or corrosive sub- 

 limate solution before they are cut and planted. 



In 1912, the writer has the opportunity of seeing a crop of 

 potatoes harvested from some strips of land across which 

 scabbed potatoes were planted in 1893 3.nd 1894 for experimental 

 purposes. It was possible to tell by the occurrence of scab 

 where the scabbed tubers had been planted previously, although 

 eighteen years had elapsed, and no potatoes had been grown 

 there during the interval. This shows that the germs of the 

 common potato scab can live for years in a soil on the decaying 

 vegetable matter or that they at least remain active for the entire 

 time without having a potato crop to feed on. The lesson from 

 this is of vast imprtance to a potato-producing state like Maine. 

 In fact there ought to be, if there is not already, a state law 



